Very good of you to make these tutorials available in the spirit of community that is still graces the Internet, much appreciated. and one capacitor control the free-running frequency and duty cycle. I had already told her no need to download the circuit board mask or to order it through the project website, I could see right away that I can breadboard it relatively easily but I wanted to be able to explain what the parts that I solder to the 8-pin IC socket actually do, especially wrt the capacitor charge-discharge, so thanks for your work with this tutorial (and others that I’ll check out later) I now feel confident to draw the 8-pin “box” at the center of the schematic showing her the two comparators and the resistor ladder, the RS latch and the discharge switch (transistor) I would have been very embarrassed if I could not do that and explain for her it very simply. The LM555 timer is a very stable timer device that generates accurate time delays. 555 Timer Astable Pinout PIN 1 Connected to ground ( GND / Vcc-) PIN 2 The trigger brings the the output HIGH when the voltage supplied to it drops below one-third of Vcc+ PIN 3 Outputs up to 200 mA of current at 1.5 volts. 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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