Smart Locomotive R2LC Motherboard Project

I like this idea. Would give much more functionality than a Mini Commander EX. Any idea on the cost for the motherboard when complete?

Net yet, I just wanted to toss the initial design out to see if it resonated or folks told me I was crazy.

I did think of adding another connector for the PWM motor outputs, that would make this useful for powered units and give you some added functionality. 

I may also add a buffer to the serial data as adding serial stuff sometimes overloads the serial line.  I'm thinking an op-amp circuit with a 2x gain to give me a nice 5V rail-to-rail serial data stream with more oomph so that it'll drive multiple inputs.

Id buy one, and I'd wire it correctly too......this time......

great idea, let me know when ready.  I have one dunny waiting for this upgrade.

Marty

I don't know if it would need motor outputs. That would pretty much make it a DC commander. I like it for more outputs for a fully functional dummy unit that would be easier to wire than the Mini Commander EX.

Well, the motor outputs are just the PWM signals from the R2LC, I'm not suggesting I'd add motor drivers!  I have wired a few diesels with a simple motherboard and the Cruise Commander M board.  The reasoning is that the CC-M has ditch light outputs, so I can have fully functional ditch lights.  With the addition of one 4-pin connector, I cover that base.

 on the board idea.  I especially like the 5VDC supply.

Steve

@gunrunnerjohn posted:

Well, the motor outputs are just the PWM signals from the R2LC, I'm not suggesting I'd add motor drivers!  I have wired a few diesels with a simple motherboard and the Cruise Commander M board.  The reasoning is that the CC-M has ditch light outputs, so I can have fully functional ditch lights.  With the addition of one 4-pin connector, I cover that base.

I miss read. I thought you were adding motor drivers as well. 

I have a non powered that I put power trucks on with smoke and lights ready for something like this. I’d buy one

I can use the 5v DC output - what is the max amps if a heat sink is added to the 7805?

I was thinking about the 5V output.  I think I'll do a little rearranging and give room for a little switching module, the one I use on the Super-Chuffer.  It has the same pinout as the LM7805T, just needs slightly more room on the board.  Of course, if you're drawing more current, another consideration is making the filter caps more robust, that's another limiting factor.

I thought about the design overnight, and I realize that I will have to shuffle some things around, but I'll keep the capability the same.  I do want to buffer the serial data as I've had issues in the past overloading the R2LC output data line.

I am interested also. Could use a couple of these.

Richard

It's still a "work in progress", but I've been thinking about this for some time.  I know there are tons of R2LC's wasting away in various parts boxes, and this is a cheap way of reviving them.  I also thought about the current requirements for stuff like smoke, and I'm going to rearrange things a bit to make it easier to route stuff with heavier traces.

Updated with my latest thinking.

If you don’t already have them on this board, would adding a TVS diode to the board for protection against voltage spikes and adding a PTC to the board to protect against derailments where the rollers are shorted (one roller on center rail & other roller on an outside rail) be worthwhile?  The PTC would mean using a three position connector rather than the two position shown along with modifications to the board traces.

I'm not sure how a PTC on board would really accomplish anything, that has to be done earlier in the wiring.  If the roller is on an outside rail, the short is through the frame of the locomotive, not through the board.  Exactly what do you have in mind?

OTOH, the TVS is a good idea, I'll find a spot for that.

Just going off this schematic (and the subsequent PCB) I developed that I posted in one of the LED lighting threads here on the forum.

Oh, and here is a rather interesting post from that same thread regarding the use of a PTC. 

Yep, I do that a lot for passenger cars because the wiring they use in many of them is very small.  If you're using the typical 22ga wire for an engine or dummy, I don't see adding to the PTC for that.  Besides, one of the issues in bringing the current through the PCB is the potential for cooking traces on the PCB.

OTOH, I could see possibly having a PTC in the power lead that protects the PCB.  If the user wants to protect his wiring, he can add his own PTC.

My boards are in process, I ordered three from OSHPark to try it out.

Very smart looking too!

Useful to have one sitting around to test R2/R2LC boards if you don't already have a test setup.

FWIW, I have plenty of Non powered units. What I install are:

• LED HEadlights both ends
• Red Marker Lights to light up at the opposite ends
• Sound unit
• a Train America Studios Smoke unit [specially for ALCo's] with an On-Off mini switch underneath.
• Add full cab interiors with lighted gauges if possible.

I bet folks with four motor AA PS1 locos or dead PS2 5V boards driving a slave board and four motors in MTH four motor AA units would go for a motherboard with plugs for two DCDRs to replace what ever was in their MTH 4 motor locos.   I was adding 15A triacs and a better heat sink  to TAS cruise boards but have used my stash and not found any lately.          j

@Jim Sandman posted:

Useful to have one sitting around to test R2/R2LC boards if you don't already have a test setup.

Got that covered Jim.   I started with a simple motherboard, and I keep adding stuff as new situations come up.  I can test virtually all the TMCC and many modular Legacy boards on this rig now.  My only regret is if I knew it was going to grow like this, I'd have probably planned the layout a bit better.

