While recalling the fun one could have with the project kits and parts found in the Radio Shack of the 1970s, I found a little board I made in 1978 (as usual stumbling across it while looking for something else). Every part on this thing came from Radio Shack. The IC is a National Semiconductor LM3914N, which is a 10-LED bar/dot display driver which at the Shack cost $2.49. Solderless breadboards were a new thing back then, with CSC (that is Continental Specialties Corp.) being the primary vendor at the time. Radio Shack offered the perma-proto board seen here for about $1.79. The LEDs were sold in packs of 2 for $0.79 and with the wire, switch and a few passive parts the entire project cost about $10. The short demo videos show the bargraph and dot display modes.
I went on to make a stereo VU meter later that summer, again all parts from Radio Shack:
And while it came with a data sheet, remember–this was Radio Shack–they had Forrest Mims notebooks. This exact circuit is used twice:
I went on to do more with the LM3915, such as build a 70-LED spectrum analyzer. However I will save that for another day. (read: I have to find it!)
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