Thyratron Frequency Divider




23rd November 2004

This stems from the work done on the thyratron pulse generator, to provide a 1Hz signal to drive an electronic clock. The original pulse generator was rather unstable, so, given the power requirements of the clock, I decide to try and synchronise the 1Hz ouput to the 50Hz mains. I found a simple thyratron based frequency divider, which is basically a non-retrigerable monostable, with the delay time set to a multiple of the input frequency.

The basic test circuit is here.

The timing is set by the resistors and capacitors in the cathode circuit, though the value of the anode load does have a small effect. Positive bias is needed on the grid, as the cathode is effectivly floating at a significant voltage above ground. With the values shown, it is possible to achieve a divide-by-ten ratio, with a 6.3V RMS input (chosen so a spare heater winding could be used to supply the synchronising voltage). It is more stable if the division ratio is reduced to about 5.

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Copyright J.Beacon & M.Wroe-Parker 2004