Re: Dumb question on TTL control of a relay from parallel port

You can use a transistor and clamping diode, or if you need multiple
outputs with this capability you can take a look at the ULN2003.

Parallax shows how to use the ULN2003 in the documentation available
on their website.

Tony

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "washcomp" <jeff@w...> wrote:
> I've got a parallel breakout board giving opto-isolated TTL level 5
> volts. I'd like to control a relay for my mist coolant. I can get
a
> 5 volt relay (typical coil current 30-60 ma), but I seem to
remember
> that TTL level isn't designed for the required current (?).
>
> If the above current is too high, is it best to try to find a
> miniature reed relay to control the coil of the "power relay" or is
> there a better way?
>
> Clueless in New York,
> Jeff