Translucent Leaf-Button Lighting 101

[Knievel]

They are blue, from Wico. All that info is up top ^

[Druin]

I just discovered this thread and thought I'd give my 2 methods for finding out what value resistor I need for an unknown voltage LED. 
I hope I don't make any stupid math mistakes in calculations since I just woke up, but the method is right even if my numbers came out wrong. I'm doing it as I go. 

Method 1:   
Since I have a lab bench power supply with adjustable voltage outputs, that's usually my first method - let it be known that you ONLY need a series protection resistor to limit current on the LED if you are going to supply the LED with more voltage than it is rated for.  IF you supply the LED with the exact voltage it's rated for, then it automatically draws the proper current that it can handle.  As you increase voltage beyond that, there is also more current and eventual destruction. 

So if you supply less than rated voltage, nothing happens because there isn't enough voltage to forward bias the diode and it's just open circuit.  I start the power supply at 0volts and slowly increase it until the LED starts to turn on.  I adjust it until it seems safe, not too dim, not too bright, and then whatever voltage I'm giving it is what I'm going to consider its rated voltage.  Say it's 1.8 volts.  If I'm going to power from a 12v computer power supply, then the resistor I need is  12v - 1.8v = 10.2v expected across the resistor I add in series.  Then I measure the current actually going through the LED with my experimentally determined voltage, I stick a multimeter set to measure current, in series between the LED and one of the power terminals...say it's 10mA.    Resistor needed is 10.2v / 10 mA = 1020 ohms so I'd stick a 1K resistor in series with the LED on a 12v supply.
I'd probably want to double check the power ratings of the resistor as I start using higher voltages so I don't burn it up.  Most common resistors are 1/4 watt.  Power = current squared x resistance,  0.010amps squared times 1000 ohms = 0.1 watts.  1/4 watt is 0.25watts so I have more than twice the power rating.  No problem.
Suppose the power calculated grater than my resistor rating, just split the resistance up between several resistors in series, like make up 1K out of two 470 ohms in series to get close to 1K, and twice the power rating for 1/2 watt total.  Add another 56 ohms if needed to get closer to 1K using standard component values (996 ohms)

When you add a resistor and a higher-than-rated voltage to the LED, the voltage measured across the LED will remain the same (rated voltage) and the rest of the power supply voltage will show up across the resistor if you happen to measure that.  So running a 1.8v LED on 24volts would give 22.2v across the resistor and still 1.8v across the LED.     22.2v / 10 mA = about 2.2K resistor needed in series with the LED.  It's only about 0.2 watts, still safe with a 1/4 watt single resistor in that case. 

So that's method 1.  Set a variable power supply at 0v, slowly turn up voltage until LED is satisfactorily lit, measure the current through the LED, calculate resistor needed with (expected power supply voltage minus LED voltage) divided by measured LED current, and make sure the power rating of the resistor can handle the calculated power dissipated by that resistor at that voltage and current.


Method 2:

If you have the fixed voltage power supply you are going to use, say 12v, and the LED, and you have no idea what resistor to add in series, obtain a variable resistor of a reasonable value - from the above example even with 24volts you'd only need a few K, so don't get a pot rated at 100K or 50K or even 25K maybe, because the "few K" area of the pot is going to be such a short travel near the end, you'll zoom through it too fast and maybe blow the LED.  If you get say 5K pot it should be ok to work with.  Ignore one of the end terminals on the pot and work with the other 2 as your 2 resistor wires.  WHen you adjust the pot you'll vary the resistance of those 2 leads between 0 and full range ohms. 
Set the pot dial in the middle, then you'll have half resistance across the 2 terminals without needing to worry about which end-of-travel direction of the dial is going to be full or zero ohms, and accidentally blow the LED in ignorance.  So you have a power supply, an LED and the POT 2 leads all connected in series.  Power it up.  Most likely the LED won't be on.  Slowly adjust the pot in either direction until it comes on - if it doesn't come on, you're probably turning the pot the wrong way and increasing resistance, lowering current.  Turn it slowly the other way until it comes on.  If it still doesn't,  maybe the LED is backwards.  Reverse it and have the pot set to center again and start over.

When you get the LED to light as desired, disconnect the pot and measure the resistance between those 2 terminals you used.  THat's the value you need for a fixed resistor.


If there's any typos, calculation, or logic errors in all that, it's because I just woke up...at least gain some ideas for approaches from it.

[AlanS17]

I was cursed at birth with impatience. I admire all the time put into it, but I doubt I could ever do it because I simply can't sit still long enough.

[Level42]

Thought I would bore you guys with my implementation of Knievl's great idea...

I chose red buttons and....yes red LEDs....mainly because my cab is black and red colors. May take some time before I re-theme it...one step at a time !

My original metal CP had square (Lorenzo Industries) pushbuttons. Although they were lighted, I think this kind of button belongs on gambling machines (slot machines, whatever you call them) and are not suitable for videogames.
Also they use microswitches, which I hate.

Had to make one exception: P1 and P2 buttons don't come in leaf versions, and I don't really care for them to be leafs....makes sense I hope.

The holes that the original buttons needed were smaller then the proper translucent Suzo buttons. So I had to use my Dremel (clone) to make them larger. Lots of patience and work....

[Level42]

Finished....not too bad, although some minor markings are visible  May have to put something under the buttons to cover it up. But when I re-theme it, there probably will be a new CP anyway. That is also the reason why I didn't isolate the solderings to the leds, and kept the led wires pretty long.

