The following fuzzy picture is of my prototype hysteresis free 120V phase angle controller board... I am still tweaking it for maximum performance range but it does work very well for managing power input over a wide range... Starting with the potentiometer turned all the way clockwise the controller is off... Once the potentiometer is turned clockwise a small amount the controller starts producing power at around 5 volts and continues producing up to about 107 volts... The high end is where I need to improve the performance... If I can get it to produce right up to 114 - 117 volts it will be performing as well as several of the other phase angle circuits I have built... Essentially, 5% to 95% of voltage control range is about the best we can expect from phase angle control...
The Parts
BR1 - 100V 1.5A diode bridge
R1 & R2 - 2.2K Ohm 1/2W resistors
R3 - 2.2K Ohm 1/2W resistor
C1 - 250V .1uF capacitor
DIAC - 32V triggering voltage diac
POT (not shown) - 250K Ohm 1/2W potentiometer
Wiring Connections
MT1 - goes to MT1 terminal of the power triac which receives mains voltage
MT2 - goes to MT2 terminal of the power triac which also connects to one terminal on the
heating element
GATE - goes to the gate terminal of the power triac
TO POT - goes out to an end terminal of the potentiometer
FROM POT - comes back from the center wiper terminal of the potentiometer
I will be playing with different component values for R3 and C1 in an effort to boost the high end voltage because at 107 volts the controller is only producing ~1193 watts from a 1500 watt element... Boosting to 117 volts would yield ~1425 watts... Then adding a jumper would allow for a full 1500 watts...
Stay tuned as I will be working on this controller circuit, albeit slowly, over the next several weeks as time allows... I will provide a schematic and additional pictures as the project progresses...