3V Dark Detector Circuit

[Suraj143]

Can somebody Give me a circuit diagram of a Dark detector using discrete components with a snap ON, OFF ( built in Small Hystersis ) which can operate from two AA cells.

Thanks

 

[audioguru]

Here is my Dark Activated LED circuit with two transistors, a low supply voltage and an LDR. But it has no hysteresis since it switches fairly quickly:

 

[Pommie]

Could a resistor be added from the PNPs collector to the NPNs base to introduce some hysteresis?

Mike.

 

[alec_t]

How much load current must the detector source/sink?

 

[audioguru]

Could a resistor be added from the PNPs collector to the NPNs base to introduce some hysteresis?

Mike.

I think that will cause the transistors to turn on but never turn off, unless the new resistor value is very high.