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Son of Joule Thief

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Chat Zone » Archive through 15 June, 2015 » Son of Joule Thief « Previous Next »

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jaybee
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Username: jaybee

Post Number: 53
Registered: 11-2006

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Posted on Saturday, 02 May, 2015 - 07:03 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Having had an interest in Joule Thief type circuits, I was drawn to some small modules sold on an auction site. They are very inexpensive and deliver a steady output of 5V from cell voltages as low as .9V

At 0.9V the maximum output current is said to be about 200mA and with 3V input it goes up to about 600mA. A very useful little module that can suck joules out of a cell all the way down to 0.9V

At the following URL T.K. Hareendran gives a very good explanation of how it works and what the controlling chip might be.

http://www.electroschematics.com/10935/pfm-module-circuit-surgery/

Does anybody else have any further enlightening information they could add?

John
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g0hjq
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Username: g0hjq

Post Number: 78
Registered: 02-2010


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Posted on Saturday, 02 May, 2015 - 07:32 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

http://shop.ciseco.co.uk/powerpod-ncp1402-3v3/

I've got one of these, and it works superbly well, powering a white led at full brightness for hours off a super capacitor.

The output voltage is stabilised down to inputs of 0.3volt
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gordon
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Username: gordon

Post Number: 1067
Registered: 05-2005

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Posted on Sunday, 03 May, 2015 - 04:17 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Looks to be a useful module. There are loads of converter ic's out there, but this might be similar to the one in the module.

http://www.belling.com.cn/upload/bl8530_en.pdf
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g0hjq
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Username: g0hjq

Post Number: 79
Registered: 02-2010


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Posted on Sunday, 03 May, 2015 - 04:30 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Mine used the ncp1402. ....

http://www.onsemi.com/pub_link/Collateral/NCP1402-D.PDF
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bruce
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Username: bruce

Post Number: 1095
Registered: 04-2008

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Posted on Monday, 04 May, 2015 - 06:07 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Theres something fishy about this: it claims 200mA @ 5V from a knackered AA cell? It would need to draw 1 Amp!
Supermarkets have dozens of discarded batteries, many of which may have useful energy left, but whether it's a practical proposition to access it is another matter.
An EPE subscriber, Z. Kaparnik, in 2000, published a circuit for a blocking oscillator using a micro ferrite bead. It looked jolly clever and I made several variants. However, it flopped: I found that the circuit drew 30mA on no load! I'd used it in a device powered by a solar panel and, as you can imagine, that was a non-starter.
Even one of the ics ( LT do a lot ) which upregulate from 1V, are no use if you're using knackered cells, IMO, unless you want to constantly mess around changing batteries. But I can see potential for very low voltage super capacitors and solar panels.
Bruce
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ian_field
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Username: ian_field

Post Number: 249
Registered: 05-2012


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Posted on Monday, 04 May, 2015 - 06:39 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

If you want salvage batteries - raid the recycle bins for lithium laptop packs.

In theory; one dud cell can scrap the whole pack - but so far, all the ones I've rescued for my E-cig have been good.

Maybe they have a "fuel gauge" chip that tells the laptop the battery is finished after a set number of discharge cycles.
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gordon
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Username: gordon

Post Number: 1068
Registered: 05-2005

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Posted on Monday, 04 May, 2015 - 07:25 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I think the 5 volts at 200mA is with a fresh (1.5V) battery. At 0.9 volts, the current would be a lot lower, maybe 20mA? If Jaybee has a variable supply, it would be interesting to know how the module performs.
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cjay
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Username: cjay

Post Number: 204
Registered: 10-2013

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Posted on Tuesday, 05 May, 2015 - 01:11 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Regarding laptop batteries, many people scrap them because the onbord 'fuel guage' IC loses track of available capacity, recalibrating the pack by running it flat outside of Windows/Linux etc. then fully recharging it can often recover significant capacity.

You're using 18650 cells for an e-cig though?
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ian_field
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Username: ian_field

Post Number: 250
Registered: 05-2012


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Posted on Tuesday, 05 May, 2015 - 07:41 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Obviously most laptop owners aren't that technical savvy.

18650s work very well - anything over 2Ah lasts all day, and well into the next if I forget to change them over.

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