Incandescent Clock PCBs04 Jan 2016
I’m in the process of making a large digital clock out of tubular incandescent bulbs. I designed my own power circuitry for this clock, because it is a cheaper and more reliable option than what is available. I don’t trust the crude results of a PCB mill with high voltages, so I decided to try out DirtyPCBs.
Each board contains four relays, which can be directly or serially controlled. The 4-bit latching shift register allows the boards to be daisy chained. Each relay slot can be occupied by either a mechanical or solid state relay in the same footprint.
The dimmer emits a “zero-crossing” pulse for each time the input sine wave crosses zero volts (ex. 120Hz in US). By delimiting the waveform, the circuits allows a microcontroller to control the connected AC load by powering it for a portion of each sine period. The duty cycle corresponds (non-linearly) to the dimming intensity.