[NTLK] Wireless Charging (Grant Hutchinson)

DXH dxh at woh.rr.com
Wed Dec 22 14:55:50 PST 2021

There are a number of issues regarding incorporating the circuitry in the battery tray.

Batteries: The current battery arrangement uses 4X AA leaving little room for additional stuff. Sure, you could use special batteries but why?

Coil: Chargers work by electromagnetic induction. The Tx and Rx coils need to be as close as possible and also in alignment to ensure maximum power transfer. A coil in the battery tray would need to be small (not good) and the base of the Newton would need to be positioned over the middle of the charger (also not good).

Voltage: Yes, most of the shelf charger boards are 5V output. There needs to be at least a couple of volts overhead to run the Newton  charger circuit. That’s why the wall-wart is 7.5V nominally. There is a possibility of modifying the circuit to output a higher voltage or using a boost DC-DC converter but every addition takes something from the power budget.

Power: A lot of the charger boards are around 1W. This would take forever to charge. I would be looking for at least a 15W charger. Even that is low.

My advice is to take the 30,000 ft view and use what is already in the Newton. So, leave the battery pack alone and find out the best way to supply ~7.5 V or so to the existing charger circuit. The Rx coil could fit in the case back occupying a more central location. I would use a positional coil charger as opposed to a single coil. That way, placement is less critical.


Sent from my iPad

> On Dec 22, 2021, at 4:35 PM, Noah Leon <moosefuel at gmail.com> wrote:
> Yes, I think the chargers are based on the Qi standard if that is what the iPhone uses. I know Jake Bordens and maybe some others had done some work mapping out how the charging circuits work on the Newton, I wonder if there is enough room inside the case to put a coil directly inside the back? Most of these chargers are 5v circuits, and the Newton’s is 7v, so again I’m not sure if this would work.
> Creating a special battery pack might work ok but I think I would have to perhaps use smaller cells to make room for the chip and the coil, ad it would have to be a smaller coil. Then I don’t know much about how charging circuitry works so I am at a loss of how to direct the electricity to the right place.
> But if I had a little more info it might be a cool project for early next year. If I knew the best way to go about it I certainly would.
> Noah
>> On Dec 22, 2021, at 3:00 PM, newtontalk-request at newtontalk.net wrote:
>> The board itself is pretty small and the optional receiving coils are flat. You might be able to built this into a standard battery sled.
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