Help Me Set Up A Relay

**Curiosity** · 09-10-2009, 01:37 AM

You're going to find that the relay takes more power than 3 RFP amps. Let's make it simpler.

A single transistor can amplify the power. The 3904 is a general purpose so if you can find any NPN local or online we can look up the specs. Most should work. It would hook up like so.

**Maheriano** · 09-10-2009, 05:48 PM

This? How do I hook up something like that? Just solder the 3 pins the way you showed in the diagram?

**Curiosity** · 09-10-2009, 06:06 PM

Yep. Basically. That's an NPN with at least 100mA collector current right?

Base to J6
Collector to 12V (battery or PSU output)
Emitter to amplifiers

**Maheriano** · 09-10-2009, 08:03 PM

Well I went to The Source and bought everything listed. I got an auto relay which is 12 volt in case I need to go the relay route. I also got some NPN-Type Switching Transistors that look just like the picture I posted. The back information says:
Silicon - NPN
Typical - 200

Maximum Ratings:
VCE - 30V
IC - 800mA
Dissipation - 1.8W

Is this it?

Here's a link to it: http://www.thesource.ca/estore/produ...ine&tab=1#more

**Curiosity** · 09-10-2009, 09:19 PM

That's it.

**Maheriano** · 09-10-2009, 10:29 PM

You are definitely a genius, I believe we just became the first members to post a solution to this problem with the M2-ATX, it worked perfect! I hooked up one of those transistors and I'm now typing this from my laptop in the trunk of my car looking at my 2 amplifiers running beautifully. Thanks for your help, to pay it forward I'm going to make up a D.I.Y. tutorial to show others how it's done.

So now how can I mount this transistor safely? Like where can I put it so it's not banging around? Maybe just use heat shrink tubing so the pins aren't exposed and let it lay wherever? Or is there some way to secure it? If so, where?

Also, Mini-Box should take a look at this, they can put one of these 10 cent transistors on the board and save people the headache.

**Curiosity** · 09-10-2009, 10:38 PM

Yeah, they could have just used a better output circuit. Heatshrink should do well as long as the leads don't bend too much or get pulled hard. Small shrink over each lead and a larger one over the whole thing as a stress relief. Might be easy to solder it inside the box depending how it's laid out or replace a lower power transistor if that's what it is, but that'll do.

**Maheriano** · 09-11-2009, 01:02 AM

It's all hooked up now, just got to throw the subwoofer in tomorrow and pound some Dr. Dre to find out how it handles it. All I know now is the amp is on so I'm expecting it to work.