Detecting 220VAC - Page 1
Forum section: electronics / projects

author: headingwest
author_rank: Newbie
timestamp: August 14, 2014, 11:17:31 pm
content: Hi,I have a component (Solenoid valve) that gets switched by 220V AC. These are fairly low power devices - 4 to 8 watts.I'm looking for a simple switch to detect when these are powered. So almost a reverse relay that uses 220VAC to switch a signal - instead of using signal current to switch 220VAC.What's the simplest way to do this??Thanks for your help.

author: David Hess
author_rank: Super Contributor
timestamp: August 14, 2014, 11:50:54 pm
content: An optocoupler can be used to do this. Use the same circuit that would be used to directly drive an LED from 220 volts AC.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 15, 2014, 12:16:42 am
content: When you say "detect" what does that mean exactly?Do you mean a human visible indicator? Like a pilot-light?Or do you mean something that can be connected to some electronic system?If the latter, then these modules are specifically designed and rated for exactly such applications...IAC5A AC Input, 180-280 VAC, 5 VDC Logichttp://www.opto22.com/site/pr_details.aspx?cid=4&item=IAC5AThe IAC5 input module is used to sense ON/OFF AC voltage levels at 180-280 VAC. All AC input modules are designed with filtering on the input and a hysteresis amplifier for high noise rejection and transient-free clean switching. Each module provides up to 4000 volts (transient) of optical isolation between the field inputs and the logic output of the circuit.Typical uses and applications include sensing the presence or absence of voltage or sensing contact closures from sources such as: Proximity switches, Limit switches, Float switches, Selector switches, Push buttons, Toggle switches, Thermostats

author: headingwest
author_rank: Newbie
timestamp: August 15, 2014, 02:07:30 am
content: Thank you for your replies.I was hoping to have a simple switch that didn't require VCC input. Like a packaged reed switch sensitive enough to detect a small AC current. Also with a digital on/off rather than an analog output.For example these require analog:http://www.ebay.com.au/itm/TA17-03-Octopus-Non-invasive-AC-Current-Sensor-Brick-Module-For-Arduino-/321175364393?pt=AU_B_I_Electrical_Test_Equipment&hash=item4ac78b2329&_uhb=1

author: penfold
author_rank: Frequent Contributor
timestamp: August 15, 2014, 08:17:38 am
content: A sensitive current transformer, that's self powered.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 15, 2014, 11:07:16 am
content: Whats wrong with a normal 220V coil relay?

author: David Hess
author_rank: Super Contributor
timestamp: August 15, 2014, 02:36:18 pm
content: Those solutions seem a lot more expensive than what I suggested. I would use a circuit similar to the third example shown here:http://electronics.stackexchange.com/questions/96087/how-detect-ac-signal-in-avr

author: PepeK
author_rank: Regular Contributor
timestamp: August 15, 2014, 02:47:53 pm
content: Which goal do you want to achieve ?Be sure valves are on ? It is not enough to detect 230V voltage on them, their coils can be broken ...It is better to detect a current through them - a current transformer or 3 x silicon diodes in series (in both directions !) plus resistor and input diode of optocoupler ...

author: David Hess
author_rank: Super Contributor
timestamp: August 15, 2014, 03:07:17 pm
content: Quote from: PepeK on August 15, 2014, 02:47:53 pmI agree but only a current transformer and its simple signal conditioning are needed for this and it is only proof against an open circuit which admittedly is probably the most common failure. The current transformer conveniently provides good galvanic isolation.

author: mij59
author_rank: Frequent Contributor
timestamp: August 15, 2014, 03:10:57 pm
content: Hi,If you want to detect voltage here's an other one.http://www.dextrel.net/diyzerocrosser.htm

author: Artraze
author_rank: Contributor
timestamp: August 15, 2014, 03:44:25 pm
content: One added benefit of current detection is that, depending on the solenoid and the sensitivity, you can also detect if the solenoid actually fired. When the plunger is in place the inductance will go up and increase the reactance and decrease the current.That said, I'm under the impression that the OP is not looking to detect failure, but rather just detect if it was turned on. That is, something else is switching the solenoid and he wants to daisy chain off that. If that's the case, I'd second the 220VAC coil relay.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 15, 2014, 03:58:54 pm
content: Alas, this is a typical muddled mess of an unclear question, and people randomly shooting in the dark attempting to help because the OP has not clarified the design requirements.

author: Seekonk
author_rank: Super Contributor
timestamp: August 15, 2014, 04:52:16 pm
content: There are go/no go relays where you pass a single wire through a toroid that powers a device. CR Magnetics and RK come to mind. This verifies that the pump or whatever is actually drawing current and that a fuse has not opened. That current induces a voltage that closes a relay. There are also LED versions. Relay versions generally require ten amp turns. One pass if the current is 10A, 20 if it draws .5A. In you case the non contact approach probably won't work. You could insert a small DC relay in series with the solenoid using a full wave rectifier and capacitor. The relay should match current of the solenoid. That will give you a dry contact.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 15, 2014, 07:18:31 pm
content: All those solutions...Get a coil (or hall sensor), put it near, measure. Solenoids emit field!Get a piezo, put it on, measure peaks. Solenoid emit a "click".Get a speaker, put it on, listen.But, please, get a relay.http://nl.farnell.com/omron-industrial-automation/mks2piac230/relay-dpco-230vac/dp/1691484Reading about "reversed relays" makes me think you don't know there are AC relays as well.