Hi there.
I'm a mechanical engineering student tackling a group project at the minute. It's the design and build of an underwater vehicle. I volunteered to do the electronics (expand the mind and all that) and am in need of some advice.
Basically, the craft will have 6 motors. They'll be controlled using an arduino microcontroller, which as I understand it puts out 5v logic. The motors will be drawing up to 6.5 amps, and each motor must be bidirectional and be capable of running independently, which means 6 motor controllers. I've struggled to find a commercial driver I could buy 6 of, and still stay reasonably within our budget. So, I've opted to build my own.
I breadboarded one yesterday and got it working, but this was using 4.5v from three 1.5v batteries to drive a small test motor and to configure the logic of the bridge. I then tested the bridge using a 12v lead acid battery for the bridge, connected one of the 'big' motors, and again used the three 1.5v batteries to configure the logic of the bridge, and... it shorted the right hand side of the bridge, and my high and low side mosfets melted, on that one side.
I've had a bit of advice elsewhere that, if I understand it properly, suggests that the 4.5v wasn't sufficient to 'open' the p types, so they were always closed, the n types came online, and shoot through occurred, thus frying the mosfets. This, I can live with.
The advice I'm looking for is regarding the schematic I've attached. I basically have three key questions:
Will using the mosfet driver, in all likelihood, be able to activate the gates of both the P and N types sufficiently?
Are the diodes I've opted for, with a forward current rating of 7.5A, necessary, and if possible, could I use smaller rated diodes?
I've sometimes seen capacitors used in the power rail in H bridges to provide extra capacitance, and 1k pulldown resistors in the base leg of the mosfets to set a default state for the bridge. Are these required given I'm using a mosfet driver?
I should probably also state we're not looking to utilize PWM control, and the motors are unlikely to be switching on and off very fast...
Cheers folks...
I'm a mechanical engineering student tackling a group project at the minute. It's the design and build of an underwater vehicle. I volunteered to do the electronics (expand the mind and all that) and am in need of some advice.
Basically, the craft will have 6 motors. They'll be controlled using an arduino microcontroller, which as I understand it puts out 5v logic. The motors will be drawing up to 6.5 amps, and each motor must be bidirectional and be capable of running independently, which means 6 motor controllers. I've struggled to find a commercial driver I could buy 6 of, and still stay reasonably within our budget. So, I've opted to build my own.
I breadboarded one yesterday and got it working, but this was using 4.5v from three 1.5v batteries to drive a small test motor and to configure the logic of the bridge. I then tested the bridge using a 12v lead acid battery for the bridge, connected one of the 'big' motors, and again used the three 1.5v batteries to configure the logic of the bridge, and... it shorted the right hand side of the bridge, and my high and low side mosfets melted, on that one side.
I've had a bit of advice elsewhere that, if I understand it properly, suggests that the 4.5v wasn't sufficient to 'open' the p types, so they were always closed, the n types came online, and shoot through occurred, thus frying the mosfets. This, I can live with.
The advice I'm looking for is regarding the schematic I've attached. I basically have three key questions:
Will using the mosfet driver, in all likelihood, be able to activate the gates of both the P and N types sufficiently?
Are the diodes I've opted for, with a forward current rating of 7.5A, necessary, and if possible, could I use smaller rated diodes?
I've sometimes seen capacitors used in the power rail in H bridges to provide extra capacitance, and 1k pulldown resistors in the base leg of the mosfets to set a default state for the bridge. Are these required given I'm using a mosfet driver?
I should probably also state we're not looking to utilize PWM control, and the motors are unlikely to be switching on and off very fast...
Cheers folks...
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