Circuit Breaker

[Inferno]

hello there....
i need help in something..sorry i am not that expert in electronics..
what i need is something small that can break the circuit when the DC motor is overloaded ( so the motor won t be damaged ) this "thing" has to make the current pass again automatically when the motor is not loaded...
to make my idea clear... i think about the following example:
the power windows system in a car... when i push the button ..the windows goes up ..when it reach the maximum there is either a metal device that break the circuit or a push button... something like that...but i knowt that there is some electronic devices that can do the same thing.. something that senses that the motor is overloaded ( the current is going high) and upon that he breaks the circuit and the motor is safe...
thanks in advance for your help
By the way this "thing" has to be able to handle about 40 amp and 12 v ....

 

[Optikon]

hello there....
i need help in something..sorry i am not that expert in electronics..
what i need is something small that can break the circuit when the DC motor is overloaded ( so the motor won t be damaged ) this "thing" has to make the current pass again automatically when the motor is not loaded...
to make my idea clear... i think about the following example:
the power windows system in a car... when i push the button ..the windows goes up ..when it reach the maximum there is either a metal device that break the circuit or a push button... something like that...but i knowt that there is some electronic devices that can do the same thing.. something that senses that the motor is overloaded ( the current is going high) and upon that he breaks the circuit and the motor is safe...
thanks in advance for your help
By the way this "thing" has to be able to handle about 40 amp and 12 v ....

40A, 12V sounds like a job for a mechanical relay. Develop an overload detection circuit (maybe it is just a mechanical stop with micro-switch) that will open the relay contacts that are supplying power to the motor. I've seen some bi-directional schemes on the web.

 

[Hero999]

PTC resistor aka polyfuse?

 

[ikalogic]

40A, 12V sounds like a job for a mechanical relay. Develop an overload detection circuit (maybe it is just a mechanical stop with micro-switch) that will open the relay contacts that are supplying power to the motor. I've seen some bi-directional schemes on the web.

at 40A... i think a thyristor would also be suitable

 

[Hero999]

You can buy thermal auto resettable circuit breakers - most electrical distributors sell them.

 

[jbelectric777]

I agree with Hero999 , Thermal overload protection w/ auto reset.

 

[mneary]

at 40A... i think a thyristor would also be suitable

Please explain the circuit where a thyristor would work as a circuit breaker. IIRC, they only conduct better as the current increases.

 

[Hero999]

I wouldn't recommend it for this application though. R2 would dissipate >28W, D1 would switch of when the motor's commutator interrupts the current (can be solved by connecting a resistor across it) and it's likely to blow when the motor is turned on (unless C1 is pretty large), Tr1 would dissipate a huge about of power (could be fixed by replacing it with a MOSFET though).