Recently, the AIS-gPPT3-1C Series Integrated Propulsion Module passed its first major testing milestone. The board electronics were soldered up and tested in air. The testing included verification that the load switch for enabling and disabling power to the EMCO HV supply, as well as testing the EMCO supply output. In addition, the ignition circuit was tested in atmosphere, to check rough output voltage and successful triggering via Arduino. Below is a short video of one of the ignition tests.
HV enable is cycled with commands from the Arduino. HV is first powered on, then ignition started. The EMCO supply is powered via 3.3V from the Arduino, as it would be powered by standard PocketQube systems. The thyristor is triggered with a 1V, 100ms pulse from the Arduino, set to a repetition rate anywhere from 0.25Hz all the way to 2Hz. Despite the pulse, no interference was found with the Arduino. The load switch was verified, as well as high voltage output. No board arcing or shorting was observed between any components, verifying that spacing should be good for the high voltage components.
Originally, the ignition arc was much weaker than expected, with the ignition transformer under-driven at 258V vs. 300V. Quick simulation however showed that doubling the cap from 0.047uF to 0.1uF and raising voltage to 290V would not affect charging times.
The above video shows the second atmospheric ignition test with the new igniter circuit changes. Increasing the cap from 0.047uF to 0.1uF, and boosting voltage from 258V to 289V had a noticeable improvement in performance, resulting in a much stronger output arc and higher peak voltage. The repetition rate was set at 0.25Hz. The igniter output wire to ground spacing was set at 5mm, making the output arc around 5kV. The arc could comfortably fire at that distance, with a max firing distance of maybe 8mm or so. My initial ignition voltage goal was set to a minimum of 4kV, so there should be plenty of overhead for ignition in vacuum with the tight spacing between the igniter and cathode electrodes.
With this initial round of preliminary testing complete, and all thruster components currently in, work can begin for the final assembly of the full thruster module, and preparing the assembly for high vacuum ignition testing.