5 Volt Superbright LEDs?

[Oldskool]

My IPAC arrived yesterday, and I'd like to use the LED support to illuminate start buttons. (The IPAC supplies 5 volts.)

 I've read the "superbright led driver board" tutorial on oscarcontrols.com, but was wondering if I can purchase superbrights (or similar) that can used on 5 volts supply, without the driver.

Thanks.  

[MrDT]

If i understand correctly, you're asking if there are leds available that can run directly off a 5v line with no additional components required?

This is certainly possible, there are leds available that go up to (and maybe go higher than) 12v without need for resistors etc. However, you could probably find lower voltag eleds cheaper, and it's just a matter of adding the correct resistor to one of the legs.

Take a look here:
http://www.thecoolingshop.co.uk/tcs/comersus_viewitem.asp?idproduct=732
that might be all you need.

Also, have a look here to work out the resistor value required for different leds:
http://www.liquidcrystaltechnologies.com/LED_Resistor.htm

Hope this helps, and I'm not completely missing the point...

[daeven]

My understanding is that the limiting factor is the current available.  When I did this with my Hagstrom encoder, the Hagstrom specification only allows for a certain current draw (mA was the unit, I believe).  The Superbrights almost certainly will pull more Amps that the IPAC is designed to provide.  I assume this could damage the IPAC, or at best will just make the LED illuminate dimly.

[MrDT]

All the superbright LEDs i've seen have a 20mA forward current which isn't incredibly high. Do you want the leds to flash on and off under a start button when a player has credit, or just have them lit constantly? If you have them lit constantly it would be simpler to rig up the leds to usb or a 5volt line from your pc psu...

Chances are you want the flashing start button though eh?

[ErikRuud]

All the superbright LEDs i've seen have a 20mA forward current which isn't incredibly high.

But is is more than twice what the IPac is rated to handle.

You really need to use an interface between the IPac and any superbright LED's.

[Oldskool]

Do you want the leds to flash on and off under a start button when a player has credit

Yes, that's what I'd like to do.

Credit in - start button flashes (on applicable games).

My hope was to swap out the existing 5 volt LEDs that came with the I-PAC for Superbrights, without any extra work.

But, if the IPAC can't deliver enough current, I may be stuck....

[MrDT]

Upping the current shouldn't be too difficult. It sounds as though you've already found some plans (sorry, didn't follow link as I won't be using an ipac). A small inverter (or similar little electronic component that i don't know much about lol) should do the trick i think

[ErikRuud]

Oscar's driver circuit is easy to build.  It is also easy to customize.  I built one that only drives two player start buttons(instead of threee)  and two other LEDS(instead of ten).

[pfriedel]

Just out of curiousity, what will happen if you don't put in the driver circuit?  LED's no workie, or will the magic blue smoke be let out of the iPac?

[pfriedel]

OK, you'll have to scuse the guy who just only stopped seriously burning himself with the soldering iron, who is completely new to transistors - I just soldered up a quick components-onna-wire version of Oscar's Amplifier circuit.  10k (oops) resistor to the base, 100 Ohm to the collector, 100 Ohm to 3.7V 20mA Blue LED.

  Then I hook up my bench power supply's +5V to the emitter and ground to the LED's negative leg.  Nothing happens.  This is expected.  How do I test the iPac trigger?  I can get the LED to light up if I run another test lead from ground to the 10K.  Now I'm _thinking_ this is right, because that's what I'm connecting on the iPac - the grounds, not the 5V feeds.  But I'd like to have someone who knows this better'n theory doublecheck before I plug god-knows-what into my precious iPac.  So is this how it should work, or did I get something backwards here?   I guess I'm worried that I'll *oops* shove 5V where the iPac ain't expecting it and break something.

  Also - the info for my transistors say the legs are BCE (not EBC)- is that normal (and EBC is just a convenient way to draw 'em), of am I using a high grade Chinglish manual? I connected them with that assumption and it produced the above results..  (yeah, I stole the parts out of an electronics experimenter kit that has never gotten past the first 2 or 3 builds.  I know, if I'd actually followed the lessons, I'd probably know this.  It's on my list of things to do.)  If this works, I can cut it down to a nice little button-hugging size, really.

