[Aborted] Wireless Charging

[CPGOD]

Following a post on G+ about getting wireless charging on TS https://plus.google.com/u/0/113668328412632358673/posts/AAQL8jJUdfm, I decided to record my investigations in this area.

I'll map my thoughts and experiences as I go - at the moment, I dont have wireless charging, and the final outcome may be naff, but it might inspire others.
Indeed, I couldnt even get my TS to charge outside of the cradle (documented in the post entitled SUUNTO charger), nonetheless, lets persevere.

Some things needed -
QI wireless charging base = transmitter.
QI wireless foil = receiver. This is can be got on eBay or Amazon, and is the bit that provided power to your battery. There are several sizes (mostly for branded phones) and typically fit inside a phones case, or behind the back if the phone has a removable back. You need to find the smallest available that will deliver 500mA at 5V. The ones Ive obtained so far are too big, and I may end up trimming the non-functional area to get it to fit.
Some clever way of attaching the receiver to the TS or cradle (WIP) - its possible to solder the receiver to either the TS or cradle, but we need to keep it detachable so the USB port can be used.

Some observations -
Because the TS cant lie flat, due to the wrist strap/band holding antennas not flexing horizontally, having the ability to just place the TS on a charging plate may be a non starter. [Maybe we could tolerate the foil flapping open, or being hinged to 180 degrees when charging].
As the TS has an Alu or steel back, thus creating wireless interference or insulation, having the receiver inside the TS may be a non starter.

Before I go down the route of trying to get a receiver behind inside the TS itself, (which would entail opening it up and voiding the warranty ) Im going to look at getting it to work via the charging cradle.
The inside of the cradle offers more space to get a receiver foil in, looks as though it could be done without serious soldering work or permanent damage. However, the only advantage is that it only dispenses with the USB cable - the TS still has to be placed inside the cradle.

The attached pics show the cradle components.

More posts to come later, reserving a few spots below for updates.

 

[CPGOD]

Reserved 1

This picture shows the underside of the USB connector. It appears there are two resistors (the tiny rectangle surface mount components) - I guess these are creating a voltage divider to put +2.8V and +2.1V to the centre two pins. This doesnt seem to materially affect just applying 0v and +5V to the outer two though.
View attachment 2891869

 

[CPGOD]

Prototypes

What Im doing isnt really rocket science - Im just plugging in QI receivers to the TS. This successfully chargers the TS wirelessly, but as you can see, is not practical.
Hopefully I can find a way of making this neat, but I fear that, as I mentioned before, because the strap doesnt bend, you cant lay the TS flat.

 

[CPGOD]

Giving Up

With some judicious trimming of the receiver foil (after separating the liner), I was able to get it to fit inside the TS cradle.

However, the thickness of the plastic of the cradle base means the charging current wont reach the receiver. I even shaved off some of the extraneous mouldings on the base to try and get the receiver closer. I think if I persevered, and scraped into the base itself, it might work. With the extra moulding removed, I sometime get a hint of a blue charging light on my ZENS charging pad, but it never sticks.

If I could get this working, I would be faced with the last hurdle, which I fear is unsurmountable - the inability of the strap to bend. I would need a charging 'block' rather than a pad. Something that was less than 45mm between the straps. From what I can find, there aren't any; the smallest (without too much searching admittedly) was 90mm.


So this, and the fact that I couldn't find a foil small enough to go inside the TS itself, plus the TS case having the same interference problem as the cradle, means Im going to stop here.


It was a small, fun, diversion, and it would have been nice to get it working, but the retail products, and my engineering/manufacturing skills, don't exist to get us there.