User:Jstapko/EngLab/LampDimmer

=Lamp Dimmer=

An electronics project to build a control for the acrylic sheet bender

potentially useful links

 * neon lamp dimmer Figure 2 on this page contains a circuit that may allow me to use back to back zeners instead of a diac
 * Incandescent lamp dimmer using neon lamp instead of diac
 * bristolwatch.com triac tutorial, including how to test triacs
 * AllaboutCircuits page on SCRs
 * Allabout Circuits page on Shockley diodes
 * Understanding Shockley Diodes really helps to understand SCR's and triacs


 * alternate circuits for neon lamp based triac dimmers
 * very detailed discussion of dimmer topics
 * triac heater control circuit
 * page explaining quadrac
 * bridge rectifier/mosfet dimmer controlled by arduino PWM
 * video showing how to spread heat sink grease

Links found while working on the diac problem, August 14
Major points inclued:
 * learnabout-electronics page on diacs
 * diac is roughly equivalent to 2 diodes back to back with cathodes connected together internally
 * introduces opto-triac, an optoisolator that switches ac instead of dc
 * diacs, triacs, and SCRs can introduce large amounts of RF hash due to switching transients, and efforts should be taken to reduce or contain this

major points:
 * allaboutcircuits page on the Triac
 * triacs tend to start conduction at different voltages in one direction than in the other (which would create pulse widths of unequal width, depending on polarity)
 * assymmetric firing of triac introduces harmonics, particularly even harmonics, into the power system, an undesirable condition
 * one way of improving the symmetry of triac conduction, and thus reducing harmonics, is to use a Diac
 * another way to increase the symmetry is to use individual SCRs for each half of the cycle (like the ignitron motor drives of the late '40s)
 * a triac will fire reliably without using a diac, with a simple RC network
 * triac main terminals are NOT interchangable

Other Options

 * have HCC buy a dimmer
 * have HCC buy a variac
 * search "arduino dimmer"

Next Steps

 * search semiconductor supplies for a diac and triac
 * if necessary, mount triac on heat sink, using thermal grease and muffin fan
 * try to build a neon lamp oscillator, using neon lamps and a triac from the lab
 * use an SCR instead of a triac, a bridge rectifier to make AC appear as DC to the SCR like in the arduino version, and an RC network for triggering instead of a diac, as shown on the allabout circuits page for triacs