Trouble with LED button wiring

[ShadeValryn]

I'm trying to use a 12V 500ma power supply to power 8 LED buttons (coin and start for 4 players).  Splicing it and testing it seemed to work okay on the one button.  I had some of these EZ Off harnesses from paradise arcade shop so I figured I'd give them a try too.  I managed to get it working to where the light turns off when I press the button, but I'm a little unsure now where to put the ground wire that typically daisy chained from another button to this one.  The post for the signal wire is open and I can see obviously where to connect that then go back to the iPac 4, but I was just unsure what to do now that the LED ground is now occupying that microswitch common ground post.  Do I connect it to the ground that is daisy chained all the way down to the iPac 4?  Do I daisy chain it somehow to the other LED buttons then back to the 12V power supply and just keep the signal wire seperate that goes to the ipac 4?  Pictures below as to how my little test setup is.  Any advice on where to put that ground?  Does the signal wire require a ground return to the ipac4 or can it just have a ground from the 12v power supply?

[PL1]

Here's one way to wire it so the LED turns off when the button is pushed.  That is the effect you're going for, right?

The five red dots are the 5 QD terminals (2 LED socket + 3 microswitch)



NOTE: This won't work with an x-arcade encoder which uses a series of isolated commons (not tied to ground) or a ZD encoder. (active high device)

Using a ground from another source works with KADE, Xin-Mo, and Mini-Pac -- tested/confirmed by shorting to ground from a different USB cable or computer PSU frame.

You can use the ground from the LED lighting harness since "ground is ground."

It should also work with an IPac, Keywiz and any other active-low encoder that uses a real ground.


Scott

[ShadeValryn]

So I can connect the ground back into the daisy chain of ground that goes back into the ipac no problem?

[ShadeValryn]

Also, I just tested my sample with a multimeter and fond the bulb to be drawing 13.5v and 1.83A.  The power supply is rated at 500mA, should I be concerned?

EDIT: I feel like an idiot, i was testing the amperage wrong.  it's 1mA

[PL1]

So I can connect the ground back into the daisy chain of ground that goes back into the ipac no problem?

Electrons have a negative charge.  They move from ground to positive.

Picture drinking through a straw
-- Ground is lilke a cup full of liquid and the straw is the circuit
-- When you suck on the straw, (apply a positive voltage) the liquid (electrons) flow through the straw (circuit)
-- If the straw is cut in the middle, you get an open circuit

The ground of the LED power supply will provide the few mA of electrons that the encoder draws -- no need to directly tie the LED supply ground and IPAC ground together.

If you don't believe me, short an encoder input to your PC power supply case and the encoder will output the corresponding keystroke.   

If something goes wrong with the LED supply ground wire and the LED daisy chain ground is directly tied to the IPac ground, the IPac ground will have to supply the current for both the LEDs and the encoder which could damage the encoder, depending on how much current the LEDs draw.

Instead of a big straw (LED power supply ground) and a little straw (IPac ground), the little straw would have to handle the full amount of liquid.

For the switches that you want to turn off when you press the buttons, wire them like the diagram above and use the ground from the LED power supply.

Also, I just tested my sample with a multimeter and fond the bulb to be drawing 13.5v and 1.83A.  The power supply is rated at 500mA, should I be concerned?

EDIT: I feel like an idiot, i was testing the amperage wrong.  it's 1mA

1mA doesn't sound right at all -- should be closer to 20mA for 12v LEDs with a 12v supply.   

Did you put your meter in series or parallel with the circuit to be measured?

Your amperage test setup must be in series (like below) so all the current has to flow through the meter. (all liquid through one measuring straw)

+V----red lead--multimeter--black lead----LED----ground

  or

+V----LED----red lead--multimeter--black lead----ground

Any path around the meter like putting it in parallel (below) will give a false amperage reading because some current will flow through the meter and some will flow through the LED. (drinking through two straws, but only one measures how much liquid is going through it)

        red lead--multimeter--black lead
          |                                          |
+V-----------------LED-------------------ground


Scott

[ShadeValryn]

Here's one way to wire it so the LED turns off when the button is pushed.  That is the effect you're going for, right?

The five red dots are the 5 QD terminals (2 LED socket + 3 microswitch)



NOTE: This won't work with an x-arcade encoder which uses a series of isolated commons (not tied to ground) or a ZD encoder. (active high device)

Using a ground from another source works with KADE, Xin-Mo, and Mini-Pac -- tested/confirmed by shorting to ground from a different USB cable or computer PSU frame.

You can use the ground from the LED lighting harness since "ground is ground."

It should also work with an IPac, Keywiz and any other active-low encoder that uses a real ground.


Scott

Okay, I've wired it like this, and the ground is from the power supply ground so it can actually handle the voltage (grounding the buttons to the ipac results in tripping the overvolt protection).  Now my buttons all light up just fine, and turn off when pressed, but now whenever the button is pressed, the ground that is no longer there so the LED shuts off also is preventing the button from sending a signal to the ipac that "hey! i'm being pressed!".  Any thoughts?

