My wife has gone to bed so I did a quick search for a refresher on the 555 (I am 69 years old and I did not want to admit that I could not draw the block diagram of a 555 from memory to show her how the brightness control circuit works!)
Thanks very much, I am an internationally experienced industrial control geek and have had the honour of teaching basic Electronics at the local community college but, while of course I have some 555s in one of the scores – perhaps hundreds – of little plastic drawer cabinets in the basement (labeling has faded with the years but I had no trouble reading 555 and 556) I must confess that I’d forgotten what the internal block diagram looks like and my wife is building the Flola table lamp project (a young Czech designed a lamp with flower petals that are opened and closed by a stepper motor under the control of an Arduino that reads the position of a joystick in the lamp base) and the brightness is controlled by a 50K rotary potentiometer which is built into the Arduino joystick but actually has nothing to do with it: it varies the duty cycle of the 555-based astable which drives a MOSFET that sinks the LED current.
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