see the previous posts Wireless Challenge .... the other bit Beyond the Phone - eLIST progress 3 eLIST progress 2 , eLIST progress , eLIST - KOBO Touch , 5W Load Schematic
As I said in the other blog, I had an idea to replace the lamp with EL film.
The results were not what I expected, and not because I let the smoke out of the transistor, but the current drain was higher than expected.
There is room for improvement, however as time is marching on, it will need to wait until another day.
For some reason when I entered this challenge, I thought the charging distance would be greater.
My years of experience should have warned me that its basically a transformer with some intelligence, rather than some death ray device beaming energy across the room.
If you can't directly power the item using wireless charging, the option is to charge a storage device and then release the charge when you need it.
Hence the EL film and inverter were not really going to work too long at the currents I observed.
Since the item in question already has wiring into it, why not power it by this ...
Well there's no fun in that is there, besides this is a Wireless Charging Challenge and the idea is to explore other uses ... hence the title 'Beyond The Phone".
Prototype or Proof Of Concept
The idea below is for a POC (Proof Of Concept), and a final product will have much of the hardware integrated into one pcb.
Generally you never see the prototypes, and if you did they may not resemble the final product.
These challenges are different, in that you see the prototype and the design process (although some are very polished prototypes), so its not unrealistic to see a collection of parts rather than a single PCB.
There is often a paradox between a custom designed item, and using off the shelf parts that others can use to duplicate the project.
For both my designs I have tried to use parts that others can purchase or adapt in order to suit the maximum audience possible.
Construction
When my item finally arrived, a few measurements showed I had to be careful with the overall height.
The opaque disc was 80mm in diameter, but the total thickness of the mount and both discs is only 18mm.
This is sufficient to mount the components, but having the illumination source against the disc is not going to work (the film would have been fine).
I decided to use one of these as the illumination source
Photo courtesy of the supplier ... adafruit
While I was there, I also purchased one of these
Photo courtesy of the supplier ... adafruit
These need a controller, and since its only a single wire, then an ATtiny85 will work fine.
I have a few Digisparks http://digistump.com/products/1 (and some new DigiSpark Pro versions on order).
As you can see the regulator is bigger than the Attiny85, and once its programmed I don't need the USB and other components.
Luckily I remembered that Hadley had a version he used in his Orblink
https://nicegear.co.nz/electronics-gear/orblink-kit/
It had a removable chip and was about the right size to use.
A small 500mAH LiPo battery would hold sufficient charge, and a USB LiPo charger was in my parts box.
During my other purchasing I had brought one of these, initially to compare the results between the TI/Wurth solution and this.
It might have fitted inside the KOBO or other device, so it wasn't a total waste of money.
As luck would have it, the receiver section fitted without trimming or modification.
Sponsors
About this point I should explain why I haven't used all Wurth or TI equipment, who are sponsoring this challenge.
edit .. since my Adafruit wireless charger arrived today, I decided to peel back the cover on both the wired and universal charger.
I'm happy to say both use the TI BQ51013A or BQ51013B chip, just as the Adafruit one.
The truth is when I applied for this challenge, I only had one item ( Hardware ) that was taking some of my spare time.
I'd finished the article for the magazine, and apart from some fine tuning of the text, my part was finished or so I thought.
Just before going to print we found the original shield supplier stopped making it, so we scrambled to make a new shield and have it manufactured before the article came out.
I started on the Webserver part and found my software skills were lacking, which seems to consume much more time than you can imagine.
While struggling through this, Futureintechs 'Arduino in Schools' project became a necessity and the funding for the kits had come through.
Since I had planned it, I became the one to purchase, as well as write the lesson and arrange the teaching of the mentors, while sorting out the kits, software examples and load the software onto the laptops.
A few domestic problems appeared which should have taken a few hours, but as a government department was involved, hours turned into days, and not just one.
The added tasks didn't stop there, so my time available to learn how to use Eagle, design a board, send it away to be made and sort out any mistakes was removed.
In an ideal world with no added complications, I would have used the Wurth and TI products in a custom designed board for this Proof Of Concept.
My apologies to our sponsors but if you happen to market a 48 Hour clock, please send me a link to buy it.
I'm not suggesting this is a final product, and this is where there is room to make amends.
Some of the other challengers have designed other parts that will be suitable as the final product, or the design incorporated into it.
In the meantime I have ordered one of these, which uses the TI chip
Mockup
I'm not quite ready to show the final product this illuminates, but its already drawn some attention as I carried it through the office at work.
This is the mockup of the parts to be used sitting on the opaque disc.
minus the USB to LiPo charger which somehow wasn't in the photo
For safety reasons I will be swapping the LiPo shown here.
This was obtained for a RC application and the 20C at the end indicates it has no protection mechanism.
Adafruit have provided a very good article that helps de-mystify the LiPo minefield.
https://learn.adafruit.com/li-ion-and-lipoly-batteries/overview
So if you want to avoid this
Use a LiPo with protection, or stick with a LiON from a cell phone which has a rigid case and inbuilt protection device.
Hopefully my next post will show a working illuminated ?????
mark
edit 14/06/14 to show the universal charger uses the TI chipset.