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DarrellR posted:

  1. You wrote "... I designed a simple 2-channel MOSFET power switch board". Did you ever post this design? I'm interested in PWM of a smoke heater unit as you describe in your post.

No, I haven't posted that yet. I'll see if I can get something put together.

Your use of the LokSound AUX outputs to control the smoke heater and fan was critical to me for selecting the LokSound L as the DCC decoder for a dead-rail conversion of a Sunset 3rd Rail UP "Late" Big Boy originally with TMCC. I needed a DCC controller that will operate the fan-driven smoke unit, so your post was decisive for me. Since you mention the LokSound XL in your article, I read the "Reference Manual for LokProgrammer" downloaded from here, and under section "11.2. Special Settings for LokSound XL" it states "…The function „Smoke Generator“ cannot be connected to the AUX outputs.”  I was warned off using the XL version because of this, and the L version seems well-suited O, but others might want to use the XL version. Do you have any experience/info that the XL's AUX output can be used for fan-driven smoke units as you describe in your post? It might be I am misinterpreting the manual's statement, and you can set me straight.

Smoke setup is one area where the otherwise outstanding ESU documentation is woefully lacking. A lot of what is written appears to assume you are exclusively using one of their smoke units. I had to basically reverse engineer all of the decoder configuration steps I describe above, especially for the steam chuffs. So it's awfully hard to say if a specific smoke-related function can be assigned to a given output on a particular decoder.

That said, I use the XL in a couple engines, and have them configured to drive the smoke outputs as I describe. They are both diesels, however, so they don't need the chuff. The project setup for the XL in the Lokprogrammer does have the same smoke unit settings and function outputs as the L, though, so I imagine it would work.

DarrellR posted:
In regards to my first question regarding the PWM-compatible "relay," I came across some Omron Solid State Relays G3MC-202PL-DC5 (w/o zero crossing) and G3MC-202P-DC5 (w zero crossing), and MOS Trigger Switch Driver Module FET PWM Regulator High Power Electronic Switch Control Board (cheap, $2.94). The latter claims a PWM bandwidth of 0 to 20kHz. I have purchased all of these for testing, but I would, of course, welcome anyone's comments on the suitability of the devices for PWM of the smoke heater. The zero-crossing capability of an "AC Relay" is discussed at this site, where the relay is controlled by the "ESU Version 4" to modulate AC power to the smoke heater. I suppose the zero crossing capability is useful for preventing output surge currents on the heater, but it would not work if the power to the smoke heater was DC, as it might be for dead-rail applications.

Again, thanks to Sinclair and Jonathan.

Hate to be the bearer of bad news, but...

The data sheets for those SSRs suggest switching times of around 1ms. This is far too slow for typical PWM use.

Consider: 20kHz PWM means a full duty cycle takes 50us. If you want, say 10% duty cycle, like for a dim light, that means the on-time of the signal is 5us. For that 5us pulse to be meaningful, the switching times need to be a small fraction of that. So the max switching times that will be feasible in that case will be less than 1us. (For comparison, the switching times of the MOSFET I use on my boards are around 10ns.)

The FET driver module is triggered by a high logic input. This is not readily compatible with the decoder output, which will float when off, and be low when on, as I describe above. If you can find a p-channel version of it, you may be in luck.

These are just the sorts of issues that led me to cook up my own board.  

Last edited by thor73

Thanks for the detailed and helpful reply, THOR32. I very much look forward to seeing your post on the MOSFET power switch since I've been noodling around methods for the PWM-compatible switching myself, but you clearly have thought about this longer and more deeply than I have.

Perhaps you could take a look at the link I provided earlier (MOS Trigger Switch Driver Module FET PWM Regulator High Power Electronic Switch Control Board  to determine if it would work as a PWM-compatible switch for our application, especially since it's pretty cheap ($2.94). My main doubt about this device is that its control inputs are "signal PWM+" and "signal GND". The open circuit operation (for off) of the AUX outputs gives me pause for our application, since floating input conditions may not be accounted for in the device's design.

I think ESU would LIKE for us to use their smoke generators using the specialized outputs/input on the L and XL, so your reverse engineering is very valuable for simpler smoke generators.

