Hi All,
New to the forum, so play nice
My name is Chris and I know little about electronics. I have a sound knowledge of Kirchoff's rules and paralleled vs series circuits, so I'm probably not a complete nooob, but I am still struggling with things like transistors. Don't even start on ICs! Woah!
Anyway, I have built an electric motorcycle which I am racing in the Australian TTX-GP. It's great to be a part of electric motorsport, especially now when it's still a bit underground. Mission Motors has already blown the field away in the US, so it won't be long before the big boys muscle us back-yarders out of the way.
My bike is called Voltron, the Electric RG and it's pretty cool. Actually, it gets very hot, hence the need for the thermistor circuit... I managed to crack 180 km/h down the straight but the two DC motors I am running seemed to go out of balance and one took the full load. It overheated in no time, and melted, spraying molten tin over everything
So I think a thermistor circuit could have saved the motor. The Agni motors are brushed DC motors which have nominal power of 12 kW, and a peak of 30 kW. They get very hot if you abuse them, or try to dump 800 amps into it.
So what I would like is to set up a circuit that makes use of the thermistors which are mounted in the brush housings. These thermistors are about 40 kΩ at room temp, and 2kΩ at maximum acceptable temp. I found a circuit on the web which uses a couple of transistors to activate an LED when the thermistor is heated, presumably because 2kΩ is too high a resistance to light up an LED. The circuit is found here:
http://www.technologystudent.com/elec1/therm1.htm
But there are no values for each resistor. I figure this would be a neat little circuit that I can use, with a super bright LED staring me in the face so I can see it, even when I'm focussed on the next turn.
So how do you recommend I determine what each resistor needs to be? The supply voltage will be 12 V, not 9 V, so the resistor in series with the LED can be about 900Ω to prevent it from burning out. What should the preset resistor be?
Keen to hear some tips and advice! Thanks and hello!
Cheers,
CHRIS
New to the forum, so play nice
Anyway, I have built an electric motorcycle which I am racing in the Australian TTX-GP. It's great to be a part of electric motorsport, especially now when it's still a bit underground. Mission Motors has already blown the field away in the US, so it won't be long before the big boys muscle us back-yarders out of the way.

My bike is called Voltron, the Electric RG and it's pretty cool. Actually, it gets very hot, hence the need for the thermistor circuit... I managed to crack 180 km/h down the straight but the two DC motors I am running seemed to go out of balance and one took the full load. It overheated in no time, and melted, spraying molten tin over everything


So I think a thermistor circuit could have saved the motor. The Agni motors are brushed DC motors which have nominal power of 12 kW, and a peak of 30 kW. They get very hot if you abuse them, or try to dump 800 amps into it.
So what I would like is to set up a circuit that makes use of the thermistors which are mounted in the brush housings. These thermistors are about 40 kΩ at room temp, and 2kΩ at maximum acceptable temp. I found a circuit on the web which uses a couple of transistors to activate an LED when the thermistor is heated, presumably because 2kΩ is too high a resistance to light up an LED. The circuit is found here:
http://www.technologystudent.com/elec1/therm1.htm
But there are no values for each resistor. I figure this would be a neat little circuit that I can use, with a super bright LED staring me in the face so I can see it, even when I'm focussed on the next turn.
So how do you recommend I determine what each resistor needs to be? The supply voltage will be 12 V, not 9 V, so the resistor in series with the LED can be about 900Ω to prevent it from burning out. What should the preset resistor be?
Keen to hear some tips and advice! Thanks and hello!
Cheers,
CHRIS