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junaid_766
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 « on: February 18, 2009, 06:20:08 06:20 »

i m attaching a circuit diagram which is step down the 220V AV to 7-8 V

can anyone explain the working of the  1 M ohm  resistance and 1uF capacitor ,how they work and step down the voltage?
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vgg60
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 « Reply #1 on: February 18, 2009, 07:07:41 07:07 »

1uF capacitor works as voltage-dropping resistor for alternative current.  1Mohm resistor is to discharge the capacitor after disconnection from ac network. R(C)=1/(2pi*f*C)
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newboy
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 « Reply #2 on: February 18, 2009, 09:35:38 09:35 »

i m attaching a circuit diagram which is step down the 220V AV to 7-8 V

can anyone explain the working of the  1 M ohm  resistance and 1uF capacitor ,how they work and step down the voltage?

Can you share the original file please. Seem it's useful for me.

Thanks.
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FranzW
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 « Reply #3 on: February 18, 2009, 03:17:51 15:17 »

The 1uF capacitor is used instead of a resistor in the voltage divider circuit, because it will not produce heat.
At a mains frequency of 50 Hz, the capacitive reactance of the 1 uF is 3183 ohms, this means that it is substituting a resistor of 3183 ohms.
The 1 megohm resistor is just to discharge the capacitor after the input voltage has been switched off.
Regards,
FranzW
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