I may do a little reverse engineering of my own of an ESU smoke generator with temperature sensor to determine how it's producing the "temperature" output, be it a thermocouple, resistance temperature detector (RTD), etc. It might even be a good idea to put a simple, low-cost temperature sensor on simpler smoke generators anyway. Of course, calibration is the bear and may not be worth the trouble. 

Thanks again for your original post and follow-up answers.

-Darrell

DarrellR posted:

Perhaps you could take a look at the link I provided earlier (MOS Trigger Switch Driver Module FET PWM Regulator High Power Electronic Switch Control Board&nbsp to determine if it would work as a PWM-compatible switch for our application

I wasn't real clear above - the following was referring to that module:

The FET driver module is triggered by a high logic input. This is not readily compatible with the decoder output, which will float when off, and be low when on, as I describe above. If you can find a p-channel version of it, you may be in luck.

Well, I did the reverse engineering I mentioned. Here is a longish post:

It is possible to modify a non-ESU smoke unit so that it connects to the LokSound L or XL decoders just as an ESU smoke unit does by connecting the smoke unit to the specialized ESU smoke unit terminals: HTR+/-, MOT+/-, and TMP+/-. This capability allows you to take direct advantage of all the LokSound capabilities provided for ESU smoke units. The missing component in some smoke units is a Negative Temperature Coefficient (NTC) thermistor.

What started me down this road was a “deadrail” conversion of a Sunset 3rd Rail Big Boy (3-rail, “Late Version”) originally outfitted with TMCC and a nice Lionel smoke unit with dual output (photo below).

IMG_5130.JPG

 

I wanted to retain this beauty and use a LokSound L V4.0 decoder that is controlled by an Airwire CONVRTR-60. THOR73’s posts inspired me to work through using this smoke unit with the LokSound L V4.0 decoder. I thought that if I could figure out how the ESU smoke units created their “temperature” inputs to the LokSound decoder, then I could retrofit the Lionel smoke unit so that it would be “input compatible” with an ESU smoke unit. This retrofit turned out to be simple.

I reverse-engineered an ESU 54678 smoke unit by measuring the resistance between the heater resistor leads (HTR+/-): ~23 ohms; motor leads (MOT+/-): ~16 ohms; and thermistor leads (TMP+/-): ~100K ohm at room temperature. Each of these components is electrically-isolated from the others. When powered by a 14.8V LiPo battery, the LokSound L V4.0 decoder I had on hand produced the following results on the ESU Profi board using the LokProgrammer (with ground measured at the Profi board's ground terminal):

Terminal

Smoke off

Smoke on (Throttle=10)

HTR+ (not connected to heater resistor*)

13.4V

13.2V

HTR-

Open

Switched open/ground @500Hz ~30% duty-cycle PWM

Fan+

0V

Pulsed <= 5V (difficult to determine with low Frequency chuffs)

Fan-

0V

0V

TMP+

5.1V

5.1V

TMP-

1.3V

3.7V

* Battery+ (14.2V) connected to heater resistor + input

 

 

The difference in TMP- between unheated and heated conditions suggests, but does not prove, that the thermistor’s decrease in resistance with increased temperature is manifested by a voltage increase at TMP- as part of a voltage divider where the thermistor is in series with a fixed resistor resident in the decoder, possibly with a low-side voltage offset:

thermistor_circuit.png

So right off the bat, the ESU smoke unit’s heater resistance (23 ohms) is similar to Lionel’s (27 ohms), and both smoke units use 5V fan motors. The Lionel was missing only the thermistor. Lower resistance smoke units (around 8 ohms) might be problematic to convert unless retrofitted with a heater resistor in the 20 ohm neighborhood or use an externally-supplied, lower HTR+ voltage. The heater and fan motor similarity between the ESU and Lionel smoke units seemed to make this particular Lionel smoke unit an excellent surrogate candidate.

Thermistors with 100K ohm resistance at 25 Celsius are commonly-available, usually with a “B” parameter of around 3900 Kelvin. You can Google what this parameter means (simplified Steinhart-Hart Equation: R(T in Kelvin)=R@TRef*(exp(B/T-B/TRef)) ). While I was not able to verify that the ESU smoke unit used precisely this type of thermistor, testing described later supports this selection.

