26 Mar 2017, 14:13
Hi,
So below are instructions for generating the transmission coil inside the watch:
Materials
- Wire/Coil - you have to use coil wire, this means that it has to be coated in lacquer but all coil wires are manufactured so. The type of coil that I used has 0.025mm cross section. I tried with 0.04 mm but it did not work because it has lower resistance per meter and the volume of the resulted coil is too large for the space you have to fit it in.
- Conformal coating - the purpose of this is to spray on the finished coil while it is still on the spool, this will make the coil stay together as you transfer it from the forming spool to it's place inside the watch.
Tools
I am sure the coil is achievable with other tools but here is what I used:
- Microscope - I have a 20x binocular microscope, this was used during the coil forming process so I was able to see and guide the coil while I reeled it onto the forming spool
- Forming spool/tool - this is a homemade tool that essentially has 2 spools, one spool has the big spool of wire and the other is empty and has a small crank that is operated manually. The objective is to crank the second spool and start transferring the wire onto it's mould.
- Molud - this is what is used to from the coil - basically I used a roll of electric isolating duck-tape. I dug a channel around the perimeter of the tape that essentially made the mould for the coil.
Calculations
According to the manual of the watch the transmission coil has to have between 3-5 kOhms.
My 0.025mm coil had a resistance of 34 Ohm/meter
This means that 100 meters of coil is 3.4 kOhm which should be in the 3-5 kOhm margin
The diameter of the space reserved for the coil inside the watch is 24mm
This means that the perimeter of the coil is pi*24 = approx 74.4 mm which is 0.0754 m
Ok, so 100 m of coil divided by 0.0754 = 1326 rotation have to be achieved for a 3.4 kOhm coil.
In the end I did 1500 rotations which got me a measured 4.3kOhm coil which WORKED!
As a future plan I will stick to the 1326 roatations or maybe 1400 as that would mean the coil would have a smaller volume.
I will have to make a video at one point to illustrate all the above.
Hopefully it is of some use to someone.
Cheers,
Tibi