LED Circuit?

Question

I'm trying to apply a tally light system: a Panasonic video switcher that sends a signal, and I want a couple of LEDs to turn on 150ft. away whenever that signal is on. That's it.

Whether I'm building it myself or not, I need to understand what the switcher does and doesn't handle, so I don't overload any of the Panasonic's components - it's a $11,000 device. Here's the information I have about its (D-sub15) control output:

formatting link

Is it designed to drive LEDs directly, or would you recommend a relay? What should also be in there to protect the unit (diodes)?

The signal has to go through 150 ft. of 26 AWG (7x34) Stranded TC wire, rated at 38.5 ohm/Mft.

I might be able to use an off-the-shelf tally system - Datavideo TB5

formatting link

Since it's designed to connect to their own video switcher, there isn't much info available. All I have is the Datavideo switcher diagram, which the TB5 is designed for:

formatting link

Given the right cable, should I be able to connect the TB5 to the Panasonic directly and suppose everything will work fine, or not necessarily?

Andrew Holme · Accepted Answer

That diagram shows it driving an LED (with a series current-setting resistor) directly.

You could use a relay or an opto-isolator. I would go for the latter. You'll need a local DC power source either way.

A diode could protect against reverse polarity; you could also include transorbs (transient absorbers) and use a screened cable with the screen connected to chassis-earth at both ends.

Looks like it.

They call it an RS232 cable; but it's not RS232. They might as well call it VGA judging by the D-connectors.

LED Circuit?

Join the Discussion

Didn't find your answer?