# Wireless phone charger

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#### Steve Wolf

##### Guest
Just for fun I thought I would make a wireless phone charger. I'm not really going to use it but I wanted to build it and just see if it actually worked. The circuit uses two coils and a 2n222 transistor very simple.

Well I can't really get it to work maybe I could get half a volt maybe to past through induction. Then it seems to stop. I connected my meter to the receiving coil to test.

I was using 30 gauge wire which I had although the circuit calls for 32 gauge that may be part of the issue.

However my question is , as I began to think about it and a little bit of science that I know is that induction I thought had to be AC current because there had to be movement caused by ac going up and down. The circuit as far as my reading however puts in 5 volts DC in the Base unit and passes it to the receiving coil. I'm not sure if that's going to work?

The question then is, in a simple circuit can you use DC in induction.

Thanks

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#### Nife Sima

##### Guest
On 24.02.2020 18:27, Steve Wolf wrote:
Just for fun I thought I would make a wireless phone charger. I'm not really going to use it but I wanted to build it and just see if it actually worked. The circuit uses two coils and a 2n222 transistor very simple.

Well I can't really get it to work maybe I could get half a volt maybe to past through induction. Then it seems to stop. I connected my meter to the receiving coil to test.

I was using 30 gauge wire which I had although the circuit calls for 32 gauge that may be part of the issue.

However my question is , as I began to think about it and a little bit of science that I know is that induction I thought had to be AC current because there had to be movement caused by ac going up and down. The circuit as far as my reading however puts in 5 volts DC in the Base unit and passes it to the receiving coil. I'm not sure if that's going to work?

The question then is, in a simple circuit can you use DC in induction.

Thanks
No, you can't use DC here. In fact you should not have any DC on the
coil... If you put DC in it you would get an electromagnet (or a lot of
smoke). What frequency are you driving your coil at? How many windings
does the each coil have?

QI chargers usually work at between 100 and 200 kHz for low power and
~500kHz for medium power.

Cheers, Nife

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#### Steve Wolf

##### Guest
https://youtu.be/QPL37V7JDNQ

Here is the utube video.

I have looked for for diagram but can't find one.

Perhaps I misunderstand the ac adapter he is using but it looks like an ac/DC adapter.

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#### Steve Wolf

##### Guest
PS base is 15 x 15 and recever is 20

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#### Nife Sima

##### Guest
On 24.02.2020 19:45, Steve Wolf wrote:
https://youtu.be/QPL37V7JDNQ

Here is the utube video.

I have looked for for diagram but can't find one.

Perhaps I misunderstand the ac adapter he is using but it looks like an ac/DC adapter.

It's VERY sketchy and the way they did that I'm not sure how long will
the protection diodes in the phone hang on. Having said that, the
transistor with two coils forms a flyback transformer running at some
unspecified frequency. So that takes DC and generates AC. Again, the
video implementation is super shady. More on flybacks here

As for the phone killing aspect, DO NOT connect the USB directly like
they did.. USB is DC voltage. the coils give AC voltage! Your phone is
NOT gonna be happy being slammed -5 volts repeatedly where it expects +5.
I'd put that video in the same category as coca cola can DIY crap. They
even use hot glue as well!

S