The photo below is the Lionel 27 ohm smoke unit PCB, part #610-PCB1-045, Rev C (Lionel replacement part #691PCB1045), that was retrofitted with an “axial,” glass-coated 100K NTC thermistor with a B of 3892 Kelvin. (Well, it’s actually a Lionel replacement PCB since I cut some traces retrofitting on the original PCB that I regret doing. Interestingly, the original PCB did not have the mangled lettering of the replacement PCB that some like GUNRUNNERJOHN have noted.)

The 3-pin power plug on the PCB can be used to power the heater resistor since the outputs from the rectifier/5V converter on the PCB do not connect to anything after removing the fan motor plug. The ground on the PCB MUST be isolated from the heater unit metal case since the PCB’s “ground” wire will be connected to the LokSound L’s HTR- terminal that regulates the heating resistor’s current path to ground! Electrical measurements revealed good electrical isolation of the metal case from the heating element.

IMG_5160.JPG

Two holes were drilled in the smoke unit’s PCB board, and the thermistor was inserted and soldered to two wire leads that connect to the LokSound L’s TMP+/- terminals. High melting-point solder was used in the off chance that conventional solder might melt at the high operating temperatures of the heater resistor and thermistor (max around 250 Celsius according to documentation for the ESU smoke unit). 

The two heater wires from the three-pin PCB plug connect to the LokSound L’s HTR+/- terminals. (Pins 1 and 3 are shorted together on the PCB and connect to one side of the heater resistor. Pin 2 is ground and connects to the other side of the heater resistor.)

The motor wires directly connect to the MOT+/- terminals. Out of sheer luck, when the red motor lead from the smoke unit is connected to MOT+, and it’s black lead to MOT-, the fan motor spins in the “correct” direction.

As GUNRUNNERJOHN has suggested, I also replaced the original 27 ohm ceramic resistor with a Lionel 27 ohm replacement #6008141055. 

Once the smoke unit’s six outputs were connected to the LokSound L’s ESU smoke unit terminals, there were some modifications needed in the ESU sound files and decoder set-up, since they did not originally activate the ESU smoke unit. First, follow THOR73’s directions regarding the connection between sound and smoke chuffing under the “Smoke unit” menu. Note especially that the smoke unit’s automatic power-off time should be reset since the default is 0 seconds. I don’t know if 0 means never turn off, but a non-zero setting seemed like a good idea to me.

unknown.png

What differs from THOR73’s discussion is the sound-file set-up for an ESU smoke unit. Editing the sound files reveals that most “nodes” have an option to set the “ESU Smoke Unit” parameters. Frequently these settings are turned off, but there are some useful “presets” you can select and experiment with.  An especially interesting preset is the “preheating” preset that is available in the stopped state.

Mute State:

unknown_1.png

Here are the other states I modified, but I am by no means expert or knowledgeable about these settings. Usually, I chose a “Preset” and then selected the “Steam Chuff” checkbox, which preserves the parameters of the preset (unless you change them), but turns off the Preset name.

Stop State:

unknown_2.png

DCX State:

unknown_3.png

Coast State:

unknown_4.png

After editing these sound nodes, the next step is to set an “F#” to turn the smoke unit on/off on the “Function mappings” menu. The “logical” outputs column provides an “ESU Smoke Unit” selection, so I selected F23 as the ESU Smoke Unit on/off toggle.

unknown_5.png

A TESTING WARNING: The ESU 53900 Profi Decoder Tester does not appear able to provide adequate power to either an actual ESU Smoke Unit or surrogates described here! In actual operation, the LokSound L is perfectly capable of providing sufficient power, but the Profi board is, in my experience (or inexperience), NOT able to do so. I initially thought the culprit was the puny AC to DC converter provided to power the Proof board, but power connection to a very hefty 14.8V LiPo battery did not solve the problem. The workaround is to use either THOR73’s high-side MOSFET switch mentioned in this thread or use the low-side MOSFET switch described in the same thread. Either way, you will need to take power (about +14V DC) from the source providing power to the Profi board and use the Profi board’s HTR- output to control the MOSFET switch that will, in turn, control the smoke unit’s heater. If using THOR73’s high-side switch, then you connect the smoke heater as he describes. If using the low-side switch I presented, the smoke unit’s HTR- connects to the switch control input, and the switch’s ground connects to power ground. 

