My uncle has a 7 1/2" guage train track. He currently has 1 gas and 1 steam engine. We would like to make an electric train that would be very simple and safe to operate, such that an average 10-year-old could manage it.
I am planning to use a 12V car battery/batteries for power, and I have an extra 2000-lb winch motor I can use. I have taken the gearing out of it, so the shaft spins quite fast. I will make a PWM circuit for it, with either a set speed (or a couple of them), and basic on/off and forward/reverse. If it has enough power, I would have a normal throttle for the big kids (adults :) ) to use. The body I am going to use for the train weighs about 150lbs.
I'll use mosfets to link the PWM to the motor, but I'm unsure of a few things:
- How do I measure/calculate how much current my motor will draw, so I can select the proper mosfets?
I have hooked the motor straight to a battery, and if it's not more than the 10A my meter can handle, I'd measure that, but I'm more concerned about surges and variations due to load etc.
- How can I avoid burning the motor out if it stalls (too much weight/ uphill/stuck)
Being a winch motor, I don't know if I have to worry about it. Wouldn't winch motors have that kind of thing built in?
- Is there a problem if the train goes downhill? Will it feed back and melt stuff? If I use a controller with a current feedback/current set- point, will that keep the motor from going too fast?
And, of course, is there anything else I should consider? (Yes, I will be using fuses!)
I have considered buying a prebuilt controller, and I'm quite happy to, so long as I know it will handle the current. It would be fun to make my own though ;)