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Electronics => Electronics => Topic started by: karmax on December 09, 2009, 07:39:29 AM

Title: control 230V ac
Post by: karmax on December 09, 2009, 07:39:29 AM

i have 5v output from my sensor by which i want to control 230 V ac .i want to switch off or switch on using that 5v .it takes 25ma current only.please help me regarding the same thanks in advance

Title: Re: control 230V ac
Post by: waltr on December 09, 2009, 08:19:21 AM

The simplest and safest way is with a relay. This provides total isolation between your controller and the AC mains.

Title: Re: control 230V ac
Post by: Soeren on December 09, 2009, 08:47:10 AM

Hi,

Yes, but use an SSR (Solid State Relay) with zero cross shift, then the noise will be the minimum possible and the sensor won't need further circuitry (as it would with a regular relay).

Title: Re: control 230V ac
Post by: karmax on December 09, 2009, 08:50:34 AM

Quote from: waltr on December 09, 2009, 08:19:21 AM

The simplest and safest way is with a relay. This provides total isolation between your controller and the AC mains.

i have to control ac voltage but my controlling signal is dc.will relay works...

Title: Re: control 230V ac
Post by: BEAMer on December 09, 2009, 10:40:37 AM

yes very well...

use a transistor as a switch to control the relay coil. Your 5 V DC can switch the transistor ON and OFF..

BEAMer

Title: Re: control 230V ac
Post by: BEAMer on December 09, 2009, 10:43:01 AM

I just did a google image search and found this.

http://interactive.usc.edu/members/phoberman/relayCircuit.gif (http://interactive.usc.edu/members/phoberman/relayCircuit.gif)

This is what i am  talking about

BEAMer

Title: Re: control 230V ac
Post by: definitionofis on December 09, 2009, 10:50:49 AM

Also, a thyristor (triac) can turn on AC with a very small DC current source.
The only snag is that is stays on until the AC goes to zero and resets the device.

You might like that functionality, like a latch.

http://www.technologystudent.com/elec1/thyris1.htm (http://www.technologystudent.com/elec1/thyris1.htm)

Here is a discussion regarding isolating the 230 VAC from the 5v circuit by using an opto-thyristor:
http://forum.allaboutcircuits.com/showthread.php?t=24187 (http://forum.allaboutcircuits.com/showthread.php?t=24187)

Alternistors and snubberless triacs:
http://en.wikipedia.org/wiki/TRIAC (http://en.wikipedia.org/wiki/TRIAC)

Title: Re: control 230V ac
Post by: chelmi on December 09, 2009, 11:03:37 AM

Quote from: definitionofis on December 09, 2009, 10:50:49 AM

Also, a thyristor (triac) can turn on AC with a very small DC current source.
The only snag is that is stays on until the AC goes to zero and resets the device.

You might like that functionality, like a latch.

http://www.technologystudent.com/elec1/thyris1.htm (http://www.technologystudent.com/elec1/thyris1.htm)

A triac is two thyristors. And since it is used to switch AC, there is no observable latch effect: the current  is null every half cycle.
I used a triac to control a light with a photoresistor, it's very easy to use.

Chelmi.

Title: Re: control 230V ac
Post by: definitionofis on December 09, 2009, 11:17:05 AM

I had a hunch I had something mixed up there.
Thanks.

Here is a mechanical relay.
It does need 72 ma to trigger it at 5V.
So you would need a transistor circuit someone mentioned above.
http://dipmicro.com/store/JS1-5V (http://dipmicro.com/store/JS1-5V)

The Triacs can trigger directly on tiny currents.

Title: Re: control 230V ac
Post by: Soeren on December 09, 2009, 03:11:34 PM

Hi,

With one of these (http://www.panasonic-electric-works.com/peweu/en/html/solid_state_relays.php), you'd only need a single resistor in between and you have total optical isolation.

Title: Re: control 230V ac
Post by: Razor Concepts on December 09, 2009, 04:25:49 PM

SSRs are very cheap and easy to use (mine required no external circuitry)
http://razorconcepts.net/ssr.html (http://razorconcepts.net/ssr.html)

$7 shipped from ebay  ;D