Wiring Atari volcano buttons in series?

[maraxle]

Hi.  I'm trying to get 4 Atari volcano (cone) buttons to be always lit on my control panel.  Can I wire them in series to either the +5V on a KeyWiz or straight to the PC power supply?

[RayB]

I think so, but you'd need some resistors.
Search this board for "Atari lit buttons" or "Atari volcano button" and maybe the word Resistor too.

[NoOne=NBA=]

They will need to be in parallel, or they won't get 5v.
If you wire them in series, they will only get 1.25v each.

Think of it like cookies.
If you pass one cookie down the line to four people, everyone only gets 1/4 of a cookie.
If you pass out FOUR cookies to start with, everyone gets a full cookie.

I'm not sure on the resistor part though.
They may have one in the case, but I'd check the specs somewhere before you hook it up.

[Witchboard]

From what I've read doing my own searches you'll need 330R ohm resistors on your +5V line.  I think some body mentioned the switches actually say "Max +-2V" on them.  Of course I would do my own searches to verify this if I were you.    Let me know if my findings are the same as yours.

[rdagger]

You could run them in series, but you would need a power supply greater than 5 volts.
First you need to determine the LED voltage which I believe is usually about 1.7 volts for a red (not a super bright) LED.  Next you need a power supply that can supply well above the total voltage used by all the LED's.  You don't want the total LED voltage to exceed 80% of the supply voltage.  If you used a 12 volt power supply and assume 1.7 volts & 15 mA per LED then you would use a 360 Ohm resistor.
Formula:  
(Supply Volts - Total LED Volts)/Current
(12-6./.015 = 347
Then find the next standard resistor value above 347 which is 360.

Here's an online LED Series Resistance Calculator:
http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm

If you have to run them off 5 volts than you could run them in parallel.  It is recommended to use a separate resistor for each LED.  You also need to make sure your KeyWiz can provide enough current; otherwise you could damage it.

[maraxle]

The searches on this board don't work for me for some reason.  Even though I have the max days set to 999, I only get results back to September of '04...

Anyway, the markings on the buttons say L2V, 125VAC, and 0.1A.  So does that mean I could wire 4 in parallel with a 47 Ohm resistor on the 12V line of my power supply and be okay?  According to that calculator linked above (thanks, by the way), 4 LEDs at 2V each with 100mA each and a 12V power source needs a 39 Ohm resistor, and 47 is the closest I can find.

[rdagger]

Anyway, the markings on the buttons say L2V, 125VAC, and 0.1A.  So does that mean I could wire 4 in parallel with a 47 Ohm resistor on the 12V line of my power supply and be okay?  According to that calculator linked above (thanks, by the way), 4 LEDs at 2V each with 100mA each and a 12V power source needs a 39 Ohm resistor, and 47 is the closest I can find.

Your LED is NOT rated for 100mA.  It should be between 10 and 20 mA.  I would start with a 390 ohm resistor and see how it looks.  You could then try lower values if it is too dim.  You can not damage the LED's by using a resistor value that is too high, but you can ruin the LED's instantly if you use a value that is too low.

I've bought a few volcano buttons and after 20+ years most needed to have their LED's replaced.    You can go to Radio Shack and buy 4 new red LED's and they should come with specifications.  This will insure that all the volcanos are the same brightness.  Don't use super bright because they will be too bright.

[maraxle]

These things are so not worth the hassle, but it's not for me, so I don't have much choice.  I am just dying to get this cabinet out of my house...

Maybe I'll just wire them in parallel on the 5V line with the 330 Ohm resistors since that's known to work.  This is the second to last thing to do on the cabinet (t-molding is last) and then I can get my friend to come pick it up.

[NoOne=NBA=]

That's the safest bet.

Another question this brings up is:
Were the resistors on the PCB in the original cabs?

[RayB]

The original cabs used a special power regulator circuit board that output a variety of voltages...

[NoOne=NBA=]

Duh.

I've gotten so used to the 5v/12v thing, I completely overlooked the obvious.

[maraxle]

I ended up wiring them in parallel with 330 Ohm resistors.  They look good.  Thanks for the help.