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To triac or not to triac...

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mneary

New Member
So called RFI filters can take care of that
I'm not mentioning RF, what I'm describing is that if you turn on for a few cycles and off for a few cycles, the distortion on the line is between between about 10 and 25 Hz. This is visible on many types of light bulbs. You're also supposed to avoid drawing a DC component, which means no half cycles.

Of course if you aren't exposing this to regulatory approval, you'll probably only annoy yourself with the flickering.
 

Boncuk

New Member
to triac or not to triac

Hi winterhunter,

actually you don't require a PID control. A PI control will do for heating purposes. Compare the desired temperature with the actual temperature. If the difference is very high there will be the "D" automatically switching the Triac at each zero crossing. As the values get closer you just cut every second control cycle and further cut more and more. You might used fixed values based on measurements (e.g. temperature rise time) If the temperature overshoot is too high, just note the overshoot and stop heating shortly before max temperature is obtained. (due to the "battery like" accumulation of heat in the heater)

The same way it is done with my temperature controlled soldering station and it keeps the temperature almost constant, although the circuit receives disturbance by the damp sponge from time to time.

Don't complicate things if you can get good results investing little time in measurements.

This circuit is not going to have the same accuracy as an auto pilot. That one has to take care of tendencies already.

Regards

Hans
 

eblc1388

Active Member
mneary said:
You're also supposed to avoid drawing a DC component, which means no half cycles.

You simply have the TRIAC conducts even number of cycles, then skip multiples of even cycles.
 

Hero999

Banned
A good way to increase relay life is to add a series resistor to the freewheel diode so the current decays as quickly as possible, causing the contacts to open as quickly as possible which will reduce arcing to a minimum.
 
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