CurtPalme.com Home Theater Forum

ecrabb · Posted: Mon Oct 27, 2008 10:56 pm Post subject: 12v trigger options...

I need a little help from you electronics propeller heads.

I need to build or buy a box so I can turn my three Crown amps on and on off with my prepro remote. The Crowns draw 500w max, so about 12.5A for all 3. I was looking at Rat Shack relays with a 12v coil and heavy duty switched sections, and I found this one:

http://www.radioshack.com/product/index.jsp?productId=2049722

It's a 10A DPDT, so I'd need more than one (ideally). Figured I could just use three of them so each amp would have it's own relay. (I know I could use two and use 2 poles on one, and one pole on another, or possibly even just one.) But, I like to overbuild stuff, anyway...

But, then I noticed that the coil draws 130mA. The trigger output on the Integra prepro is rated for 100mA max. Probably not a good idea to use the Integra's output to actually power the coil relay, right? Must stuff probably just tests for the presence of 12v, but doesn't really load the trigger output, right?

Instead, could I use a small micro relay - small enough that the Integra would drive it - on concert with a small 12v power supply to drive the coils in the larger relays? So, the trigger output on the prepro would drive the coils on the micro relay - the load is only 37.5mA. Then, the secondary on the micro relay closes the circuit on the other three larger relays where a small DC power supply - say 500mA - would drive the coil on the three big relays that had the line AC on them.

http://www.radioshack.com/product/index.jsp?productId=2062481

I know I could also use a transistor on the low voltage side and let the Integra drive the junction, but I don't know enough about circuit design to know where to put isolation, etc. so the whole thing doesn't melt down if something goes wrong. So, that's probably out...

I could also just buy a Panamax M8-HT-PRO "power conditioner" power strip, which has a built-in trigger... But, it's $150... and that seems to be the cheapest option I can find. Middle Atlantic makes a nice stand-alone 20A module for just under $100, but it only has two outlets - so I'd need two if I didn't want a cheesy outlet expander situation. Argghhh... They go up from there.

I could probably build something pretty decent for <$50, I'd imagine.

What do you guys think?

Thanks,
SC

Axatax · Posted: Mon Oct 27, 2008 11:17 pm Post subject:

You can "cheat", and replace (or augment) the mechanical switch on a power strip with a relay which is closed by 12V trigger from the Integra.

Tom.W · Joined: 09 Mar 2006 Posts: 6635

This is pretty cool...

http://www.electronickits.com/kit/complete/elec/ck1615.htm

Tom.W · Joined: 09 Mar 2006 Posts: 6635

You could also use a switched outlet on your receiver or preamp to power a 12 volt transformer to switch the main power relays on and off.

**Curt Palme** · Posted: Tue Oct 28, 2008 12:54 am Post subject:

You need this:

http://en.wikipedia.org/wiki/Solid_state_relay

Back when I thought I could build everything better than the manufacturers (and a lot of times my stoned designer/installer did!) we used those in AC switching packs all the time when we did nightclub installs.

Here's one place to buy them:

http://search.digikey.com/scripts/DkSearch/dksus.dll

Sheeet, they have gotten expensive! Send me an email, I might have a couple lying around...15 amp, 110 volt

ecrabb · Posted: Tue Oct 28, 2008 4:32 am Post subject:

Thanks for the help, guys. Tom, the reason I didn't just go the switched outlet route is because the prepro has a delayed turn-on feature for the 12v triggers. So, the 12v triggers turn on 1,2,3, etc. seconds AFTER turning on the prepro to avoid thump. Oh, that and the fact the prepro doesn't HAVE a switched outlet. Wink

Eventually, I'll use the 12v triggers on my AMX controller, but who knows when I'll get that thing running. Just too damn busy. So, I wanna whack something quick together I can use so the prepro will drive the power amps.

