Advice please: controlling a transistorised relay board with anopen collector output
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Posted by Frank Sweeting on November 29, 2004, 9:23 pm
Please log in for more thread options I'm not up with modern electronics & I'm struggling a bit with this: if anyone can give me any advice or suggestions I'd be grateful I have a device with an open collector output which can be controlled ON/OFF remotely by phone. I'm told I have to be careful about the amount of current supplied by the open collector output so I chose to use the open collector output to switch a relay with a transistorized relay board to trigger its relay. I've got a 1.5k resistor between 12V on the device & its open collector output, the output then goes to the trigger on a relay board. When the output is ON theres 10.5V on the trigger, & when its OFF theres 0.7V on the trigger Powering up the device has the open collector output ON & the relay is triggered ON, BUT, when I command the Open collector OFF the trigger voltage only drops to 0.7V, & the relay stays ON So I haven't got control of the relay as I wanted because I cant turn it off! I've experimented & found I have to get the trigger voltage down to about 0.1V before the relay goes OFF So heres the question, how can I get the open collector output down to 0.1V or if I can't is there a work around TIA Frank Frank Sweeting frank@sweetingfam.freeserve.co.uk | |||||||||||||
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Posted by Active8 on November 30, 2004, 12:20 am
Please log in for more thread options You don't need any. Try a 2k pull up. -- Best Regards, Mike | |||||||||||||
> I'm not up with modern electronics