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Automatically Powering on Pro Amps via Relay (guide w/ pics)

post #1 of 319
Thread Starter 

Update: I ended up using amplifiers that required 30a service. I am now using the following relays and they work great. Omron G7L-1A-TUB-J-CB-DC12

According to the datasheet, the Omron G7L-1A-TUBJ-CB-DC12 consumes 158ma (1.9w)

 


I recently purchased two Marathon MA-5050 amps. The idea of having to power on and off gear with a toggle switch seemed archaic to me, so I sought out a solution. This is nothing new, or novel, but I've seen the topic come up enough I figured I would post up some pictures and explanations.

At first I was going to use a mechanical relay, but decided to use a solid state relay instead. Browsing the Mouser website it seemed they have a bunch of high current solid state relays to choose from. I went with the Omron G3NE-220T-US 240V/20A relay with a 12VDC trigger. Since my receiver has 12VDC trigger outputs, this simplifies things a bit. If your receiver doesn't have 12V triggers, one alternative is to use the receivers switched outlet if it has one, and a relay with an AC trigger such as the Omron G3NA-220B AC100-120.

The parts I used for this are below. You can get most of these at local stores (radio shack, home depot, etc). The only special order item here is the solid state relay.
G3NE-220T-US-DC12 240V/20A 12VDC Trigger Relay or if using a switched AC outlet G3NA-220B AC100-120
12-Gauge Insulated Female Quick Disconnects
.110 Female Quick Disconnects
3.5mm Mono Plug to RCA Jack Adapter
12ft Male to Male RCA Cable
15ft 12gauge 2 conductor SJOOW Cable (can get this from Home Depot or any other store like that)
NEMA 5-15P Plug (Home Depot)
Square Box (metal) (Home Depot)
Single Gange Square Box Cover (Home Depot)
20A Outlet (Home Depot)
Cable Clamp (I used a 1/2" knockout plug, but can't find a link online, HD)
#4 bolts and nuts (2)

This is what the relays look like. There are two here since I built two of these boxes.



The first step was to mount the relay into the square box. The backs of the relays are metal so they can dissipate heat. I drilled two holes and mounted it up with some #6 bolts and nuts I had. Make sure its mounted flat so that it can use the box as a heat sink.



Once the relay is mounted up, you can wire everything up. Ground to green, neutral(white) to white(silver) screw, and hot (black) to brass screw. Make sure you have everything wired correctly and the same on both the plug and the outlet.



The hot wire will be cut, and run through the relay using the 12 gauge quick disconnects, instead of being directly connected to the outlet. The small terminals on the relay are for the 12VDC trigger, and the larger terminals are for the load (AC outlet). I cut the end off of an RCA cable, which I am using for the trigger wiring, and crimped and soldered some female mini quick disconnects on. I then shrink wrapped them since finding insulated versions in this size is near impossible. Red goes to +, and white goes to -. Make sure (with a voltmeter) that you don't have any current either shorting or leaking to the trigger wires before plugging it into your receiver. Bad things will happen if you feed a 120VAC current into the triggers on your receiver. Those who are paranoid may want to put inline fuses on the trigger wires.



This is the box all closed up and ready to go.



I'm using the Mono 3.5mm to RCA adapter to connect this to the 12V trigger on my receiver.



Here it is with the amp off.



And now with the amp on.

 


Edited by notnyt - 1/26/14 at 10:41pm
post #2 of 319
Omg, thank you! I need to put one of these together real soon but this thread would be a valuable resource for everybody.

Subscribed.
post #3 of 319
cool
post #4 of 319
This looks like a sticky to me.
post #5 of 319
Great contribution!

Great resource for all!
post #6 of 319
Sweet! a project for this weekend, thanks!
post #7 of 319
Dude, you rock. Awesome contribution to the forum. I guarantee that lots of people will be building these for themselves (including me).
post #8 of 319
Are you absolutely sure this is going to work? I mean I don't see any notes about cryogenically treating the wire and that looks like a standard box that can be bought at Home Depot! And the wire you used....will that get you all the current you need? I don't see any flashing covering or anything that would make the cost go up!