 

Reiterating, THIS SPECIALIZED MOSFET SWITCH IS ONLY NEEDED FOR TESTING WITH THE Profi BOARD! In actual operation, the LokSound L is designed to adequately power an ESU smoke unit by direct connection to the decoder’s ESU smoke unit terminals, as is the modified smoke unit described here. 

Here's the "proof in the pudding" video:

 

Please forgive the disassembled state. I haven’t finished the deadrail conversion, but this video does demonstrate battery power with the LokSound L V4.0 controlled by an Airwire CONVRTR-60 wireless receiver.

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_SurrogateESU_SmokeUnit
Last edited by DarrellR

Hey Darrell, great investigation and write up! More fodder for fun mods... 

Looking at your numbers (13.2V, 23-27 ohms, and 30% duty cycle), I see the ESU and Lionel smoke unit heaters are running around 2W to 2.25W, which is pretty consistent with where the MTH ones end up - usually around 2.25 to 2.5 W. So the decoder seems ok with that power output at a current around 0.6A. Tempting to try it on an MTH unit (at a lower duty cycle, to get the same average power), but I'm guessing it might choke on the ~8 ohm element, as that would be in the neighborhood of 1.5A while powered on.

Nice hack with the thermistor on the heater board! It makes a lot of sense that the ESU smoke unit has that built in. Were you able to tell while experimenting if the temp sensor is actually in the control loop for the heater? For instance, does the heater run near 100% duty cycle while first heating up, and then drop to the 30% steady state once hot? That would suggest the thermistor is actually used to control the heating, which makes a lot of sense. If not that, maybe it's just there for overtemp protection or something. The wording in the manual is a little vague.

I'm a little surprised you had to dig into the sound file like you did. That option is not available on the Loksound Selects, and they clearly are supposed to support the smoke unit as well. Here's the text from the Loksound Select supplement:

The decoder reads the data from the temperature sensor and controls the heater based on the desired settings, so the smoke unit could never burn out. Please note that the settings for the smoke unit need to be included in the sound project file. While you could easily change these settings on LokSound L V4.0 decoders, the settings in LokSound Select L decoders could not be altered by yourself. ESU will do the conversion of the LokSound Select files to be compatible with the Smoke units.

I wonder if that particular sound file just wasn't updated recently or something?

Thanks, THOR73 for reading my post. 

On to your questions/comments:

Tempting to try it on an MTH unit (at a lower duty cycle, to get the same average power), but I'm guessing it might choke on the ~8 ohm element, as that would be in the neighborhood of 1.5A while powered on.

I think you can do this by using the 5V powering scheme you described in your post and use the HTR- as the MOSFET switch control: "high-side" as you posted or "low-side" as I have used. That was what happened when I had to power the heater resistor when testing with the Profi board. 

Were you able to tell while experimenting if the temp sensor is actually in the control loop for the heater? For instance, does the heater run near 100% duty cycle while first heating up, and then drop to the 30% steady state once hot?

The duty cycle did indeed change with time. For instance, on first power-up, the duty cycle appeared to be 50% and then changed to the roughly 30% I mentioned. I never saw the duty cycle exceed 50%, but I noticed some slight jitter on the steady-state duty cycle, suggesting feedback. It's difficult to know if the cheap digital scope I used was doing a credible job of estimating the duty cycle. I have no real way of knowing if that was feedback, but since the sound file setting for the ESU smoke unit list temperatures, I surmise the decoder must be measuring the TMP- voltage and converting the voltage to temperature.

If you set Rfixed and Voffset well in the voltage divider, then the T vs. V curve is approximately linear over a limited range, say from 100C to 250C. I won't bore anyone with the quantitative details (which I have) unless there is interest.

I'm a little surprised you had to dig into the sound file like you did. That option is not available on the Loksound Selects, and they clearly are supposed to support the smoke unit as well.

