Doug-in-the-woods
09-09-2007, 06:29 AM
Kust curious about this zero crossing stuff. I know the Renard works but what about this 15-20 hz flickering??
still wondering about a stand alone candle flicker circuit.
Zero cross switching will minimize noise in switchign and dimming. Unfortunately that appriach is not very practical for lampi dimming. At 60 Hz line frequency, you'd be limited to turning the lamp on and off at discrete 120 Hz intervals. You'd easily end up with a rather nasty 15-20 Hz flickering, unless the dimmer-driver can do some sort of dithering to spread out the flicker spectrum. I've never seen a dimmer of this sort being used.
In some occasions a single diode can be to dim a light bulb when wired in series with the lamp. The diode then passes only the positive or negative half of the mains voltage to the light bulb. If you put a switch in parallel with the diode, you end up having a dimmer wich has two settings: full on and dimmed. Diode will indeed work on small loads, but with larger loads the DC component this diode causes is not good for the distribution transformers in the electrical distribution system (will cause them them to heat up more than in normal use)
still wondering about a stand alone candle flicker circuit.
Zero cross switching will minimize noise in switchign and dimming. Unfortunately that appriach is not very practical for lampi dimming. At 60 Hz line frequency, you'd be limited to turning the lamp on and off at discrete 120 Hz intervals. You'd easily end up with a rather nasty 15-20 Hz flickering, unless the dimmer-driver can do some sort of dithering to spread out the flicker spectrum. I've never seen a dimmer of this sort being used.
In some occasions a single diode can be to dim a light bulb when wired in series with the lamp. The diode then passes only the positive or negative half of the mains voltage to the light bulb. If you put a switch in parallel with the diode, you end up having a dimmer wich has two settings: full on and dimmed. Diode will indeed work on small loads, but with larger loads the DC component this diode causes is not good for the distribution transformers in the electrical distribution system (will cause them them to heat up more than in normal use)