DCDC-USB Connecting to power button?

**rodionsh** · 05-13-2011, 02:03 AM

Hi, I have a DCDC-USB power supply and a Zotac Mini-PC. The problem is that the power button on the Mini-PC has a led that is always on. If I connect directly to the power button it has a voltage output of about 3V depending on the color of the led, how do I get rid of the voltage so I don't fry the power supply?

**soundman98** · 05-13-2011, 05:33 PM

are you sure that the led is part of the same circuit as the switch? usually the led is integrated into the switch bezel, but use completely different wire traces.

**2k1Toaster** · 05-13-2011, 10:14 PM

Originally Posted by soundman98

are you sure that the led is part of the same circuit as the switch? usually the led is integrated into the switch bezel, but use completely different wire traces.

+1

I have seen the power LED run through the power-on trace before, but these are on OLD dinosaurs with MMX processors and Packard Bell logos...

**rodionsh** · 05-15-2011, 01:50 AM

I am almost sure the led is integrated into the power button circuit, it in located in the center of the button itself, the button only has 2 legs, positive and negative, maybe some kind of circuit to solder? By the way it's one of the latest mini-pcs from Zotac ZBOXHD-AD01.

**rodionsh** · 05-26-2011, 04:47 AM

Anyone have any ideas, I am really stuck

**soundman98** · 05-26-2011, 05:38 PM

pics might help.

**rodionsh** · 05-27-2011, 12:53 AM

Here are the photos of the Power Switch button

**nivanov** · 05-27-2011, 08:19 AM

Yeah, +1 for pics. I would be very surprised if there are indeed only 2 contacts coming from the button and they are used for LED power and POWER SW. Sometimes the contacts can be "under" the button so you wouldn't be able to see them. If you discover more contacts, I'd unplug your computer, attach an ohm meter to them and see which ones short when you press the button.

**soundman98** · 05-27-2011, 04:36 PM

to me, it looks like the power switch traces are completely different then the led traces. though, i have never measured the voltage of the power switch pins, so i can't tell you if the voltage is normal.

**rodionsh** · 05-28-2011, 06:15 AM

Originally Posted by nivanov

Yeah, +1 for pics. I would be very surprised if there are indeed only 2 contacts coming from the button and they are used for LED power and POWER SW. Sometimes the contacts can be "under" the button so you wouldn't be able to see them. If you discover more contacts, I'd unplug your computer, attach an ohm meter to them and see which ones short when you press the button.

I did what you suggested and the + pin is shorted to any ground on the board when the button is presed, what is also strange, is that there is a resistance of about 50 ohms between + pin and -pin