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Yep, that's about right.  Actually, the tach sensor board is about 1/4 wide, and I could just put two of them on one design to make the size.  Add a cut line in the middle and you just hack it in half.  Six of the PCB's that way would probably cost you around $1.75 total, and they ship free.  For that price, I normally order several orders.

One bonus of doing your own board and soldering the sensor is you can get it the right height.  Many times I have to unsolder the sensor and reposition it.

Last edited by gunrunnerjohn
@stan2004 posted:

Right.  Please share any DIY findings/insights!

For the cheapskates (like me!), I found this on Aliexpress.com.  If you are a new customer you can get 10 pieces of the QRE1113 for a net price of <10 cents each after $2 new user coupon.  Yes, you'll have to cool your heels for a month or so as the proverbial slow-boat-from-China meanders across the Pacific but it's hard to resist the price!  Maybe I'm just lucky, but I've had no problems with aliexpress.com to date; OTOH I have had issues with eBay-Asia for inexpensive components like this.  In other words, one of those Your-Mileage-May-Vary.

qre1113 new user

"We" (the OGR gang) may want to take GRJ up on his offer to design a DIY board for the QRE1113.  I don't know what the MSRP is for an official MTH tach board...but for the DIY'er who knows which end of a soldering iron to hold, I'd think you could make PS2/PS3 tach boards for less than 50 cents each!

Well, time will tell.  This may end up a total flop but there's only one way to find out.  I'll share whatever I happen to learn...

PS2 tach board

...

One bonus of doing your own board and soldering the sensor is you can get it the right height.  Many times I have to unsolder the sensor and reposition it.

I was looking at a PS2 tach board on an open engine and it has the sensor chip flush on the board (photo above right).  Yet, on the OP's photo the sensor chip is clearly off-the-board quite a bit with some kind of "foam" spacer:

ps2 sensor above board

Since the old sensor chip needs to be replaced anyway, here's a one-off idea that may allow the existing board to be used AS-IS with only a modest amount of wire/lead bending...and still account for the change in pin-out between the EE-SY124 and the QRE1113.

The Idea is to notice that the PS2 board connects the A and C pins of the sensor chip together (and this then goes to the Gray wire).  This A=C connection can be used to advantage as it then makes the 4 sensor holes in the correct orientation for the QRE1113.  Yes, the 4mm x 1.75mm is now 1.75mm x 4mm but I think that can be worked-with since the chip is above the board (would be more difficult if chip is flush to board as in my photo).  The 4 terminal leads could be clipped close to the sensor chip leaving 4 wires sticking up; the QRE1113 chip would then be soldered to the 4 stand-up wires.  Not sure this makes any sense!

But if it does work out, I'd think there would be future application for guys who need to repair one (1) PS2 tach board.

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  • PS2 tach board
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Last edited by stan2004

MTH sells a few tach sensor boards.

  • Tach Reader board (no spacer)  AG-0000033  for Mabuchi motor w/ 30mm flywheel
    Tach Reader board (1.5 mm spacer)  AG-0000047  for Mabuchi motor w/ 27mm flywheel
    Tach Reader board (2.2 mm spacer)  AG-0000041  for Pr Steam with 30 mm flywheel
    Tach Reader board (no spacer w/ resistor)  AG-0000048  for LocoSound board in tender 30mm
    Tach Reader board (1.5 mm spacer w/ resistor)  AG-0000054  for LocoSound board in tender 27mm
    Tach Reader board (no spacer) with hole in pcb  AG-0000058  for RK L-3 Mabuchi w/ 30mm flywheel

And also the sensor, though I suspect they are out of them.

  • Optical sensor component  AG-0000078  Omron part EE-SY124

Such a wealth of knowledge!

mth tach board

So I looked at a few, and from what I can tell the MTH tach board have an MSRP of about $7.  It's fascinating that they sold "just" the tiny sensor chip for $5.  I wonder how many of those they sold.

I also saw some LocoSound tach boards which apparently have a resistor added.  Do you have any "Service Bulletin" type info given to Authorized MTH Techs that explains the need for this resistor?  Hard to imagine why they would have a different design for the Locosound sensor vs. PS2/3??

Also, as for an OSHPark version that supports the QRE1113, I'd be amazed if MTH or whatever MTH becomes would have interest in frying such a small fish...they surely have bigger fish to fry.  That is, if I understand it, the only difference between some of the tach boards is the spacer distance.  Hence a raw PCB for anyone to order from OSHPark for $2 (shipping included) would be (IMO) a contribution to the hobby.   

And while:

Nothing is so easy as the job you imagine someone else doing!

Perhaps there's someone else on OGR who sees this DIY PCB design and wants a real "project" to experiment with.  I mean this is what the OGR discussion forum is all about....right?!

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  • mth tach board

Got it working!

