Switching an appliance on and off


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by aeary » Sun Jun 17, 2012 7:25 pm
How would one go about using the basic GPIO as simply dry contacts to trigger passive relay? I.e. GPIO goes high and completes a circuit then triggering said relay. Would you be using the shared ground and the GPIO pin?
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by rurwin » Sun Jun 17, 2012 9:36 pm
No. The GPIO outputs are not voltage free. They are a source or sink of a few milliamps at 3.3V
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by patrikg » Sun Jun 17, 2012 10:58 pm
Have you look at gembirds products ??

Via USB
http://www.gembird.nl/item.aspx?id=3234

Via LAN
http://www.gembird.nl/products.aspx?sg=239

I have seen linux ports of programs.

http://sispmctl.sourceforge.net/


Best regards
Patrik
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by aeary » Tue Jun 19, 2012 5:46 pm
Backstory, I am a computer/networking guy that is more than adept with a soldering iron but still fairly fuzzy on anything more complex than a basic circuit. I have seen suggestions of using an optical isolater (octocoupler) or a solid state relay to do what I am attempting to do...does anyone have any more specific information on setting this up in conjunction with the GPIO pins to simply complete circuits?
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by abishur » Tue Jun 19, 2012 6:19 pm
aeary wrote:Backstory, I am a computer/networking guy that is more than adept with a soldering iron but still fairly fuzzy on anything more complex than a basic circuit. I have seen suggestions of using an optical isolater (octocoupler) or a solid state relay to do what I am attempting to do...does anyone have any more specific information on setting this up in conjunction with the GPIO pins to simply complete circuits?


My thoughts on this after a whole lot of research:

1) Since we want to control appliances with the GPIO it makes sense in this application to design it with a pull down resistor making sure the optocoupler doesn't getting floating voltages

2) Optocouplers aren't designed to directly control circuits, they're designed to control triacs (Which control the circuit).

3) For mains voltages SSRs are basically prepacked Optocouplers+triacs, so you're really just making a diy, cheaper relay

4) Here's some links to resources I've been reading to get a hand on the GPIO controlled circuit design. (The following lines are all links)

First one by our forum's very own Grumpy Mike

Sparkfun describes the differences between a pull up and a pull down resistors

An Ardunio tutorial, it uses 5V rather than 3v3 but the information it provides is priceless!

I was originally looking at the MOC3010m, but I think it requires too high a mA current to drive it, so I revised my optocoupler to the Vishay VOM160NT, it only needs 5mA to drive it, so I think it will work a lot better in the long run, especially if you want to control more than one thing at a time using nothing but the power/current provided by the gpio pins.
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by thienson30 » Tue Jan 21, 2014 12:35 am
Check out my youtube video at http://www.youtube.com/watch?v=5dmvT6vTV2w

Hardware (85volt to 260volt RF Relay Receiver) is available at http://www.ebay.com/itm/271337832780?ss ... 1555.l2649
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by Richard-TX » Tue Jan 21, 2014 12:42 am
Why don't you use solid state relays?

- 3-32 volt triggerable
- Opto isolated
- up to 40 amps@240 volt capable.
- Not expensive.
- Silent

I use them for a variety of things; from controlling lamps, to controlling air compressor tank drains, to controlling two 1000 watt audio amplifiers.
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