Hi,
Without providing circuit details (I have no schema, I would need to draw one, I'll do that if it becomes absolutely necessary),
I have a question about LDRs.
I have made a little circuit, that switches a relay on or off, depending if it is dark or light... Simple stuff. LDR + some resistors + Schmitt Trigger + transistor + relay.
It works pretty well, and has been doing so for 2 months or so.
However, the LDR seems to become less sensitive for each week that goes. The delta resistance seem to decrease for light and dark.
I had this problem before, and redid the schematic to provide some protection (diode + capacitor) to the LDR, so it would not get any peak voltages from the coils in the relay going on or off.
The first experiment lasted two weeks, and then the LDR was basically useless. The second, 2 months or so, and the LDR is still going. But it does seem to degrade, though more slowly.
Some details:
The power supply is 12v, and because of the setup, the LDR should be getting about half of that.
The Relay needs 12 volt to switch.
The LDR is placed outside, to catch daylight. It is protected by some cellophane, and it it's place in a little box so it does not get wet when it rains. Together this gives it double moisture protection (I hope)...
So, has anyone any idea what could be going on?
Thanks
DaC
Without providing circuit details (I have no schema, I would need to draw one, I'll do that if it becomes absolutely necessary),
I have a question about LDRs.
I have made a little circuit, that switches a relay on or off, depending if it is dark or light... Simple stuff. LDR + some resistors + Schmitt Trigger + transistor + relay.
It works pretty well, and has been doing so for 2 months or so.
However, the LDR seems to become less sensitive for each week that goes. The delta resistance seem to decrease for light and dark.
I had this problem before, and redid the schematic to provide some protection (diode + capacitor) to the LDR, so it would not get any peak voltages from the coils in the relay going on or off.
The first experiment lasted two weeks, and then the LDR was basically useless. The second, 2 months or so, and the LDR is still going. But it does seem to degrade, though more slowly.
Some details:
The power supply is 12v, and because of the setup, the LDR should be getting about half of that.
The Relay needs 12 volt to switch.
The LDR is placed outside, to catch daylight. It is protected by some cellophane, and it it's place in a little box so it does not get wet when it rains. Together this gives it double moisture protection (I hope)...
So, has anyone any idea what could be going on?
Thanks
DaC
Last edited: