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Super bright LED driver board for I-PAC

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RandyT:


--- Quote from: Sasquatch! on March 11, 2003, 08:12:03 pm ---M-M-M-MONSTER BUMP!

I actually have a question about the driver that OSCAR built: Why the separate 5V power supply?  Doesn't the IPAC supply 5V?  Just curious (and yes, I am an LED dummy).

--- End quote ---


I could let OSCAR answer this one...........Nahhh!  ;D

It's because you have a limited amount of current available on any device that plugs into a PS/2 or USB port.  The way the LED board was designed, you have all the +5 power of the power supply (less what the computer uses :) ) available for LEDs without worrying about blowing your keyboard fuse.

RandyT

Sasquatch!:


--- Quote from: RandyT on March 11, 2003, 08:17:48 pm ---It's because you have a limited amount of current available on any device that plugs into a PS/2 or USB port.  The way the LED board was designed, you have all the +5 power of the power supply (less what the computer uses :) ) available for LEDs without worrying about blowing your keyboard fuse.
--- End quote ---
Ah, since the IPAC gets its 5V from either the PS/2 port or the USB port, right?  Gotcha.  Danke!

By the way, RandyT, my initial posting that said that the Hagstrom KE72 puts out 1.5ma of current was WRONG (even though that was a direct quote from Hagstrom, dammit!)...the KE72 puts out 8.0 ma:
http://www.arcadecontrols.org/yabbse/index.php?board=1;action=display;threadid=5322

Dak-ak:


--- Quote from: SirPoonga on February 23, 2003, 12:36:30 am ---The schematic could can control 8 relays.  Actually, if someone knew how to control do microcontroller programming you could control 256 relays since there is 8 data lines on the parallel port.  (USB would be simular) Would involve alot of hacking mame, but some relay cool custom hardware could be made.  

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im not an electronics genius (far from it), and ive probably missed the boat on this one, but heres my experience trying to control "high voltage" stepper motor (much higher voltage and draw then the TTL lines could provide).  i think what oscar created with his diagram is a "darlington array" (so ive heard them called) a ULN2003 will work great for this project.


(this diagram is for stepper motors... if you charge line 3 on the left side with +5v, line 14 on the right recieves the +12v... it will control 7 different lines)

the idea is you use low voltage (or is it draw?) inputs to trigger high voltage outputs.  With some pnp resistors, you should be able to form some AND gates to use the control and data lines of a parallel port (one to the base, and one to the emittor... only charge the collector when they are both lit up, right?  im not taught in electronics, so this is mainly guesses, but thats diffenitly what oscars diagram makes me think).  Using those, you can then control one or two or three uln2003's to control all the leds.  I think.  :-)  (hafta try and give back to BYOAC any way i can)...

~Dak~  

Frostillicus:

Ok old thread, but I have a question about this since I'm transistor clueless here...

Does the common ground in this circuit get hooked to the IPAC ground, too?  All I see in the diagram are the three wires coming from the scroll lock, numlock, etc.  

Also, would it be possible to use a 13.8V power supply instead of 5V? Or is that too much voltage to put on the emitter?
 
Thanks!


OSCAR:

No ground wires go back to the I-PAC in my circuit.  Only the LED signal wires (Num/Caps/Scroll) are connected to the circuit.  If you aren't using a PC power supply hook up like I did, then you can go back to the I-PAC ground for the LED's cathode instead of connecting it somewhere else if it is more convenient.

You can use 13.8V, but the resistors in line with the LED's will have to be adjusted accordingly.  I believe the emitter/collector voltage rating for these transistors is around 30V or more.  A Google search should turn up a data sheet for the specific transistor you plan to use.


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