Pulse generator (Variable duration, frequency and amplitude)

By Radu Motisan Posted on October 9th, 2011 , 1141 Views (Rate 1.94)

To control the GRID of the TGI2 400/16 Hydrogen Thyratron in order to switch it on, I have designed a pulse generator with variable duration, frequency and amplitude all configurable using three potentiometers.
The pulse generator is based on my 20KV pulse generator. In this case, the induction coil is replaced with an inverter, that generates a configurable voltage in the 200-300V interval. Two 555 timers are providing the variable duration and frequency generator and one additional 555 timer drives a mosfet to control a small ferrite transformer to generate 200-300V and store it in a capacitor. A second mosfet provides pulses of this voltage (instead of feeding the induction coil like in the first setup).
All the three parameters can be adjusted, as shown in the video.

The video shows an old NOS Western Electric 313CD Neon tube, which is actually a thyratron itself. I will be using this pulse generator to turn on my high power TGI2 400/16 Thyratron tube. The first pot controls frequency, and the second pot controls the pulse duration. There is a third pot to control the amplitude.

For the TGI2 400/16 there are a few requirements:
Pulse duration on Grid: 4-5ms
Grid voltage pulse: 200 - 400 V
The pulse repetition frequency: 450Hz
Anode current time delay with respect to the voltage grid: 0.26 - 0.6ms
Pulse of the anode current spread: 5ns

Here are some more pictures of the PCB board I've designed for this generator: