Pulse Inverter circuit (positive to negative)

[gigabyte3000]

Hello,

I'm trying to trigger some ccd's using trigger pulses from a master clock. Looking at it in an oscilloscope, the pulse is a positive voltage pulse. For some reason, my cameras do not trigger when I input this pulse, yet they do trigger when I transfer the pulse through an intermediate trigger manager which transforms it to a negative square pulse. I'm guessing that this is the problem, so I was wondering if anyone could give me a relatively simple way of inverting the pulse. Thanks in advanced.

 

[crutschow]

Depending upon the voltage and speed, you can use either an inverter digital IC or a transistor connected as a common-emitter inverter.

 

[gigabyte3000]

Thanks for your reply, I'll look into those options.

 

[Reloadron]

If you are getting at remote shutter release it really depends on the camera. I do this on a pair of Canon DSLR cameras, a EOS 10D and a EOS 7D. On both of them they use a 3 pin remote connector. One pin is shutter release and another is auto focus. The third pin is ground. Both shutter release and AF are held high by an internal pull up at 3.3 volts. Connecting either to ground fires the function. This is pretty common for most digital cameras with remote shutter release. Again, depending on the camera. If you have a 2 pin remote shutter release you may want to measure across the pins with a voltmeter and see if there is a voltage present. If yes, short the pins and see if the shutter triggers.

Just a Thought.....

Ron

 

[gigabyte3000]

There's actually a dedicated pin for the trigger on these ccd's. I actually just realized however, that the pulse duration of the pulse from the master clock is around 10 microseconds, whereas the lower bound for the ccd is 1 ms, which means I need to stretch the pulse. I still need to invert the pulse however, so thanks for everyone's help.

 

[Reloadron]

Depending on the current a chip like the 4049 Hex Inverting Buffer may work or if more current is needed a transistor approach as Carl suggest. As to the pulse stretcher, a Google should bring up circuits, if not just come back and ask.

Ron