# Pen Size Flashlight?



## Rich219 (Sep 17, 2010)

I just saw a pen pen on my desk and thought that it would be crazy cool to have a flashlight inside of a regular pen body.

I know I could just buy one of the pen size flash lights but how hard would it be to custom build myself a light that I could fit into a pen body?


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## MikeAusC (Sep 18, 2010)

AAAA are about 6mm diameter - you could fit two in a pen.

You could buy a 1.0-3.0 volt driver on a 17mm disc and totally rebuild it to fit inside a pen !!!!


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## Rich219 (Sep 19, 2010)

MikeAusC said:


> AAAA are about 6mm diameter - you could fit two in a pen.
> 
> You could buy a 1.0-3.0 volt driver on a 17mm disc and totally rebuild it to fit inside a pen !!!!




Really!

I know nothing about building a custom flash light but would love to do this as a project. 

So please forgive my newbness but what is a volt driver and what is a 17mm disc?


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## tylernt (Sep 22, 2010)

Not sure why you'd want to use a 17mm disc on a 10mm pen unless it was to harvest the components, and even then it'd probably be easier to get the components separately:

For a single-cell AAAA light, you could use the Joule Thief circuit (see http://www.bigclive.com/joule.htm) or a ZXLD381 chip and an inductor (see https://www.candlepowerforums.com/posts/2954378&postcount=4).

If you're willing to use a stack of 3 silver/alkaline button cells, you could direct-drive, possibly with a small current-limiting resistor to avoid burning out the LED. SR41/LR41 is the smallest diameter with useful capacity IMHO. You can get watch batteries that are smaller but they won't be able to light the LED brightly or very long.


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## MikeAusC (Sep 23, 2010)

tylernt said:


> For a single-cell AAAA light, you could use the Joule Thief circuit (see http://www.bigclive.com/joule.htm) or a ZXLD381 chip and an inductor .


 
A ZXLD381 will drive the LED up to 55mA. I've been looking at a "1-cell to USB" converter PCB to achieve up to 500mA LED drive.





tylernt said:


> Not sure why you'd want to use a 17mm disc on a 10mm pen unless it was to harvest the components, and even then it'd probably be easier to get the components separately:


 
That's not my experience - I find it far easier to get non-standard SMT parts by buying a known working module and redoing the mechanicals.
I needed a small 4x7135 driver - so I cut a 17mm PCB in half.


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## Rich219 (Sep 23, 2010)

Since I have absolutely no idea where to begin but really want to do this project can anyone direct me to a tutorial on what is needed to build a custom light? 

How bright could I make a light this small?


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## tylernt (Sep 23, 2010)

Rich219 said:


> How bright could I make a light this small?


Using a 5mm LED and alkaline battery, maybe 10 lumens. 

Using something like a Cree XP-E and a lithium battery, you could probably exceed 70 lumens.


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