Relays needed to control lights via MC?

I just bought a Make Controller at the Maker Faire this past weekend, downloaded mchelper, plugged in the MC to my laptop via USB, and verified that I could control it (by controlling LEDs through mchelper).

I have a project in mind where I need to control three 100W incandescent light bulbs via the MC. I am new to electronics and am trying to get up to speed on it. My question is, must I buy 3 separate relays and hook them up to the digital outs for MC controllability? If so, what kind? My basic requirements for the switching of each light bulb is that it be electronically controlled via the MC (obviously), fast (because I want to be able to support a strobe-like effect), and reasonably silent (I don't want audible clicking during switching, if possible).

Just yesterday, I also purchased the Make Controller 9V 1.7a AC adapter here at MakingThings. Will the power from that be able to drive the MC board *and* the 3 lights (and relays, if needed)?

The actual triggering of the switching is still to be determined. It may be via sensors or via commands received through the MC web server. I figured that part shouldn't matter at this point (unless maybe the same 9V AC adapter's power is also used to drive those sensors?)...

Sorry for the newbie questions and thanks in advance,

Mike

Oh, and I forgot to mention that those three 100W light bulbs need to be independently controllable. You may have inferred that, but I didn't explicitly state that requirement above. The 3 light circuits should also be normally open (i.e., each light should not light up unless the MC sends power (or a control signal) to it (or its relay))...

Mike

first. Your wall adapter will NOT be nearly enough to power your lights, you'll probably need a 110 outlet.

second. 3 relays will work for your application but for bigger relays you may hear some subtle clicking.

third. A relay will have a switching frequency maximum, you'll want to check that out when you purchase it.

fourth. you should be able to pick up a good relay at radio shack. For my projects i have controlled normal lights with an automobile relay, just make sure you pick up one with a current rating that seems high. (5-10A). and that should do it.

If you can't stand the clicking, you'll probably have to either build a special flash circuit (maybe with disposable camera flashes) or buy something off the shelf

What Aaron said, plus...

fifth.  There exist devices called "<a href="http://en.wikipedia.org/wiki/Solid_state_relay">solid state relays</a>".  They are expensive, but they operate silently, and should be trivially easy to connect to the MC.

sixth. With a 100w non-inductive load, it should be possible to do what you want with 3 triacs (and biasing/support parts).  Of course, you'd need to build the circuit for that.  If MC ground cannot be tied to the mains neutral line (I wouldn't advise doing that for safety reasons if nothing else), you'll need optoisolators between the MC and the triac gates.  There are optoisolators with triac output stages, which are probably the best choice for driving a triac gate.  <a href="http://vitsch.net/projects/lightcontrol/">Here is a project</a> that somebody wrote up about doing pretty much exactly what you want.  It includes the aforementioned optoisolators.

I assume you already know to exercise due care when working with mains voltages.

There is a limit to how fast you can strobe incandescent light bulbs because they take some number of milliseconds to light up and to turn off.  If you've ever been waiting in traffic behind a car with incandescent turn signals (as opposed to the newer LED ones), you know what I mean.

good call on the solid state relays, hadn't thought of that...

Aaron & Lou, thanks very much for your tips. I have a long way to go before I can intelligently design this thing, but you've given me great ideas. Thanks again!

Reading a back issue of Make Magazine, I found a Halloween controller board project which utilized three Crydom D1225 SSRs for AC devices (plus a couple other Crydom SSRs for DC devices). The D1225 sounds perfect (but a bit overpowered, allowing 25A current), so I've bought one on eBay for experimentation.