Special thanks to GC for pointing me in the right direction regarding AC motor control using triacs.  Rooting about on the web, I found an excellent Word document describing AC power control using a microcontroller.  Basically, the technique is the same as using PWM using DC motors, except that timing becomes more critical.  Power is turned off when the voltage crosses the origin, for whatever the PWM period is, and is turned back on for the remainder of the cycle.

Ok.  This was my second attempt.  Along the way, I discovered that printing on a color printer is a bad idea.  Why?  High end color laser printers put a waxy coating on top of their toner to protect the stuff they print out.  Now, reverse that coating when ironing on to a circuit board you can imagine that the protective coating prevents the toner from transferring to the board.  And, it makes it a pain in the ass to clean the board afterwards.

You may notice that this board isn't quite as pretty.  It looks like someone might have hand drawn some of the traces...Here is the thing, electronic circuits like big, round, fat traces (they make the rockin' world go round)! ...

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I just tried hooking both servos up to my prototype board, to no avail.  I had already been concerned about power problems, which is what prompted the design of the printed board.  Unfortunately, I made some serious errors on the board and will need to modify the plans.  Namely, the pads need to be larger, and I printed the circuit on the wrong side of the board (it was mirrored).  I'm not real pleased with the toner transfer method of printing boards, although I will try it again before I drop it altogether.  Next I'll try the screen printing method already noted, and after that I intend to try direct printing on the board.

On the plus side of things, I had suspected power and\or noise would become and issue for me-and it did!  Since I'm in a small holding pattern with printed PCBs, this will give me a chance to mod my original prototype and work through these issues.

I've been working on some AVR circuits lately, and of course I've run into some limitations with my prototype board.  Namely, it's enormous, and I prefer to work from a CAD design (thanks Eagle).  In order to shrink my design I decided to try the toner transfer PCB method.  It goes like this:

Print mirrored circuit design on transfer paper Prepare copper clad board (scuff and degrease) Iron toner sheet onto board Soak in water to remove paper This is a step I added-bake the board in the oven at 400 degrees for 10 minutes.  My initial attempts had problems with the toner lifting from the board. Touch up the traces with a marker\paint Etch After trying this out, I can tell you...it is not easy or free of frustration.  It is cheap, though, and it would be great for prototyping surface mount boards.  My board is a through-hole board...so I still have lots of drilling to do.  A more promising method might be to use high resolution screen printing to get the resist onto the board.  This way, one screen...

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My name is Gary Holbrook, and you can view my resume at www.garyholbrook.com, or you can email me at gholbrook at digitalintuition dot com.  By day I am a C# developer.  By evening, I like to work on electronics projects.  Since my background is in programming, I am naturally drawn to microcontrollers.  Atmel is my manufacturer of choice because I like the price of the Winavr suite of tools.

I build my own circuit boards from scratch, using a photo transfer process and ferric chloride etchant.  This is all part of my philosophy on electronics, which (in summary) dictates that the best electronics projects are the least expensive!