crchisholm
New Member
I am using a 555 timer to close a circuit that fires the shutter on a camera when the resistance drops across a sensor. The output of the 555 is closing a 5v relay that closes the circuit that fires the camera. When the camera isn't hooked up and I test with pull-up resister and an LED across the 9v and the ground to see if the relay is closing, everything works perfectly. When I attach the leads to from the camera (2.5v and 0v) to the relay, then the relay somehow causes the 555 to fire over and over. I suspect that the inductance of the coil in the relay is firing the 555 through the output line. I have the camera set to keep the shutter open as long as the relay is closed.
If I set the camera to close the shutter automatically after being triggered, and the pulse from the 555 to be of shorter duration than the time it take to open and close the shutter, it works fine. If, however, the shutter is open longer than the pulse, the 555 will fire again and again. This is only a problem in that I wanted to control the shutter open time with the variable resister (thus the pulse width) of the 555 circuit.
:? Is there a way to use transistors to isolate the and close the circuit of the camera. I have tried a few simple transistor circuits and the leakage from the transistors was enough to trigger the camera. Is there a completely leek proof transistor?
:? Is there a way to keep the 555 from firing from activity on its output (3) line?
As you can tell, I am not completely sure of what I am doing.
Charlie
If I set the camera to close the shutter automatically after being triggered, and the pulse from the 555 to be of shorter duration than the time it take to open and close the shutter, it works fine. If, however, the shutter is open longer than the pulse, the 555 will fire again and again. This is only a problem in that I wanted to control the shutter open time with the variable resister (thus the pulse width) of the 555 circuit.
:? Is there a way to use transistors to isolate the and close the circuit of the camera. I have tried a few simple transistor circuits and the leakage from the transistors was enough to trigger the camera. Is there a completely leek proof transistor?
:? Is there a way to keep the 555 from firing from activity on its output (3) line?
As you can tell, I am not completely sure of what I am doing.
Charlie