Do you really need 1.25 F? Reason I ask, there are some smaller supercaps, like the Eaton PB-5R0V105-R, that are rectangular and a pair of them would probably fit in a 9 V battery outline with room to spare (for the electronics.) But, a pair of them would give only .5 F.

Thats way over my head. I just wait for you to manufacture an item then I buy it.

Rof Miller

hello guys and gals.......

Maybe make a BCR-3 for it ?

Tiffany

PLCProf posted:

Do you really need 1.25 F? Reason I ask, there are some smaller supercaps, like the Eaton PB-5R0V105-R, that are rectangular and a pair of them would probably fit in a 9 V battery outline with room to spare (for the electronics.) But, a pair of them would give only .5 F.

That's a good question, I don't know at this point how much would be required.  The ones I specified are not all that much larger than those Eaton ones.  If I were going for size, maybe maybe I should just consider these on eBay, they're 5.5V 1.0F and would much more easily fit into the 9V form-factor.  They're $1.50 each and shipping for as many as you buy would be $2 total.  I actually have a bunch of this type of 1F capacitor in my parts box.

eBay: 162139053842

 5.5V 1F KAMCAP H Type Coin Electric Double Layer Farad Super Capacitor

Tiffany posted:

hello guys and gals.......

Maybe make a BCR-3 for it ?

Tiffany

What's a BCR-3?

gunrunnerjohn posted:

Tiffany posted:

hello guys and gals.......

Maybe make a BCR-3 for it ?

Tiffany

What's a BCR-3?

Maybe it's a BCR-2 which is 3 volts...and thus the 3.

Chuck, why would I make a 3V replacement, I'm targeting the TMCC/Legacy 9V battery replacement.  The only 3V requirement for a BCR clone is PS/2, which already has charging capability.

gunrunnerjohn posted:

Chuck, why would I make a 3V replacement, I'm targeting the TMCC/Legacy 9V battery replacement.  The only 3V requirement for a BCR clone is PS/2, which already has charging capability.

I don't know why, just got interested in researching what a BCR-3 might be

I presume this is for those who run in conventional mode, yes?

The reason I ask is I've yet to install a battery in a TMCC/Legacy loco as I have never seen the need when operating in command mode.  Have I overlooked some reason for installing a battery in a command operated TMCC/Legacy loco? 

I like this idea though, a 9 volt "battery" that won't go flat or leak. I have one engine that drops out the sound if there is no battery in it on some layouts...

We see dropouts of some locomotives in command mode, both TMCC and Legacy in certain conditions, so I see a need for a battery in command or conventional mode.  If I use a battery, I want one that I never have to change and doesn't leak.

Obviously, if you perceive you have no issue, this topic probably isn't of interest to you.

I'm going to try the two 1F caps in series and see how long they'll hold up the RailSounds board, they may be all that's required.

Do you know the resistance of that cap?  Most coin-style supercaps have resistances measured in the 10's of ohms.  For example, eBay (182260239593) with similar pricing shows 15 ohms:

So two stacked caps would be 30 ohms.  So let's say you need 1 Watt of power to drive the audio during track power interruptions.  The 9V battery would need to deliver over 100 mA so that would be a drop of 3V thru the caps' internal resistance and you'd only have 6V available to the electronics.  Additionally, a 1/2 Farad cap discharging 100 mA drops 0.2V per sec; I don't know how long the TMCC sounds run but this would be another consideration.

The Eaton supercap mentioned earlier has an internal resistance of less than 1 ohm due to different technology.  This is the type used in the BCR devices and in the MTH PS3 engines.  The coin-style caps are typically used in low discharge current applications and of course are much less expensive.   

I did note that Stan,I figured I'd try them and see what happens.  I have a few so I can give them a test and see how they do on a RailSounds board.  If they don't work, well, I haven't invested anything. 

Well... you're right, I was hoping that wouldn't be too much internal resistance.  I guess I'll keep looking...

I'd like to find a lower cost alternative to the $5 capacitors, that bumps the price up quite a bit.  I'd like to be able to get all the parts for something like this for $10 or less, including the circuit board.  I'd also like it to be as small as possible.

I'd buy them for all my TMCC/Legacy locomotives that take batteries, as it'd save me from having to make my own.  Now, the next question is, you have looked into adding this to a locomotive that doesn't have a battery, like the VLBB and the B6sb?

sinclair posted:

Now, the next question is, you have looked into adding this to a locomotive that doesn't have a battery, like the VLBB and the B6sb?

No way to do that for those that don't have a battery.  If the circuit on the sound board isn't there, that's all she wrote.

I have a couple thoughts, but not sure about any of them.  

The first is to perhaps use 3 of the inexpensive Caps, to allow maybe a 12-15v charge level.  This would require input and output regulators, so adds a step of complexity, but it may be less expensive that way.  

Second idea is to use just 1 good quality super cap, and a boost module to raise it's 5v to 9v.  Here, I'm unsure if a booster would provide enough current. 

The last is more of a question, while a 9v battery is used for the sound system, is the railsounds board actually running at 5v?  if so, would it be possible to add the supercap to the board in a way that bypasses the step down from 9v to 5v?  It would make for a more complex install, obviously, but may make for much fewer parts as you pretty much only need to limit in-rush current to the cap.  

JGL

John, I looked at both of those options, but I think just using two of the proven 5V supercaps is the way to go.  Trying to add multiple regulators seems like way more complicated than this project should be, and boosting it requires either using one of the cheap eBay switcher modules, or laying out a boost regulator.  Neither of these are attractive options, at least to me.

