I've been doing some research about braking a DC motor. I am building an electric model train, and I will definitely need some sort of brake or speed limiter (or both ;).
I've read that shorting the motor, or opening both of the high or low sides of an h-bridge driving the motor, will cause the motor to "work against itself" and slow it down. I understand that, but in my situation, the motor will be going downhill with anywhere from 200-600 lbs of weight on a certain section of track, for up to 20 seconds. It seems to me that shorting the motor in such a case will likely result in a burnt motor or h-bridge (or both). I am assuming that the downhill situation will likely generate a lot more current than the motor draws under normal operation.
So, I looked into dynamic braking - I like the idea, and it doesn't seem too expensive to buy a pre-designed dynamic brake resistor pack, but I would do without it if I could.
There's also regenerative braking, but I am assuming that it might be bad to put a high current back into the battery. It's a car battery, so it might be OK, but I haven't looked that up yet, but, would it supply enough braking action anyway?
Am I correct in saying that I will not get any braking action by simply reducing the PWM frequency to the h-bridge, other than friction in the motor and elsewhere? ie, I will definitely need some sort of "active" brake?
I would like to somehow set a maximum speed for the motor, but to have that speed adjustable, so I can have different settings for kids and adults. I would like to tie the brake to this speed, so that it kicks in automatically, rather than having a manual brake.
Would it be possible to connect a second motor that I could use as a "braking" motor? Just make it oppose the direction of movement?
There's also the option of disconnecting the motor from the circuit if there's too much current, and have a mechanical brake.
Thanks in advance.