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Author Topic: Safer brushless motors...?  (Read 1045 times)

dodgy geezer

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Safer brushless motors...?
« on: October 09, 2009, 05:18:40 PM »

Overheating is a big problem for marine brushless motors. We don't run in a draught, and it's hard to know how hard the motor is working when the boat is running. And if a motor overheats it loses magnetism, draws more current and up go your windings and esc in rapid succession.

Over on the GiantCod forum I was suggesting a resetting thermal fuse or thermistor on the windings, which would cut the motor and save the boat, when gandalf added to the proposal by suggesting that the radio input to the esc be cut, thus knocking out the motor. This would make a very simple and cheap safety unit. Have any electrical wizards got any comments...?
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malcolmfrary

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Re: Safer brushless motors...?
« Reply #1 on: October 09, 2009, 05:33:35 PM »

Having the temerature sensor control the input to the ESC rather than the output makes sense - you only need one design of unit.  Presumably the wiring would go from RX output to temperature guard to ESC, with a sensor head on the motor wired back to the guard unit.  Either allow control pulses through or not.  All it needs is someone good with LM348 op-amps.
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787Eng

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Re: Safer brushless motors...?
« Reply #2 on: October 13, 2009, 01:28:48 PM »

Or a PIC chip even easier  :}
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malcolmfrary

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Re: Safer brushless motors...?
« Reply #3 on: October 13, 2009, 01:49:40 PM »

Could be a horses for roundabouts job - the temperature sensor would be an analogue device, temperature being an analogue thingy.  The PIC chip would almost certainly need a few extra components to realise an ADC, which would probably bring it up to the same component count and board area as the quad op-amp, which is a much cheaper and more voltage tolerant chip in the first place.
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787Eng

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Re: Safer brushless motors...?
« Reply #4 on: October 13, 2009, 06:37:17 PM »

Nope!
Doing something very similar in another project. The 12F675 has all you need and more with VERY little external components. no external components required to get the PIC to run as a micro controller. The 675 has a 4 channel 10bit D/A built in......

Voltage range for the PIC is 2.0 to 5.5V, cost is just over 1 pound.
 
Mark
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