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Registered Member #2405
Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140
Here is a few pictures of my small table top audio coil. I have reached 9" sparks with it but it gets pretty warm when run that hard. I am using IRFP260's in a half bridge configuration. The audio controller is a combination of Op amps a couple transistors and a 555 for developing the PWM signal the input source was a boom box I used the headphone output. I have made the controller able to handle right and left stereo channels with seperate controls for each channel along with LED signal level indicators for each channel. I added a couple pictures lighting up some lights the light photo was about 35Vac input.
Registered Member #4362
Joined: Sat Jan 21 2012, 03:44AM
Location: Texas
Posts: 98
Looks nice. good size sparks with what looks like loose coupling. I have a similar setup but my primary is directly around the secondary. I may move it out and see if I can get 8-9 inch sparks.
Registered Member #2405
Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140
I have tried tight coupling and loose coupling on this paticular coil, and it seems right where I have it seems to work the best. Originally I had the primary wound on the same form as the secondary a couple of inches below the secondary winding and that did not work well. So then I took a piece of 6" PVC and wound the primary on that and then slid the primary up and down the PVC until I found the sweet spot using that 6" PVC former.
It is possible that this will work even better if I can tighten the coupling up a little I just did not have formers to wind on that would fit over the 4" inch diameter secondary except for the 6" piece. So the experiments with it will continue.
I did do some reliabilty testing on it to see how long I could run it without a fan connected and blowing on it and using small heat sinks that you see in the photos there is no thermal grease on the heat sinks, and at full power it will last about a minute then the IRFP260 FETS start to complain thats really pushing them to the limit. Around 35 AC Volts input seems to work pretty good but of course sparks are only a couple inches long but the audio is very good even at that small level.
So I think with a little larger heat sink and a decent fan and a little more coupling experimenting I believe it will be a winner. It does give out some nice audio, MIDI files sound real good and music from CD or DVD sound real good as well.
The controller I made for it has stereo input and two outputs so two coils can be run from it...right channel and left channel. So once I get the details under control on this one coil I will build up another and then have a pretty neat looking stereo system.
I have a bunch of the FETS so I may try runnimg them in parallel and see if that allows me a little more power on this small coil once I get through playing a little more with the coupling.
Registered Member #2405
Joined: Fri Oct 02 2009, 12:59AM
Location: Wisconsin
Posts: 140
Thought I would post a picture of my mini coil again now that I have been able to get back on it and put it on a base. I have been able to reach 9" sparks when used with a standard interrupter and about 6 inches when in audio mode. I do not have a midi controller so I input a CD player to it and it works fine but gets pretty hot, when I input just audio tones from a signal generator seems to like that a little better. So I need to get a MIDI controller for it then it should be much happier.
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Table top Audio SSTC
