Step 1: Disassemble + drilling holes
The most important things we need are inside the Original Flash lights. This means we need to disassemble the whole thing.
First we disassemble the lights head, because we will need all the inside components later. We need 1 pen with both sides sending IR light, so we need the light head two times. This means we have to take of the second lights head too and do the steps below.
Second of all we take out the fixing ring. This ring provides a fixation but also conduction (this will be explained later).
After taking out all the parts, we can start with disconnecting the leads from the little PCB with a soldering iron.
Last off all we need to disassemble the back switch. This is a bistable switch that we will need later. (On the picture on the left side, next to the monostable switch on the right side). We only need to do this on one light (we need just one bistable switch).
We need to drill 2 small holes in the tube for the position of the 2 switches. Try to drill with a fixed drilling machine; this makes the hole straight and in the correct position. After drilling, use a Dremel saw to work the edges.
We also need just one tube, so there no need to drill the holes in the second light tube.
Step 2: Solder
The next step is basically just soldering the leads and the ground contact.
With 4 leads we need one color led and one IR led on each side. The position of the IR led is important, the color led may be placed the way you want.
The function of the color leads are to indicate if the IR leads are working.
The IR led (black) must be placed in the middle of the PCB. Otherwise it will not send its infrared light in full capacity. Make sure the leads are connected with the plus and minus in the right way.
After this we need to connect the PCB with the housing (thread). We do this by using two small conducting wires.
We bend a little corner to solder them to one of the four spots on the side of the PCB. Make sure that they make contact with the housing case of the light head.
At last we drill a little hole in the middle of the plastic assurance. This provides a little space for the IR led on that position.
Now that everything is fixed we can return the PCB, along with the other parts, back in the light head.
Step 3: Battery holder & switches
Here comes the hardest part.
We are rebuilding the battery holder to a super compact (with switches) non-slid component.
First we need to take out all the batteries and take one battery holder away (later to fix the switches). We take this holder away by taking away the plastic material with a filing device. Take away just enough material until the bistable switch fits in perfectly (picture 2). The monostable switch can be attached on top of the bistable switch. Make sure that the switches match with the positions of the drilled holes in the tube.
After positioning the switches, it's basically just following the wiring diagram from the picture. We need to make contact between the plus and minus of the battery holder (yellow wire). Also contact the switches to the minus side of the battery holder.
After contacting the switches, we soldered a spring on to the end of them, to make contact with the housing case. We bend the spring a little up so the contact is ensured.
It is hard to explain all this detailed electronics, because every flash light you buy is different. The flash light we bought is normally standard. But if you make sure that the wire diagram is correctly attached, normally the leads will work.
IR light is not visible by the human eye, or at least very bad. When you check if the IR leads are working, you simply look through your Phone camera and point it to the led. Then you can see clearly if the IR led works or not. Also if the color leads are working, the IR leads will work to.
When your electronics work, you just need to put back the whole battery holder into the tube. Now there's a problem: The switches are in the way to slide it properly into the tube. This can work perfectly if you push down the big switch and then slide it into the tube. Make sure that you first slide it in the tube NEXT TO the holes for the switches. When it's deep enough, just rotate the thing and the switch will click up out of the hole.
As you know, we have 2 sides of the light. De first side can be fixed just by rotating it over the thread. This is the side where you can replace the batteries if necessary. The other side will be completely fixed with glue, so there's no possibility to make it open anymore.
To fix the other side I simply clamped it on the tube with two-component glue between it.
Step 4: Protection
In most cases this protection won't be necessary, but in ours it was needed. We made this pen for a client with mental disabilities. She breaks everything she gets in her hands, so protections were really a requirement here.
The protection we used can also serve as an aesthetic value.
The best flexible material for protection is a bicycle inner tire. Make sure the tire is from an ordinary city bike, not from a racing bike (tire is too small) or mountain bike (tire is too big).
Search a tube that has a smaller diameter then the pen and slide the tire over this tube.
You need this to roll up your piece of tire, otherwise it is impossible to slide it over the IR pen (this has been tried). When your tire is rolled up you pull it a little over the IR pen and slowly roll it off.
Watch out! Do not use the whole pen directly. You still need to replace the batteries and it wouldn't be possible to get it over completely.
Use the biggest part of the pen (with the glued part) and roll the tire over the whole thing. After this is done, just cut away the other piece of tire on the end.
After this, put back on the light head on the other side (thread) and slide a smaller piece of tire over it.
If you want, you can make the tire a little longer and bend it over the edge. Afterwards you can glue it directed to the center (like our product).
Finally we cut out a small piece of tire to make the switches visible.
Author: by Ward Meeus found on Instructables.com