What kind of power supply should I be using to power the incandescent bulb inside the Big Dome Push Button?

Question

I have a Big Dome Push Button as the activation switch for a photo booth project I'm working on. The problem is, I don't know how to power the incandescent bulb inside of it. I don't want to do anything complicated, I just want the bulb to always be illuminated.

The button has two pieces: the switch and the bulb. I have the switch successfully hooked up to an Arduino that's controlling the camera, so now all I need to do is power the bulb. The specs say that it's a T-3.75 [email protected] incandescent bulb.

Is there some sort of battery I can use? Or do I need a power supply? I have a few 12v power supplies sitting around but how can I tell if they're too much current?

This is probably a really basic question, but I've been googling for an hour now and haven't found anything that makes sense to me yet.

Answer 1

At 1.2W a battery will last a couple of hours, and you'll have to place several in series. IMO the best solution is a 12V wall-wart, those are usually capable of a delivering few Watt.

Answer 2

You calculate the required current by dividing the power of 1.2 watts by the voltage to find 100 mA. Most (though not quite all) wall-wart type 12v supplies say they are rated for comfortably more than that.

Batteries are rated in milliamp- or amp-hours, which roughly gives an idea of how long they can sustain a given load - for example, a 1200 mAh battery pack could run your bulb for something on the order of 12 hours (however, many rechargeable battery chemistries can be damaged if you continue to draw power from them with a "dumb" load like a lightbulb filament after they fall below a critical output voltage).

As your bulb probably has a standard base, you could also purchase a replacement of comparable (or at least sufficient) wattage for a different filament voltage - for example, you might find 5v more compatible with your other power needs for the arduino. A 5v 1.2 watt filament would of course draw proportionally more current - 240 mah. However, there are now lots of nice compact and efficient (don't even get warm) switching mode 5v supplies on the market rated for at least 500 ma, and sometimes as much as 2 amps.