12V Trigger specifications/standards

[TedT]

Hi,
I am in the process of modifying an amplifier that does not have a 12V trigger input. I am trying to decide if I can run the relay directly from the 12V trigger or do I need to add a small power supply in the amp to run the standby mode and drive the relay?

I can not find any documentation of a "trigger standard" as to voltage or current. Is there any guaranteed voltage or current level at all 12V trigger outputs?

Thanks for your help - I am in China and any info would be appreciated!
TedT

[brucek]

I am trying to decide if I can run the relay directly from the 12V trigger

Not really common practice to do so.

When you have found the suitable relay that can handle the 15amps and voltage >~125volts you'll be switching, then determine the coil current required from its coil resistance spec. You'll find that a relay of this size usually requires being driven from a transistor or another smaller relay. Don't forget to back bias the coils with diodes.

You can certainly use an internal 12volts found in the amplifier to drive these parts.

A 12volt trigger would generally be able to source about 80 ma. That spec would be available with the equipment you'll use to send the trigger from...

brucek

[TedT]

Hi,
The 12V in the amp is not available unless the amp is turned on, so a small standby power supply is required.

Sounds like the 12V direct drive method will be difficult, so I will need to add a standup supply.

Thanks
Ted

[brucek]

Sounds like the 12V direct drive method will be difficult, so I will need to add a standup supply

Why not just buy a product like this from Xantech instead of modifying your amplifier?

brucek

[TedT]

Mainly because I am designing it for a production amplifier we are building here in China...
Thanks
TedT

[brucek]

I am designing it for a production amplifier we are building here in China

a small standby power supply is required

Well, normally you wouldn't want a supply to be running when the power is off.

Generally you would use a zero crossing triac such as this MOC3041 (download its spec sheet for sample circuits) that would switch the AC hot on. This allows you to defeat the amplifiers trigger system with the front panel switch and also enable it without any current being drawn in standby.

The opto-isolator trigger input of the triac could easily be driven from a small LDO voltage regulator that uses the external trigger voltage as its input and could accept a wide voltage range of triggers in DC or AC(rectify the input with simple diodes).

This way there is no power supply on in standby........

brucek

[TedT]

Hi Bruce,

OK, thanks for the advice. I'll pass the datasheet and suggestion to my engineer. Is the schematic in the datasheet, or do you have a real working circuit?

Thanks
TedT

[brucek]

Is the schematic in the datasheet

The url of the triac in my post has a link to the data sheet. I assure you an engineer understands using a triac as an AC switch. Since you have to ensure the trigger circuit works with a wide range of external triggers, a voltage regulator used as a trigger for the triac is quite common. A voltage regulator will easily work with voltages from 4 -15volts and will output a fixed trigger voltage to the triac. If you rectify the input, it will also accept ac triggers. That will cover all form of triggers from many types of equipment.

Standby supplies are usually only used when there is a need for a remore control. In the case of an amplifier it is far easier and less costly in parts to use a triac and regulator when all you need is a trigger circuit.

brucek

[TedT]

Hi Bruce,

OK, thanks for your help.

TedT

[MdntTrain]

Bruce, I posted a related question about controlling an AC outlet from a 12v trigger to turn on a Panamax. Problem is, the AC1 thing you suggested above is expensive. Have you any low cost solutions, such as perhaps some 12v trigger power strip? Thanks much, ~ J

[brucek]

such as perhaps some 12v trigger power strip?

I remember looking around a while ago for a power strip controlled by a trigger and only came up with the Xantech product. I would have thought there'd be lots of inexpensive decices like that, but I never found any.

Maybe someone else knows of a product?

brucek

[MdntTrain]

Bruce, the only thing I had found prior to seeing your post re the AC1 was this:

http://www.onecall.com/ProductDetails.aspx?id=24936

Available elsewhere too.

An even more expensive solution than the AC1, but much more versatile.

~ J

[brucek]

An even more expensive solution than the AC1, but much more versatile.

You are getting quite a bit for the price. Looks like a nice unit.

brucek

[MdntTrain]

Bruce,

I think I figured out a solution... might surprise you.

On a notion that the AC master control of the panamax didn't really need 120VAC to trigger, I connected a variac to it and observed that the unit would trigger with very low voltage.. around 7VAC.

Then, another whim, I connected a 9volt battery across the two AC cord terminals (just the right width).. and the 9VDC also triggered the panamax!

I then measured the current requirement at 0.37mA... or 370uA... which according to what you wrote elsewhere should easily be handled by a regular 12V trigger.

So it would appear all I need to do is make my own cable with an AC socket on one end, and the 12v trigger plug on the other. Simple, cheap solution.

~ J

[brucek]

might surprise you

It does surprise me. Too funny... I guess it's a very high input impedance (as evidenced by the draw), and so just about anything will trigger it. Great....

brucek