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UV Bulb in three tube array. It is possible to have a four tube array on the ballast but that is at it's limit & the tubes take a while to strike. So I went with a three tube array as it is far more reliable.
UV Bulb in two tube array mode.
The perspex bottom allows the user to see the guts, such a shame the morn is to hide them away from public view. I found that only one starter was required. Adding one for each tube made none of them strike.
Another capacitor on the second tube. The caps had to be reasonable large in the non-electrolytic family as the bulbs would not strike. The right values were found by trying random capacitors until the tubes struck & lit.
Starter with case removed so you can see it light up when the tubes are still striking. Like all starters it goes open once the tubes have struck & the current mostly flows though the tubes. The capacitors allow the current to flow though the filaments before the tubes are about to strike.
The starter lit up. This one is filled with neon, the other type is filled with argon & thus glows a nice shade of blue.
The use of a gas & a capacitor allows current to flow though the filaments to warm them up so they are more efficient at emitting electrons into the gas in the tubes. The electrodes also heat up & are made of a bimetallic strip that will bend & short the starter out & it cools down & releases the short a massive voltage spike is created in the ballast inductor that will create an ark that is then sustained due to the hot filaments.
The shorting plug for two tube mode. The plugs look to be of vintage origin. Funnily enough designed to 240V applications, probably vintage lighting.
The plug socket that connects to the third tube or shorting plug when in two tube mode.
The ballast used was the smallest one I have. A 13W one it could run ether two 8W tubes or one 13W tube. It also gets stupidly hot so I added a heat sink. Not sure how good it's gonna be sealed in a plastic box, but time will tell. When running three tubes the ballast is only driving the tubes over by one watt. However when driving two tubes they are overdriven by 5W, hence they & the ballast gets a little toasty.
The schematic is stupidly simple. A magnetic ballast light aka an inductor is not far off the simplicity of an incandescent light. This lighting technology came into use after WWII & was probably invented during it. However other lighting technology's similar have existed longer.
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