Thread subject: Homeroasters - Home Roasting Coffee Community :: Presto Poplite Wiring Problem

Posted by ChicagoJohn on 11/18/2018 5:27 AM
#7

Quote

renatoa wrote:

Standard dimmers, i.e. zero cross based, does not like inductive loads as are transformers... or induction motors...
We are using here PWM DC dimmers, placed in series with the motor.
There principle is different, they are chopping the rectified sine, or DC, in multiple high frequency pulses, about 500 Hz, with variable duty cycle.


Rheostat / coil-based voltage regulators (autotransformers) don't work well with inductive loads. However residential light dimmers of the rotary type are dual-SCR based devices that produce a chopped AC with varying pulse width at constant frequency.

I used a common rotary light dimmer from Home Depot on both of the popper builds I did on the 120VAC primary side of the 24VAC transformer with a full-wave bridge rectifying the output to unregulated DD, and they continue to work fine. On the larger air-roaster I did, I used a cheap SCR (triac) to control the 120VAC universal vacuum motor.