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Help with computer controlled dry latch relay

jediborg

New Member
Hello,
I'm the closest thing to an IT Tech/Engineer at a small community "leased-access" station. I need a dry latch relay setup that will work with the computer that plays our content. The goal is to provide our content to a different "entity" via IP stream, but when our local commercials run, a GPO trigger would latch the relay and the "entity" could insert their own commercials. At the end of the commercial break, the latch would be released and our content "appears" again.
I have a usb "multi-gpio" box from the system maker. It has 6 GPO slots and 2 GPI slots and connects to the computer via USB. I need a dry latch relay, and clearer instructions than a vague diagram on how to wire it.
Each slot on the GPIO Box has a Positive and Negative terminal.
I would prefer a relay that flips it's state every time it's triggered (if possible), to keep things simple in the programming of our playlist, with the need for just one GPO Trigger. If we need to use a relay that requires two different triggers, one to close the relay and a second to open it back up, then that's ok too, but that's where I get really confused because I cant mentally picture which wires should go where and why.
I've tried googling items and looking for them, but there is just so much info and so many different items, it gets very confusing fast.
If it helps, we use the RushWorks A-List Playout Automation software. I'll attach a picture of the GPIO Box.
GPIO.jpg

So, I need a link for a dry latch relay. Presumably, a link for the power source for the relay. and instruction on which wires get hooked to what inputs.

Thanks in advance.
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
Latching relays are usually magnetic latch, one polarity to latch, the reverse polarity to unlatch.
Both require a momentary pulse of the required polarity.
One advantage they remain at the last state, even with no power on the system..
 

rjenkinsgb

Well-Known Member
Most Helpful Member
If you have the ability to use two different triggers for on & off, can't you just switch a single output on at the start and off at the end, and drive a conventional relay from that contact?

If there were a glitch of some sort with a latching relay, it could stay in "advert" mode for the duration of the following program, which I'm pretty sure would cause complaints!

A simple on-off relay run from a GPIO output should be simpler and more reliable.
 

jediborg

New Member
If you have the ability to use two different triggers for on & off, can't you just switch a single output on at the start and off at the end, and drive a conventional relay from that contact?

If there were a glitch of some sort with a latching relay, it could stay in "advert" mode for the duration of the following program, which I'm pretty sure would cause complaints!

A simple on-off relay run from a GPIO output should be simpler and more reliable.
I'm not sure how the system that we are feeding is setup. I don't know if the need for the relay is to kill the broadcast signal, or let the "add on" box add some sort of subcarrier signal to the stream. I just know that the specs call for a DRY-LATCH relay.
The on-off relay run might be what we need. My biggest issue right now is finding the right relay, I see hundreds of relays, but I'm not sure how to tell if they are dry-latch, or which ones require constant current to maintain the relay's state as opposed to the power necessary to trigger the state change.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
Have a look at two coil / twin coil latching relays.

They are the simplest to control if you must use a latching type, as you power one or the other coil momentarily to switch the relay on or off.

Example, a 5V coil one in stock at Mouser:

If the description does not say it's a latching type, then it will be a normal one that needs continuous power to stay energised.
 

eTech

Well-Known Member
So, I need a link for a dry latch relay. Presumably, a link for the power source for the relay. and instruction on which wires get hooked to what inputs.

Hi

There is critical information missing.
What is the box's output providing to interface to the relay?
Is it a contact?
Is it a voltage that changes polarity? or is it a voltage pulse? Is it a toggled voltage (on/off)?

I think the answers will have to come from the manufacturer.

Maybe...
Connect a 10k resistor across one channel of the GPIO output terminals, then connect a voltmeter across the resistor. Send a command to activate the GPIO and see how the output behaves.
 

jediborg

New Member
Hi

There is critical information missing.
What is the box's output providing to interface to the relay?
Is it a contact?
Is it a voltage that changes polarity? or is it a voltage pulse? Is it a toggled voltage (on/off)?

I think the answers will have to come from the manufacturer.

Maybe...
Connect a 10k resistor across one channel of the GPIO output terminals, then connect a voltmeter across the resistor. Send a command to activate the GPIO and see how the output behaves.
If it's anything like the GPI...and I can't see why it would be anything else, my guess is it would be a momentary pulse. The GPI is a simple spring loaded push button switch. The circuit is completed when the button is pressed. Doesn't matter how long we hold the button down. A quick tap and a "press and hold" produce the same result. The GPIO box doesn't have external power, though I am informed that:
"The Multi-GPIO has TTL GPOs (5VDC) and power comes from the USB port. Typically the other end is selectable as our GPI ports are. If you need to change the configuration or timing in A-LIST let us know and we can assist."
 

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