230V => 5V smart Solution

[BigBenz63]

Hi there,
does any one have an smart idea how to pick up a 230 AC signal and convert it into a 5Volt DC Signal. ....Without using a relais
I do need pick up a on /off 230AC signal like a pump being switched on and off. Is the an easy and smart way to convert this in a 0/5Volt Signal the can be processed by an Adruino analog or digital I/O?
Any help is highly appreciated .... I was thinking on a opto IC or similar but could not find any.
Thanks for your response.

[bigred1212]

You want a current sensor.

You don't say what kinf of amperage we are talking about.

Something like this appropriately sized:
http://www.seeedstudio.com/depot/Noninvasive-AC-Current-Sensor-100A-max-p-547.html

Edit:
This might be helpful as well.
http://www.homautomation.org/2013/09/17/current-monitoring-with-non-invasive-sensor-and-arduino/

[eehobbytoronto]

This one can be used as an AC or DC isolating step down transformer:
http://www.ebay.ca/itm/HALL-EFFECT-DC-TRANSFORMER-STEP-DOWN-VOLTAGE-ISOLATING-ARDUINO-COMPATIBLE-/231069056757?pt=LH_DefaultDomain_2&hash=item35ccc9fef5

[Grumpy_Mike]

You want a current sensor.

It sounds to me more like he wants to detect when some AC device is switched on.
The best way to do that is with an opto isolator. Have a resistor and diode feed the LED in the opto and connect the output between the arduino input and ground and enable the internal pull up resistor.

[bigred1212]

Well in that case, one could use something like:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_320653_-1

but I would have zero idea (and zero confidence in) how to hook that baby to 230AC.  

[Grumpy_Mike]

but I would zero idea (and zero confidence in) how to hook that baby to 230AC. 

Like the circuit below but note that I would use 15K rather than the value shown here.
Also if you want it to be a constant indicator then put a 0.1uF capacitor across the LED.

[bigred1212]

See, I'm confused because the specs on the 4N33 say:

Input Type   DC
Number of Channels per Chip   1
Maximum Input Current   80mA
Maximum Reverse Voltage   5V

Output Type   DC
Maximum Forward Voltage   1.5V

[jremington]

Here is a useful discussion http://www.raspberrypi.org/forums/viewtopic.php?f=45&t=9617
The simplest circuit is attached. It will give a pulsating 50/60 Hz signal. The capacitor should be rated at 330 VAC continuous operation, minimum.

[bigred1212]

Hmmm.  A 330v AC capacitior makes me nervous.

http://www.grainger.com/product/DAYTON-Start-Capacitor-2MEL3

And it's US$13.

[jremington]

Hmmm.  A 330v AC capacitior makes me nervous.
http://www.grainger.com/product/DAYTON-Start-Capacitor-2MEL3
And it's US$13.

That motor starting capacitor is about 650 times larger than the 100 nF capacitor specified in the design I posted, and is correspondingly more expensive. The 220 VAC line is very dangerous and should be interfaced only with components designed for the purpose, with human safety in mind.

Capacitors like the one in the design are often used as noise filters, connected directly across the AC line, and can be salvaged from the power supply section from almost any piece of reasonably modern, but junked equipment.

[Grumpy_Mike]

See, I'm confused because the specs on the 4N33 say:

Input Type   DC
Number of Channels per Chip   1
Maximum Input Current   80mA
Maximum Reverse Voltage   5V

Output Type   DC
Maximum Forward Voltage   1.5V

What is the problem with that?
The diode makes the input DC and stops any reverse voltage. The resistor limits the current.
Yes you can use a capacitor in place of a resistor, it is just that capacitors at this voltage are far more expensive than a resistor.

[BigBenz63]

@ Grumpy-Mike
yes that suggest solution sounds feasable.
@ jremington
yours is also looking good.
I thought that these setups might be availbale of the shelf.
Opto Coublers are quite common but I've never used them before.
I only need to pick up a digital 230AC voltage signal (on / off) and convert it to (on / off 5 Volt, HIGH / LOW Signal)
I've been looking and found a 230V AC mini relais based solution for about € 10.
I thought that others would have the same issue when dealing with home automation issues.

[michinyon]

What is the problem with that?
The diode makes the input DC and stops any reverse voltage.

So,  when the bottom connection of the AC is positive and the top connection of the AC is negative (  which happens half the time ),    then how is there not a large reverse potential across the input side of the optocoupler ?

[Grumpy_Mike]

then how is there not a large reverse potential across the input side of the optocoupler ?

Because of that series diode, it is not conducting and so there is no circuit.

[michinyon]

The other thing with this approach,  is that you are connecting to both lines of the A/C.

With a current sensor,  you only need access to one of the lines of the A/C.   With some situations,  that can be more convenient.