As an alternative, I did find a nice rackable Belkin power conditioner for ~$130 that should do the job nicely. I'm sure I'd have well over $50 in cord, relays, box and outlets if I go the DIY route. This way, the work is done and I don't have to dink around with the Dremel and solder iron for a couple of hours.

Thanks, Curt - I'll do a little more looking and if I decide to go DIY, I'll email you.

SC

ecrabb · Posted: Wed Oct 29, 2008 9:36 pm Post subject:

Guys

OK, I have a new idea and would like your opinion...

In thinking about building something, the numbers keep adding up - $50 plus, and it'll certainly look a little cheesy in the back of my rack in some Home Depot J-box contraption. OTOH, anything commercial with a 12v trigger is at least $100 - more like $130.

As an aside, if you wanted something nice to start with, Furman makes a nice rack-mount PDU w/10 outlets for $30 - the D10-PFP:
http://www.aiconsol.com/d10-pfp-furman.html

So, I was scrounging around in my stash downstairs, and remembered I had an old Niles AC3 I got with a big lot of equipment when I bought my HT recliners. That's cool, because the AC3 is about $125 new. The only drawback is it only has two switched outlets and one that's always hot. I need 3 switched outlets. I know I could use a strip or an outlet multiplier, but I'm trying to keep my rack clean here, right?

Well, I cracked the AC3 open, and it'll be really simple to mod it to switch all 3 outlets - I just wanted to see what you guys thought would be the best way.

I could drill a hole through the PC board next to the other two, but I'd have to remove the solder mask and there's no pad to speak of, so I'd be removing trace area. I don't like that idea.

The best way I thought of was making a "bus bar" out of a piece of 14-ga copper with the insulation only removed in strategic locations, and just soldering and capping the end of the bar to the (currently) unswitched outlet's hot lead.

Look OK to you guys?

Thanks,
SC

**AnalogRocks** · Posted: Wed Oct 29, 2008 11:43 pm Post subject:

You don't just want to jumper to the unswitched outlet and disconect and cap the old unswitched wires? Seem's it woulb be easier.

ecrabb · Posted: Thu Oct 30, 2008 3:56 am Post subject:

Hmm... I guess I figured if Niles ran each outlet pack to it's own pad on the board and didn't use jumpers, I shouldn't, either. I was concerned maybe the trace wasn't designed to handle the whole 15A the box is rated for, but then I guess my mod wouldn't change that, would it?

I also assumed I wouldn't want to mess around near the outlets themselves because of the nylon (wouldn't hold up to well to the heat from the iron, would it?

I guess I could just cut the hot to the unswitched outlet, cut the hot to the adjacent switched outlet, and solder them all together and screw a nut on, couldn't I? I suppose the 14 ga wire used on a single outlet is designed to handle a 15A load all on its own... so two amps on one hot isn't an issue, is it?

Duh.

SC

**AnalogRocks** · Posted: Thu Oct 30, 2008 4:31 am Post subject:

How much do the amps draw?

ecrabb · Posted: Thu Oct 30, 2008 5:01 am Post subject:

500W x 3 amps or 1500w - or about 12.5A. Of course, that's peak, and these are audio amps we're talking about, so they'd only over draw that much for very brief durations... As in fractions of a second. Turn-on would probably be the heaviest instantaneous draw of all, but that's probably only for 1/100 of a second or something. Even during really loud scenes at close to reference volume, I bet each amp would probably be drawing half its rated power, or about 6-8 amps.

SC

**AnalogRocks** · Posted: Thu Oct 30, 2008 5:10 am Post subject:

There you go you should be fine. You know you're drawing too much power off the AC line when your TV screen gets smaller.

You have it all figured out already.

jask · Joined: 17 Mar 2006 Posts: 10187 Location: kamloops BC

check the rating on the relay.

ecrabb · Posted: Thu Oct 30, 2008 11:13 am Post subject:

I did - it's a big'un. Huge, actually. 30A/250v. So, no prob there for sure!

SC