No way I want to screw around tapping into the RailSounds board, that is messy beyond belief!  Besides, this will be a project that the great unwashed masses might want to use, and there are very few people that would be able to hack into the boards to attach this, and even fewer that would want to.

gunrunnerjohn posted:

sinclair posted:

Now, the next question is, you have looked into adding this to a locomotive that doesn't have a battery, like the VLBB and the B6sb?

No way to do that for those that don't have a battery.  If the circuit on the sound board isn't there, that's all she wrote.

Do we know the circuit isn't on the board, or is it there, but unpopulated, or is it there and populated but just doesn't have a battery connector?  I was under the impression the boards were mostly modular, they just changed the sound chips.  If they spun custom boards for these locomotives, then I understand that's all there is to it.

Well, you're certainly welcome to research it.   I don't see how 99% of the populace here would be interested in hacking into their $100+ VL-BB sound board in the hopes of adding a battery!

I have a couple of Legacy diesels that I would be interested in adding your super cap 'batteries' to. Haven't had a problem with them, but you never know. However, after reading about the VLBB above, I better look to see if they can even accept a battery. I think the project does seem like a good idea, I have seen a few posts with folks wanting to have a battery of some sort in their TMCC engines. 

Also, probably a dumb question, but why would they leave the battery connection out of the VLBB, or any other engine for that matter? Is the VLBB long enough, having more pick-up rollers so it's not needed? And would space could be a problem in the smaller engines? Just curious on your thoughts about this.

Well, the 9V (8.4V) BCR retails for $24.95.  I realize it's not exactly apples-to-apples since, as I understand it, for TMCC it is a nice-to-have sound option whereas for MTH PS2 it is required.  So if this is something you're planning to make available to others it seems you have a kind-of-sort-of benchmark which, to me anyway, suggests you have a reasonable amount of wiggle room wrt squeezing out the last penny from the design.

In your testing, have you noted actual power/voltage/current requirements?  I'd think the 9V battery is powering a step-down regulator to, say, 5V?  And if so does this mean it works with 8V, 7V, 6V, ?V at the terminals?  And what is the current and for how long?

From what I've seen, the cost of the low-resistance supercaps has not fallen dramatically especially compared to semiconductor regulator components/modules.  If you're trying to develop a "kit" for others to mess with, learn from, etc., that's one thing.  But if you're trying to engineer a product I'd think a dual regulator configuration stepping-down to the storage voltage...then stepping-up to 9V (or whatever is needed) is worth a look.  The MTH PS2-3V with ~2.5V batteries is a dual regulator configuration.

The $25 BCR doesn't have a charger, so that's not exactly an apples to apples comparison.

I check the power requirements for a standard RS4 board when just running normal sounds, I cut the track power and measured what the board drew from the battery.  It was around 82ma and dropped a bit as the volume went down at the last of the shutdown sounds.  With two series 2.5F caps, I could run the shutdown four times before the board doesn't get enough voltage to run, that was about six and a half volts on the caps. 

If I could find the 1F or 1.5F caps significantly cheaper, it would probably make this a better deal, but I didn't find anything close.  There is one eBay vendor, but he couldn't tell me the internal resistance of his product, so I was reluctant to order those.  It appears that .5F would be plenty for the purpose, it only has to hold the sound for a second or two in real life.  I'm pretty sure fully charged the .5F could manage one shutdown sequence.  I was really looking for something smaller, but the 1F caps seem to be almost as large as the 2.5F ones I'm using.

My idea of this is a kit or perhaps just the board, I don't see any way I'd tool up to make 100+ of these, too big an investment for an uncertain return.  However, I'm sure some folks would like to equip their fleet with some of these.

I realized that it was somewhat of a kludge with two boards, so I tried it with one board. three boards are $4.90.  The supercaps go on the back laid on their side, and all the other components go on the front.  the regulator, being the tall component, folds down on the board.  I would think you'd simple heatshrink the whole affair after attaching the track power wires and the battery clip.  with the caps sticking out the end, it's a bit less than 2" long, .8" wide, and 5/8" thick.

wow john, sign me up for 4. it is a great idea.

I'll sign up for 5.

I just bought some capacitors that might work and be cheaper than the $5/ea ones I now have.

Seeing as how the battery in TMCC/Legacy is not "mission critical" as it is in the MTH stuff, might not a NiMH battery and charger be the least expensive solution? All you'd need is a trickle charge of 5 mA or so. If the battery poops out, no harm is done.

Or am I missing the point?

I have a NiMH, I think, (might be a NiCad) in the ZW-C add on volt/ammeter. It seems to work well, but I do worry about it from time to time. I'd feel safer with capacitors.

Actually years ago I made little circuit to show if one desk phone was off the hook of a couple phones on the same 2 wire line. I used a regular alkaline 9 v battery and trickle charged it with a 100K or so with the phone line voltage always present...forget what that was. Anyway it lasted many years that way.

The NiMh battery wouldn't be nearly as much fun.   Besides, the object of the exercise was to totally eliminate any battery replacement issues.

gunrunnerjohn posted:

The NiMh battery wouldn't be nearly as much fun.   Besides, the object of the exercise was to totally eliminate any battery replacement issues.

I have no problem with that.

(Shifting to science project mode)

cjack posted:

I have a NiMH, I think, (might be a NiCad) in the ZW-C add on volt/ammeter. It seems to work well, but I do worry about it from time to time. I'd feel safer with capacitors.

