Author Topic: Railpro for 7 1/2 gauge  (Read 123 times)

Cbrocco

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Railpro for 7 1/2 gauge
« on: January 23, 2021, 01:56:35 PM »
So I'm thinking out the box on this one. I use Railpro for G scale now and have been adventuring into 7 1/2 gauge making a custom engine. I would like to use the LM-3s-g unit to be the brains of the train because all the sounds and controls would be the same but obviously the amps would be way too high for the unit in this case.

I was thinking of using some sort of Electric Speed Controller (ESC) to separate the LM-3S-G from the higher 24v 20 amp circuit just like people do for RC cars and trucks.

Problem I'm having is finding an ESC that doesn't use PWM signals meaning I can take the motor outputs from LM-3S-G and use it to control the higher voltage circuit.

Does anyone know of device that does this or have any other insist to a setup like this?

thanks,
Chris


Alan

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Re: Railpro for 7 1/2 gauge
« Reply #1 on: January 23, 2021, 02:29:43 PM »
Use the LM-3S-G motor output to drive a heavy power transistor(s). Much like the way high wattage stereo amplifiers drive speakers. There are available many transistors capable of carrying 100 amps or more. Tim Ring could dial you in on the specifics.

Alan

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When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

Joel W

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Re: Railpro for 7 1/2 gauge
« Reply #2 on: January 23, 2021, 03:22:40 PM »
This controller (for heavy robots, etc.) is in the range you want voltage and current wise, and allows for analogue control as well as other control methods.  It's output appears to be PWM so it may not work for you:

https://www.robotshop.com/ca/en/sabertooth-dual-2x32a-6v-24v-regenerative-motor-driver.html?gclid=CjwKCAiAr6-ABhAfEiwADO4sffRVFYHCTpkeaa4FepGFeWbzvmVUJkHAWaEEa837vxnXDZLrdW_UexoCXIoQAvD_BwE
JoelW
Rushbury Valley Railroad
Burlington, Ontario

Cbrocco

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Re: Railpro for 7 1/2 gauge
« Reply #3 on: January 24, 2021, 02:19:01 PM »
Thanks Alan. Do you know the best way to contract Tim Ring?

I also took a try at making a 2N3055 and equivalent PNP transistor H bridge circuit like you mentioned. I attached it below. I believe this would work and provide speed control as well as motor direction too. I just don't know about grounding. Does the common of the LM-3S-G have to share the same ground as the 24v circuit?

Alan

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Re: Railpro for 7 1/2 gauge
« Reply #4 on: January 24, 2021, 03:03:34 PM »
Thanks Alan. Do you know the best way to contract Tim Ring?

I also took a try at making a 2N3055 and equivalent PNP transistor H bridge circuit like you mentioned. I attached it below. I believe this would work and provide speed control as well as motor direction too. I just don't know about grounding. Does the common of the LM-3S-G have to share the same ground as the 24v circuit?


Call Tim on the phone. (219) 322-0279

Yes, a common ground is required else there will be no base-emitter differential (VBE).
Alan

LK&O Railroad website

When I was a kid... no wait, I still do that. HO, 28x32, double deck, 1969, RailPro

G8B4Life

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Re: Railpro for 7 1/2 gauge
« Reply #5 on: January 25, 2021, 06:33:52 AM »
Out of curiosity what sort of 7 1/2" gauge locomotive are you making? a scale model where the models scale is proportionate to the track gauge or ride-in miniature railway type stuff (usually 1/6 scale with the track gauge ending up being narrow)?  If your intending to haul passengers such as at a miniature railway that is some serious juice you'll need to put through your electrical system. Not sure how you'd end up powering the loco; it's been eons since I was a member of a miniature railway but everything we had (besides live steam) was petrol electric, diesel hydraulic or experimental third rail. Battery power was limited to small single occupant trolleys.

- Tim

Cbrocco

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Re: Railpro for 7 1/2 gauge
« Reply #6 on: January 25, 2021, 09:46:33 AM »
Hi Tim,
I'm making a small single locomotive that my son can ride on. I know the circuit components I picked out are only rated for 15 amps, but I figured if I can get the circuit correct then I could upgrade the components to handle more amps and heat dissipation (heat sinks), like changing the 2N3055 to a 2N3771 which can handle 30 amps etc. The  engine or trolley is going to be 3d printed polymer making it much lighter then conventional engines and rolling stock in this gauge. I have already tested a Bettendorf bogie in this gauge and had success. It is able to handle 125lb load so far. So my next step would be a powered bogie probably a single EMD style B-B to house an electric scooter motor from ebay.
As you guessed, true scale in 7.5 gauge isn't a priority to me as much as functionality. As I add more components to this trolley, I plan to measure the amps through the circuit and heat build up from the high power transistors and change components accordingly as loads increase. I'm just not 100% on circuit layout. I'm a mechanical engineer so electrical circuits aren't my forte. I appreciate all the help I could get on this circuit. What I have so far is attached below.

thanks,
Chris