# 220 Volts to 15 Volts Capacitor Resistor circuit

Discussion in 'The Projects Forum' started by RodneyB, Sep 19, 2013.

1. ### RodneyB Thread Starter Active Member

Apr 28, 2012
646
13
I don't know what the name of the circuit is but using a capacitor and resistor the voltage can be dropped to a lower required voltage and then rectified. I am aware of the draw backs but from an economic point of view this just may be the practical route.

I would Like to know how to calculate the components to build the above at 220 Volts to 15 Volts DC.

Many thanks

Rodney

2. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,787
973
transformerless power supplies are against the rules of this forum for safety reasons..

how many amps do you need.. you can get 100-240AC to 15V power supplies for as little as \$10-15

3. ### RodneyB Thread Starter Active Member

Apr 28, 2012
646
13
Sorry I didn't even think before I posted. I want 200 mA I will look at a small power supply like that. Again my apologies

Oct 15, 2009
4,787
973
5. ### wmodavis Well-Known Member

Oct 23, 2010
737
150
Use ohms law.

The capacitor has impedance at the frequency used that can be calculated using standard equation for capacitive reactance.

A voltage divider circuit with that capacitive reactance and the resistor in series can be used to reduce the voltage.

Sep 9, 2010
12,374
3,226

7. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,787
973
If one knew how to do it properly and safely they wouldn't have to ask the question here.

8. ### wmodavis Well-Known Member

Oct 23, 2010
737
150

Yes it can. It is a technical fact that can be done. I'm not the police just a humble technical person answering a question. My job is to answer questions if I so desire to not to pass judgment on what you may consider verboten for some reason. Your job, if you decide to accept it is to lock the thread if you feel that is the thing to do. The thread was not locked when I responded with some technical facts you seem to want to deny.

9. ### wmodavis Well-Known Member

Oct 23, 2010
737
150
If one knew all about electronics he wouldn't have to ask the question here. Right? What are you here for?

10. ### mcgyvr AAC Fanatic!

Oct 15, 2009
4,787
973
The point is that this site has rules.. Their rules do not allow discussion of transformerless power supplies for safety reasons.. Just because a moderator has not come along yet does not mean you should keep talking about it.

As a forum member you should respect the rules of the forum or find another one.

11. ### Georacer Moderator

Nov 25, 2009
5,151
1,266
It seems unfair to close a thread where the OP doesn't really know what circuit he will use to do the rectification. So far the discussion was quite abstract, so I'll let it live for now.

@RodneyB
The suggestion of post #4 is a good one. For this kind of run-of-the-mill needs, a ready-made commercial solution is the cheapest and easiest.

@wmodavis

12. ### #12 Expert

Nov 30, 2010
16,665
7,310
Lucky Geo is on duty. Bill would have rapped your knuckles with a ruler.

13. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I thought strongly about moderating all of wmodavis replies, but decided to post this instead. The Terms of Service are for everyone, not just the OP. Since the OP has shown a willingness to consider a Wall Wart or some other isolating power supply I will not close this thread as is our usual policy. However, another moderator may feel differently, or if the subject of this conversation continues down the path I will close it.

There really are ways to do things wrong, and to do things right. Let's keep it safe.

Edit:

Bill is always on duty, but sometimes it takes me a while. I missed the second part of the thread when posting the above.

14. ### Georacer Moderator

Nov 25, 2009
5,151
1,266
Bill is always watching, mostly from the shadows...