Author Topic: Transmitting power through a window  (Read 518 times)

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Offline hindenbugbite

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Transmitting power through a window
« on: May 13, 2021, 01:06:04 pm »
I have a usecase that seems like someone should have solved already. I want to mount my IP camera on the outside of my window and provide power through the glass without drilling through the wall. My IP camera uses 5V from a micro USB cable and typical USB charger (1A) and the window is double pane about 10-15mm gap. It seems like a wireless charging setup would be able to couple power through the glass and power the IP camera without too much effort.

I could cobble a bunch of wireless charging parts together to try, but has anyone seen or heard of a ready solution that does this? I see basically a USB power only cable that has a break in the middle with some wireless transmit and receive pads.

From a DIY perspective would it be more efficient to transmit a higher voltage (i.e. 12V) and then step it down for the device at the receiver?
 

Offline Just_another_Dave

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Re: Transmitting power through a window
« Reply #1 on: May 13, 2021, 02:27:31 pm »
Wireless charging seems to be a good solution for your problem, but you should notice that if the primary side of the converter is located near an aluminum or metal piece (like some window frames) the efficiency might drop significantly as it will also induce currents in those pieces.

If you want an off-the-shelf solution, in the past some manufacturers provided wireless charging solutions for mobile phones that didn’t include that feature (they might still make them nowadays). As the secondary side provided a microusb or a similar conector for charging the phone, it might work with your camera.

On the other hand, if you prefer a DIY solution a 2 step converter might be easier to implement, as it will allow you to use a DCX converter or a low bandwidth loop at the wireless stage, avoiding the need of high speed wireless communication channel to send the measured output voltage from the secondary side back to the regulator (wireless converters usually produce interferences in nearby antennas if they aren’t correctly shielded). Additionally, I would recommend you using PCB inductors for this stage as they are usually easier to manufacture

Regarding the voltage, using higher voltages allows to have smaller currents in the inductor which is a nice thing for reducing power losses, yet it is not critical for such a small power application. I would choose it high enough to be sure that the secondary stage can be implemented with a buck converter, but small enough to use low voltage rated components
 

Offline alexnoot

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Re: Transmitting power through a window
« Reply #2 on: May 13, 2021, 02:32:55 pm »
I'm fairly sure I've seen something like this for car antennas, like a powered/active part on the inside of the glass, and an outside part that is inductively coupled or something like that.
The problem with dual or triple pane windows is obviously the gap, a single pane would probably work with any wireless charger. The gap probably too big for anything off-the-shelf.

Also, some windows have special coatings for reduced thermal transfer, that might be a problem.
 

Offline Marco

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Re: Transmitting power through a window
« Reply #3 on: May 13, 2021, 04:54:35 pm »
Wireless charging modules are all over the place, both QI and non QI.
 

Offline hindenbugbite

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Re: Transmitting power through a window
« Reply #4 on: May 13, 2021, 09:06:23 pm »
Wireless charging modules are all over the place, both QI and non QI.

Thnaks for the link. I guess I was initially hoping there was an product that was ready to stick on a window and maybe sealed from the elements. Otherwise my research into mainly Qi charger standards left me skeptical it could handle a 15 mm gap.

But your search terms added something I didn't try before, "modules" did bring up some non QI products I had not come across in my last search. Especially the one designed to charge small electric vehicles and robots are designed for a larger gap.
 

Online NiHaoMike

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Re: Transmitting power through a window
« Reply #5 on: May 13, 2021, 11:38:25 pm »
Salvage some "flat flex" cable from some discarded electronics and add a few layers of tape to make it a little more robust. Now you can put it through the window and carefully close it to make it a through connection.
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Offline f4eru

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Re: Transmitting power through a window
« Reply #6 on: May 14, 2021, 11:58:43 am »
Yes, exactly. FPC cable is the easy solution for your case.

Offline hindenbugbite

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Re: Transmitting power through a window
« Reply #7 on: May 14, 2021, 05:30:13 pm »
Salvage some "flat flex" cable from some discarded electronics and add a few layers of tape to make it a little more robust. Now you can put it through the window and carefully close it to make it a through connection.
Yes, exactly. FPC cable is the easy solution for your case.

Thanks for the flex idea! I just might have some in the bin somewhere.
 


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