I have been all over the web looking for help with this topic and no one has been able to help me with this or they dont have the time to help me. I do a lot of volunteering through Scouts Canada as a first aid attendant and most of that is dealing with children. Getting through to them is hard so we try and include as much comic or other child based stuff into out items as possible, for example we have a Batman logo on a lot of our stuff and they seem to like that. But what I really wanted to do is to make a Blue Lantern ring.
(from the Green Lantern comics expanded universe) but through a 24.5mm (Rechargeable CR2450) in there and making a limiter and wireless charger to have placed in the inner loop of the ring (hugging the finger) and that way I can place it on like a wireless charging device to charge it. All it needs is 1-3 blue smd leds, a charge circuit (wireless when on the mat, I have noticed the SMD voltage regulators have an enable pin allowing them to only be on when receiving power) and and a battery to hold the charge (I could be swayed to use a supercapacitor as they will charge faster but will only last about 2-3 hours instead of 2-5 days.
I have been working on circuit after circuit after circuit trying to make it work but I am still new"ish" To electronic designing and was hoping to get some help from on here.
Another idea I had was to make the whole thing a micro crystal radio and put the circuit inside that so that you would be able either draw power from that (with or without a battery) that is another thought.
The ring its self has leyway on the actuall size of it But I am aiming for under 24.5mm so that the biggest part is the battery(on the top of the ring) and the coil that goes around the finger but under whatever I make the ring out of.
I am thinking of making a silicon mild for the ring and casting it in resin making it waterproof but again Even if it is just the LED, the battery and the charge circuit I would be happy!
I would be glad to get any input from anyone who has any on this topic! I know this is a really odd one but if is for a good cause!
Links: to understand what I am trying to do…
Pics of the ring;
http://www.google.ca/imgres?imgurl=http … =0&ndsp=12
http://www.google.ca/imgres?imgurl=http … 12&ndsp=26
Wireless power examples;
http://www.instructables.com/id/Wireles … -Fast-Way/
http://www.instructables.com/id/Wireless-Ipod-Charger/
https://www.youtube.com/watch?v=hg6d1IxBBqg
Got some input from a friend on the subject they suggested putting metal contacts on the front of the ring instead of a wireless charger. thus being able to have more control over the voltage coming through to the device and not needing to have an onboard voltage regulator. Any thoughts?
It’s your project. But having a direction connection is so much simpler. Why don’t you use the metal contacts until you have a working prototype, then later see if you can incorporate the wireless charger?
ldickson:
Got some input from a friend on the subject they suggested putting metal contacts on the front of the ring instead of a wireless charger. thus being able to have more control over the voltage coming through to the device and not needing to have an onboard voltage regulator. Any thoughts?
I had no idea of what a Blue Lantern ring would look like so I Googled it. Seems there are a lot of toys made in that image, not that that should stop you. Looking at those I thought a single LED through the proper diffuser would look like most of the rings I saw. I also wondered if an edge-lit acrylic art type of ring might be a little different. In any case I think leaving the charger out of the ring and into a separate base is a good idea. I can envision a single charger charging multiple rings and so saving some $$s there.
Yea I think that for now anyways, using the metal contacts on the ring for the power input until I can design a better more efficient wireless charger. Though this now brings the question on how to charge https://www.sparkfun.com/products/10319 It is a Lithium Ion 3.6v 110mah battery, I believe I can use a https://www.sparkfun.com/products/674 Though it says that the min output is 100mA, would I be able to use resistors to lower the current output so that it would be around 30-40mA so that I wont blow up the battery, or even lower for a more long charge so that I can leave it overnight (from like 1am till around 6am) or even another means of charging the battery would be nice!
I think this poster had it right re: the battery you linked to …
CaptainKirk / about 4 years ago / 3
A rule of thumb for most lithium batteries is that you should be safe with anything around 1/3 C or lower for charging and discharging. (C being the amp-hour rating of the battery.) So limit the current in or out of this one to about 37 mA or so. I’d recommend ½ C (55 mA) as a maximum. Any more and the overall charge discharge cycle life of the battery will suffer.
A typical charger will first check the battery condition by using a low value test current, then charge for a couple hours or more at a constant current until the voltage reaches the design limit (typically 4.2 Volts). At that point the voltage is held constant and the current is monitored. When it falls to 10% of the main charge current the current is turned off. You must not trickle charge lithium batteries. And usually the temperature of the battery is monitored while charging.
For SFE’s basic charger sku: PRT-10217 you’d want to change R4 from 2 kOhms to about 30 kOhms.
This is for plain vanilla lithium batteries.
There are batteries for RC cars and copters and such that can handle 10C, 20C or more, and folks are working on batteries for cars that can be charged at 100C (essentially taking the same amount of time it takes to fill a gas tank).
So if you lower the charger current, you don’t have to worry about “full charge”, the IC will take care of it.
