Control AC Outlets

Chris Dunn

I am looking to do a small Xmas light display and need to control some AC outlets.· I am wondering what is the easiest/cheapest way to control AC. I have seen some topics for relays, triacs and MOSFets.· I am rather new to the basic stamp, and everything I have ever interfaced/controlled is DC circuits. Just looking for some guidance.
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Chris

Stephen Swanson (Parallax)

Chris,
·Safest and easiest way would be with X-10. No Ac wiring needed and the code is really easy. The units you would use can be found here http://www.parallax.com/detail.asp?product_id=27940·for the interface and here for the module http://www.parallax.com/detail.asp?product_id=27941






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Stephen Swanson
Technical Support
Parallax, Inc.
sswanson@parallax.com

Jon Williams

Stephen's right -- for your application X-10 is the way to go. The BASIC Stamp has a command called XOUT that can work with differnent types of X-10 modules. Lamp modules, for example, have dimming control so your BASIC Stamp could modulate the brightness of a string of Christmas lights.

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Jon Williams
Applications Engineer, Parallax
Dallas Office

Gerry Shand

A few quick pointers here too:

a. Relays are the simplist but must be chosen with respect to load currents and voltages. John and Stephen mention the safety issue, which is very important. Relays also work in switching applications where the cycle time is 1 second or greater.

b. Triacs are good high speed solid state switches but need extra circuitry between them and the stamp. These devices have no moving parts so they lend themselves well to high speed switching.

c. In my work, MOSFETS work well in PWM applications switching DC at high rates of speed. In order to make them switch AC, you need to rectify to DC, filter and then use more than one (two or four depending on how you want to operate them) to build an inverter bridge. Lots of circuitry and work involved plus potential safety issues.

So the X-10 route is the better way to go for the least amount of fuss.

Gerry Shand

allanlane5

Note you can also use the X-10 'Firecracker' package. This does *not* use the 513 interface. Instead, you get a small module which you connect to three pins of your Stamp (X, Y, and GND). This module is powered from the Stamp, and uses RF to communicate with a module plugged in to your house wiring. From there, it controls Lamp and Appliance modules in your house.

This kit also gets you an RF remote, so you can control your house yourself.

The only drawback is I don't know of an off-the-shelf command (like the XOUT command) to implement the communications from the Stamp to the 'Firecracker', so you'd have to implement the protocol yourself. The protocol is very well documented, though.

Also note using the 513 you'll have to wire from your stamp to the module. With the Firecracker, you can be rooms away.

AlWilliamsAWC

Once again, a past project of the month: http://www.al-williams.com/firecracker.htm

Hope that helps!

Al Williams
AWC
http://www.awce.com
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allanlane5

*OUTSTANDING* Al! What a nice, complete example.

There, that fills in the only question. Now I would go with the Firecracker without hesitation.
You get an RF-driven solution, so your BS2 and BOE (or whatever) can be anywhere in the house.

AlWilliamsAWC

The link to the underlying protocol document is dead. If you really want to read it, try http://meltingpot.fortunecity.com/lightsey/52/common/cm17a.html.
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mikeslaney

We've been using Crydom SSRs for switching AC circuits with our Labview/Fieldpoint DAQs. They've been working great for controlling our lab heaters. If you're pulling a decent load on the AC side, make sure you order the "Random On" model. Crydom # ASO241R.