Hi
is there any way to make a circuit that will stop the motor when current rises. for example 12v DC motor runs and u stop it by hand current rises and then circuit stops him and only after reset will it start again and is there any way to make it stop at certain current level.
thanks in advance !
Wouldn't it be curious if there wasn't a way to do that?
It can be done of course. It is not too difficult but will require soldering together an integrated circuit and some basic components.
The attached circuit should work. This is the idea.
-the motor M1 is controlled by relay K1 (contact K1.3).
-the relay coil (K1.1) is energized firstly by N-fet Q1 which is turned on by comparator U1.1. More on that soon. Q1 provides the ground connection to the coil.
- When pushbutton S1 is closed it provides 12V to the relay coil and the relay closes. S1 also forces the fet to stay on as long the switch is depressed. This takes care of any starting current spike.
- once the relay has closed its own contact K1.2 will keep it closed and the motor will run.
- Motor current is turned into a voltage over R8. R8 needs to be a small value in order not to affect motor operation. For that reason amplifier U1.2 raises the level to something comparator U1.1 can handle.
- RC filter R6C1 will remove any spiking and average the motor current to avoid false trips.
- U1.1 compares the amplified actual current value to a reference set by R3. Once the actual exceeds the reference U1.1 output goes low turning the fet off. Relay K1 releases and the motor stops. When the current goes to zero, U1.1 again turns the fet on, but the relay is off so nothing happens.
- Once S1 is closed again the cycle repeats.