I am working with a friend trying to complete a project and we need to send a square wave from 0-5 volts to a camera continuously after a hall sensor is triggered. I know nothing about transistors and I am having a hard time trying to figure this out. The power supply is 5volts and the hall sensor ranges from .6 volts normally to 1.2 volts when triggered. I am thinking that I need a transistor as a switch to turn on when 1.2 volts. Then another type of gate to provide power there after and then maybe a 555 timer to create the square wave from 0-5. Does anyone know how to do this?
The logic hall sensor isn't water proof. The sensor is going to be a foot under water. I'm using a cam sensor from a gmc car because its water proof. I tried to use a transistor but I can only get it to work in a basic circuit. When I put the sensor to the base of the transistor it just stays on all the time. I have been trying to look at LDR circuits to get some type of basis but it still just stays on all the time.
There are a few unanswered questions:
Do the pulses turn off when the Hall turns off? This circuit does
What frequency of pulses? I just picked one
Note the first pulse from the 555 is longer than the rest. This is how it comes out of reset. Is that ok?
Here is how I would do it. Set the 5K Pot about 3/4 of the way from the bottom, until the voltage at "RC" pulls all the way to ground. The time-constant of R1*C1 determines how long the 555 stays triggered after the Hall pulse goes low. Useful range of R1 is 10K to 10meg.
I believe both of your schematics will work. The frequency I believe should be around 10hrtz but I'm not positive. I'll have to go and check the manual for the camera. I will try both out. What transistor should I get for MikeML and what op-amp for Ronv?