# RC Controlled locomotive for about $60



## Brandon (Jul 6, 2011)

I had the Utah Garden Railroad Society over today and several people were interested in my RC equipped locomotive and rather than just posting it to our group, I thought others might be interested.

I will be automating my railroad with rfid chips and readers on locomotives (and AI) but while I'm doing that I wanted to run trains, after all it took 4 years to get my layout in ( http://forums.mylargescale.com/29-beginner-s-forum/20612-named-railway-build-thread.html ) I had decided to use Pololu motor controllers and C.H.I.P.s and one day I noticed Hobbyking had 2.4ghz radios for $25 and thought, why not use that since the pololu does PWM (RC control) in addition to USB control.

So how to do RC locomotives for about $60. First thing, realize some of these parts come from China or Hong Kong so shipping can be up to a month for parts to arrive, but most things are free shipping.

The Most important thing I've found to make any battery locomotive work well is the motor controller. Some people do RC car or boat ESC's but those don't work really well at high volts and amps (brushed motors aren't designed for that really). But a company called Pololu makes a 18v7 motor controller for robotics (everything from toys to commercial) which can handle up to 30v (I wouldn't go over a 6s lipo though due to peak voltage) and 7A continuous (more than enough for our locomotives and it also does 30amp peak for short periods which is perfect for the stall current if your motors stop turning for any reason which is critical for our trains that run 15amp to 25amp stalled) I've found these controllers for $22.50 at Bay Area Robitics' but they are currently out of stock but other places sometimes carry these for deals at times. In addition, you can plug a usb cable into the board and your composer and set acceleration rates, deacceleration rates, motor braking, direction delay, min/max safe voltages, and a huge number of parameters if you want to really want to go nuts with things. This board also has a built in 500mah BEC which can be used to power your RC receiver (No need for a separate BEC)

https://www.pololu.com/product/1372

Next is the transmitter and receiver. 2.4ghz can be used for air or surface so here's what I recommend for trains (but never would for planes or anything critical)

http://www.hobbyking.com/hobbyking/store/__9042__Hobby_King_2_4Ghz_6Ch_Tx_Rx_V2_Mode_2_.html

They also make a 4 channel version for about $2 less but I'd recommend staying with the 6 channel in case you want to add more lights or sound triggers.

To connect the 2.4ghz receiver to the pololu simple motor controller you'll need one of these, but they're sold in packs of 10 for $2:

http://www.ebay.com/itm/262174752856?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Next is the battery. You can start cheap with something like this that will give you a couple to maybe 3-4 hours of runtime depending on your locomotive:

http://www.hobbyking.com/hobbyking/...y_1000mAh_4S_20C_Lipo_Pack_AR_Warehouse_.html

Or for $5 more you can go with this one that's three times the run time which I did but next time I'll be going for a 2000mah or so because I don't plan on running my trains for 10+ hours a day, and I'd prefer to recharge in an hour and have a smaller battery to fit in my locomotives (I don't run trailing cars). I also do use a 5S rather than a 4S on SD-45's, but FA1's and U25's I think 4S is enough, but people who like "really fast trains" may want to do a 5s on FA1's and u25's and 6s on SD-45's and Dash-9's.

http://www.hobbyking.com/hobbyking/...Flightmax_3000mAh_4S1P_20C_AR_Warehouse_.html

To connect a lipo battery to the motor controller I prefer XT60 on all my planes and batteries so you'll need one of these:

http://www.aliexpress.com/item/Whol..._3&btsid=f178d039-7ce4-4d77-b4d9-2b213f67a2a0 

You just need the male plug, but the female side could be used for something else in the future (and you can often find packs of 5 or 10 for not much more)

The hardest part to "build" is this:

http://www.ebay.com/itm/141976510503?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

You need to break one of these down to the size of the aristocraft "dcc header", it's the location on the locomotive where the Revolution connects to). There's a jumper on it already so just remove that and keep it around for if you want to return to original design. Solder a wire to pin 3 and another wire to pin 10. Here's Greg's page for wiring information on this header: http://www.elmassian.com/index.php?option=com_content&view=article&id=562&Itemid=682

You might also find out that the 12 pin connector for the header that you soldered up is a bit fragile, I've broken a couple. I personally put a bunch of epoxy along the header to make it hard to break this part, but hot-glue or something else might work. 

That's it! You will need to do some reading about where to connect wires to the motor controller but it's pretty straight forward. I'll also recommend insulating the pololu controller in such a way that it won't touch the aristocrafts circuit board and potentially short anything.