So I had those QRE1113s on the way from digikey but I'm not particularly patient.

Amazon had some breakout boards available via prime next day that included a QRE1113 on them.  I ordered a set of 3 for 5 bucks and it showed up this afternoon.  I removed the QRE1113 from the board and based on the schematic for the QRE1113 and the EE-sy124  determined that the boards are just a mirror layout of each other.  So with that I soldered the QRE1113 to a small piece of PCB, laid out my connections in reverse, and bam, we have a running Hudson.

Thanks everyone for your help.  Figuring these little projects out is my favorite part of this hobby.

Stan - as for the resistor on that version of the board... i think thats needed in both circuits.... the newer locos look to have it on the large board in the tender.  probably the resistor working as the other half of the voltage divider circuit opposite the phototransistor...?

Either way, its not on my tach board (the old broken one or the new one i made)

*Edit: Actually looking at that picture of the resistor closer, that resistor is on the ir led cathode, limiting current through the led.  still something that's probably being accomplished on the tender board in ps3 version.

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Last edited by Loochy88
@stan2004 posted:

PS2 tach board

I was looking at a PS2 tach board on an open engine and it has the sensor chip flush on the board (photo above right).  Yet, on the OP's photo the sensor chip is clearly off-the-board quite a bit with some kind of "foam" spacer:

ps2 sensor above board

Since the old sensor chip needs to be replaced anyway, here's a one-off idea that may allow the existing board to be used AS-IS with only a modest amount of wire/lead bending...and still account for the change in pin-out between the EE-SY124 and the QRE1113.

The Idea is to notice that the PS2 board connects the A and C pins of the sensor chip together (and this then goes to the Gray wire).  This A=C connection can be used to advantage as it then makes the 4 sensor holes in the correct orientation for the QRE1113.  Yes, the 4mm x 1.75mm is now 1.75mm x 4mm but I think that can be worked-with since the chip is above the board (would be more difficult if chip is flush to board as in my photo).  The 4 terminal leads could be clipped close to the sensor chip leaving 4 wires sticking up; the QRE1113 chip would then be soldered to the 4 stand-up wires.  Not sure this makes any sense!

But if it does work out, I'd think there would be future application for guys who need to repair one (1) PS2 tach board.

Just saw this!  This would probably have been easier, but somehow I got the wire bending to work.  Either way I'm thrilled its up and running!  Sorry if I seem like I'm not following but I'm sort of learning as I go.  I dont really have any background in this stuff... just a youtube education of how electronics work.

Last edited by Loochy88

So, a universal board would have a spot for a resistor and perhaps a trace that jumpers it out for PS/2 use.  Sounds like a pretty easy thing to do.

So are you volunteering?  If so, I'll make some caliper measurement of a PS2 tach board and "we" can average the measurements to come up with the dimensions.  Like you say, it probably makes sense to design a 2-up board that can be easily cut-sawed-broken in half so you get 6 boards in an OshPark design.  Obviously anyone going thru the effort to deal with OshPark is a card-carrying DIY'er (!) and knows how to solder, etc.  I figure with Aliexpress pricing for the QRE1113, OshPark, and such you could make MTH tach boards for 50 cents or at most a buck.

You measure and show me a schematic for the QRE1113 version, I'll do the board design and post it.  I'll make it a share on OSHPark so anyone can find it.  I figure we'll add the resistor and a trace around it, for LocoSound you add the resistor and cut the trace.  It'll be useful for me, I have lots of the QRE1113 sensors, and I won't have to look for tach boards any more.

Last edited by gunrunnerjohn

Looking at my own illustrations and the board here in my hand.... I just came to the realization that both boards are the same (if you have the non resistor version).  If you remove the phototransistor components you could essentially solder either the QRE1113 or the EE-sy124 to opposite sides of the board, and have the same thing.....  Probably would have been a lot easier than the pcb hack job I came up with. 

Last edited by Loochy88
@Loochy88 posted:

Looking at my own illustrations and the board here in my hand.... I just came to the realization that both boards are the same (if you have the non resistor version).  If you remove the phototransistor components you could essentially solder either the QRE1113 or the EE-sy124 to opposite sides of the board, and have the same thing.....  Probably would have been a lot easier than the pcb hack job I came up with. 

That's interesting, never considered that the sensor change would be a mirror image.

I found a tach board that has a reference corner etched on the board suggesting pad placement might be relative to the corner:

ps2 tach dimensions

That's an interesting observation about the mirrored pinouts.  I suppose the new board could be used for either version with the silk-screen on each side showing version.  OTOH, the EE-SY124 is obsolete so why bother...but then again I'd think there are equivalent parts that use the same pinout.

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  • ps2 tach dimensions

If the board can be reversible, why not?   The only wild card is where to position the optional resistor for LocoSound applications.  The other consideration is the wiring would be backwards, so that would have to be made clear.

