Some more LED questions

[cdbrown]

I've read through previous posts on illuminating the pushbuttons using LEDs.  They all go into higher mcd meaning brighter LED, the amps and voltage.  I didn't notice an actual size (1/4", 3/8").  I have looked at a local supplier and the size that has the right brightness is 3/8" and over.  This sounds large but as I don't have a button to look at it is hard to visualise  

I also went to this link
http://www.7volts.com/led_resistor.htm
I don't know about having LEDs in a series.  I read somewhere that you add the mA of the LEDs and use that in the graph - but it looks like you can only get 2 20mA LEDs in series using 12V supply.  Someone said you could get 6 or more from a 5 volt supply.  Maybe I'm looking at it wrong but it doesn't work out for me.

Could someone please set me straight on this.  I was hoping to wire up quite a few pushbuttons with LEDs which could mean I need a few power sources?

Very very confused

-cdbrown

[Carsten Carlos]

Hi!

That graph is so confusing -I'm to busy at this moment to explain this, plus I won't work with this method anyway.

So, here are some short answers, maybe a look on my homepage can help also, I explained some things regarding LED's there, too.

If you put the LED's in series, you simply add the voltage, NOT the current! If you go with 2,2V LED's, you have to take 5-6 LED's to match. On a 5V supply you can take 2-3, with two they would have a bit to much voltage (2,5V), but this shouldn't be so much of a problem.

Don't know why you want to put them in series, either. Just put one in the button (bright 5mm LED), and get the resistor. To calculate the resistors, just look on my homepage, you will find it under "interfacing".
I hope I wrote it understable enough, otherwise just ask.

Good luck,

Carsten

[Frostillicus]

I checked out your site, carsten- very cool.  I'm a little new to all this, and I like the temporary set-up for your control panel.  I'm gonna try that myself when I get to that stage.

LED question: I understand for some games 2 LED's blink for start 1 and start 2 - my question is what does the 3rd blink for? and what do you have it lighting up?
My guess is that it's some type of in-game signal for scoring or such, but am I wrong? Thanks!

[Carsten Carlos]

I checked out your site, carsten- very cool.  I'm a little new to all this, and I like the temporary set-up for your control panel.  I'm gonna try that myself when I get to that stage.

Thanx, you are welcome! We were quite joking here to build the entire cabinet with carton and paper

LED question: I understand for some games 2 LED's blink for start 1 and start 2 - my question is what does the 3rd blink for? and what do you have it lighting up?  
My guess is that it's some type of in-game signal for scoring or such, but am I wrong? Thanks!

Whee, got some problems with the 3rd LED also! There was one game where the LED blinks when any coin is insert - so it is not divided between 1up and 2up. There was also a game where the LED lit when you got something special during gameplay, at least I think so - don't know where I exactly got that?
I wanted to put the 3rd LED under the trackball (for know I got a hacked one which can be illuminated), but this could change if I get the used Happ trackballs.

Don't wanna leave the 3rd one out, but actually I have no special idea either!

[1UP]

You could always use the 3rd LED to drive your coin door lights!  You might need an inverter though, so it blinks out instead of on, and then remains on the rest of the time...

[Frostillicus]

ah the coin door sounds like a good idea. Or maybe mount a separate light on top(like APB or something) - just wish I knew exactly what that 3rd light is for.  I've looked all over the big mame sites and can't find a thing.  You guys have been pretty helpful, though, this forum is really handy  

[cdbrown]

So, here are some short answers, maybe a look on my homepage can help also, I explained some things regarding LED's there, too.

Carston, I have looked at your site quite a lot and I think that may be where I got the idea of lighting up my buttons.

If you put the LED's in series, you simply add the voltage, NOT the current! If you go with 2,2V LED's, you have to take 5-6 LED's to match. On a 5V supply you can take 2-3, with two they would have a bit to much voltage (2,5V), but this shouldn't be so much of a problem.

Ok I understand 2 LEDs @ 2.5v - use the 5v supply - would I still need a resistor even though I don't want to remove any voltage.

Don't know why you want to put them in series, either.

I heard this is the way to do multiple LEDs

Just put one in the button (bright 5mm LED), and get the resistor. To calculate the resistors, just look on my homepage, you will find it under "interfacing".
I hope I wrote it understable enough, otherwise just ask.

Good luck,

Carsten

I was hoping to light up most of my buttons.  I thought it might look cool if the player buttons were lit not just the start buttons - probably could have said that in teh first message (4 players, lots of buttons).  Not authentic but I thought would be different.  If I were to light up around 20 LEDs - 4 different colours.  Is this going to be possible??  Or just a silly dream .  Colours blue, red, green, purple to match the buttons.

Also when I looked at the local supplier only 10mm LEDs were bright the 5mm were only around 60mcd.  I'll have to look a bit harder.

