Joule Thief

[stprue]

I would recommend getting a cheap DMM $20-$30 and then an Oscope.  I still don't have an Oscope yet but will probably get a handheld like Jeanna has.

[resonanceman]

:)Hello, its freepow, Can anyone tell me, when making Joule thiefs... is it better to have an oscilliscope or digital multi-meter
I am thinking of purchasing a 10Mhz oscilliscope for $148 Aust, as i dont have heaps of money, can I measure DC or AC more acurately on a oscilliscope from a JT ??  or a Multi-meter ??
would a 10mhz oscilliscope help or would it be not worth having??
Any comments would be much appreciated, thanks

Freepow

JTs  are  basically a simple oscillator and a coil.
They  work  mostly  by creating  a magnetic field in the coil  then  shutting off
When  the magnetic  field collapses it creates a  back EMF pulse ( flyback )

With  a oscilloscope  you  can see  the  spikes
You can also  get a good idea of the  voltages   of the spikes  as well  as the rest of the  waveform .
You can also  get  a good idea of  the frequency  that  the JT is running at .

10 MHz  certainly is fast enough for  the slower JTs   but it might not  be fast enough to catch  the spikes  from  a fast JT.


This is the  scope that someone suggested to me .
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170361338511&_trkparms=tab%3DWatching
At 25MHz  it is  fast enough  to  do most of the  things I would   want to do.
It is  2 channel so  I could look  at lets say  a JT primary and secondary at the same time It also  has  the  highest   input voltage   of  all but one of the   scopes   I  have looked at .It  also has  a USB connection  so it  possible  to inport   a  scope  shot  to my computer without needing a camera



gary

[jeanna]

digital oscilloscope
Xoscope is a oscilloscope using input from a
sound card or EsounD and/or a ProbeScope/osziFOX and will soon support
Bitscope hardware. Includes 8 signal displays, variable time scale,
math, memory, measurements, and file save/load.

Web site: http://xoscope.sourceforge.net/

This package is  already in Ubuntu  includet.

Just type "sudo apt-get install xoscope" in a shell

Norbert

@Gary and everybody else.
When Norbert posted this I pm'd him a bit.

I did not have ubuntu on my computer yet, but I do now, and look it is part of my package. I will try it immediately.

It should work on an ordinary MS pc machine too... and it is free. All you need is a probe.

It is a good way to try out the concept.
Just be careful at first. and only use it on the primary, then only use it with a 7 turn secondary, then increase the turns and prove to yourself it is
1- capable and
2 your computer will be safe.

@freepow, you should be able to test the dc on the scope, but I agree with stprue. Just use your dmm for dc and then the scope for looking at the wave and the ac.

The scope will show you the voltage peaks and shape. It will also show you the frequency which is as essential as the voltage.

My scope is a 10Mhz scope (Velleman 10HPS)  and it does just fine. I am limited in the earth battery by it because you can only read 1/10 of the sampling with any accuracy which means I can only accurately read 1Mhz.
The Joule thief circuits I have are all under 200Khz so, this scope is fine. I have been troubled by not being able to photograph my scopeshots.
This free one using a computer screen will be easier either through the screenshot method or the photo method.

I hope this helps.

jeanna

[resonanceman]

I did not have ubuntu on my computer yet, but I do now, and look it is part of my package. I will try it immediately.

Jeanna

Aint  Linux great   

I  have not switched to it yet  because of  my  internet card ......but I am working on it .

Here is  a thought ................. Almost  all  newer  computers  now have  the sound card built in .     What about  adding  an  old  sound card in an expansion slot   just for  the  scope .      I think I might  have  an old  sound card   or 2 around here somewhere .
If  the  sound card   had its own   input   chances  are if  you   fried anything  .... chances are  it would only be the  extra sound card.



@ all

What happened  to  the   4 toroids  connected  with  one  winding?
I  do not remember seeing  anything  about  it other than the   picture
Did  I miss it or   has  there not been anything more posted/

My  90 LED array still has  the electronics  connected .
It  feeds the LEDs in  4 sections .
I thought that the  QT   ( quad toroid )   setup  would be ideal  for this  array .


gary

[jeanna]

Hi Gary,

Yeah, I am liking the linux. It works and like here, on the ubuntu forum, there are people to help. More, in fact.
I went to sourceforge and downloaded the xoscope but it did not install itself. I am not very sure how to do it, so I emailed the guy for the manual, which I did not see. So, anybody else who wants to try, we can work it out  together.


I was/am also waiting to hear about the quad. I s'pose it wasn't too great, or we'd have heard about it.

You say the spot led array is being fed by 4  separate toroids??

I didn't realize that! I must be mistaken about what you mean.

I am glad to hear the array is still going.

jeanna