The other oddity is some of the tach boards have a hole in the tang, I'm sure there's a reason for some application.  Maybe my universal board would also have the hole, it doesn't appear to affect it's use to replace ones without the hole.

Silkscreened on both sides, the proper sensor and also the corner cut orientation should be added as well.

If the board can be reversible, why not?   The only wild card is where to position the optional resistor for LocoSound applications.  The other consideration is the wiring would be backwards, so that would have to be made clear...

I think the pads for the resistor might need to go on both sides.  Especially for the case of a spacer under the sensor, the resistor must go on the other side of the board.  I don't have a LocoSound tach but it looks like an 0805 might fit (as shown below).  It appears they violated some design rules placing the resistor pad overlapping the sensor pad depicted in red below.

locosound tach hack

I'd think a thin trace between the 2 pads might be simplest.  Cut the trace (thin blue line) if installing the resistor. Of course you'd have to cut the trace on both sides of the board; or run vias thru the two SMT pads so the shorting trace is only on one side.

Since I'm not doing the work I can only make peanut-gallery comments, but it seems like the instructions to support either chip is much more complex than if just supporting the QRE. 

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  • locosound tach hack
Last edited by stan2004

Yep, I might just make a board to support the readily available sensor.  Perhaps we're gilding the lily with all the options.

I figured the resistor would be on the opposite side from the sensor.  FWIW, for my Chuff-Generator, I don't have any spacer, the sensor is just extended on it's leads.  The spacer doesn't do anything that useful unless you're ham-handed.

Last edited by gunrunnerjohn

Speak now or forever hold your peace!   Here's what I have for the QRE1113 replacement. Check it over and see if there are any wiring or dimensional issues that you can see.

I measured my sensor boards, they're all 17mm long, so that's what this one is.  I added the hole that some have as it doesn't seem to affect the usage where they don't have a hole.  Finally, I added the provisions for a 0603 resistor and it's jumpered in the copper.  If you want the resistor, cut the jumper and add the resistor.  The resistor is only for Locosound, they supply 5V to the sensor LED without current limiting, PS/2 supplies the proper current limited drive voltage for the sensor LED.

Top & Bottom Board Layout and Dimensions

Tach Sensor N1Tach Sensor N1a

Top & Bottom 3D Views

Tach Sensor N2Tach Sensor N3

Schematic Diagram

Tach Sensor N4

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  • Tach Sensor N1
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Last edited by gunrunnerjohn

The corner cut is in the silkscreen as well as the square pin-1.  Hopefully, anyone that's going to "roll their own" is aware enough of pin numbers and designations that they can orient the opto sensor correctly.

As for functionality, it won't make any difference.  We'll see if Stan has any additional comments and I'll get a set of these from OSHPark.

Last edited by gunrunnerjohn

I admit I only measured the pad diameter, but why are the holes for the harness wires smaller than the holes for the sensor chip?  On my board(s) it's the other way around as indicated in my earlier diagram (1.5mm pad diameter for wires, 1.3mm pad diameter for chip...with holes sizes presumably commensurate).

Any chance you can fit 0805 pads for the resistor?  I realize you can typically/likely fit an 0805 onto 0603 pads but it's all about option.  I think 0805 are generally easier to find than 0603...and working with 0603 is probably pushing it for any of us fixed income retirees.

You should by all means take credit and initial the board design, I suggest you silkscreen the letter B O G (instead of JWA) below the 3 pads where the harness Blu, Org, Gry wires ENTER the board which, in all tach boards I've seen, are on the opposite side of where the sensor chip is mounted.

BTW. For anyone following along who is not familiar with the process of designing a circuit board for market, you are witnessing a so-called "time-to-market" that is unheard of in this industry!

Last edited by stan2004

I forgot the Stan Memorial dual-board configuration, so here it is.  This is two of the boards on one design to minimize the PCB costs at OSHPark.  Six PCB blanks will be $1.90.

I'm still alive!

I'll bet OshPark complained about the 1-board version as it's less than 1/4 sq. inch.  LOL.

Any chance the OshPark design rules allow you to drill a string of closely spaced holes along the 2-board cut-line so that you can more easily snap the board into 2...perhaps using just diagonal-cutters instead of needing a hobby-saw.

That's pretty cool.  $1.90/6 =  32 cents per board. And that's delivered to your door! 

To summarize what just happened (in record time I might add), if you are a DIY'er with a soldering iron, you can make your own MTH tach boards for less than $1 each.  And that includes shipping!

The QRE1113 sensor chip is WIDELY available.  In addition to the aliexpress (Asia) site I showed earlier where the chip is ~25 cents a piece, it is available from essentially everywhere - eBay, Amazon, and of course DigiKey and other mainstream parts distributors.

qre1113

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