This forum is a continuation of the printed column "Q&A", where I answer questions about all aspects of electronics, including computer hardware, software, circuits, electronic theory, troubleshooting, and anything else of interest to the hobbyist. Feel free to participate with your questions, comments or suggestions on answers printed in the magazine. Send all NEW questions to: [email protected]
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I think that Tim sort of missed the boat in his response to Jeff's question. Dr. Helgoe wanted to know what parts were available to flash a neon bulb using the simple circuit he had dredged up from an old electronic hobby journal. Tom conceded defeat because he wasn't able to find a suitable substitute for the transformer called for in the original circuit. I was able to find all the necessary parts in my junk box. I had these parts on hand: SCR MCR100-6 (Mouser 863-MCR100-6RLRMG), zener 1N5235B (Mouser 512-1N5235B) and for the transformer is used a Xicon 42TL013-RC (Mouser 42TL013-RC). The transformer I used a small 1 Kohm to 8 ohm audio transformer. The primary has 756 turns and the secondary has 60 turns. Using the center tap on the secondary side give a 756/30 turn ratio matching the 25-1 turns ratio that the original circuit called for. You would attach the secondary side to the SCR and the primary side to the neon bulb to step up the voltage. These parts worked for me. Other parts my work as well. It's a cute little circuit and it flashes a long time on a 9V battery. It tends not to run in a dark room because the neon bulb needs external light to help the gas ionize. Anyway I think this vintage circuit which flashes a glowing orange neon bulb is more interesting then the run-of-the-mill 555 LED flasher offered as a substitute.
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