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Russell McMahon ♦
Russell McMahon ♦
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I was reading Hack Into a Timer AC Socket and when I got to this paragraph:

The design firstly have a RC buck? (not sure how to call correctly in English) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

WARNING - ALL PARTS OF THIS CIRCUIT SHOULD BE CONSIDERED TO BE AT AC MAINS POTENTIAL AT ALL TIMES.

Capacitor C1 MUST be an "X RATED" capacitor specified by its manufacturer
for "across mains" use. NB NOT 'Y' rated.
Examples of X & Y rated capacitors

Schematic

I was reading Hack Into a Timer AC Socket and when I got to this paragraph:

The design firstly have a RC buck? (not sure how to call correctly in English) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

Schematic

I was reading Hack Into a Timer AC Socket and when I got to this paragraph:

The design firstly have a RC buck? (not sure how to call correctly in English) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

WARNING - ALL PARTS OF THIS CIRCUIT SHOULD BE CONSIDERED TO BE AT AC MAINS POTENTIAL AT ALL TIMES.

Capacitor C1 MUST be an "X RATED" capacitor specified by its manufacturer
for "across mains" use. NB NOT 'Y' rated.
Examples of X & Y rated capacitors

Schematic

Added title to naked link. Tried to bring schematic here, but couldn't.
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Ricardo
Ricardo
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What's the name of this circuit, and how does it work?

I was reading http://blog.electrodragon.com/hack-into-a-timer-ac-socket/Hack Into a Timer AC Socket and when I got to this paragraph:

The design firstly have a RC buck  ? (not sure how to call correctly in englishEnglish) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

Schematic

What's the name of this circuit, and how does it work

I was reading http://blog.electrodragon.com/hack-into-a-timer-ac-socket/ and when I got to this paragraph:

The design firstly have a RC buck  ? (not sure how to call correctly in english) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

What's the name of this circuit, and how does it work?

I was reading Hack Into a Timer AC Socket and when I got to this paragraph:

The design firstly have a RC buck? (not sure how to call correctly in English) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?

Schematic

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Nathan Friedly
Nathan Friedly
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What's the name of this circuit, and how does it work

I was reading http://blog.electrodragon.com/hack-into-a-timer-ac-socket/ and when I got to this paragraph:

The design firstly have a RC buck ? (not sure how to call correctly in english) circuit to step down the voltage from 220V AC to 5V AC, a 0.33uf safety capacitor (yellow one) used here, accompanying with a 1M discharge resistor. And after these two there is another current limited big resistor to prevent pulse and shock.

I was curious - I didn't even realize you could change AC voltage levels without a transformer (or at least not cheaper than with a transformer).

I understand that a resistor will lower voltage for a given current, but I would have expected AC mains to be too much power for a cheap resistor. And I don't get what the capacitor does - even if it is helpful here to get smoother DC power, wouldn't it interfere with anything else on the same AC line?