PS, I disconnect ALL wires from their boards on the aristocraft engines, this reduces the chance of shorting anything, including sending power to the track, smoke system, etc.


Now for the "advanced" locomotive with lights, smoke control, couplers, and sound.

With the extra channels on the receiver, I buy a bunch of these to act as relays:

http://www.aliexpress.com/item/2A-S..._3&btsid=05123281-dc93-489d-859d-e9e0532badc1

They do have "dual channels" but so far I've only been able to get one version of a dual channel to turn both on and off together (so this didn't work for forward and reverse lamps with just one, I had to use a second) and the other would turn on both channels or the second mode would alternate the two channels on and off which would be perfect for ditch lights, but not forward/reverse lamps again. So just buy 2 for forward/reverse lamps. Here's the link to the one that works as ditch lights: http://www.aliexpress.com/item/DAL-..._3&btsid=1e5dfe02-3f3a-41b8-8025-c39b70f4d3a7


One note is these will take up to about 25v and still function but their output is what you provide it. Some people will want this same-voltage passthrough, but I find that extra voltage just to be a battery drainer (I don't need a "full speed" lamp all the time. So I bought this:

http://www.ebay.com/itm/262226954716?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

This takes voltage up to about 24v and changes it down to 5v. I find 5v gives plenty of light to LED's without wasting power. I plug this between the battery and the LED light controller, obviously. You also wouldn't use one of these for smoke, you'd want your smoke unit using the full voltage from the battery to get maximum white stuff out.

For smoke you want something like this: 

http://www.aliexpress.com/item/DAL-..._3&btsid=c9b9f47e-5dcb-472f-a933-73a8784d58dc

This is a 20amp relay, much more than you'll need for smoke. If you exceed it's limit, chances are your locomotive is already on fire and melting. 

For connecting relays to lamps or other things, these are the correct connector type. I actually used these between my LIPO battery, voltage regulator, and all non-motor power connections since they're a standard connector for RC.

http://www.ebay.com/itm/152064801298?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I also didn't want to cut wires or do anything special to the locomotives so I just unplugged the connectors for the lamps from the boards on the locomotive and then pushed these into their connectors (they fit perfectly and a dab of hot-glue guarantees they won't come out)

http://www.aliexpress.com/item/free..._3&btsid=7a72f651-51d2-4837-a7e7-4cc9b5987c70

I then soldered those bread board jumper wires to the connectors in the "Servo Extension LiPo" paragraph (which I believe are a jst or similar connector and not really a servo or lipo extension wire). You will want to CAREFULLY check your wiring on your locomotive, I found my wiring was different on various locomotives and if you're wiring direct, you need to be sure you're not passing 5v or higher to the wrong leads.

Next is if you want to do a trailing car, or just don't want to pay Aristocrafts high price for MU wires, but some soldering of course is required to join the same gender:

http://www.aliexpress.com/item/10pa...2454498328.html?spm=2114.13010608.0.80.C1RGC1

For those using xt-60's lipo connectors, you might find this. Simply cut the wire in half and you have jst cable that hooks into your led controller lighting or your 6v-24v to 5v voltage regulator like I used to reduce led voltage to 5v. 

http://www.aliexpress.com/item/XT60..._3&btsid=f178d039-7ce4-4d77-b4d9-2b213f67a2a0


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## CliffyJ (Apr 29, 2009)

Thanks for all the great info Brandon. I've used Pololu programmable controllers before,but not for RC. Thanks for all the links.

Cliff


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## Greg Elmassian (Jan 3, 2008)

Bluerail is $75 for a 2 amp, 8 amp stall decoder, assembled and ready to go.


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## Brandon (Jul 6, 2011)

Bluerail specs say 1.25amp continuous, 2 amp for 15 second and 4 amp for 2 seconds (and most people will stall their locomotives wheels for faster longer than 10 seconds sometimes unless they never blink). Bluerail also require you to also buy a compatible transmitter, battery, and can't do lights or smoke directly (20mah limit) but would require you to buy relays as well. So a full bluerail setup is likely to cost $50 or more over the cheap option I posted, but for those who have low amp locomotives and don't want to build their own bluerail is a good solution. I've tested stall current on my u25's and SD-45's and stall was around 8 amp and 15 amps, so that would exceed what bluerail could safely handle. The pololu is 8amp constant (at 30 volt) and 30 amp for 30 seconds (unless you add a heatsink then it can do higher but you could have two sd-45's run off one pololu and never have to worry about stalling frying the board, and if you do it's $25 to replace rather than $75). I personally think the bluerail is not a powerful enough solution, but for lady bugs or single motor locomotives it does look like a good option.


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