Actually years ago I made little circuit to show if one desk phone was off the hook of a couple phones on the same 2 wire line. I used a regular alkaline 9 v battery and trickle charged it with a 100K or so with the phone line voltage always present...forget what that was. Anyway it lasted many years that way.

In 1972 I received as a gift an electronic flash unit(!) that ran on the uncommon rechargeable alkaline batteries.

44 years later, the flash doesn't work, but the batteries and charger do! Must be some kind of record. I put them in my "museum" drawer along with the 100 kilocycle crystal and recording wire.

Using your current measurement of 82mA from a 9V battery for 2 seconds, that's 1.5 Joules of energy.  A 5V, 1/2 Farad supercap stores just over 6 Joules of energy.  So if you used a dual-regulator design, perhaps even piggy-backing with a 75 cent (free shipping) eBay step-up module, I think you might be able to cram it and the charger into a 9V battery outline.

There are only 7 components on the boost converter module which claims over 1 Amp output capability.  And of course you wouldn't need the rather bulky voltage adjust trimpot since you'd set the boosted output voltage to a fixed 6.5V (or whatever minimum you need).   And if you only need, say, 100mA of output current you can probably get by with a smaller inductor which is the 2nd largest component on the module.

A nice feature of the boost module is it operates down to about 2V input.  Note that if you use two stacked 5V supercaps, you are leaving a good chunk of energy on the table.  That is, it appears you're clamping the supercaps at 9.4V.  So you only get energy as the caps discharge from 9.4V down to 6.5V.  So you only use about 50% of the available energy.  OTOH, if you have a 5V supercap and you can draw it down to 2V, you use about 75% of the available energy.  Of course there are efficiency losses in stepping up voltage but I think the numbers are worth crunching.

Well, we also need the charging circuit for the 5V supercap.  I'm somewhat loath to start sticking eBay modules into the mix, they tend to come and go.  It would be nice to come up with a switching regulator design that didn't take up too much space, I should look into that.  I presume the charging circuit could be limited to around 100ma or less and still do the job.

I recall the discussion on boosting a single supercap as opposed to using two we had previously.

Well, that 3 Watt charging resistor did initially strike me as an elephant in the corner.  Again, it depends if this is to brute-force a simple solution that gets the job done...or to engineer it for philosophical or to polish the walls on the ivory tower.   For example, constant-current charging is as "simple" as a LM317 plus a resistor.  A voltage cut-off circuit to stop rapid charging and revert to trickle-charging is also not rocket-science.  I think another design question is how fast the battery has to be ready to hit the ground running...and with what kind of duty cycle.  For example, taking the MTH battery as an extreme case, it has huge capacity and can handle many power interruptions one after the other...but takes quite a bit of time to initially charge to even operate one interruption.  I'd think you have similar trade-offs with this design especially if limited to a modest charging currents like 100 mA which of course is on par with the discharge current.

The 3W resistor was a hammer, but it worked.   Didn't you see, I dropped it a 2W resistor later.

I did think of constant current, but then I thought about voltage cutoff and decided to take the easy way out.   If we had a simple voltage cutoff, I don't know as we need trickle charging, when the voltage falls, it would start charging again.

I found this Microchip part for less than $1 in quantity one, and it allows up to 5.5V in and a variable voltage out.  Seven parts, not too bad, and I could program it for 7.5 to 8.0 volts out, that should insure positive result.  It'll do up to 200ma at 7-8 volts, should be sufficient, and it's a small footprint part.

So are you saying you're willing to consider the dual-regulator step-down/step-up approach using a single 5V supercap (low-resistance type)?  More components for sure but unless those supercaps come way down in price it sure seems the dual-regulator approach has an undeniable cost advantage whether it be 7 more components or even double that.   I couldn't find an easy-to-find source for the MT3608 AeroSemi boost converter, but I guess it comes as no surprise that its topology is identical to the MCP1661 Microchip converter.  In fact, it seems you could layout with a SOT-23-6 footprint to handle both chips!

I've given up pondering how you can get quantity 1 assembled (and presumably tested) eBay module with all 7 components shipped to the U.S. for less than the price of just the MCP1661 from DigiKey!

Anyway, as I see it, the charging method depends on the requirements for how fast, how often, this battery replacement needs to be called into service.  I have no problems with the simple 2W resistor current limiter if it does the job...

Ive noticed Johns solutions are direct and pointed to the problem at hand with an emphasis on simple. I'd say its worth a little more on the front side to stay withing the confines of simple. The best solutions are the ones that are the shortest rout to the answer. John, when you get the design hammered out and if you decide to sell a bunch of kits Id easily take more than 10 maybe 20. I cant stand when my command locos drop sound its alwasy a pita to get the sound back up

stan2004 posted:

So are you saying you're willing to consider the dual-regulator step-down/step-up approach using a single 5V supercap (low-resistance type)?  

Sure, if I was not going to consider suggestions from the bench, I'd just build one.

stan2004 posted:

More components for sure but unless those supercaps come way down in price it sure seems the dual-regulator approach has an undeniable cost advantage whether it be 7 more components or even double that.   I couldn't find an easy-to-find source for the MT3608 AeroSemi boost converter, but I guess it comes as no surprise that its topology is identical to the MCP1661 Microchip converter.  In fact, it seems you could layout with a SOT-23-6 footprint to handle both chips!

