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Philco Shadow Graph Rebuilt With Arduino
09-25-2018, 09:42 AM
I did this project a while back. My son was in town and insisted he film it. -- Mark K8KZ
Video: https://www.youtube.com/watch?v=SXlzx2DwkJw
09-25-2018, 10:10 AM
Clever idea.
For me it's just easier to rewind the original. When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry 
09-25-2018, 02:10 PM
What's in the blue box?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
09-25-2018, 02:27 PM
09-25-2018, 04:46 PM
I thought it is a motor, but was wondering how fast the reaction would be: it needs to be very fast.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
09-26-2018, 03:42 AM
It's likely sluggish compared to the original movement, which was just a form of variometer like an analog Ohm or Volt meter, which just moves with changes in AGC voltage rather then having to think about things first.
Regards Arran
09-26-2018, 08:04 AM
>>which was just a form of variometer
you mean - galvanometer? It's a crude form of Weston/D'Arsonval galvanometer, indeed used in all analog meters. People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
09-26-2018, 09:14 AM
(09-25-2018, 04:46 PM)morzh Wrote: I thought it is a motor, but was wondering how fast the reaction would be: it needs to be very fast. They can be very fast. All of the gasoline powered inverter generators that I have worked on use the same sort of system for engine speed control, and that has to be at least as fast as this indicator.
09-26-2018, 11:49 AM
I hope so.
Motor is not as reactive. It takes more time for the engine to rev up, then for a human hand to pass the station when rotating the dial while looking at the indicator: the angular speed could be quite high even with slow rotation, and very little needed to pass the tuning point. People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
09-26-2018, 12:19 PM
It's not a great solution. It is a little slow, and you can even hear the servo make a bit of motor noise as it turns. The servo, the little blue thing, takes commands from the Arduino microcontroller to turn to an angle between 0 and 360 degrees. I did it as more of a novelty than anything else.
I am usually one for authenticity, and this is reversible if I get a working shadow meter. I tried rewinding the coil twice, and I couldn't seem to get t to work very well. Mark
09-26-2018, 01:20 PM
Have you tried to re-magnetize the magnet?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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