Funny you should mention that. I was just on the phone with Tony's Trains, where I purchase the LokSound L's, in regards to a Cab Forward sound file. It's only available as a Select file, but they were concerned that it might not have the ESU smoke activated. I indicated that they should go ahead and send me a LokSound L Select loaded with the Select version of the Cab Forward, and I will determine if smoke is activated. If not, then I will contact ESU USA to get that corrected.

Thanks, THOR73, again for taking the time to read my original post.

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DarrellR posted:
Funny you should mention that. I was just on the phone with Tony's Trains, where I purchase the LokSound L's, in regards to a Cab Forward sound file. It's only available as a Select file, but they were concerned that it might not have the ESU smoke activated. I indicated that they should go ahead and send me a LokSound L Select loaded with the Select version of the Cab Forward, and I will determine if smoke is activated. If not, then I will contact ESU USA to get that corrected.

Perhaps you could have ESU make a non-select version of the Cab Forward.  If you want someone else to join you in making the request, let me know.  My MTH PS-1 equipped RailKing Cab Forward is in my queue for DCC conversion and I was concerned that they only had the sounds for Select decoders.

Perhaps you could have ESU make a non-select version of the Cab Forward.  If you want someone else to join you in making the request, let me know.  My MTH PS-1 equipped RailKing Cab Forward is in my queue for DCC conversion and I was concerned that they only had the sounds for Select decoders.

If you look at the following link at the ESU website, you will find project 74409, which links to an "HO" version of the Cab Forward sound file 74409-LSV4.0-Steam-Cab_Forward-R1.esux. I have not examined this file yet, but I doubt is has ESU smoke activated, but since it's a V4.0 sound file, it can be edited to add ESU smoke. Editing this file is possible because the link specifically states:

ANY LokSound V4.0 Sound file can be written to ANY LokSound V4.0 decoder. This means you can write a Micro(N Scale) 748xx file to an 8 pin or 21MTC V4.0, and alternately a 744xx(HO Scale) file to a Micro or V4.0 Direct decoder. The ESU LokProgrammer software will recognize the difference and ask you to proceed. By Accepting you are giving the permission needed for the LokProgrammer to automatically make the conversion needed.

Maybe after I/you/we edit it, it can be submitted it back to ESU.

I will ask ESU to make an "L/LX" version of the V4.0 sound file with ESU smoke added. I have five KTM/Sunset cab forwards to convert...

My MTH PS-1 equipped RailKing Cab Forward is in my queue for DCC conversion and I was concerned that they only had the sounds for Select decoders.

Maybe you already know that if you convert your PS-1 to PS-3, you can set the DCS/DCC pin on the PS-3 board to "DCC," and you get DCC control. I used this recently on a Sunset 3rd Rail Allegheny that I converted to PS-3 so that I could then connect the PS-3 board to an Airwire CONVRTR-60 that provides DCC to the PS-3 via an Airwire T5000 wireless throttle. Here is a specific link to Ray's Electric Trainworks where I got my PS-3 board since the Allegheny as originally received was PS-2, which is harness-compatible with PS-3 (saving me some work because all I had to do was remove the PS-2 board and replace it with the PS-3 board with NO wiring harness mods). Ray is a great guy.

The MTH instructions for PS-1 to PS-2/3 conversion are very highly detailed and seem to be well-done. The PS-3 has pretty good sound, but I did not check the smoke (yet)... 

Perhaps you could have ESU make a non-select version of the Cab Forward.  If you want someone else to join you in making the request, let me know.  My MTH PS-1 equipped RailKing Cab Forward is in my queue for DCC conversion and I was concerned that they only had the sounds for Select decoders.

Just to follow up, I made a request at the ESU website: 

Topic:          L/XL Conversion for sound project 74409
Your question:  
Would it be possible for you to make conversions to project 74409 (V4.0 version for Cab Forward) so that it supports smoke and any other features of the LokSound L/XL V4.0 decoder? There are several of us who would like to use it in the O gauge community.

I will post if I get a response.

Wow, you found one, I never did come across that sound file when I searched.  It's downloaded now for future reference.  Please do let me know if they reply to you.

