Homebrew pulse transformer using a ferrite bead core. - Electronic Circuits Projects Diagrams Free

Hero999 · 3rd February 2008, 07:15 PM

Most of use have heard of the Joul thief but did you know that ferrite beads make handy core for pulse transformers?

Take a ferrite bead.

Wind 10 turns of 0.125mm of enamelled wire for the primary.

Wind 3 turns of megathin PVC insulated hook-up wire for the secondary.

Don't use enamelled wire for both of the windings because the insulation won't be good enough for mains isolation. Most PVC wire can stand 2kV for short periods of time and enamelled wire can't.

I've tried using one turn for the primary and one for the secondary but it took 532mA on the secondary to trigger the triac. With 10 on the primary and 3 on the secondary it would trigger at 10mA.

This simple technique removes the need to buy big and bulky overpriced pulse transformers or opto-triacs.

mvs sarma · 3rd February 2008, 07:31 PM

Nice Idea and very useful innovation HERO999. perhaps to to top as a sticky.

rjvh · 4th February 2008, 11:40 AM

picture would be nice
Robert-Jan

stevez · 4th February 2008, 03:49 PM

Hero999 - thanks for sharing. This kind of stuff is incredibly useful to many of us.

Regarding the ferrite bead - please describe it in a bit more detail. I do have ferrite beads - I recall that they are available in different sizes and mixes - likely to affect the performance.

Hero999 · 4th February 2008, 04:37 PM

I'll post a picture when I find my digital camera.

The ferrite bead has a diameter of about 4mm and a length of about 5mm.

The PVC insulated hook up wire was about 0.5mm thick, including the insulation.

Hero999 · 6th February 2008, 07:35 PM

I've found some suitable wire in RS components.

359-857
http://uk.rs-online.com/web/search/s...duct&R=0359857

Roff · 7th February 2008, 02:58 AM

Some ferrite beads are intentionally lossy, and are generally used for EMI suppression. I wouldn't think these would work as a pulse transformer, and I don't think they look significantly different from beads meant to be used as inductors and transformers. Ferrite beads come in a huge variety of permeabilities, effective frequency ranges, etc. Can you give us a part number, or at least a material type?
Otherwise, I guess a guy could just take an unidentified bead, wind a transformer, and see if it works.

EDIT: of course, I could be wrong. If so, I'm sure someone will let me know.

eblc1388 · 7th February 2008, 03:29 PM

New CFL lights are selling at 68p each in our town shop now.

Inside one can find some diodes, two high voltage transistors and two high frequency transformers. One being the main output transformer and another would on a toroid and looks like a pulse transformer of some sort.

If you have throw away your old/damage lights without opening them, you're out of luck. In may cases, usually only the tube got darken and the electronics are in good order.

rjvh · 8th February 2008, 02:49 AM

Quote:

Originally Posted by eblc1388

New CFL lights are selling at 68p each in our town shop now.

Inside one can find some diodes, two high voltage transistors and two high frequency transformers. One being the main output transformer and another would on a toroid and looks like a pulse transformer of some sort.

If you have throw away your old/damage lights without opening them, you're out of luck. In may cases, usually only the tube got darken and the electronics are in good order.

this is info i can use greatly
those components are almost imposible to get separate here and i do need them once in a while

THANKS for the tip

Robert-Jan

Hero999 · 9th February 2008, 12:28 AM

Quote:

Originally Posted by Roff

Some ferrite beads are intentionally lossy, and are generally used for EMI suppression. I wouldn't think these would work as a pulse transformer, and I don't think they look significantly different from beads meant to be used as inductors and transformers. Ferrite beads come in a huge variety of permeabilities, effective frequency ranges, etc. Can you give us a part number, or at least a material type?
Otherwise, I guess a guy could just take an unidentified bead, wind a transformer, and see if it works.

EDIT: of course, I could be wrong. If so, I'm sure someone will let me know.

You have a good point but I thought they were only lossy at HF. The Joule Thief uses a standard ferrite bead which works excellently and a simple pulse transformer doesn't need to have brilliant magnetic properties just to couple enough energy to trigger a triac.

I tried a couple of ferrite beads, one of them was WURTH ELEKTRONIK 742 700 11 and I don't have a part number for the other. Both worked well enough and imagine that it isn't very critical for a simple pulse transformer.

Hero999 · 24th February 2008, 10:36 PM

Here's a picture as promised.

The TRIAC used was a TICP206.

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3rd February 2008, 07:15 PM	#1
Hero999	Homebrew pulse transformer using a ferrite bead core. Most of use have heard of the Joul thief but did you know that ferrite beads make handy core for pulse transformers? Take a ferrite bead. Wind 10 turns of 0.125mm of enamelled wire for the primary. Wind 3 turns of megathin PVC insulated hook-up wire for the secondary. Don't use enamelled wire for both of the windings because the insulation won't be good enough for mains isolation. Most PVC wire can stand 2kV for short periods of time and enamelled wire can't. I've tried using one turn for the primary and one for the secondary but it took 532mA on the secondary to trigger the triac. With 10 on the primary and 3 on the secondary it would trigger at 10mA. This simple technique removes the need to buy big and bulky overpriced pulse transformers or opto-triacs. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

3rd February 2008, 07:31 PM	#2
mvs sarma	Nice Idea and very useful innovation HERO999. perhaps to to top as a sticky. __________________ Regards, Sarma.

4th February 2008, 11:40 AM	#3
rjvh	picture would be nice Robert-Jan

4th February 2008, 03:49 PM	#4
stevez	Hero999 - thanks for sharing. This kind of stuff is incredibly useful to many of us. Regarding the ferrite bead - please describe it in a bit more detail. I do have ferrite beads - I recall that they are available in different sizes and mixes - likely to affect the performance. __________________ stevez

4th February 2008, 04:37 PM	#5
Hero999	I'll post a picture when I find my digital camera. The ferrite bead has a diameter of about 4mm and a length of about 5mm. The PVC insulated hook up wire was about 0.5mm thick, including the insulation. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

6th February 2008, 07:35 PM	#6
Hero999	I've found some suitable wire in RS components. 359-857 http://uk.rs-online.com/web/search/s...duct&R=0359857 __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

7th February 2008, 02:58 AM	#7
Roff	Some ferrite beads are intentionally lossy, and are generally used for EMI suppression. I wouldn't think these would work as a pulse transformer, and I don't think they look significantly different from beads meant to be used as inductors and transformers. Ferrite beads come in a huge variety of permeabilities, effective frequency ranges, etc. Can you give us a part number, or at least a material type? Otherwise, I guess a guy could just take an unidentified bead, wind a transformer, and see if it works. EDIT: of course, I could be wrong. If so, I'm sure someone will let me know. __________________ Ron Last edited by Roff; 7th February 2008 at 03:01 AM.

7th February 2008, 03:29 PM	#8
eblc1388	New CFL lights are selling at 68p each in our town shop now. Inside one can find some diodes, two high voltage transistors and two high frequency transformers. One being the main output transformer and another would on a toroid and looks like a pulse transformer of some sort. If you have throw away your old/damage lights without opening them, you're out of luck. In may cases, usually only the tube got darken and the electronics are in good order. __________________ L.Chung

24th February 2008, 10:36 PM	#11
Hero999	Here's a picture as promised. The TRIAC used was a TICP206. Attached Thumbnails __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.