I am building a circuit using a PIC12F675. The supply voltage is 4.9Volts. I need the voltage to go low as part of the circuit. I have used an LDR and a 33K resistor, The voltage drops to 3.4 Volts. Is this considered as a "LOW" in terms of an input for a PIC.

My circuit does not seem to be seeing it as a low.

any thanks

Rodney

 

I am building a circuit using a PIC12F675. The supply voltage is 4.9Volts. I need the voltage to go low as part of the circuit. I have used an LDR and a 33K resistor, The voltage drops to 3.4 Volts. Is this considered as a "LOW" in terms of an input for a PIC.

My circuit does not seem to be seeing it as a low.

any thanks

Rodney

No, a PIC requires close to zero volts as a logic low. You probably will need a pull-down resistor; post a schematic.

 

I have retested and the voltage does not go below 3.6 Volts. If I was to remove the 33k Resistor would the current flow through the LDR not damage it.

 

You need to connect the LDR to an analog input and calculate the light level. It's not a digital device.