• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

convert GPI to a fader start pulse?

F

Fenris

Our college radio staion is looking for a cheaper alternative to our Denon DN-C635 CD players, which are slow and horribly unreliable. It's important to have remote start from the Audioarts R-60 console, which means converting the GPI trigger output of the console to a fader start pulse that will work with the 1/8" remote input of a Stanton, Numark, or similar. Apparently they both use +5v DC but the timing is different. Can anyone tell me how to do this?

Alternatively, I could install a small relay inside the CD player, wired to the play button, and trigger it from the console.
 
For most consumer stuff, I put a relay inside. They usually don't like wires going to the outside world.
I have a handful of the Stanton dual players, which we like. They give no trouble, and are so cheap that if they begine to, I'll toss and replace. I >think< they want a plus pulse, which our Wheatstone consles happily spit out on request.
 
I've done the relay trick on some Stantons, and they worked fine. It was easy to do, since I just paralleled the buttons on the front panel. There is plenty of room inside the case to put whatever you want inside.
 
Yes, I do the same. Solder a pair across the start button and terminate to a small relay placed inside the CD. I then drill the rear of the case, install a 1/4 TRS, and connect the relay pair to TR (tip & ring). Works great.
 
I have a follow-up question on this one. It turns out the console does not use a GPI pulse, it has an extra pair of contacts on the channel ON switch that can be used for remote start. I got it to work with a Stanton C402 CD player, but not very well. This model has a combined play/pause button, and if you hold down the channel ON button it behaves unpredictably. Unfortunately, it looks like ALL the rackmount CD players in the $200 range have a combined play/pause button. Is there such a thing as a momentary relay that closes and immediately opens again, even if the control voltage stays on? Or do I need a circuit that generates a momentary DC pulse?
 
I think I know what you're asking. You're asking to convert to a pulse, correct?

Yes, put a cap in series with the relay and a bleeder resistor parallel to the cap. Once the cap charges, the relay will no longer "see" a voltage across it. Once voltage is removed from the circuit, the cap will slowly discharge through the resistor. The rate of discharge is determined by the size of resistor.

Yes, it's common practice to place a diode across a relay for protection.

The above circuit is simple and works well.
 
It should be noted that, while you can convert a steady on to a momentary, there are some caveats. First, while the cap discharging, the relay won't operate. The time will be short, but during that period, a second push of the button will not operate the relay. Second, after the cap has discharged, hitting the start button a second time will close the relay potentially pausing the deck. If they accidently pause the deck, they won't be able to quickly push the button again to restart it while the cap waits to discharge.
 
Another question: can I eliminate the relay? Can I wire the extra contacts on the channel's ON button in parallel with the CD player's Play/Pause button, and put the capacitor and resistor between the ON button and ground?
 
The buttons on the player are likely scanned by it's CPU - they may not be referenced to ground. Running a long piece of wire from the button may upset the scanning or cause unwanted interference or erratic operation. I usually put a 4N25 optocoupler in the player (paying attention to the output polarity and the button) and trigger that from the console button and its supply voltage (with properly sized limit resistor).
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom