when we shipped the first batch of Foldscope; we made the decision of including only a limited number of light modules. The rational was to encourage users to do day-light outdoors microscopy. Since most of these packages were going to far away places; we were worried about if the battery might get screened.

Here I will describe a quick trick to turn your “solar” Foldscope to include a cheap light module. The idea originates from a walk I was on and saw this “art piece” where people throw lit LEDs on a structure to make art. Here is an example of throwie led on a lamp post:

So; we thought as a design challenge – we should have users make a simple light module. Now you have to remember; half the microscope is in how light is brought to the sample; so you should take care and do a good job in mounting.

All you need is a watch battery and a led and some copper tape. I will post the exact part numbers for these here

I will soon post the exact part numbers for the three components needed. They are:
1. Watch Battery (CR2032 Lithium Button Cell 3-volt Batteries)
2. Led  (Digi-Key, 160-1727-5-ND, LED WHITE 3MM RND WATER CLEAR)
3. Copper tape with conductive adhesive (McMaster-Carr, 76555A713, Conductive Copper Tape with Conductive Adhesive, 3/4″ Width X 6 yds Length)

Now, this happened a little bit by accident – but the outside diameter of the led had the exact same dimension as the inner diameter of the first aperture towards the back side of the microscope. So all I did is connect the watch battery and the led; taped it up nice and tight. Two important points here

1) If you don’t press the tape hard; your lights will Flickr. You could use the magnets in a spare magnetic coupler to use them as a means to apply constant pressure on the leads so you have great contact.

2) be careful not to short your battery. The Battery will heat and run out of juice. If you are not using the light source; you should disconnect it.

Now; all you do is gently insert the led into the bottom aperture; and you have a beautiful light source. This is useful when you want to record your experiments on a cellphone where you do need a nice light source from the bottom. You can use some extra tape if you want for mounting the battery. Remember; the extra tape used to stick the battery to the bottom surface of the Foldscope should not hinder with the mechanics of the microscope.

Happy exploring..

Manu

Note: I just used this trick in a class that I taught. Here is a picture of Foldscope assembly in progress.