Re: TTL Relay

DRigotti@... wrote:

> From: DRigotti@...
>
> Gentleman,
> I'm looking for a relay that will take a TTL signal directly and turn on
> and off a 35V 8A supply. Can anyone give me some help?

Do you want to turn the AC power for the 35V 8A supply on and off,
or leave the supply powered up, and turn the 35V DC circuit on and off?

The first is simple, any 120 V solid-state relay should be able to do that.
It usually works better with real TTL chips to make the logic low be on,
because these chips sink current 10x better than they source it. You hook
the + input of the SSR to +5V DC, and the - input to the TTL output.

IF you want to switch the DC, there are opto-relays from Omron,
Grayhill and Opto-22 that will do this. They will probably be more
expensive than the AC switch. One word of caution : If the DC
load has decoupling or energy-storage capacitors, then connecting the
DC supply (with, presumably an energy storage capacitor bank)
to the de-energized load (with its capacitors) will cause a current
surge of large magnitude, which will likely exceed the ratings of
the DC solid state relay.

Jon