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Camera tally lights


splodge360

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Got a camera tally port on my Barco camera/ laptop vision mixer, thought it might be useful for switching on a red light on over the laptop that's now live, or triggering playback start on a brightsign media player, or triggering playback on a laptop through interspace mastercue v5 hardwired button remote xlr.

My question is are tally lights just internal relays in the mixer so you feed power in and the internals switch that power voltage back to the output pin, or does the mixer internals give out voltages to the external devices ( like camera ccu tally in connection)

Just curious to fiddle in this down time!

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My question is are tally lights just internal relays in the mixer so you feed power in and the internals switch that power voltage back to the output pin, or does the mixer internals give out voltages to the external devices

 

The answer is - it depends. In my experience, an open collector output is more common though. Have you managed to source a manual for your vision mixer? It should have the details in there. I had to build one of these myself fairly recently (for a little For-A Hanabi) and I used a ready made board with opt-isolated inputs and relay outputs (readily available for not much money from Electronic Bay. This protected the switcher as it was only driving the inputs of the onto-isolaters and the relay contacts on the outputs gave me a bit more choice in what I hung off the end of it.

 

E2A; just found this ....

https://www.cameratim.com/electronics/tallies/

Edited by p.k.roberts
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Got a camera tally port on my Barco camera/ laptop vision mixer, thought it might be useful for switching on a red light on over the laptop that's now live, or triggering playback start on a brightsign media player, or triggering playback on a laptop through interspace mastercue v5 hardwired button remote xlr.

My question is are tally lights just internal relays in the mixer so you feed power in and the internals switch that power voltage back to the output pin, or does the mixer internals give out voltages to the external devices ( like camera ccu tally in connection)

Just curious to fiddle in this down time!

My extremely limited experience has been a 0V signal from the mixer, (either an open colector transistor or relay contact to ground) and there is usually 0V, +V available on the connectorThe camera (or monitor) has a grounded lamp ie needs a +V to activate, which is normally available on the same connector.

My solution has been to install a small relay (and reversed biased diode across the coil).

I have had situations where the camera needs a +V and it's associated monitor needs a 0V so a double pole relay has always been the order of the day.

 

From talking to colleagues fairly recently it seems the camera inputs now tend to be higher impedance electronic input which accept either a +V or a 0V to operate the lamp and don't need such interfaces so often.

 

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