Anymore help would be great
-cdbrown

[Carsten Carlos]

You could always use the 3rd LED to drive your coin door lights!

Whee, 1UP, that's a smart idea! Thanx, I guess I'll do this unless I keep this hacked crystral trackball!

Ok I understand 2 LEDs @ 2.5v - use the 5v supply - would I still need a resistor even though I don't want to remove any voltage.

No, thats quite ok -you only need the resistors when you have to much voltage which would kill your LED! 2,5V is slightly higher than the suggested 2,2V, so it should make no harm.

If I were to light up around 20 LEDs - 4 different colours.

Ah, that's something different! Don't use to dark buttons -I tried the purple and the dark blue buttons from Happ just for fun, and you won't see much lit there. Some colors work good, some not so good, maybe just try it out. You can see it fairly if you take the upper part of the button out and hold the LED underneath.

Colours blue, red, green, purple to match the buttons.

Also try the white LED's, maybe it looks good on a green button, too! Although I also wanted a purple LED (this is the multiple "RGB" LED, there are 4 LED's in ONE housing), but the problem is you won't get these with high brightness. It's bright enough for flashing under a white button, but it might not be enough compared to the other LED's, especially when it is just simply lit all the time.

The other colors are all available with 1300-6000(!) mcd- I even heard of types were you are not allowed to look directly in their light, so be careful, and don't hold them 10 inch under your eye without a button between when you get such a bright burner! No fear, normally you won't get these, but you never know.

You can even get 3mm high brightness LED's, but this is far to small for our purposes.

To put them in series -there is also one problem left. Who said this is all so easy?
Only put the same type of LED's in series - if you mix up different colors, some'll be brighter then others. This could even happen with the same type, so better try it before you install the whole thing.
Best thing is always one resistor per LED - it might be some more work, but it's worth it. Anyway, resistors are damn cheap, and you have only to calculate its value one time.

[cdbrown]

Thanks for all the help Carsten - here's a couple more which will hopefully clear it all up.

Ah, that's something different! Don't use to dark buttons -I tried the purple and the dark blue buttons from Happ just for fun, and you won't see much lit there. Some colors work good, some not so good, maybe just try it out. You can see it fairly if you take the upper part of the button out and hold the LED underneath.

Would a high brightness white LED be any good under the purple and blue or only the green?

The other colors are all available with 1300-6000(!) mcd- I even heard of types were you are not allowed to look directly in their light, so be careful, and don't hold them 10 inch under your eye without a button between when you get such a bright burner! No fear, normally you won't get these, but you never know.

You can even get 3mm high brightness LED's, but this is far to small for our purposes.

OK - I'll try to get the 5mm high brightness LEDs.

To put them in series -there is also one problem left. Who said this is all so easy?
Only put the same type of LED's in series - if you mix up different colors, some'll be brighter then others. This could even happen with the same type, so better try it before you install the whole thing.
Best thing is always one resistor per LED.

I was planning on only using the same colour per 'group' of LEDs.  But it's just a matter of getting enough power to drive them all.  Using one resistor per LED - would this mean using one 5v supply for each resistor/LED? I was thinking of using my old PC power supply to run them all - is this going to be possible if I were to still run 20?  Am I able to splice the 5v power cable and run multiple LED's in parallel - would this be a better idea?

Thanks again for the help
-cdbrown

[Carsten Carlos]

Would a high brightness white LED be any good under the purple and blue or only the green?

Doesn't work very well, best thing is to try it out with the buttons you have -I don't know anymore how it did look with a green button, it wasn't very good to see either.

Using one resistor per LED - would this mean using one 5v supply for each resistor/LED?

Nope.

I was thinking of using my old PC power supply to run them all - is this going to be possible if I were to still run 20?  Am I able to splice the 5v power cable and run multiple LED's in parallel - would this be a better idea?

Yep, this is the way to do it! Don't worry about your power supply - it can run one hundred and many many more of them if you like. With 20 LED's, you may consume as much power as a modern harddisk would do.
Just get a power cable out of your MAME-PC to drive them -that's the way I did -you don't need an extra power-supply only for the LED's!

[cdbrown]

Thanx Carsten.  If only I'd asked the right question at the start  .

So put the LEDs in parallel with the resistors by splicing the spare HD power supply.  I guess thats why you questioned the whole "putting them in series" in your first reply.  Sorry to have you answering silly questions - I'm just not that well versed in series/parallel and electrical stuff in general.

Cheers for the input.
-cdbrown

[Carsten Carlos]

You are welcome! It's always fun to give something back to the group - and, as I see, this works pretty good in this forum  

By the way, did you changed the text under your avatar during this thread?  

[cdbrown]

You are welcome! It's always fun to give something back to the group - and, as I see, this works pretty good in this forum

[Goose]

I was wondering if there was a web page or list somewhere on the internet that details which games use the keyboard LEDs.

Thanks