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Gruber
HobbyMasters
M.L. Toys
KidsWheels
HobbyMasters M.L. Toys
Gruber
KidsWheels
Need new batteries? Going from 12V to 18V or 6V to 12V? Wiring Questions?
#148630
I have a 6V PW Corvette that I'm converting to 12V. I'd like to also add soft start/stop to it (using an Arduino), but all the motor drivers that can handle the 85A (?) stall current are more expensive than the car. Even if the stall current for the factory motors is half that, driver boards that handle that still approach or surpass $100 US.

So what I was thinking is this: I use the stock pedal/shifter/etc to tell the Arduino the state of things (pedal depressed, high gear, etc). And from a start I just use some code to soft start until I get to 95% or whatever of full throttle, and then use an automotive relay to switch the power away from the motor driver and route it directly to the motors for full speed. Since the throttle won't be proportional (initially, anyway), most of the driving time will be spend at full throttle anyway. So no point heating up MOSFETs unnecessarily for something a simple relay can do (powering the motors at 100%).

Then taking the foot off the pedal could just have the motors short through a 10-watt .47 ohm (or whatever) resistor to do the soft stop.

The primary advantage of this would be that I wouldn't need to spend $100+ on a dual-channel motor driver that handles 85A per channel. I'd really like to avoid that. And whatever I do has to be compatible with an Arduino so an Electronic Scooter Controller isn't going to work. There are other things I'd like to do to this car, and it'll be easier with an Arduino than being boxed in with a scooter controller. IMHO.

Thoughts?


#148636
Hi jdh23,

I can't answer your question about using a relay, but FWIW, here are a couple of other threads about using an Arduino with a (cheap) H-bridge to add soft start/stop:

viewtopic.php?f=46&t=17511
viewtopic.php?t=17787

I played with the Arduino sketch and tested the slow start behavior on a pedal/motor assembly, but I haven't gotten around to actually putting everything together back in the car. :(

Hope this helps.
#148637
Thanks. I've seen those threads and have already gone down the path of using cheap Chinese boards. I was originally going to use a Monster Moto Shield clone, until I discovered it used fake components and only works up to a few hundred RPM. So now I'm trying to use only parts from known manufacturers, while also not spending a fortune. And I think that using a lower power (cheaper) motor driver that hands off to a 12V relay might be the way to do that.

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