Revised FL circut

[RobC]

My first schematic was far to complicated sorry about that. Thanks to John and Amanda this one should easier to build. Now on to the circut. If you change the settings of R1&R2 besure to use an amp meter in line because current draw can easily jump to over ten amps and then the magic blue smoke starts. Any comments or ideas are welcome.

[commanda]

The 300 uF capacitor, which you have marked as may not be needed, is electrically in parallel with the other big cap, 1000-2000 uF. It's use would depend on your exact physical layout. Although I would probably add a 0.1 uF in parallel with it, help mop up any rf noise generated.

I'd also use larger value pots, possibly decreasing the value of the 0.0047 uF cap. As shown, each adjustment only spans a 6:1 range. The giveaway here is your statement that in your setup, R2 = 6K works best. You're at the end of your adjustment. Maybe R2 = 8K, or 10K, might work even better?

Also be aware that the 2 pots interact.

I have to query your statement about setting R2 to 6K to start with. This just looks wrong.

And don't skimp on that flyback diode across the fet. The circuit will work without it, though the mosfet is more likely to go bye-byes.

Amanda

[RobC]

Actually I used 10k pots in the testing phase. The downloadable 555 timer program I use is from Electronics-lab.com and I also use this one http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm

Thanks for the afirmative on the flyback diode. Actual values for .0047 cap were according to my program  R1 3.070k and 6.139k for R2. If I change cap size I can use much larger values for r1 and r2. Thanks for the heads up on the RF interference issue I need to check that. I am wondering thought if this circut would be more efficient at the 30 to 40Khz range instead of 20Khz? I wouldn't mind I had a little more light out of the 8ft tube also. Well at least this circut has been running smoothly for 48 hours now and the components are only slightly warm. Two things I forgot mention is use a heatsink on the fet or it will burn up and If you can't find the right ferrite parts go to ebay and search under ferrite transformers there is a guy there who sells 2 complete e-cores with plastic bobbins for 8 dollars plus postage. Flyback transformer cores should also work great. We should also be able to buy factory wound transformers off the shelf if I could find a supplier.RobC

[commanda]

I have to query your statement about setting R2 to 6K to start with. This just looks wrong.

Thinking about it a bit more, with a slighly clearer head; of course you're right. R2 should be set to max for initial startup. Gives minimum pulse width. Therefore least current draw.

My excuse is I didn't sleep well last night, worried about my sick ferret. He was at the vet's, and didn't improve at all overnight. Just went downhill even more. I've just come inside from burying him.

In a properly optimised circuit, both pots should be close to mid-position. If using a ferrite core, you'll probably find the efficiency will increase with frequency. Computer switch-mode supplies usually run in the 50-85 KHz region. Laminated steel cores will usually run best in the audio range. Ones I've built using audio coupling transformers from transistor radios usually run around 15 - 18 KHz. If you've got good hearing, you can hear them whistle.

Amanda

[RobC]

I think that just for the fun of it I will recalculate all of the timing values and see what happens at 50Khz. Sorry about your ferret I'm very attached to my own animals myself and when you lose one it really ruins your day. RobC

[jimjjnn]

Amanda,

Sorry about your Ferret. Must be a bad week for many of us. Oldest dau had to put her dog down yesterday. He was my little buddy. Not only a pound puppy, but a darn good one.Lived to be 17. I believe in recycling unwanted pets too.

[healerenergy]

Sorry to hear about your pet we have a 14 & half year old large dog with problems so who knows how long we can have our four legged friends around.

[jimjjnn]

Pound puppy had his own cat too. Dau got kitten that was very sick in pet shop.Brought it home so it could die with someone caring for it. Pound puppy adopted it right away and curled up around kitten all the next week and brought it his own food for the kitten to eat. That cat is now 9 years old and now lays in my lap since his buddy is gone. Guess he smells pound puppy on my clothes. He follows me everywhere I go for the last 2 days. I don't care for cats but this fat butterball is getting to me in a pleasant way. New buddy for me.

[RobC]

Incase anybodys still following this thread I used some of the e-cores I bought off of ebay. These worked great however I could only get 400 turns or less on the plastic bobbins and still have room for the 17 awg primary windings. This was not a problem there is still more than enough output. As far as I am concerned testing is finished circut works great.RobC

       

[RobC]

Should be ifr640n-nd not ns. And change primary winding to 14 turns 16 to 14 awg wire. One more thing tv flyback cores by far work the best. One more thing it also works better if you separate the ends of the cores  from each other with a 1/16th plastic spacer. RobC