Quick and inexpensive LED squeezee light

I do amateur astronomy, and one of the tools is a red flashlight (If you turn on your white light and ruin your astronomy buddies night vision, he'll probably knock your block off). But with the popularity of the new white LED's, red LED flashlights, especially inexpensive squeeze lights, are getting hard to find. This instructable will show you how to make your own squeeze light so cheap and easy, you won't mind loaning them to you friends that forget to bring things back...

Step 1: Gather the parts

There are so few parts, this shouldn't take long at all.
Needed:
1 empty film canister (if you've gone all digital, go down to the local developer or camera store, they just throw these things away).

1 9vlt battery (doesn't even need to be a new one, I've found that ones run down to 7vlts will still light the LED's. So go replace the ones in your smoke detector, and use the old ones in your light.)

4 red LED's (I've used everything from the dimmer red "indicator" ones to the clear "Super-Ultra Bright") just make sure they are all the same.

A piece of packing foam, sponge, or packing "Peanut", about the size of the battery and about half as thick.

Comments

[Colonel88]

How is this a squeeze flashlight?

[cheeto4493]

Because you have to squeeze down on the top to get it to light. See intro pictures. If you bend the wires down away from the lid, it will stay on continuously. The 9vlt is just a hair short of making contact on its own.

[Kent]

Red LED's drop a little more than 1.6 volts. A 9V battery will run 5 red LED's at a reasonable current, because under load, a 9V battery will drop to 8V. With only 4, they will very likely burn up quickly. The total light will probably be the same with 4 overdriven or 5 at normal current. Another combo that works well is 2 white LEDs and 1 red.

[professorred]

Just as a point, If you put a resistor in series with the leds, this will take out any voltage not used by the leds. Out of curiocity, I went up to ~20V on a 2.5v led with a 1k ohm 1/4 W resistor. Without this extra safety, leds life can go from 10000 Hours to .1 second

[cheeto4493]

Maybe, Possibly, worth considering, but 3 things to realize. 1. I generally use used 9vlt that are already down to around 8 volts to start with. 2. Never burned up one yet. Being a squeeze light, it's never on more than a minute at a time. If I reduce the LED's life expectancy by half, that's still like what, 9,000 hours. Way more than I'll ever keep by finger on the switch. 1a. I'm using Ultrabright or super-ultrabright LED's. They have a forward voltage of 1.9v-2.5v and a current rating of 30ma. If I were using a lesser LED, I could see your point.

[iectyx3c]

Hey try this in the Pocket Sized Instructables contest. - I am voting +1 for you -- you should enter this. I am trying for it too.

[cheeto4493]

Thanks, but it has to be a new instructable to go into a new contest.

[GorillazMiko]

Really cool and smart idea! But I would definitely add in a resistor, the LEDs would burn out quickly, but really awesome idea again. Great Instructable!

[cheeto4493]

I've built one with a potentiometer that I leave on for long periods, for dimmer control, but even if your battery has a 9.6vlt charge that comes out to only about 2.4vlt across a LED, and I've never had one burn out yet. Wouldn't hurt but I'll take my chances, more of a possibility that an LED will short (or be shorted) and up the current on the others.