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Ferrite Grade for joule thief?

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smilem

Member
I have noticed there are many ferrite types, what do they mean and what is best for joule thief circuit?

For example:

FERRITE RING CORE, 6.3X3.8X2.5, N30
Ferrite Grade:N30
External Diameter:6.3mm
Internal Diameter:3.80mm
Ae Effective Cross Section Area:3.06mm²
Al Tolerance Value +:25%
Effective Magnetic Path Length:15.21mm
External Diameter:6.30mm
External Length / Height:2.5mm
Inductance Factor, Al:1090nH
Internal Diameter:3.80mm

Also does it matter how many windings I have some say 10 others 20, 50 etc.
Does it make sense to make more or it just changes frequency?
 

mneary

New Member
The Joule Thief isn't a really critical circuit. It works with a wide variety of cores (even a nail).

I suggest that you try different stuff on the bench.

Be aware that simulation doesn't always work! Your simulator must understand saturation of the transistor and inductor.
 

Speakerguy

Active Member
Any grade ferrite will be fine for a joule thief. The type is only critical in stuff like RF and power conversion applications where you care about frequency characteristics and saturation. A little old joule thief won't care what you use.
 

stevez

Active Member
I can't comment on the requirements of the joule thief. If you want to know more take a look here: https://www.amidoncorp.com/pages/specifications

If you focus on a toroidal (like a donut) core you'll see a lot of information that can be confusing. One factor that tells a lot is the Al - which more or less describes the number of turns required per unit of inductance. A higher Al suggests that less turns is required for a given amount of inductance.

Many of the suppliers (Amidon, Micrometals, Fair-rite, etc) provide some simplified applications information - suggesting materials that are better suited for an application.
 

smilem

Member
I ask because I tried some green and yellow cores and they did not seem to work, when I use black (graphite color) core it did.
 

mvs sarma

Well-Known Member
I ask because I tried some green and yellow cores and they did not seem to work, when I use black (graphite color) core it did.
you need to use ferrite cores and not Iron powdered cores , those are used in RF communication and may not offer the high AL values needed for circuits like Joule thief. perhaps you may use torroids that are found in electronic ballasts.
 
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