@JohnActon posted:

I bet folks with four motor AA PS1 locos or dead PS2 5V boards driving a slave board and four motors in MTH four motor AA units would go for a motherboard with plugs for two DCDRs to replace what ever was in their MTH 4 motor locos.   I was adding 15A triacs and a better heat sink  to TAS cruise boards but have used my stash and not found any lately.          j

I'm pretty sure to drive two DCDR, DCDS, or CC-M boards, you'd want to buffer the PWM outputs.  They feed opto-isolators, and the load of two of them is likely to cause issues with the amplitude of the R2LC outputs.

@gunrunnerjohn posted:

I'm pretty sure to drive two DCDR, DCDS, or CC-M boards, you'd want to buffer the PWM outputs.  They feed opto-isolators, and the load of two of them is likely to cause issues with the amplitude of the R2LC outputs.

One transistor and a plug.  Aw ComeOn John !          j

Well, there are two PWM outputs, not one.   Oh, and see my signature line, the last line.

John this is a cool idea and I can envision several I could use. And I really like the idea of building an R2LC R4LC test board with your board as the basis. This may be premature, but would you be offering complete boards, or kits, or possibly gerber files for those that might want to build their own? 

Rod

I probably won't be offering complete boards, I can't imagine enough of these being sold to be able to justify an assembly run.  Once I verify that all the features actually work, I'll post the BOM and Gerber files.

Will you have boards drilled and unpopulated available? I’m just thinking about my self that I can easily do SMD...in fact it’s fun...one or two😎

I may order a quantity of boards just to have some for my assembly and use.  The nice thing is, if you don't want some of the features, you can just leave those parts out.

👍

@gunrunnerjohn posted:

I probably won't be offering complete boards, I can imagine enough of these being sold to be able to justify an assembly run.  Once I verify that all the features actually work, I'll post the BOM and Gerber files.

Hi John, just wondered how the prototyping is coming along? Inquiring minds are anxious to know! 

Rod

I haven't gotten the boards back yet, they're supposed to be on their way for Monday.  It did get to test the serial data buffer/amp circuit as I did a little PCB with just that on it. 

My first attempt at serial data buffering with a 2x amplification was a bust, it didn't work at all!  Then I looked closer.  Turns out the Microchip op-amp I was using had a dizzying array of different pinouts for their part, even with the same footprint!  I happened to pick one pinout for the board layout, but another one for the actual part!  I truthfully still couldn't figure exactly which package ordering option was supposed to be the pinout I was using from the datasheet.  Since I had a TI part with the same footprint and without the confusing multiple pinouts, I used that.  It worked perfectly and did exactly what I expected.  Very annoying that the Microchip part was so obtuse in their datasheet!   That being said, I'll be using the TI part in both the MB and my separate serial port buffer.

John I see what you mean about that microchip datasheet; very confusing. Good that the TI part will work with no issues. I forgot that OP are running about 2 weeks out on board deliveries. Looking forward to your experience with the new boards once you get them!

Rod

Monday I'll have the motherboard, and I have a project on my bench that needs two of them, so that will use up two of the three I ordered.

I just got a prototype sound board with a new interface I'm trying, but I'm still waiting on chips.  I am going to finalize it and have a quantity assembled as I think sound boards are in demand.  This is a 1.9" x 1.2" board that used a canned MP3 sound board and has five optically isolated inputs for five sound clips.  It also will offer an option to plug in a 4-channel RF receiver for remove control of the sounds.  The MP3 module plugs into the two headers on the right, the RF receiver on the bottom left.  I'll have more to say when I get the chips and can do a test. 

I was looking at my motherboard and thought, gosh it would be cool to have the ability to have the "motion" output indicate stopped instead of motion.  Turns out, that was easier than I thought.  I can just swap the XOR gate for a NOR gate and it inverts the sense of that output.  Now it's useful for automatic control of a cab light.  If you want an indication of motion in either direction, you just tie the two "forward" and "reverse" outputs together, they're open drain FET's, so that works great.

Very cool idea John, that sounds quite useful. Do all the other functions work as you envisioned?

Rod

I haven't put it together yet, just got the three boards.  I happen to have a project in-house that I need two motherboards for a couple of dummy locos, so I'm going to assemble just what I need on those and ship it out.  The third one will get the whole chip complement when I get my Digikey order later this week and I'll give it a test.  I think I'll wire up a little test harness with some bulbs so I can exercise all the functions.  If that test works out, I'll do a final "look around" and make any tweaks and then order a larger quantity of boards from one of the volume board makers.  Paying $5/ea from OSHPark ain't gonna' do it, I'd rather pay 60 cents each.

So your two dummy engines will be SN 00001 and SN 00002. I am sure they will work great!

Might you have time to run a short video after completion? And as far as cost goes, besides the completed board itself you need an R2LC, plus whatever additional peripherals are to go in the unit, right?

Rod