Ferrite...two kinds- soft and hard. That's about it. Hmmmm. Some one here will tell us.

  David

Yes you can just buy one. Rat Shack or your local equivalent carry blank ferrite antennas. Or scrounge one or more next council cleanup day. Anything that looks like an AM radio should have one.

The circuit you are about to build is excellent and performs well.

I did post an entry on this site about a week ago entitled COIL NOISE, but the thought police seem to have erased it which I thought was a bit unfriendly.

Suffice to say that two of my coils run silently whilst the other two emit a slightly audible whine. Why is this and what can be done to stop it?

Finally, make sure you use some good size heat sinks because the TIP 3055 does get very hot to the point where the solder will melt thus relieving the contact wires from the TIP legs.

I will try and post some photographs in the next 24 hours so that this article is all inclusibe on the same subject.

One more request. Can anyone recommend the number of wire turns for this circuit to suit a 24 volt DC operation.

I hope you find my contribution helpful

lol
Jon M

Hi Flux,

I look forward to reading you comments as your broad knowledge and clear explanations make it easy to grasp whats what.

Sorry about pressuring you.
Jon M

I installed 42 of these FO30T8's in a paint spray booth that we use at work, last week. I upgraded the ballasts aswell, They are intellivolt AC balasts single phase that operate from 110vac to 277vac.

 This IOTA(high-watt) solidstate 12dc ballast behaves exactly the same as the'solidstate AC' intellivolt.

 When I make and brake the connection, to one end of the bulb, the arc I pull from the gap is totally identical, in both color and intensity.

 With the DC ballast there is less flicker from the bulb, and I think its abit brighter. but the ark is identical.

I have to be careful when I pull an arc of the end of the bulb, the wire lead to it gets mighty hot real fast.  

 When I set the scope on this bulb, im going to take and compare the readings from both AC and DC ballasts.

As Flux pointed out, these are crude inverters. God knows I had my share of hand winding ferrite cores for that circuit. I tried different shapes and sizes, they all work (in principle) as long as you keep the no. of windings as requested.

For me, best results came out by using a ferrite ring (I think it was a filtering ferrite ring. Hand-winding that was a real torture, took me 2 days and had to make a special tool (a long nail with all the wire on it that I was able to squeeze thru that ring's hole). The resulted transformer was whining but after trying different cap values I found one that stopped that noise AND made the transistor much cooler. However, 12V gave out blinding amounts of light but quickly heated things up. Best use for mine was at 6V, with a smaller 4W tube, and it doesn't even need a heatsink. That was almost as bright as the AC inverter I had for that tube.

Eventually I managed to fit the entire circuit inside a 15W CFL bulb base and re-used the tube from that bulb. It works fine, taking 0.5 Amps @ 6V but the light wasn't quite up to the 3W it used.

Later I purchased a 12V/5W CFL solar bulb and a 12V/8W CFL tube inverter too and realized that my best efforts couldn't match the amount of light or the efficiency those things exhibited. I realized that the time I spent trying to make mine was more expensive than the commercial unit's price. Eversince, I'm a buyer.

I see the plans as an excellent tool for educational purposes for exposing kids to many of life's lessons.  I am glad it was posted.

I salvaged a number of "Emergency Ballasts," removed the charging aspects of them, as well as the boiled out nicads, and most worked well straight off 12 volts, but a few died quick deaths, but the replacement transistors had enough design difference from the originals, that a 2 volt resistor of significant wattage was needed.  These are typically a double ended system.  But are only rated at 70 Lumens on a 4 foot tube.  But they work well on the 20 Watt tubes down to some undercabinet T12 types.

The emergency ballasts lighting circuit is essentially upsized from the Zetex circuit I have mentioned several times.  Which BTW, is not much more than a freerunning inverter supply.

"Q" is in an oversimplified way- how sharp can you tune your tuned circuit?- which is what you actually have with florescent lighting.  Which also explains in a nutshell most of the problems people have described so far.

BTW, Lead in CRT's is actually the clarifying agent for glass.  If your monitor is a CRT, you are reading this through fine lead crystal.  Between 2 and 6 per cent content.  Anything higher leads to weak glass and an implossion hazard potential.  Most of what you read on CRT's is circular hype by someone who meant well.  Nipping the end seal where the pins are is a reasonably "safer" method of dealing with the static charge they may hold, as well as eliminating the implosion hazard, and there is no mercury in a CRT.

On matters of noise: In the audible spectrum, been covered well. In the RF range- most electronic ballast circuits will emit Amplitude Modulated noise.  It's inescabale  Put an AM pocket radio next to one, and you should hear a whine.  It is a matter of where you locate your operating frequency for your lighting circuit that may or may not interfere with some modes of communications.  GPS is not an AM signal, so it will be immune.  Longer wavelength HF can be where you will hear your RF interference- when my batteries get low, tunning below 5 MHZ is tough.  HF gear is in an oversimplified description an AM mode reciever.