Overload Current indicator / detector

[SHWETHAREDDY]

Over Current indicator

Hi,

Can u help to design a circuit which detects/indicates the current if it exceeds the reference/fixed value.



Regards,
Reddy

 

[Tahmid]

Over Current indicator

Hey,
Here is a simple circuit, which I believe should work:

Added after 8 minutes:

As for the components marked with an asterisk(*):
PSU: must be less than 18v, but more than 8v.
R4 controls the gain of the non-inverting amplifier. Change as required.
RV1 adjusts the overcurrent level, ie, at which current level to show that overcurrent has occurred.
U1B is shown as an opamp. A comparator could be used in place.
U1A has to be an opamp. A comparator will not do.
R8 is the current limiting resistor for the LED, change according to your LED current requirement.
RS is the sense resistor which is the shunt here. This may get VERY hot according to your current level.
Let's assume your PSU is 12v, RS = 0.01ohm. Then at 20A current, assuming this is your current limit, V=20*0.01 = 0.2V[ohm's law].
P=0.2*20=4W, so resistor must be atleast 8W. Beware 4W is dissipated by the resistor as heat.
Gain is set at 1+(10/1) = 11 for U1.
So Vout = 11 * 0.2 = 2.2V.
Adjust RV1 to approximately 2.1v, so any voltage above this will result in a positive output from U1B, turning on PN2222, turning on the LED.
This circuit only works to indicate overcurrent. It does not cut off the supply. To do this, you could simply connect a relay inplace of the LED and set it to cut off the supply when overcurrent limit is reached.

Added after 8 minutes:

Like this:

 

[FvM]

Over Current indicator

Unfortunately, the circuit doesn't work with TL082. You need an OP with common mode range down to negative supply voltage, e.g. LM324, TLC082 or a recent rail-to-rail OP.

 

[SHWETHAREDDY]

Thanks Tahmid for ur solution,it is very helpful por me...



Regards,
Shwetha.S

 

[SHWETHAREDDY]

HI,

THANK U VERY MUCH...............

REGARDS,
SHWETHA