For some strange reason, the red translucent buttons are only available in short length. Also Suzo only had the small (less thick) buttonholders for wood cabs...
I solved this by placing two layers of board on top of eachother, make the holes in proper places, and this is what it looks like, the board is also a nice isolater. I put the LED's in series with 1 resitor (under the isolation, top-left) per three buttons. The power comes from the original 12V power lines that lit the lamps. So not from my PC power supply, but from the cab.

[Level42]

The result: Great if I say so myself.

O, forgot to mention that I used only 1 LED per button. Drill the hole trhough and through on one side, then the LED will throw it's light straight to the other side of the holder. The result is great. Very evenly lit, only experts will know there is only one led lighting it. This also saves a lot of money, those hi-brite leds are very expensive.....

[gl.tter]

Good work.

[gl.tter]

Very evenly lit, only experts will know there is only one led lighting it. This also saves a lot of money, those hi-brite leds are very expensive.....

BTW, there are some great LED deals on Ebay.  I just needed 45 x 3000mcd 5mm pinks.  Bought them from Hong Kong for $13 inc shipping to England!

[Level42]

O, and drill with GREAT care ! This is what happens if you don't 

[Grasshopper]

Just has a thought for people building their CPs out of wood (and this would also work with the new translucent microswitch buttons).

Why not just use a router or drill to make some shallow LED shaped slots around the button holes. The LEDs could then be placed in the slots and kept in place by the button nut (if you're using microswitch buttons) or the leaf switch holder (if you're using leaf switch buttons).

[Level42]

Maybe also will work ok, but then you definitly need at least two LED's, like Knievl's original. The fact that the LED is IN the buttonholder makes that the light is transmitted within the plastic of the buttonholder too (not only directly in the button itself) I guess this gives it a more "even" lighting...not sure though didn't test, and I used Red, which is probably easier to light then Knievl's blue buttons....

[Knievel]

Nice job. Good to see someone else trying it.
If you want lighted buttons you just can't beat the leafs! The ring is definitely the secret to the even lighting.

[Level42]

Thanks Knievl. Indeed the buttonholder is doing much of the trick. Besides: leaf switches ROCK ! When adjusted properly, you can fire a lot quicker than with microswitches.
No clickerdieclick and also adjustable to your "taste" (contactmoment). It just feels better....just MHO

Anybody noticed I used a Tungsten contact leaf for my #1 (fire) button ? All the others are the (little bit cheaper) silver contacts. Figured this button will work about 10 times as much as the others. On another thread I read that the Tungsten conctacts are only really needed for high currents, and that it wouldn't make any difference in this application. We'll see. I think both are good quality so far....

I also noticed that people use the hole to screw the buttonholder to the panel. Is that really neccesary ? On the Suzo catalogue it says "buttonholder with lamp mounting" so I figured that extra hole was for mounting some kind of lamp holder...
Of course, it won't do any harm to do it Also prevents turning of the holder I guess...mmm where's that screwdriver....

[lettuce]

So the Lightable Horizontal Pushbuttons from Groovygamegear, are'nt as effective as these leafswitch mods then???

[Level42]

Hey Lettuce, I only noticed your reply just now. Remember this was done long before GroovyGameGear came up with their lirghtable buttons. I've only seen pictures of those and they too look good to me, although different in the general effect. If you put Ponyboy's leaf switches on them, I guess you must be about the same as this solution. My only thought about those small leaf switches is how they feel, since the blades are a lot smaller of course. Space wise, a GGG with Ponyboy's leafs is a lot better than this solution. And the "regular" leafs seem to be getting rare.

I personaly just don't like microswitches, so that's why I choose this solution back then.

[hypernova]

I personaly just don't like microswitches, so that's why I choose this solution back then.

Truer words were ne'er spoken.  Micros suck bad for constant button pressing.  Although I think they serve a purpose.  I kinda think the clickety sound works when pressing coin, start, or especially a mouse button, but after that, the noise is just that.  Noise.

Kneivel's method rocks.  I used it as well and it looks so great. 

[Level42]

Mmm, yeah, this actualy became a very well known word in computing: You CLICK on this or that icon....

The microswitches' click is actualy responsible for this 

How about a mouse with leafs !!!! My bet is that a LOT of people would have had a lot less damage from RSI if mouses would have had leafs......

But then....we would't have a word instead of "CLICK"....

Hyper, how did the stuff I sent you end up ? Pix ? (PM please !)

[ids]

pls exkuze da newb:  ready to start thinkn bout building a cab, gunna start with a CP, love the lit buttons.  Reading all kinds of stuff bout leafs vs micro's.  My machine will not be sitting in some public arcade, being pounded on by rabid 12-year olds.  Leafs ok?   Less noise, nice feel, worth the money?  Am thinking to order parts listed earlier, from wico, if they still around (website looking like it hasn't been updated in a long time).

Thinking of a 4 player, which also raises questions of button colours, but mebbe thats for another thread.

Much thanks in advance

[Level42]

Well, I'm a leaf man all the way, so don't ask me 

Simply put: my opinion is that leafs are worth the money, "trouble" (what trouble ?),space etc. If you do some searching here you will find plenty of threads that are discussing leafs versus microswitches.

[Kremmit]

Wico is dead and buried.  You'll have to find another vendor.

www.centsibleamusements.com
www.lizardlickamusements.com
http://homearcade.org/BBBB/

[hypernova]

Leafs are the option of choice.

[ids]

Thanks for the info, and the links.  Will get started when I get back from vacation in 2 weeks.  But judging from what I've read, I dont think it'll be complete anytime soon 

[Level42]

Wico is dead and buried.  You'll have to find another vendor.

www.centsibleamusements.com
www.lizardlickamusements.com
http://homearcade.org/BBBB/

I bought them at Suzo, but they say they are getting rare.....