Could I fry my LedWiz if I...

[Kman-Sweden]

...wire up 5v to my LED's form a alternative power source to light some buttons when the PC is turned off?

To clarify:
I use a LedWiz and RGB-Drive™ Pushbutton Lighting modules from GGG to light my buttons while running Mame.
I planed to run some extra 5V's to some of 'em from another PSU while the Mame PC is turned off. (bypassing/not using the LedWiz)
Can I do it without killing my LedWiz and/or PC?

[BobA]

Using 5V power from another PS to run additional LEDs should not be a problem for your ledwiz.

[Havok]

Should be ok. In fact, external power is necessary if you are exceeding 500ma anyways...

[Kman-Sweden]

Thanks guys. Just wanted to be sure since the 5V is not going through the LedWiz "the normal way".

[RandyT]

You may want to show a schematic of what you are planning to do.  Unless you use a switch to completely disconnect the leds (and connect them to your external source) from the output of the LED-Wiz, it may be bad for the hardware.  An external diode to prevent backfeeding to the LED-Wiz, and maybe another on the external supply, might be prudent.

RandyT

[Kman-Sweden]

We'll see how long they last... I've soldered wires to the holes labeled 1 to 4 on the RGB-drive.
+5V to No:4 and GND to the others depending on desired color.

It's powered (and grounded) by another PSU than the PC.



When the "PC PSU" is turned ON, running Mame in Maximus Arcade, the LedWiz is calling all the shots.

When the "PC PSU" is OFF the "Extra PSU" powers the LED's in buttons 1-4 with constant +5V, making them light up in a predetermined colors (Red, Yellow, Green and Blue).
This is for my NeoGeo MVS... The NeoGeo is actually powered by a third PSU that only have power when the Extra PSU has power...
I'll post some pics when the project is completed. 

[Beley]

We'll see how long they last... I've soldered wires to the holes labeled 1 to 4 on the RGB-drive.
+5V to No:4 and GND to the others depending on desired color.

It's powered (and grounded) by another PSU than the PC.

The way you have it drawn it wont work, you have shorted the 3 outputs from the led wiz together, as RandyT said you would have to put diodes in to make it work as shown (put them where you have drawn the dashed Ground lines)

[Kman-Sweden]

An external diode to prevent backfeeding to the LED-Wiz, and maybe another on the external supply, might be prudent.

RandyT

On the +5V?

[Bobulus]

I don't think diodes on the ground lines would be the way to go, but either way...wouldn't the Ground on the Extra PSU be connect whether or not the Extra PSU is turned on? (Assuming you're not unplugging it all together) That would mean, for example, that if you've got a button set to be 'red' when the computer is turned off (by connecting the RGB-drive red ground to the Extra PSU ground), that even when the computer is on, the red part of the RGB will always be on.

I'm assuming Randy was talking about diodes on the 5V lines to prevent power from going from the Extra PSU, bypassing the resistors in the RGB-drive entirely, and directly into the LedWiz, which would probably be bad.

There's probably a more elegant way to do it, but seems like what would work would be to use transistors on the ground lines to open or close them based on the power coming off the PC-PSU 5V line.

* I only took one semester of electronics. My career is in biology. These guys are almost sure to know more than me. Listen to them.

[Kman-Sweden]

I don't think diodes on the ground lines would be the way to go, but either way...wouldn't the Ground on the Extra PSU be connect whether or not the Extra PSU is turned on? (Assuming you're not unplugging it all together) That would mean, for example, that if you've got a button set to be 'red' when the computer is turned off (by connecting the RGB-drive red ground to the Extra PSU ground), that even when the computer is on, the red part of the RGB will always be on.

I'm assuming Randy was talking about diodes on the 5V lines to prevent power from going from the Extra PSU, bypassing the resistors in the RGB-drive entirely, and directly into the LedWiz, which would probably be bad.

There's probably a more elegant way to do it, but seems like what would work would be to use transistors on the ground lines to open or close them based on the power coming off the PC-PSU 5V line.

* I only took one semester of electronics. My career is in biology. These guys are almost sure to know more than me. Listen to them.

I couldn't wrap my mind around the "diode on GND" either... I think I have to give his some more thought before hooking up the PC to it again...
All help would be appricated. 

[Bobulus]

If I'm understanding Randy correctly, you want to put diodes at the two places I drew orange arrows, so that electricity can flow to the RGB-drive from either power source, but not away from the RGB drive to the other power source.

If you already hooked it up and the buttons worked, I'm probably totally wrong on the ground issue.

[RandyT]

I'm not sure how you have the 5v connected to the LED-Wiz, but whether or not this is a "safe" configuration depends on whether there is a nice big diode on the output of both of the power supplies, and whether ground is being switched out when you switch from one supply to the other.  If ground is still connected, there is still the potential for current flow from one supply to the other, and possibly through the LED-Wiz as well.  Still, it would be a good idea to put diodes on the 5v lines to prevent current from flowing from one supply to the other, just in case they don't already have diodes on the outputs.

Obviously, this is an "unsupported" application, so I make no guarantees about any of it, one way or the other.  I just mentioned the diodes as a matter of "good practice" when trying to keep current where you want it and away from where you don't.

RandyT