Advice please: controlling a transistorised relay board with

[Frank Sweeting]

Hi,
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

 

[Active8]

On Mon, 29 Nov 2004 18:23:09 +0000, Frank Sweeting wrote:

Hi,
I'm not up with modern electronics

You don't need any. Try a 2k pull up.
--
Best Regards,
Mike