Seriously, you did a great job! That is the cool thing about DIY. Finding a way around a problem only takes the one person to inspire the others with one brilliant idea! Great job!
post #9 of 319
Great stuff, I'm signing on.

Agreed about the 'sticky' part. It would be nice to have a sticky thread stuffed with these types of helpful threads.
post #10 of 319
Awesome! Thanks for posting this.
post #11 of 319
I did a similar thing with my Class D amps (2x500W with 400 VA toroidal transformer) and DCX2496 using two of these:

http://search.digikey.com/scripts/Dk...&name=PB443-ND

Simple, cheap and works fine. The relays are rated for 14A and the control coil for 18.5 mA. I thought about using a solid state relay but decided I didn't need it. Those ones you found look pretty nice, though.
post #12 of 319
how much current do each of the relays draw from the 12V source? Just curious because some receivers might not be able to put out 250 mA on the trigger line like yours does.

-John
post #13 of 319
Awesome. You have brought some fun here lately

I have grown lazy and I simply leave both of my EP4000s on all the time... power consuming, loud, and collecting lots of dust in the filters. Is there an easy-to-do for a receiver to EP4000? Looks like a lot of work and purchases there.
post #14 of 319
Thread Starter 
Quote:
Originally Posted by martiandancer316 View Post

how much current do each of the relays draw from the 12V source? Just curious because some receivers might not be able to put out 250 mA on the trigger line like yours does.

-John

One of the benefits of solid state relays is very low trigger current.
post #15 of 319
Thread Starter 
Quote:
Originally Posted by kryptonitewhite View Post

Awesome. You have brought some fun here lately

I have grown lazy and I simply leave both of my EP4000s on all the time... power consuming, loud, and collecting lots of dust in the filters. Is there an easy-to-do for a receiver to EP4000? Looks like a lot of work and purchases there.

That's what this thread is, I'm not sure how you missed that point . It's 20 minutes of work. You can get most of the supplies from home depot, and the most expensive part there is the SJ cord. The only item you won't be able to find local is the solid state relay. If your receiver is missing 12V trigger outputs, but has a switched outlet on the back, you can plug in a dc power adapter and use that to power the relay. They come in different input voltages, so you have some flexibility with what you can trigger it with. Alternatively, you can use the switched outlet to power an AC relay such as G3NA-220B AC100-120. If you're running your amp and receiver off the same circuit which I think you might have said you are, you can just get one of those smart strips, but that isn't very DIY .
post #16 of 319
I did a similar thing a few years back but instead of powering it with the 12 volt trigger of my Denon I installed it's own low voltage remote control on it.I noticed one thing with solid state relays,when you power them down there is still some residual low voltage left on them that drains slowly... The reason for having it's own remote is because sometimes my wife watches movies and she prefers not to turn on the power amp....

post #17 of 319
I had so many amps I needed to use delayed relays. Too big of a thump...
post #18 of 319
Thread Starter 
Quote:
Originally Posted by Kanaris View Post

I noticed one thing with solid state relays,when you power them down there is still some residual low voltage left on them that drains slowly...

I tested this with the Omron SSR I used. Voltage seemed to drop just about instantly as long as there was any form of load.
post #19 of 319
Great thread notnyt, I was meaning to post what I ended up building for my server rack of amps...

I was going to go with a SSR, but stereodude convinced me that mechanical was just fine and would not suffer from possible heat issues, and I also wouldn't have to worry about space concerns with a heat sink on the back of some of the SSR's with the higher amp rating as I needed to power up 6 x 4000w amps on 3 separate 30a circuits.

I ended up going with 3 of the omron 30 amp units...
There is barely any noise coming from these little guys when they are in the box, plus they are in the basement so I'll never hear them.
I still want to emphasize that they are extremely quiet - my D2v and plasma both make louder clicks turning on, so don't let that deter you from the mechanical....

Stole this pic from stereodude, as I forgot to snap a pic...


