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Hi guys, I'm trying to transfer 1

Hi guys, I'm trying to transfer 1

Hi guys, I'm trying to transfer 1

Hi guys,
I'm trying to transfer 12VDC of power by means of using air core transfomer and my goal is to have regulated 9V at the end to power up a load circuit (arduino + leds + module). The schematic is attached. I read 1.3kHz on this setup.

If I remove the load, the voltage across C4 can reach 20V, however if I put the load I only get around 4.0V.
If I probe the FET Drain-Source it looks like the picture attached. I tried putting snubber across it in attempt to minimise the oscillation (values 2 Ohm, 2.2uF and around that) but it doesn't help.

So far I've tried:
1) Lowering or increasing the frequency by changing the values of R1,R2 and C3, but it couldn't increase the output.
2) Increasing the number of loops of both coils, but it doesn't help (tried 100 turns, 300 turns, 500 turns).
3) Rewinding primary coil on a slightly bigger diameter so that it gets nearer to the secondary. This increases the output by around 0.5V only. I can't make it bigger anymore because I need the primary to spin on a motor.
4) Changing the primary to 150 turns I can have 4.5V, however further reducing it didn't help to increase the output. It doesn't follow the rule N2/N1*Vin. Is this because of the inefficiency of without using core?

Limitations: I could only increase the input supply to max 15V and max 200mA for the NE555P to operate, based on its datasheet.

One question, if the coils are not evenly distributed, will that affect the result? I did the coil manually by hand.

Perhaps anybody can give some ideas of what went wrong or any alternative suggestions how to increase the voltage?

RE: Hi guys, I'm trying to transfer 1

Didn't even look at the circuit, but...

Is your coil/transformer set up to handle the high-frequency AC signal you're giving it?

Dan - Owner

RE: Hi guys, I'm trying to transfer 1

Where is the flyback clamp? Should limit the voltage to about 24V when the FET turns off. A resistor in series with the gate can sometimes help too.

RE: Hi guys, I'm trying to transfer 1

"trying to transfer 12VDC"

This is a problem; 12VDC is a VOLTAGE not a power. What is your load current?

Your basic description is saying that the transformer can't carry the actual power that you are trying to transfer.

TTFN (ta ta for now)
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RE: Hi guys, I'm trying to transfer 1

Why invent the wheel, I would use one of these as the power source

Transmission through air can be difficult with even at a small distance. While sending power is difficult, you sensor circuits will have no problem picking it up.

RE: Hi guys, I'm trying to transfer 1

I'd say using an NE555 for this is far too new-fangled. Try with vacuum tubes.


That aside, there are plenty of contactless PSU/charging solutions out there. It's not rocket science.

RE: Hi guys, I'm trying to transfer 1

Quote (OP)

I can't make it bigger anymore because I need the primary to spin on a motor.
Your overall problem may be as much mechanical as electronic.
Generators have been transferring power from a spinning element for a few years now without the problems that you are seeing.
Dynamotors date back to WWII. They do exactly what you seem to be trying.
Why air core?
There is a bog difference between an air core and an air gap. If the length of the magnetic air path can be reduced from inches to 1/1000s of inches, they efficiency of power transfer may be increased in the same ratio.
I am not seriously suggestng a dynamotor.
The point is that with a spinning coil there are proven, dependable and efficient techniques to transfer power out.
You may not need any on-board electronics at all.
With good generator based design you may be able to use a simple off the shelf voltage regulator to regulate the final voltage.
Depending on the load you maybe able to get a voltage that is stable enough to use without any electronics.

"Why not the best?"
Jimmy Carter

RE: Hi guys, I'm trying to transfer 1

Try removing D1 and D4 and then grounding the terminal on the transformer.

God made the integers, all else is the work of man. - Leopold Kroenecker

RE: Hi guys, I'm trying to transfer 1

Of course it is going to ring. The coil should be driven with a full or half H bridge.

RE: Hi guys, I'm trying to transfer 1

For high energy transfer need high frequency transmiter/receiver system.
What is distance between coils?
Put primary coil in a H bridge to gain entire induction excursion of core.

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