I normally stick with chips I can get from a reliable source, simply because if I design something and then later decide on making quantities, I want to be able to get the parts.  I did look around for the MT3608, but as you say, they seem to be hard to buy.

stan2004 posted:

I've given up pondering how you can get quantity 1 assembled (and presumably tested) eBay module with all 7 components shipped to the U.S. for less than the price of just the MCP1661 from DigiKey!

Anyway, as I see it, the charging method depends on the requirements for how fast, how often, this battery replacement needs to be called into service.  I have no problems with the simple 2W resistor current limiter if it does the job...

I marvel at the Chinese prices, clearly they have some government help in maintaining those prices. Of course, the USPS subsidizes their shipping like the idiots we are, I'd love to understand why that policy exists! The resistor does the trick, but I'm open to a more elegant solution, especially if it costs significantly less. Let's talk about the constant current and limiting the charge to 5V maximum. How were you visualizing accomplishing that? Is there a simple trick to add to the LM317 circuit to cutoff at a specific voltage? I was thinking along the lines of a Zener diode circuit.

John, the postal service covers the inbound shipping because of a century old international agreement or treaty. When it was enacted this wasn't at all a concern and i'm sure it benefited us. It was done to help ensure reliable and consistent postal delivery around the world which it did.

Well Matt, being as it's a one-way arrangement, I don't see how it benefits us now!  I can see how it benefits me personally with cheap Chinese parts, but that's not necessarily good for the country.

As with others, many others, this is needed and would boost reliability in our TMCC related engines.  Yes, there are other products to do same on the market, but not at the savings and originality in design that John proposes along with great input from other Forum members.   I, also, am interested in this, along with other endeavors purchased from him.

Jesse    TCA  12-68275 

The savings are yet to be realized, we'll see how this all shakes out.   I've wanted to tinker with a switching supply design, so I guess this is a good time to get my feet wet.

This is all black magic to me, so me trying to figure out if the VLBB or B6sb have the battery circuit would be as effective as me doing brain surgery.  As for your design, by all means please Microchip components, that's where my dad works as a software engineer, making dev kits if I remember correctly.  And if you sold these as just PCBs for us to buy our own components to populate the board, I'd be good with that.  Then I could buy the boards I needed (And some extras.) and then build them up as I have the time and money.

gunrunnerjohn posted:

...The resistor does the trick, but I'm open to a more elegant solution, especially if it costs significantly less. Let's talk about the constant current and limiting the charge to 5V maximum. How were you visualizing accomplishing that? Is there a simple trick to add to the LM317 circuit to cutoff at a specific voltage? I was thinking along the lines of a Zener diode circuit.

Well, as charging circuit go, I don't think you can get cheaper than a resistor!  I'd go with that if it does the trick.

If you want to talk about constant current charging, I'm still unclear on where the 100 mA charging current comes from.  Is this from the drooping of the half-wave input with "only" a 150uF cap?  As shown, with the 7810 and 22 ohm resistor, on power-up into an empty supercap you're drawing ~500 mA (10V / 22 ohms) albeit dropping rapidly...but still attempting to source over 100 mA half a minute later (time constant R x C = 22 ohms x 1 Farad = 22 seconds).  So if you've done-the-math and the choice of "only" 150uF purposely starves the 78xx regulator which then limits the charging current, then that's a clever current limiting method!  Sort of like the trick of inserting a 5 cent diode into the AC path to dim passenger car lamps on command-voltage tracks.  Of course this applies to TMCC which as I understand it only operates on AC track voltage (vs. PS2/3 where you might have DC on the track).

So if the numbers work, then it seems you could have a 7805 charging a single 5V supercap with a single resistor.

Getting back to the constant current.  I'd still like to hear the duty-cycle requirement on how many interruptions must be handled, how quickly, how often, whatever.  I have little experience running TMCC engines so don't have a feel for how often the 9V battery is called into service or what the expectations are.  A constant-current 100 mA into a 1 F cap has a charge rate of "only" 0.1 V/sec.  So charging from 0 to 5V would take 50 seconds; I don't have a sense of whether this is OK.  Obviously once fully charged, I suspect the 9V battery applies to conventional operators pressing DIRECTION that get the long dropout while command operators might get fraction-of-a-sec dropouts?

I did realize that the current was more than 100ma for the charge at first but it drops quickly.  I sized the 33 ohm resistor to be a 2 watt after a couple of back of the envelope calculations.  When you start with the cap at zero volts, you have a little less than 10 volts across the resistor, (the Schottky diode drops a bit).  The resistor starts out dissipating around 3 watts and ramps down to less than 2 watts in ten seconds.  By the time you get to 20 seconds, we down to a watt of dissipation across the resistor.  Doing that it barely gets warm, so I figured I was home free.

The 150uf cap was really picked as I didn't want to go to a larger form-factor cap, so I just used the maximum value in that form factor.  I know it does happen to starve the regulator when there's excessive load, but that's an accidental happening.  When I tested the combination on the bench, it worked fine to charge the caps and didn't have any overheating issues, the object of the exercise.

The battery use with TMCC, or even conventional, is pretty low duty cycle.  The only time it's needed with TMCC is on occasion where you lose the power briefly over switches or dirty track as a rule.  For conventional, you use the battery typically when you reverse directions, that should be less than a second.  Obviously, the conventional case is more battery intensive, so I'd probably want to size the capacitor to allow for a few seconds of conventional running before dropping below the usable output for providing the output power.  With that being said, I'd probably go with at least a 1F 5V cap for the storage to give me a bit more run time.