Relay fits nice and snug just under the outlets, you don't even need to fasten it down, but I used a small piece of double stick tape to secure it.
Even without the tape it didn't move around at all, its a nice tight fit, not too tight though.




I have rolls of some nice heavy duty shielded twisted pair wire around so I just used some of that for the 12v trigger wire....
sorry about this really awful pic, that was the only one I did of the finished product....


It was suggested by notnyt that I add a snubber to the relay - which will absorb those transient kicks that produce sparks and wear out the contacts in mechanical relays. Connect each side, one to the V power in, and the other side to the V power out of the relay. They are very inexpensive ($1 - $2 each) and he also gave me a link... Thank you notnyt...
RC Snubber / surge suppressor
post #20 of 319
Thread Starter 
The mechanical relay there should work fine, but I went with a solid state relay for a few reasons.

1) Size. Easily fits in a smaller box.
2) No need for a snubber. Without one you'll have some arcs every time the relay activates, which will wear away at the contacts or cause them to stick together.
3) Less chance of mechanical failure.

Mounting it to the box should act as a sufficient heat sink. I get my amps today, so I will leave them running through it in idle for a bit to see how it does.

I think once you get up to like 30A, that SSRs become a bit more expensive. You might want to look into adding a snubber circuit to those boxes
post #21 of 319
Yeah it was basically cost and heat for my main reasoning of going with the mechanicals. The heat sinks they were suggesting for the large SSR's were really quite big...

We have been using mechanical nema size 2, 3 and 4 - 3 phase motor starters for 40 years, and have never heard of snubbers... I'm no electrical genious, I know enough to be dangerous

I'm really out of the loop about snubbers, but I will have to see what those are all about, I took a quick glace around but didn't get much of an understanding of what they are designed to do, maybe you could explain.... Thanks
post #22 of 319
Thread Starter 
http://en.wikipedia.org/wiki/Snubber

Quote:


Snubbers are frequently used in electrical systems with an inductive load where the sudden interruption of current flow often leads to a sharp rise in voltage across the device creating the interruption. This sharp rise in voltage is a transient and can damage and lead to failure of the controlling device. A spark is likely to be generated (arcing), which can cause electromagnetic interference in other circuits. The snubber prevents this undesired voltage by conducting transient current around the device.
post #23 of 319
Thanks......
post #24 of 319
This really is Sticky worthy. High current amp switching is a must for automation, hats off to you for the thread and pics !!!

KG
post #25 of 319
I think that setup is a NEC code violation. You are required to have a barrier between low voltage and line voltage wiring to conform.
post #26 of 319
Thread Starter 
Quote:
Originally Posted by J_Palmer_Cass View Post

I think that setup is a NEC code violation. You are required to have a barrier between low voltage and line voltage wiring to conform.

Are you referring to 725.55? Can you elaborate? I guess to comply you would have to have a separate entrance for your low voltage, and a non-conductive barrier separating low and high voltage.
post #27 of 319
Quote:
Originally Posted by J_Palmer_Cass View Post

I think that setup is a NEC code violation. You are required to have a barrier between low voltage and line voltage wiring to conform.


I don't care....

My house, My rules.... works fine...
post #28 of 319
Quote:
Originally Posted by J_Palmer_Cass View Post

I think that setup is a NEC code violation. You are required to have a barrier between low voltage and line voltage wiring to conform.

+1

Not to be a buzzkill but there is a very good reason for this.
post #29 of 319
Thread Starter 
Quote:
Originally Posted by FOH View Post
+1

Not to be a buzzkill but there is a very good reason for this.
Unless you're posting what the issue is exactly, and a proper fix, it isn't really helping
post #30 of 319
Are devices plugged into the wall outlet, ie not permanently directly wired to the mains covered by the NEC?

If using a mechanical relay, use a flyback diode on the coil especially if being driven from an AVR etc 12V trigger. See snubber link earlier.
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AVS › AVS Forum › Audio › DIY Speakers and Subs › Automatically Powering on Pro Amps via Relay (guide w/ pics)