I have a device that puts out "wet" contact GPIs and the device I'm interfacing with needs "dry" contact GPIs. Can anyone lead me into the right direction into designing a circuit that will take the wet contact and "convert" it into a dry contact?

Further info... the device output 10 GPIs, but my device needs only the first 6.

(Since you'll probably want to know, this is for video equipment.)

Thanks!!

 

Interesting, to me, a process guy. I'd never heard of a 'GPI'. It's a "General Purpose Interface", but it appears that the outputs or inputs from such are whatever the manuafacturer says they are. I can imagine how video could be married to motion control with such.

blurb from
http://www.tech-notes.tv/Glossary/Glos files/g.htm
A pulse or contact (switch) closure signal sent from an editor to trigger audio tape recorders, digital video effects devices, and graphics generators to activate for an edit or effect. Some external devices do not have the ability to be directly controlled by the editor. In this case GPI signal is used as a means of telling these devices when to execute a command. The choice of command itself, however, must be set up on the external device and cannot be controlled by the editor.

A TTL level signal used to trigger an event. Graphical User Interface Usually a connection on equipment where a contact closure is used to activate a device or piece of equipment. An audio tone can be used to activate a contact closure to ?roll? events. A trigger event!. Software process providing operator access to the overall software application.
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At any rate, you need to determine exactly how 'wet' the outputs are. The output voltage has to match the coil voltage of the relay.

Are the outputs TTL (5 volt logic)? The explanation above infers that they might be TTL.

If that's the case, you'll need an electrocmechanical relay with a 5 volt dc coil. The contact rating of the relay is moot, the "dry contact" is looking for relay contacts and sources minimal current.

I can think of a couple solutions.
Phoenix Contact (PC) makes a 'powered' TTL driven relay, that requires an independent 5Vdc supply; it's for those situations where TTL isn't a full 5 V output. It's PC part number 2943259 (does not include 5V supply)

PC also has standard 5V coil relays, for instance, the 5 V relay 2967992, that uses base 2980225. (relay plugs into the base).

I have to assume that there are also commercial GPI 'adapters' that convert from wet to dry, since you can't be the first guy to run into this.

David

 

It's called a relay. Crude and simple but effective. Drive the coil with your "wet" signal and you're there.

Regards

cww