Transistor as a switch
Transistor as a switch
(OP)
As a preface I will declare that circuitry is not my speciality by any means. I work in the Film business as a Steadicam Operator.
I'm trying to build a simple relay switch using a Transistor. I have a remote control focus system than has a camera start stop button. The system sends a .5v momentary signal to the camera to indicate start or stop. I would like to hijack this .5v DC signal to control an IR remote.
Using a low voltage, fast acting NPN transistor I built a simple circuit that works but might present a problem when I plug the system into a film camera.
I wired the + power supply (3v DC) for the IR remote through the collector and emitter of the transistor and wired the .5v DC output to the base and emitter.
With the pause button held down on the IR remote, every time the .5v DC pulse goes through the transistor the 3v DC power supply is momentarily connected and the IR sends it's command.
The problem is the transistor leaks power from the 3v DC into the base and thus into the focus unit which might create a problem when plugged into a film camera.
Is there a simple circuit that can be built to prevent this reverse power leakage?
I'm trying to build a simple relay switch using a Transistor. I have a remote control focus system than has a camera start stop button. The system sends a .5v momentary signal to the camera to indicate start or stop. I would like to hijack this .5v DC signal to control an IR remote.
Using a low voltage, fast acting NPN transistor I built a simple circuit that works but might present a problem when I plug the system into a film camera.
I wired the + power supply (3v DC) for the IR remote through the collector and emitter of the transistor and wired the .5v DC output to the base and emitter.
With the pause button held down on the IR remote, every time the .5v DC pulse goes through the transistor the 3v DC power supply is momentarily connected and the IR sends it's command.
The problem is the transistor leaks power from the 3v DC into the base and thus into the focus unit which might create a problem when plugged into a film camera.
Is there a simple circuit that can be built to prevent this reverse power leakage?





RE: Transistor as a switch
I would consider using a LM339 open collector quad op amp instead and reference the switching voltage at 0.25 volts. The input could be isolated with a 100K resistor. This solution only adds three resistors. Outputs could be paraleled for even higher currents
RE: Transistor as a switch
My flawed design aside, what I would like to do is use the momentary signal out of the focus unit (PRESTON MDR) to activate the 3v DC without the 3v DC contaminating the Focus unit signal.
I will try the open collector method.
RE: Transistor as a switch
RE: Transistor as a switch
2v is probably more than the momentary signal offers. It needs to be a circuit that can be triggered by 1v dc or less.
I do appreciate the help, As a member of a similar forum for Steadicam Operators I realize how frustrating it can be to deal with the likes of myself who are not educated in the field.
RE: Transistor as a switch
RE: Transistor as a switch
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Transistor as a switch
RE: Transistor as a switch
RE: Transistor as a switch
RE: Transistor as a switch