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Current Booster


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Most Helpful Member
No Bryan,
You have both inputs of the comparator shorted together.
The (-) input connects to the 3.3k resistor and the 6.2V zener diode.
The (+) input connects to the slider of the 2k trimpot, the 100k resistor and the 100pF capacitor.

At the output you have two zener diodes shorted together. One is used to limit the gate voltage to 15V and the other limits the supply (bottom of the 470 ohm resistors) when the supply is 24V.

The 0.1uF capacitor near the output should not connect to the gate of the Mosfet. It connects to the supply.

I think you have pin 8 of the comparator shorting the 1.5k load resistor.

Sorry Bryan,
I read your fine print.
Your dots are not connections. Usually dots are connections.
Last edited:


New Member

I have also reached to the same diagram... Bryan and Audioguru thanks a lot for givng your time.

Bryan, it seems that you use dots for jumpers.

I am going to build it today. Will convey you about the results.

Warm regards,


Active Member
mneary said:
It won't work? Why not? Maybe you forgot that brushed DC motors have inductance. The MOSFET turns on, momentarily providing a large current to the motor. The catch diode carries this large current after the MOSFET turns off. Then the MOSFET turns back on, boosting the current again.

It's really a simple switching regulator, with feedback tailored to the purpose. Maybe you should re-read the article.
OK, yeah, I'm reviewing it again and for a STALLED rotor, this design can increase the current and make it start. The stalled rotor is not acting as a motor load but simply a pure inductor, without the losses of doing work. The flyback diode maintains rotor current when the MOSFET is off, and the cap can provide higher current that the panel itself can when operated at high freq (this is not the situation where a simple parallel cap's trying to get the motor started, which would require a large cap, perhaps absurdly large).


New Member
Reg: Solar panel readings

Hello all,

How do you do?

Finaly I have built the Current Booster. Have not tested yet. I have come across following difficulty. Could somebody help me?

There are 2 solar panels - each of 60W (12V). Now when I tested one of them at around 2.00 pm in India (this is summer in India and the temparature at 2 pm is usually around 40 Degree Celsius), I read 20V output.

Now, when a variable resister of 2K (100W) was connected and readings were taken for different values, the range of output voltage across the resistor was:18.6 to 18.22.

When I measured the current flowing through it was hardly in mA. e.g. 2 mA most of the times.

Now as per the ratings the solar panel can source 5A. Could you guide me how to be confirm that the solar panel is providing this much current?

The person who sold me the panels, says that 20V output is purposefully provided instead of 12V!!!

Warm regards,


Well-Known Member
Most Helpful Member
18V across 2k ohms makes a current of only 9mA.
12V across 2.4 ohms (60W) makes a current of 5A.

The solar panel must be outdoors and pointing directly at the sun at noon.


Well-Known Member
Hero999 said:
I agree, I don't see how PMing a motor can help start a motor, if anything, it'll only make it worse.

For the capacitor idea to work, you need to give the capacitor time to charge before the motor is switched on.
It works because the motor rotor voltage is zero at zero speed. You still need a capacitor to provide the high current but the power required is reasonable.


New Member
Use your solar panels to power a tesla coil, transform it back down to 12v, then rectify it, and plug an inverter in it. That should give you plenty of power.


New Member
bryan1 Can you help me to purchase one of these mini maximiser as my eyesight is letting me down these days.


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Mirriulah, I doubt Bryan1 will see your post, as this thread is 9 years old :rolleyes:.
Welcome to ETO.


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The thread may be old, but Bryan1 is still around, he was here yesterday.


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