using a 12V unregulated power supply as trigger

[Blurmwood]

Hi,

I've got a Denon receiver without a trigger output, and want to trigger a Buckeye amp and an SVS subwoofer to come on and off with the receiver. So I purchased a TrickleStar power strip and this 12V 500mA DC Power Supply AC Adapter with 3.5 mm plug from PartsExpress. I thought I would plug the receiver into the control outlet and use it to turn that adapter on and off. Since it already has a 3.5mm plug it fits the trigger input. But feeling cautious before plugging it into my gear, I tested the voltage with a multimeter. It reads 18V rather than 12V. I did a bit of Google research and it sounds like this is typical of an unregulated power supply (something I don't know anything about). Apparently it's not uncommon to read a higher voltage with no load. Is an unregulated power supply an issue in this situation? Just trying not to fry my amp and subwoofer.

 

[DVDdoug]

I'd say don't chance it. The odds are it would be OK but the cost of a failure is too great.

...I'm surprised you can still buy an unregulated supply.

 

[levimax]

Unless your multimeter is true RMS it is probably measuring peak to peak in which case multiply by .707 to get your RMS voltage which would be 12.7 volts. Confirm before you try it.

Edit: Calcification / Correction. Oscilloscopes read peak to peak, an "averaging" multimeter reads peak to peak and then uses a formula to convert to RMS which is only accurate for a pure clean sine waves. For an unregulated PS it is probably not going to be a clean sine wave so the "averaging" multimeter is going to read high and be inaccurate. If you have a true RMS meter this is not an issue.

 

[Blurmwood]

Thanks both. Presumably one of these would be safer: https://emotiva.com/products/et-3-trigger-expansion-module
Just seems like a lot of money to get my amp and subwoofer to turn off and on. They both have auto-on, but sometimes in quiet parts of shows, the amp turns itself off.

 

[PristineSound]

I built my own WiFi controlled remote trigger with commodity parts from Amazon and AliExpress.

This is the core part, you will need a power supply and a case, which can be purchased on Amazon or AliExpress.

Here is the Android interface

 

[Devnull]

Put a load across the output of the power supply and then remeasure the output. A 47k resistor would work as a load

 

[Jukka]

Unless your multimeter is true RMS it is probably measuring peak to peak in which case multiply by .707 to get your RMS voltage which would be 12.7 volts. Confirm before you try it.

Edit: Calcification / Correction. Oscilloscopes read peak to peak, an "averaging" multimeter reads peak to peak and then uses a formula to convert to RMS which is only accurate for a pure clean sine waves. For an unregulated PS it is probably not going to be a clean sine wave so the "averaging" multimeter is going to read high and be inaccurate. If you have a true RMS meter this is not an issue.

But it says DC, so RMS measurement doesn't apply?

I too have been dealing with trigger signals and lately 12V DC fans, that run from quite similar power sources. My problem is that none of my devices give it trigger, but many would take in. I've used old phone chargers, usb power circuits (PD/Quick Charge etc) and step-up converters to create 12 V DC signal generators. All these parts are available at big online shops for fairly low prices.

But sure, simple power supply is a better bet and cheaper if you need just one. In some cases a power strip with a on/off switch is still the best solution for me and not a burden because it's switched on and off only once in a day, and not even every day.

 

[john61ct]

BobWire, highly reco switching devices, audio sensing outputs a trigger