On Wed, 5 May 1999 12:44:46 -0700 Tom Handley writes: While I like the proposed web interface, the single knob for temperature control is probably easier to work with! > The practical side of the user-interface has to deal with my mother... >I've selected a rotary encoder with an absolute binary output. This would >provide a range from 150F to 500F in 25F increments with 0x00 = Off... > I kinda like the use of quadrature encoders with a display. The use of the rotary control has a nice feel to it while the display gives precision in setting. A quadrature encoder should be less expensive than one with a binary output and takes less pins on the PIC. Also, you can do some dynamic scaling on it so that when you turn it quickly it makes big changes in the setting, while turning it slowly makes small changes. Also, probably cheaper than an encoder is just a pot! Run it into an analog input on the PIC and do the A/D. Only uses one pin! I think on/off control is fine for this application. You may want to experiment with how much hysteresis to put in the loop. If you do go for something fancier, a simple proportional control driving phase control of the solid state relays seems pretty straightforward. Just don't try listening to the radio while baking! Of course, you CAN move all the way to PID control. I'm not sure what this will get you. You state the heat losses through the insulation are low, so the 'droop" due to the heating load should be minimal. Even with proprtional control, you have to "tune" the loop (or at least keep the loop gain down) to keep the oven from oscillating. Harold Harold Hallikainen harold@hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]