As for converting it to PS-3, A LokSound L costs less, and allows for customizing.  Plus it'll let me keep all my DCC conversions under one brand.  I do plan on buying new MTH PS3 locomotives going forward once I have DCC fully setup.  If Lionel would just add DCC to their O Legacy locomotives like they do for S gauge, then I'd be all set.

Wow, you found one, I never did come across that sound file when I searched.  It's downloaded now for future reference.  Please do let me know if they reply to you.

I will definitely let you know if ESU responds. They are somewhat slow responding. The current file has no ESU smoke activated, but you can activate it.

@thor73 posted:

Now for the actual installations! I'll start with a general purpose installation that should work to provide fully functional smoke and couplers for just about any locomotive. I'll eventually show a couple of my specific installations as well, to show various other ways to do things, but that may be later, as I have a vacation coming up...

Basic Installation for Smoke and Couplers

For this example, I'll assume a Loksound L decoder is already installed and operating in the locomotive. It's a good idea to get the basic motor, sound, and lighting set up before proceeding to the smoke and couplers. For the purposes of this example, I'll use decoder function outputs Aux3 through Aux7. Adjust accordingly for your specific installation, of course.

Parts List

Here is a suggested parts list for the installation. For the discrete components, any equivalent part will work fine, these are just suggestions.



Rectifier and Regulator

The regulator can be assembled with both the bridge rectifier and capacitor soldered to the inputs of the regulator. The + and - leads of the rectifier get soldered to the positive and negative regulator inputs, leaving the A/C inputs of the rectifier for the track pickups. The capacitor can also be soldered across the regulator inputs. Note the polarity of the capacitor as well. The inputs to the rectifier then just get wired to the track pickups, in parallel with the decoder.

install1

Here is a way to combine the rectifier, cap, and regulator into a pretty tidy assembly:

IMG_7397 [2)IMG_7398 [2)

Be sure shrink wrap or otherwise insulate the A/C leads of the rectifier after you wire them to the track pickups.

At this point, power up the engine on the dcc booster. Hook a voltmeter across the regulator outputs and adjust the potentiometer on the regulator until you get the desired voltage (5V, typically). Now you have a DC power source ready to drive heavy loads.

Smoke Unit

For the smoke unit heater, wire power and ground from the regulator output to the power and ground inputs of the power switch. Wire the outputs of the power switch to the heater element on the smoke unit. Polarity does not matter. Wire the heater control from Aux5 to the 'SW' pin on the power switch. Configure this decoder output as described in (3) in the previous post.

install2

The decoder can drive the smoke unit fan directly, but it still makes sense to power it from the regulator. Test the fan beforehand if you're not sure which polarity results in the correct direction. Wire a power lead from the positive output of the regulator to the fan positive. Wire the fan ground to Aux3 on the decoder. Configure this decoder output as described in (4) or (5a).

Optionally wire Aux3 and Aux4 together on the decoder in the case of a steam engine installation. Configure the Aux4 decoder output as described in (5b).

Electrocouplers

For the electrocouplers, start by installing the diodes on the power switches. These act as freewheel diodes and protect the switch when used with inductive loads. Note the polarity of the diodes - the band goes toward the positive output of the power switch.

IMG_7399 [2)

Now wire power and ground from the regulator output to the power and ground inputs on each of two power switches. Wire the controls from Aux6 and Aux7 to the 'SW' pins on the power switches. Configure the decoder outputs as described in (2) in the previous post.

install3

At this point, it's a good idea to test the output of the power switches. If they are wired wrong, or if the decoder is configured wrong, the couplers could overheat and be damaged. Put a voltmeter, test lamp, or some other indicator across the power switch outputs, and make sure that they only activate for about half a second when you press the button on the remote.

After confirming things are operating as intended, wire the outputs of the power switches to the couplers. Polarity does not matter.

Done!

Here is the complete wiring diagram:

install4

Now go run it, see if the smoke works the way you like, and tweak accordingly.

This is awesome!!



Would you be willing to post the gerber files for the board by any chance? I'm looking to try this with an MTH diesel.



Thanks!

Dan

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