Lacerta PWM Dimmer for LED Flat-Field Box and Fans incl. Cable

Lacerta Dimmer for the control of the LED flatfield box

For the control of a FlatFieldBox (FFB) illumination for astronomical CCD cameras we need a flicker-free illumination AND an extremely short exposure time in the (sub-)millisecond range. Unfortunately, conventional dimmers cannot be used for this, but only a so-called PWM with a switch-on and switch-off frequency of 25 kHz or even faster!

What is PWM:

Theoretically, it would be sufficient to reduce the voltage by means of a resistor if we wanted to dim not LEDs but incandescent lamps. However, we absolutely need a dimmer with pulse width modulation, which controls the time interval in which the full voltage takes effect: the controlled instrument is switched off and on in quick succession.

Depending on the off/on frequency, various accessories can be operated: for a dew heating sleeve, switching on and off once per second or even less frequently would be sufficient because it is very sluggish. In everyday life, about one hundred cycles per second are sufficient for such dimmed LED light sources (e.g. living room lighting), because the human eye can hardly perceive the flashing any more from a frequency of 25 Hz. For FlatFieldBoxes (FFB), which were built for astronomical CCD cameras, at least 25 kHz are required to guarantee a uniformly illuminated surface even in a short exposure time.

Lacerta Dimmer