Joule thief. Can I convert this to PNP from NPN entirely + switch polarity? (I am ordering parts.)
tarakan2, Mon Jun 09 2014, 06:24AM
The second circuit.
Can I replace both NPN transistors 2N3055 with a MJ29055 PNP transistor and a 2N2222 with an old germanium transistor?
I want to do this in order to reduce the minimum start voltage of the Joule Thief. The emitter-base Voltage of a germanium transistor is 0.4V or less.
Germanium transistors are obsolete but they make sense in Joule Thieves.
Is there a Germanium transistor that has a specially low Veb?
(I will buy an old Germanium transistor on Ebay for this circuit for around $7. NTE27 is a very expensive.)
Would it make sense to add a tap to the secondary of this circuit for the feedback?
Re: Joule thief. Can I convert this to PNP from NPN entirely + switch polarity? (I am ordering parts.)
Steve Conner, Mon Jun 09 2014, 09:40AM
It should work fine. The only issue is that most older germanium transistors are very slow with a ft in the hundreds of kHz. I don't know of any fast ones that can handle significant power.
Steve Conner, Mon Jun 09 2014, 09:40AM
It should work fine. The only issue is that most older germanium transistors are very slow with a ft in the hundreds of kHz. I don't know of any fast ones that can handle significant power.
Re: Joule thief. Can I convert this to PNP from NPN entirely + switch polarity? (I am ordering parts.)
BigBad, Mon Jun 09 2014, 02:46PM
what does the magnet do?
BigBad, Mon Jun 09 2014, 02:46PM
what does the magnet do?
Re: Joule thief. Can I convert this to PNP from NPN entirely + switch polarity? (I am ordering parts.)
tarakan2, Mon Jun 09 2014, 05:41PM
I found one but I will abandon this idea because the collector current of this transistor is so small that I will burn it by driving the MJ29055 with it.
tarakan2, Mon Jun 09 2014, 05:41PM
I found one but I will abandon this idea because the collector current of this transistor is so small that I will burn it by driving the MJ29055 with it.
Re: Joule thief. Can I convert this to PNP from NPN entirely + switch polarity? (I am ordering parts.)
Sulaiman, Mon Jun 09 2014, 06:39PM
if your intention is to light the led with the signal/antenna power
you will probably have more success with a simple bridge rectifier with small output capacitor.
with a simple dipole and 4x 1N4148 I can light an led at several meters using my 144 MHz handheld.
I didn't have them at the time but if I do it again I'd use 1N5711, lower voltage, faster, and in my stock.
A typical random length wire receiving antenna would have a fairly high source impedance,
I think that it would be more suitable for a simple bridge rectifier than a 'joule thief'
have lots of 'Energy Harvesting' solutions, e.g
Sulaiman, Mon Jun 09 2014, 06:39PM
if your intention is to light the led with the signal/antenna power
you will probably have more success with a simple bridge rectifier with small output capacitor.
with a simple dipole and 4x 1N4148 I can light an led at several meters using my 144 MHz handheld.
I didn't have them at the time but if I do it again I'd use 1N5711, lower voltage, faster, and in my stock.
A typical random length wire receiving antenna would have a fairly high source impedance,
I think that it would be more suitable for a simple bridge rectifier than a 'joule thief'
have lots of 'Energy Harvesting' solutions, e.g Print this page