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General high-speed discussion / Re: driving low pressure sodium lamp without 60Hz flicker
« on: March 03, 2018, 09:30:43 AM »
Hi all,
Thanks for the input. I've got a nice system set up now, I'll describe below.
bkt, Thanks for the link to the valley fill circuit. I had been wondering why there were 7 diodes on the pcb, and it's nice to know the source of the 60 Hz that's making it through the ballast.
Tesla500, nice idea -- very simple but I would have never thought of it. I must say, I'm still a little confused how the DC is making it through the input filter on the ballast. I thought there would be an isolation transformer that wouldn't let any DC pass... ? Clearly not...
Nikon1, thanks for the schematic. What is the transformer in this circuit doing?
Since I'd love to avoid depotting any more ballasts, I opted for Tesla500's solution, feeding an appropriate DC voltage into the ballast. I didn't have a variac, but I borrowed a high voltage DC supply to test. Sure enough, with ~100V DC, the ballast produces a constant amplitude 100kHz signal (TEK00115.PNG and TEK00113.PNG, attached) and the lamp lights without any flicker. For a permanent solution, I ended up buying this power supply instead of building my own rectification circuit: https://www.circuitspecialists.com/benchtop-power-supply-csi12001x.html The controllability and current display is nice, and I'll definitely use it for other projects as well. I think the appropriate voltage is around 105-110V -- after the lamp has warmed up this puts the power draw near 55 watts.
Here's a soap film video (3kfps) without any flicker: https://youtu.be/ZzPdvUJ6nhM
Thanks for the input. I've got a nice system set up now, I'll describe below.
bkt, Thanks for the link to the valley fill circuit. I had been wondering why there were 7 diodes on the pcb, and it's nice to know the source of the 60 Hz that's making it through the ballast.
Tesla500, nice idea -- very simple but I would have never thought of it. I must say, I'm still a little confused how the DC is making it through the input filter on the ballast. I thought there would be an isolation transformer that wouldn't let any DC pass... ? Clearly not...
Nikon1, thanks for the schematic. What is the transformer in this circuit doing?
Since I'd love to avoid depotting any more ballasts, I opted for Tesla500's solution, feeding an appropriate DC voltage into the ballast. I didn't have a variac, but I borrowed a high voltage DC supply to test. Sure enough, with ~100V DC, the ballast produces a constant amplitude 100kHz signal (TEK00115.PNG and TEK00113.PNG, attached) and the lamp lights without any flicker. For a permanent solution, I ended up buying this power supply instead of building my own rectification circuit: https://www.circuitspecialists.com/benchtop-power-supply-csi12001x.html The controllability and current display is nice, and I'll definitely use it for other projects as well. I think the appropriate voltage is around 105-110V -- after the lamp has warmed up this puts the power draw near 55 watts.
Here's a soap film video (3kfps) without any flicker: https://youtu.be/ZzPdvUJ6nhM