Problems with OSCAR Superbright LED and Hagstrom KE72

[Sasquatch!]

I built OSCAR's Super Bright LED driver with I-PAC connections driver board for my Hagstrom KE72-T.  I put it together as shown on OSCAR's site, with only the following exceptions:

• I used Radio Shack 2N4401 transistors instead of the 2N4402 transistors that OSCAR used (it's all Radio Shack had, and the specs are pretty much the same)
  
• I used 100 Ohm resistors in between the transistors and the LEDs instead of the 150 Ohm resistors that OSCAR used, because I'm using blue LEDs instead of red like OSCAR did, and the blue LEDs put out 3.5V forward voltage ([5V

[froggerman]

Hi Sasquatch,

Have you check this link http://erikruud.freeservers.com/arcade/buttons.html ?
He has a little calculator you can use to check that you have used the correct current limiting resistor. My blue LEDs use a 68 ohm resistor.

As far as the transistors are concerned, you are similar but opposite transistors. Oscar has specified 2N4402 which are PNP transistors, and the 2N4401 is an NPN transistor. In simple terms this is sort of like having a diode in the wrong way around. You either need to change the circuit around to use the transisotrs you purchased or get some PNP transistors.

I hope this helps a bit. I can't explain why you are having the problem with the KE72-T. I would test the driver board you have made simply by grounding the connection that is supposed to go to the CapsLock and NumLock. This sould turn the LEDs on. Removing the ground should turn the LED off.

[Sasquatch!]

Hi Sasquatch,

Have you check this link http://erikruud.freeservers.com/arcade/buttons.html ?
He has a little calculator you can use to check that you have used the correct current limiting resistor. My blue LEDs use a 68 ohm resistor.

Yep, I've seen it.  ErikRudd lives like a couple of towns over.    I'm almost positive my limiting resistor is correct at 75 Ohms though.

As far as the transistors are concerned, you are similar but opposite transistors. Oscar has specified 2N4402 which are PNP transistors, and the 2N4401 is an NPN transistor. In simple terms this is sort of like having a diode in the wrong way around. You either need to change the circuit around to use the transisotrs you purchased or get some PNP transistors.

WHOOPS!  I didn't know that there was such a difference.  I don't know how I'd change the circuit around, so I'll probably just try to locate some PNP transistors.  Radio shack's selection is so damn tiny though, dammit.  Hmmm.  

I hope this helps a bit. I can't explain why you are having the problem with the KE72-T. I would test the driver board you have made simply by grounding the connection that is supposed to go to the CapsLock and NumLock. This sould turn the LEDs on. Removing the ground should turn the LED off.

That actually helped a lot, so thanks much!

[knuttz]

I believe you can just flip the transistors around to fix your PNP, NPN problem.  That is flip the collector and emitter.

[Sasquatch!]

I believe you can just flip the transistors around to fix your PNP, NPN problem.  That is flip the collector and emitter.

Are you sure?  I don't know either way, but I'd kinda like to get a more definitive answer than "I believe".  

Otherwise, I might just get Amplifying Transistors Catalog #: 276-1604 from Radio Shack.  They have 350mW dissipation (versus the 625mW of the 2N4402 PNPs), but I don't think that should matter, should it?

[Sasquatch!]

I believe you can just flip the transistors around to fix your PNP, NPN problem.  That is flip the collector and emitter.

Just as a follow-up, I've been doing a little bit of reading on the subject, and this is WRONG.  It's not just a matter of flipping the collector and emitter around.

Anyways, I got the 276-1604 PNP transistors from Radio Shack, and the LED driver works great now.  So yay!

[ErikRuud]

I am glad to see you got it worked out.

Oscar's board is really a pretty cool.