For the 5V regulator and resistor, I'd probably go with a 2 watt 10 ohm resistor to limit current.  When the capacitor is flat, that would give me around 2.5 watts for a few seconds before dropping well below the 2 watt rating, so that should be fine.  Within 5 seconds I have a volt on the capacitor (assuming the regulator is actually able to deliver the power, which I doubt).  In any case, the resistor is fine, the regulator on TMCC track power may be the hot item here, but hopefully the short time for maximum power demands will mitigate that issue.

It would be pretty simple if it got down to the diode, cap, regulator, and resistor.  Can't get much simpler than that!

John, I would buy a whole bunch of these if your beta test doesn't result in an explosion and house fire.

Well, it looks like the cap charge could be pretty simple, so my real mission is to see if I can lay out a switching regulator circuit and have that work as well.  Given the cheap PCB house for prototypes, I'll go right to copper and see if I can get it running.

For a couple pennies more (resistors) you could use a LM317 to generate 5.2V or whatever to compensate for the Schottky.  Charging the cap an extra 200 mV is almost 10% more stored energy.  Considering the $/Farad of the supercap, this could be the best bang-for-the-buck in town! 

Stan, I actually did consider that, I may actually do it.  OTOH, I can have two less resistors and just use a standard silicon diode and an LM7806T, since the caps are 5.5V caps.  Two less parts to put onto the board.

That's even better!  The extra 1/2 Volt adds 20% more stored energy.  And a silicon diode ought to be a few pennies cheaper too. 

The one thing that tilts the scale in favor of the LM317 would be the fact that I may have to use a different cap if I can't get the ones I normally use.  If they were 5V rated, the resistors could be adjusted to still give a full charge.  I'll have to think about that...  I'll probably do a prototype with the LM7806 and then consider the other.  I could always lay down a pad for an additional diode and just short it in the copper so it could be added for a 5V capacitor.

Here's a first cut at the configuration with the dual regulator design and a single SuperCap. 

The large cap on the back would be the supercap, it folds away from the regulator and hangs out the side.  You can see the outline of the supercap beyond the board footprint.  The whole affair is about 1.6" long and less than an inch wide.  Thickness will be around 5/8" to 3/4".  The regulator folds over the PCB to reduce the size.  The headers aren't actually installed, they're just holes in the PCB to solder wires to.  The outputs would be soldered to a 9V battery connector, the input roller and wheels would be soldered to the track power.  Polarity is important as the battery in TMCC locomotives shares it's negative with frame ground.

Soooooooooooo, when can we start placing our orders????

Don't get your shorts on fire just yet.   I will have to get a PCB and build one or two up for testing before I'm convinced it will work properly.

I know it's early in the process but have you considered some type of insulating housing / sheathing so the PCB doesn't short out in contact with the 9V battery clip? I suppose ideally, the assembly would be dimensionally identical to a 9v like a BCR for a snug fit. 

I'm personally planning when I build mine to simply put them into heatshrink.  That's how I install other modules like the Super-Chuffer, solve the problem of shorting to anything.

Trying to make it the exact form factor of a 9V battery seems a bit of work.  It's as short and as narrow, but the thickness will be close.  However, since the battery clip is going to be on a wire, you'll have more flexibility in placing it.

Since "wheel" and "bat-" are common, can't you make this into a 3-wire device?  Again, I'm not familiar with the guts of TMCC engines so not clear on how/where you pick off the roller and wheel.

Stan, there's a good reason not to.  The BAT +/- will be directly soldered to a 9V battery connector, the wheels and roller will be wires going to the track power.  I'm not really saving anything significant by doubling up one wire, and I feel this is clearer as to what is happening.

For one of these that was assembled, I'm figuring that on one end the battery connector will be soldered and come out of the heatshrink envelope.

On the other end, two wires, perhaps orange and black, will come out for track power.

gunrunnerjohn posted:

..Trying to make it the exact form factor of a 9V battery seems a bit of work.  It's as short and as narrow, but the thickness will be close.  However, since the battery clip is going to be on a wire, you'll have more flexibility in placing it.

If the BAT+ and BAT- pads were connected to edge-card leaf style rectangular pads, could a 9V battery connector of style shown below be soldered to eliminate the 2-wire 9V battery connector?  I don't know if practical but sure seems like a big plus if the finished product fit in the space where the 9V Alkaline fits now.  Sorry for the horrible 3-D rendering!

Well, I'm afraid that limits how you install it if the battery lead doesn't happen to reach where you want to put the module.  I could probably change the spacing of the holes if there were a battery clip like that that could be soldered on based on user preferences.  I see the Keystone #968, that looks like what you posted.

I wouldn't want to preclude using wires as I think that's the more flexible use.

Well, I can't let go of the idea of fitting it all into the form-factor of a 9V battery...plus the extra wire(s) to connect to the roller/wheel.

Yes, that's the Keystone connector.  Suppose the circuit board is the size of the 2 shortest dimensions of a 9V battery.  You mount parts on both sides of the board to get the necessary real-estate.  The Keystone is mounted as shown (not flush to the board) with shorter SMD components (resistors, caps, etc.) between the board and the Keystone   Kind of like the photo above except the Keystone would be mounted a bit further from the board.  The taller components such as the supercap which I assume is the tallest component would mount from the top side as shown.  Those taller components can be about the length of a 9V battery.

Stan, the board layout takes more than the size of the end of a battery.   I don't know if I can fit it into that form-factor.  I may get one made (it's cheap), just to see if everything works when it's assembled.  If so, then maybe I could try cramming it into a smaller board.  The switcher want's a pretty specific layout and they seem to strongly suggest a ground plane on the back side.  Since I want this to work the first time, I figured I'd do that.

