Simple SPST button question

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AmeerNuub
Posts: 4
Joined: Thu Dec 30, 2010 11:07 am

Simple SPST button question

Post by AmeerNuub » Thu Dec 30, 2010 11:09 am

Hello folks,

I am new to cockpit building and have made this scifi cockpit.

http://s481.photobucket.com/albums/rr17 ... ockpit.jpg

This is the full size pic of the slide cage.

http://s481.photobucket.com/albums/rr17 ... pit028.jpg

The colored buttons you may notice on the upper and lower side panels are currently unwired, because I can’t find a diagram for them, and don’t have enough experience to work from schematics.

I do solder all day long for a living, but it is manufacturing guitars and pickups, and not this particular family of electronics (though the fundamentals are the same).

All I currently want is to have the buttons light up / off when the button is pushed.

They are Phillips SPST lighted momentary switches. Their info is here:

http://s481.photobucket.com/albums/rr17 ... switch.jpg


The lamp info that I bought for them is here:

http://s481.photobucket.com/albums/rr17 ... t=lamp.jpg


I bought a twelve volt battery with which to experiment here:

http://s481.photobucket.com/albums/rr17 ... attery.jpg

I soldered separate pieces of lead wire to each of the magnet poles. After trying everything I could think if, I still cannot get the switch to light in any way. I don’t see any compromise in the lamp, and it is thoroughly seated.

If someone can tell me which wires to solder to which prongs, I’d really appreciate it.

Happy New Year, everyone. :D
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Teej
Virtual Thunderbird
Posts: 1533
Joined: Fri Jul 31, 2009 9:29 pm
Location: Milwaukee, WI

Post by Teej » Thu Dec 30, 2010 12:33 pm

As I read that...what you want to do can't be done without some extra circuitry. The lamp is not part of the button circuitry / action.

You have pins 1-2 that are normally connected (when switch is not pushed). When you push the button, they open up.

Pins 3-4 are normally unconnected, but will be connected during the time you push the switch.

Looks like you run power for the lamp to the screw holes - a-b.

Before hooking it up to a battery though, check and make sure I'm right on that a-b thing. Use a multimeter to check resistance, etc.

Also, is that "lamp" a light bulb or an LED? From the 80ma rating, I'd say it's likely an LED...and you can't simply hook it up to a 12V source or it'll fry instantly.

A light bulb will tell you how much power (or current) it will use when hooked up to a source...and it doesn't matter if you hook it up to 12V coming from a set of AAA cells or a 12V line off a 4,000 amp generator - the bulb will only take that 80ma.

An LED will tell you the max current you can feed to it - and the onus is on you, not the LED, to limit it to that.
AmeerNuub
Posts: 4
Joined: Thu Dec 30, 2010 11:07 am

Post by AmeerNuub » Thu Dec 30, 2010 4:47 pm

Teej... thanks for the info and contribution; I really appreciate it.

A friend that's going to be helping me with this was surprised about the model and rating of switch this is for the intended application. Another friend said I could match it with an old computer power supply. The guy at the electronics store (a real one, not radio shack), said that the lamp rating / wiring was separate from the switch rating / wiring unless you choose to put it in the same circuit or something. I really don't have any idea about the jargon, so if that is wrong then I'm sure it's because I'm phrasing it incorrectly.

Also I call it a "lamp" because that's what the manufacturer of the switch refers to it as in their separate lamp rating info referenced in the supplied pic. I would guess pretty heavily that it's a bulb. The only info on the lamp I bought was in the pic I supplied and unless there is a way for me to tell whether it's led or otherwise, I can only supply this pic of it for now.

http://s481.photobucket.com/albums/rr17 ... G_0282.jpg


Meter testing the switch... not really skilled enough to do it correctly. I've only ever had to know what to do for the products we produce.

The button drawing on the package says both a & b are positive... ?

For a & b together
ohms section
I get 17 under 200. Nothing else really gives anything that I can tell.


If I had to, I'd just be ok with continual light, regardless of switch activity... just want some kind of light coming from these suckers!
AmeerNuub
Posts: 4
Joined: Thu Dec 30, 2010 11:07 am

Post by AmeerNuub » Thu Dec 30, 2010 7:21 pm

Well, for anyone it may benefit reading this thread with a similar issue, I got a quick solution that gets the lights working:

"Apply your 12v(+) to pin 3,... ground(-) to pin a,... wire pin 4 to pin b. That will turn on the light when the button is pushed. If you are planning on using this switch for another function that is also enabled when the button is pressed use pin 4 or b for the signal when pushed.
If you want reverse function (light on when not pressed) use pin 1 in place of 3 and pin 2 inplace of 4...Don

BTW, to isolate the signal from the light you will need double pole switches and use half for the light and the other half for signal...safer for sensitive I/O boards".


Thanks to Don for this, and happy new year to all of you.
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