Project list

Vacuum tube SR bistable

Init

Time:

20.11.2011 7:12:39PM

Description:

After playing with nixie tubes, i decided to try something with vacuum tubes. SR bistable seemed as the most visual idea.

The hearth of the vacuum tube SR bistable is PCF80 which contains one triode and one pentode. A SR bistable uses two triodes, so the pentode is connected as a triode.

For the high voltage power supply I've used standard nixie tube power supply with NE555, but with the zenner diode in feedback loop instead of a trimmer.

The whole circuit works with a universal AC/DC 12V adapter. Same 12V is used as a negative supply for the tubes. -12V is very high negative voltage (-100V is commonly used), so there was some problems with the triodes shutting down. After I replaced resistors with a higher value ones (lower power consupmtion), the left neon bulb didn't completely shut down. Further lowering the value of the resistor R9 could probably solve this problem.

I've made a nice little metal box for this device! :) When the left button is pushed, right neon bulb glows, and when the right button is pushed, left neon bulb glows.

Schematics:

HV supply

Logic

Pictures:

First test - A neon bulb

First test - B neon bulb

PCF80

Links:

• http://www.dos4ever.com/flyback/flyback.html
• http://static.cray-cyber.org/Hardware/TubeLogic.pdf

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