  I'll attach a picture to see if it helps make it any clearer.

[OSCAR]

OK, you'll have to scuse the guy who just only stopped seriously burning himself with the soldering iron, who is completely new to transistors - I just soldered up a quick components-onna-wire version of Oscar's Amplifier circuit.  10k (oops) resistor to the base, 100 Ohm to the collector, 100 Ohm to 3.7V 20mA Blue LED.

  Then I hook up my bench power supply's +5V to the emitter and ground to the LED's negative leg.  Nothing happens.  This is expected.  How do I test the iPac trigger?  I can get the LED to light up if I run another test lead from ground to the 10K.  Now I'm _thinking_ this is right, because that's what I'm connecting on the iPac - the grounds, not the 5V feeds.  But I'd like to have someone who knows this better'n theory doublecheck before I plug god-knows-what into my precious iPac.  So is this how it should work, or did I get something backwards here?   I guess I'm worried that I'll *oops* shove 5V where the iPac ain't expecting it and break something.

This is correct.  The LED lights when the switch is activated, and when the switch is activated it goes to GND.  When the switch is open, it is about 5V.  The transistor is "on" when the Base goes to ground.

 Also - the info for my transistors say the legs are BCE (not EBC)- is that normal (and EBC is just a convenient way to draw 'em), of am I using a high grade Chinglish manual? I connected them with that assumption and it produced the above results..  (yeah, I stole the parts out of an electronics experimenter kit that has never gotten past the first 2 or 3 builds.  I know, if I'd actually followed the lessons, I'd probably know this.  It's on my list of things to do.)  If this works, I can cut it down to a nice little button-hugging size, really.

The BCE layout is typical of Japanese transistors and USA manufactured transistors are normally EBC, but of course that can vary by manufacturer.  Definitely go by the documentation you have for your transistors.

[pfriedel]

This is correct.  The LED lights when the switch is activated, and when the switch is activated it goes to GND.  When the switch is open, it is about 5V.  The transistor is "on" when the Base goes to ground.

  Sweet.  I mean, I remember from physics class how transistors work and how they evolved from tubes, but it's good to know that my diagnostic hunch is true.

[pfriedel]

And with a little bit of work, I ended up with the attached picture.  Now I find that my system doesn't send LED events down the USB interface, only out the PS2 side.  *sigh*  But it does light on boot and when I hold player 1 button 7, so I know it works.  My only remaining concern is that it's rather a lot of unsupported weight hanging off the LED, but I can't think of a good solution.  Maybe ziptying it to the cherry once the CP art shows up.

[OSCAR]

A nylon tie should work fine.  Or maybe a glob of hot glue to secure it to the side of the m'switch.

[hmy1]

Please enlighten (educate) me. I understand Oscar's circuit isolates the LED's from the IPAC. But instead of doing all that, why not simply drive the LED's directly from the PC power supply's +5V line, and not through the PS/2 or USB ports?

Howard

[OSCAR]

In my example, the LED's are being powered from the PC power supply.  The I-PAC is really just the "on-off" switch for the LED's, being controlled by the state of the keyboard Caps, Num, and Scroll Lock to indicate the P1 Start, P2 Start, and Misc functions supported by some games.

If you powered the LED's directly from the PC power supply (with resistor, of course), then the LED would always be on.  That would be desirable if you just wanted to provide illumination for a trackball or action buttons, but you won't get the flashing P1 Start when you insert a quarter in Tempest, for example.

[pfriedel]

It isn't switched, then - if I ran it off of the +5 line, it'd always glow, instead of subtly blinking/glowing when appropriate.  The transistor arrangement is simply there to allow you to run more than 10mA off of the switched iPac ports.

[hmy1]

Oops, what I meant was, if the IPAC is not able to supply enough current to power the superbright LEDs through the PS/2 or USB port, why not power them from the PC's +5V line? Eg, wire the them up as directed in the IPAC documentation, but power the LED from your PC's +5V?