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Overload Current Sensing circuit for DC Motor wanted

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jcding1980

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current sense circuit

Hi.

Anyone has circuit for overload current sensing for DC Motor with operating voltage = 12-24V. I have seen few circuit using one bjt transistor and few resistors. Is this circuit reliable?? Thanks in advance.[/u]
 

current sensing circuit

look for current sense in maxim web site
 

dc motor current sense

To sense (not limit) the over-current you need a power resitor, PNP transistor and base resistor of 1k/0.25W or so.
The power resistor will be connected to the + Supply at one end and Motor+ at the other. To power supply end connect Emitter of the PNP transistor. Base, trough the 1k you will connect to Motor+ end.
If motor current riches 0.65V/R where R is the resistance of the power resistor the transistor will start to conduct current to ... you can use LED (with 2.2k resistor) or any other indicator such as a small bulb rated for 12-24V connected between the Collector and negative pole.
 

motor current sensing

I would recommend Allegro Hall- effect sensors. They even offer now a complete
family of current sensors. But with the hall- effect sensors you are able to design
an absolutely linear current or voltage sensor according to your demands.
By this technology power circuit and current control are isolated from each other.
This is mandatory especially with high amp or "noisy" motors.

Please refer for a more detailed information to the application section at

https://www.allegromicro.com/

regards
 

dc motor overload

Depending on your current requirements this might not be a so easy task.
I will suppose that you need to work with low currents, motors of less that approximatetly 200W.
You can use a small Ohmic value series resistor as other posters suggest and a transistor. With this method you might even enable a circuit that could interrupt the motor supply if you wish.
Another simple method is to use a series self wound coil arround a reed switch. You need to experiment with this method in order to find the number of turn of the coil. When enough current passes through the coil, the reed SW is energised and you can use its contacts anyway you like, i.e. drive an indicator, interrupt the motor's power or else.
 

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