Hi internet,
First time posting here so apologies if there is somewhere that would be more suitable for this query.
In short, I have a solar cell connected to a moving coil (that moves a needle) and I want to add ~130 mV onto the whatever the solar cell is outputting. I.e. if the solar cell reads 200 mV, I want 330 mV across the moving coil. Adding a voltage source in series would achieve this right? I just don't quite know how I'd go about introducing this relatively low voltage.
This is part of an autoexposure system in an old camera that uses a solar cell to gauge the light level and set the aperture and shutter speed accordingly via moving needle. I want to change the range of film that I can use in this camera by tricking the camera into taking photos when it would normally be too dark. I have worked out that the solar cell voltage scales linearly with light "stops" and that a change in voltage of ~43 mV corresponds to a change of one stop. Overall I want to shift the exposure system by 3 stops, hence I want to add ~130 mV.
Ideally, I'd like to be able to hide any extra electronics away inside the camera - there is a small amount of space in the camera for something like a button cell battery or a DIP8 package/comapct circuit, etc.
Other misc. info.: the resistance of the moving coil is 7.2k ohms; the solar cell and the moving coil are the only two components in the circuit.
If anyone has any suggestions I would be very grateful! Let me know if there's any more info. I can add too.
Cheers
Pat
First time posting here so apologies if there is somewhere that would be more suitable for this query.
In short, I have a solar cell connected to a moving coil (that moves a needle) and I want to add ~130 mV onto the whatever the solar cell is outputting. I.e. if the solar cell reads 200 mV, I want 330 mV across the moving coil. Adding a voltage source in series would achieve this right? I just don't quite know how I'd go about introducing this relatively low voltage.
This is part of an autoexposure system in an old camera that uses a solar cell to gauge the light level and set the aperture and shutter speed accordingly via moving needle. I want to change the range of film that I can use in this camera by tricking the camera into taking photos when it would normally be too dark. I have worked out that the solar cell voltage scales linearly with light "stops" and that a change in voltage of ~43 mV corresponds to a change of one stop. Overall I want to shift the exposure system by 3 stops, hence I want to add ~130 mV.
Ideally, I'd like to be able to hide any extra electronics away inside the camera - there is a small amount of space in the camera for something like a button cell battery or a DIP8 package/comapct circuit, etc.
Other misc. info.: the resistance of the moving coil is 7.2k ohms; the solar cell and the moving coil are the only two components in the circuit.
If anyone has any suggestions I would be very grateful! Let me know if there's any more info. I can add too.
Cheers
Pat