I'm thinking if I just the 150uf cap to the other side, it might all slip into that form factor without making a tiny board.  Here's what it looks like then.  The battery is 5/8" thick x 1" wide.  The supercap and regulator folder over are 5/16" and so is the 150uf electrolytic height.  The board can be .032", better anyway as it gets 2oz copper.  The components on the other side are not 1/4" high, so it all fits in the 5/8 thickness.  The board width is .8", no problem there.  The total length of the board and folded over cap is shorter than the battery by over 1/8".  That's length doesn't consider the battery connectors sticking out farther on the real battery.  I believe it's able to fit the way it is into a 9V form factor.

Seeing as to how the original plan was 2 separate boards, perhaps another option is to do so with slightly different partitioning.  Obviously this adds to assembly complexity but with board pricing based strictly on real-estate without set-up costs...

I'm thinking putting the MCP1661 circuit on a tiny 2-layer board allowing the backside ground plane.  It would essentially be like that 5V switching regulator packaged into a TO-220 you use on the Super Chuffer.  So a 3-pin interconnect to the main board.  This sub-circuit would then be another "tall" thru-hole component that might free up enough real-estate to use the small-board Keystone method.  That is, I assume you have not closed the doors to the peanut gallery...

Well, the door is not totally closed, but there's only a crack.   I'm wondering why you're so hard over on this particular structure.  As long as I can fit it into the space of a 9V battery, it would seem we've accomplished the goal.

I think I'd like to see this function before I invest much more time in it, it could easily become a career.   I could send you the DipTrace files and let you take a whack at it.

gunrunnerjohn posted:

Well, the door is not totally closed, but there's only a crack.   I'm wondering why you're so hard over on this particular structure.  As long as I can fit it into the space of a 9V battery, it would seem we've accomplished the goal.

I think I'd like to see this function before I invest much more time in it, it could easily become a career.   I could send you the DipTrace files and let you take a whack at it.

LOL.  And I don't even have a TMCC engine!  OK, I'll cease and desist on the form-factor.  Go ahead and close the door...I'll try not to let it hit me on the way out.   And we haven't even gotten to wireless charging to eliminate the two input wires 

Wireless charging...  Now, there's a concept!

I think I'll get a board and see if the darned thing works at all and then consider the options.  The nice part is I only spend $5 on three boards, so it's not cost prohibitive.  I'm going for the .31" boards with the 2oz copper, makes the stack a little thinner and gives me lower resistance for the traces, a win-win.  I followed the layout guidelines pretty close for the switcher, but I confess as to never tried creating a switching power supply before.  With the chip, it sure looks simple, we'll see if I continue to hold that opinion.  I know the Chinese can do it for peanuts, I wish I had their component supply.

The boards are in the mix, I'll probably get them around the time of York, so after York I'll slap one of these together and see how it plays.  I'll also find out if it can fit into the 9V battery form-factor.  If so, I may figure out a way to mount the battery clip on the end to make it just like the battery with a tail on the other end for track power.  The beauty of only having to spend $5 on the boards means I can tweak them for the connector if everything else works.  Yes, I know the one silkscreen legend is under the outline of the folded down supercap, I figured I'd just leave it for this run.  Also, on the 3D run, the large cap seems to merge with the 150uf filter cap.  Since that will be folded over on the real board, that's also not an issue.

On another front, I found a bargain on 1.5F 5.5V supercaps with a nice low internal resistance that works for this project, so I got a whole fist-full of them.  When I can get them for $1, I figure that's time to jump.

Stay tuned to this channel...

Well... I got the boards in.  The good news is I got the boards and all the parts.  The bad news is, the switching circuit doesn't work.   I'm not sure what the issue is.  I actually traced out the whole circuit and replaced the switching IC in case one was bad, but no joy. 

I just populated this part of the circuit and fed 5VDC directly into it.  The output just follows the input voltage minus about .3 volts, and the switcher just sits there mute.  Obviously, the switching circuit isn't running.  That kinda' puts a crimp in this one until I figure that out.

It might be too obvious, but are you allowed to float the EN pin? Data sheet talks about 85% of Vin or higher for the converter to run, below 7.5% for shutdown mode.

I did not read every word of the data sheet, so I might have missed something. Feel free........

Most of their examples don't show anything connected, but maybe I made assumptions that weren't warranted.  It's certainly worth connecting it to Vin as a test, I see one in the datasheet that has that connection.  I'll sure feel stupid if that is it!

gunrunnerjohn posted:

Most of their examples don't show anything connected, but maybe I made assumptions that weren't warranted.  It's certainly worth connecting it to Vin as a test, I see one in the datasheet that has that connection.  I'll sure feel stupid if that is it!

That's not a thing to feel stupid about, just possibly a chance to learn one more thing.

DUH!!!

That was it!  Not only is it working now, but it's working way better than I had imagined!  It'll supply over 100ma at 8 volts for about ten seconds from the 1.5F superCAP!  I have a 62 ohm load on the 8 volt output, about 125ma of current.  I was hoping for four or five seconds!  I have to slap the rest of the components on the board and see how it works in total.  It does take quite a bit of time to charge the cap when it's flat, but it runs the converter until it's down to close to 2 volts before it drops out!  Other than taking some time to charge initially, it certainly be a worthwhile replacement for the battery.

Glad you are able to salvage the board design! Adding the jumper shouldn't be a biggie.

Well, salvaging the board design is not a big issue, it's easy to lay out something else.  In any case, after putting the other components on, I've discovered that I'll really need more bulk capacitance for the input voltage regulator, I had to hang an external cap on to get it all working with a load while charging.

On the good side, for what I was targeting, it works perfectly right now.  If you replace your TMCC 9V battery with this, it will ride out an interruption of power for 8-10 seconds supplying around 125ma, that's more than most RailSounds boards are drawing.  Since while it's charging, the battery is not being called on to deliver any power, the input regulator current draw is not an issue in TMCC use.  I'm kind of torture testing it with a continuous load, so the input regulator is working all the time.  In the real world, the input regulator will be idling 99% of the time, and only be needed when you have a power interruption.

I'm flipping a coin as to whether I should add capacitance or just let it ride.  I'm tempted to add a spot for a couple additional 150uf caps. They can be optional parts if you're doing something that draws continuous power from the battery.  That would be easy and not compromise the rest of the design.

The bottom line is it's doing what was intended!   Thanks for spotting the obvious error, that's what I get for making an assumption.

I'd say we smashed right through the size targets as well, much smaller than the 9V battery in all dimensions.  Truthfully, I'll fit in places that the 9V battery won't.

Yes, that is compact all right. I don't know enough about "Exotic" applications to comment on the need for additional filter caps. "Scope Creep" can be a killer. But, if you can make room for a few optional ones, I'd say go for it!

After assembling this one, I see where hand assembly will benefit from laying out some of the components slightly different, so I'll rework that.  I figure optional caps are free if I don't install them, so no problem there.   I also want to think about the maximum voltage on the SuperCAP, I'm right at the edge now.  They are two 2.7V caps inside the wrap, so 5.4V is the max they should see.  I'm close to that now.

If I wanted to use this to provide power all the time to some circuit, it would benefit from having additional filtering on the input regulator side to allow more current.  OTOH, it does do the TMCC battery function as it stands.

I was pleased at how much capacity the 1.5F SuperCAP had, I didn't expect it to hold up the load that long.

If you'd like some outside testing, let me know (I'll pay for it.).  I have a Lionel ten wheeler that always drops out sound going over my Atlas O72/O54 when running at anything below speed step 60.  It's a pain as I'll have it labored and then all of a sudden it quiet then chuffing along easily.  I do want to add this to all my TMCC/Legacy locomotives that have a battery spot.

Well, I'm going to do some more refinement and checking internally first.   I have a couple of things I want to look at now that the thing is working.  I mentioned the peak voltage on the SuperCAP as one, and I'm also looking at the max charging current to see if I can optimize that.  I'm gratified that it's working, and I think the first one might go into a locomotive internally to see if it functions over a couple of weeks of running.  I'm also considering revising the layout to make it easier to hand assemble, a couple of the parts are somewhat of a PITA to solder on as their orientation doesn't leave much room to work.

Well, I did some bench testing with real TMCC components, and in conventional and command, the battery replacement worked great!  Other than waiting a minute or so from a cold power on to get the cap charged, I could operate and do frequently reversals in conventional mode with no dropped sounds, even at the lowest power that the R2LC and motor driver would keep running.  I kept nudging the power down until the drive dropped out, still had the battery charging away, so it works at a lower voltage than any of the other electronics.

I think my one remaining issue is the scheme I used to limit the voltage to the Super-Cap isn't sufficient.  The LM06 and the silicon diode don't drop enough at low currents to keep the voltage below the max for the caps.  I suspect I'll have to go to the LM317 and tune the output to around 5.5-5.6 volts to insure we don't push the supercaps over the 5V rating.  I was trying to save having to add a couple more components, but obviously that's probably going to be necessary.  If I let it sit and charge for long enough, I get up to about 5.45V on the supercap.  Since the cap is really two 2.7V caps in series in the package, that's too much.  Given that we seem to have plenty of capacity for the intended purpose, I'm thinking I'll try to limit the supercap voltage to around 5V max.  That still gives me the full 8-9 second shutdown, and the cap has more to give before the switcher shuts down.

gunrunnerjohn posted:

Well, I did some bench testing with real TMCC components, and in conventional and command, the battery replacement worked great!  Other than waiting a minute or so from a cold power on to get the cap charged, I could operate and do frequently reversals in conventional mode with no dropped sounds, even at the lowest power that the R2LC and motor driver would keep running.  I kept nudging the power down until the drive dropped out, still had the battery charging away, so it works at a lower voltage than any of the other electronics.

I think my one remaining issue is the scheme I used to limit the voltage to the Super-Cap isn't sufficient.  The LM06 and the silicon diode don't drop enough at low currents to keep the voltage below the max for the caps.  I suspect I'll have to go to the LM317 and tune the output to around 5.5-5.6 volts to insure we don't push the supercaps over the 5V rating.  I was trying to save having to add a couple more components, but obviously that's probably going to be necessary.  If I let it sit and charge for long enough, I get up to about 5.45V on the supercap.  Since the cap is really two 2.7V caps in series in the package, that's too much.  Given that we seem to have plenty of capacity for the intended purpose, I'm thinking I'll try to limit the supercap voltage to around 5V max.  That still gives me the full 8-9 second shutdown, and the cap has more to give before the switcher shuts down.

Just talking, but what would happen if you proportioned the voltage divider to use a little more current? You are down in the microamp range! Would 5 - 10 mA hold the voltage down adequately?

Thinking about what you could do without adding parts.

