My first post here - and a request for a bit of assistance.
I'm in the process of assembling a night vision device based on a cascade image intensifier tube. The tube itself runs just fine off 4x AA Eneloop rechargeable batteries, right now the output voltage is at 5.2V. But I also wanted to add a control circuit that would only allow the tube to power on in darkness (to prevent accidental damage of the II tube due to overexposure). I basically copied this schematic that someone had apparently tried already:
http://www.hvlabs.com/Images/nightviscircuit.JPG
Unfortunately, it does not work as intended. The dark-activated switch performs OK - when adjusted properly, the NPN transistor switches on when it's dark enough and I get full 5.2V at the collector.
However, as soon as I attach the tube between the collector and Vcc the output voltage sinks to about 1.2V and the tube does not power on.
I assume the output current is insufficient to power the tube - which only needs 30mA. What should I do?
I'm in the process of assembling a night vision device based on a cascade image intensifier tube. The tube itself runs just fine off 4x AA Eneloop rechargeable batteries, right now the output voltage is at 5.2V. But I also wanted to add a control circuit that would only allow the tube to power on in darkness (to prevent accidental damage of the II tube due to overexposure). I basically copied this schematic that someone had apparently tried already:
http://www.hvlabs.com/Images/nightviscircuit.JPG
Unfortunately, it does not work as intended. The dark-activated switch performs OK - when adjusted properly, the NPN transistor switches on when it's dark enough and I get full 5.2V at the collector.
However, as soon as I attach the tube between the collector and Vcc the output voltage sinks to about 1.2V and the tube does not power on.
I assume the output current is insufficient to power the tube - which only needs 30mA. What should I do?