[PL1]

Okay, I've wired it like this, and the ground is from the power supply ground so it can actually handle the voltage (grounding the buttons to the ipac results in tripping the overvolt protection).  Now my buttons all light up just fine, and turn off when pressed, but now whenever the button is pressed, the ground that is no longer there so the LED shuts off also is preventing the button from sending a signal to the ipac that "hey! i'm being pressed!".  Any thoughts?

I think I've figured this out.

I was using a computer PSU molex where the ground is tied to the PSU case.

Your wall wart probably has a 2 prong plug so the ground is probably isolated.   

Sorry I didn't think about that earlier.


Scott

[ShadeValryn]

Okay, I've wired it like this, and the ground is from the power supply ground so it can actually handle the voltage (grounding the buttons to the ipac results in tripping the overvolt protection).  Now my buttons all light up just fine, and turn off when pressed, but now whenever the button is pressed, the ground that is no longer there so the LED shuts off also is preventing the button from sending a signal to the ipac that "hey! i'm being pressed!".  Any thoughts?

I think I've figured this out.

I was using a computer PSU molex where the ground is tied to the PSU case.

Your wall wart probably has a 2 prong plug so the ground is probably isolated.   

Sorry I didn't think about that earlier.


Scott

So any advice as to what I could use for a constant ground that can handle the 12v led's ground? 

[PL1]

If you are using a regualr computer PSU, why not use the 12v + ground (yellow and black) from the 4-pin molex or SATA power cable?
(use an extender/splitter cable if you don't want to cut the cable on the PSU)

 

If you're using a laptop with an unused HDD compartment, you can probably find an adapter/extender cable to tap into the SATA power connector.


Scott

[ShadeValryn]

If you are using a regualr computer PSU, why not use the 12v + ground (yellow and black) from the 4-pin molex or SATA power cable?
(use an extender/splitter cable if you don't want to cut the cable on the PSU)

 

If you're using a laptop with an unused HDD compartment, you can probably find an adapter/extender cable to tap into the SATA power connector.


Scott

Yeah... the thing is, i'm actually going to put a gigabyte brix pro into the control panel, effectively turning it into a portable arcade station.  Any other ideas on how to ground it?

[PL1]

Yeah... the thing is, i'm actually going to put a gigabyte brix pro into the control panel, effectively turning it into a portable arcade station.  Any other ideas on how to ground it?

Did you already buy it?

This review mentions potential thermal and fan noise issues.   

If you already have the brix pro, you'll need to test to see if there is some sort of ground isolation between the input power and USB ground.

With power removed, check for continuity between the USB port shell and the outer ring  of the power input socket.

If there is continuity, you should be able to piggy-back on the input voltage using a splitter cable and a voltage divider circuit to turn the 19VDC input into 12VDC for the LEDs.

If no continuity, I recommend that you consider dropping the "buttons turn off when pressed" feature and just have them lit all the time using the wall-wart or other suitable power source.


Scott

[ShadeValryn]

Yeah... the thing is, i'm actually going to put a gigabyte brix pro into the control panel, effectively turning it into a portable arcade station.  Any other ideas on how to ground it?

Did you already buy it?

This review mentions potential thermal and fan noise issues.   

If you already have the brix pro, you'll need to test to see if there is some sort of ground isolation between the input power and USB ground.

With power removed, check for continuity between the USB port shell and the outer ring  of the power input socket.

If there is continuity, you should be able to piggy-back on the input voltage using a splitter cable and a voltage divider circuit to turn the 19VDC input into 12VDC for the LEDs.

If no continuity, I recommend that you consider dropping the "buttons turn off when pressed" feature and just have them lit all the time using the wall-wart or other suitable power source.


Scott

I have not actually bought it, and I have considered trying to build a mini itx system into the control panel instead and install a mesh in the front of the control panel with a line of 80mm fans.  Maybe I'll go that route so I can have an easier time with this LED issue since I'll have a regular ATX PSU.

[yotsuya]

Hadn't heard of the Brix before. Seems like a lot of coin to drop on an emulation station, but you WOULD be near the top of the technology curve.

[mvolke1]

If you wanted to say heck with it, you could just wire each individual LED to a bunch and twist it together. You'll have more wires, but you could save yourself some headaches.

[ShadeValryn]

Hadn't heard of the Brix before. Seems like a lot of coin to drop on an emulation station, but you WOULD be near the top of the technology curve.

Well the i5 brix pro with the 4570r would handle dolphin perfectly.  At that price point, it's not too bad to achieve that goal.  The 760 version is the one that thermal throttles sooooo badly.  But for just emulating, the one I mentioned should do okay inside the control panel.  I still might cut some exhaust ports toward the front though.