The switcher when it has no load draws almost nothing idling, around 250uA.  Are you talking about dropping the resistance of Rtop and Rbot low enough to draw that kind of current?  I don't know if that would cause consternation for the switcher.  In looking at the datasheet, it does appear that would probably not change anything else about the circuit, it's an interesting idea.

I think I'll stick a 1K resistor across the battery outputs and see where the charge voltage stops.  Maybe 15ma or so across that diode will keep the voltage down a bit.

Yup. if it is truly a problem only at low current, a bleeder resistance is one way to deal with it, if you can stand the power loss and dissipation. Rtop and Rbot would be a convenient place to implement a bleeder if it is feasible.

Well... It works, but it takes over 20ma to drop it down to the desired range.  That's too much of the capacity to give away to save two resistors, so it looks like I'll go with the LM317.

I would buy 5 of these for sure :-)

Well, I have to get it working and find out what it will cost to get them assembled.  There are enough components on these that I don't fancy doing the whole job myself for any quantity of them.

Here's my rework with the LM317, the extra capacitor, hopefully ready to order another set of boards.  I also relocated some components to allow for easier hand assembly, several components were very hard to solder with the old layout. 

I'll do some more testing before I order new boards to make sure everything is shipshape.  The regulator obviously folds down over the board, and the supercap folds out to the left onto the board as well, but I didn't have a 3D model for one like that.

Id buy a butt load of these boards and build em myself. John, let me know how this works out, Id love to get rid of the loss of sounds on my Legacy locos, drives me nuts when it does drop and wont come back on until I restart the loco

I would be fine with just the boards John.  I have not sniffed any lead in a while.  :-)

Well, the boards or perhaps a kit is likely how this will be done.  If there was really a LOT of interest, I'd look into getting a run of 100 or so done.  It's just that the tooling kills you on the first run, that runs up the cost.

I cobbled up the LM317 circuit and tested it, and that solves the problem with the over-voltage on the supercap, so that's one issue out of the way.

Kits would work just fine with me. I dozen to start with for sure. Again, thanks for your time and expertise in the R&D department with these gizmos that make our hobby a better one.

It's looking like a kit would be in the 16-18 dollar range with all parts and the PCB.  I'll know more when I get the updated boards and run the reworked design through it's paces, but I don't anticipate any issues with the minor changes being made.  I am pleased that it works as well as it does, I wasn't sure when I first powered it up with the missing jumper!

If you run 100 boards, Ill buy like 20 or 25. Ive got at least a dozen 

Ill have to look at how many locos need em but I'll take the raw boards and build em as in small batches as I need them.

Hopefully you will include instructions.  Building for dummies...so to speak.  At least for me. 

"Instructions".............Real men don't need no stink'en instructions............. Just kidding.

milwrd posted:

"Instructions".............Real men don't need no stink'en instructions............. Just kidding.

I do.  Schematics mess me up.  :-)

Basic instructions will be provided.  

Remember guys, these are surface mount parts, they look big in the pictures, but you need to have the skill to solder some fairly small components to make this work!

I'm thinking back to something Stan had said, he thought the battery clip soldered to the board would work well.  As it turns out, the size allows me to consider that.  I'm going to put a couple of PCB fingers on the board spaced right for the Keystone battery clip.  It should be possible to solder that down and after heatshrinking the whole module, just have that project from the end.  The whole thing will actually perform like the 9V battery just with a couple of wires for track power dangling out.

Ouch that kills it for me.  I can't solder Surface Mount.

Don't let surface mount scare you. I tin the pad then flux paste the part and stick it to the pad apply heat with clean iron. You don't want too much solder. Use good lead solder, screw that lead free stuff. It doesn't wet out or flow like lead. When finished wash board to remove flux blow dry with high pressure air. 

gunrunnerjohn posted:

Remember guys, these are surface mount parts, they look big in the pictures, but you need to have the skill to solder some fairly small components to make this work!

Boy ain't that the truth, I need a better magnifier for these parts!!

Doug

If it's a fresh PCB, I just tin a pad with multicore or similar pb/sn solder and solder one side or lead of the part to hold the part in place. Then finish up with the rest of the part. Usually just relying the flux in the solder. If I get too much flux anywhere, I just clean it with a Q tip damp with 70% isopropyl alcohol.

I do something similar to Chuck.  I put a dab of solder on one side, and then heat it and slide the part in place.  If it's not flat on the board, I'll just hold it down with the tweezers and apply a little more heat.  Then I solder the other side.  For multi-leg parts, I solder one leg down with the part correctly aligned, then do the rest.

My weapon of choice is 99% isopropyl alcohol and an old toothbrush.  The 70% usually has oils and/or fragrance, so I'd pick at least the 91%.  The toothbrush allows me to knock off any flux.

There is one caveat with these boards when used to replace a 9V battery. (maybe)

The board you're using them with MUST have a common AC and DC ground.  The RS-4 and RS-5 modular boards do, and I'm presuming the RS-5.5 and RS-6.0 boards that still use the standard modular power supply do as well, given that the RS power supply card does. 

EDIT:

Note that this has changed with the addition of a diode to the circuit.  It seems that the new RailSounds boards have a bridge rectifier on track power and the internal DC ground is the negative leg of the bridge.  With the addition of one diode on our ground input, we duplicate that diode and our DC ground is now the same as the new RailSounds board, and it's still compatible with the older board.  You still have to be sure that the application you're using it for has AC and DC grounds common, or separated by one diode drop.  That seems to cover the intended target audience.