Joule Thief

[jeanna]

Oh dear,
I guess I am now up against tuning again.

I had a lot more secondary wire that was unwound when I took those test measurements this morning. So, I wrapped it all. 40 turns. I expected the secondary readings to go up.

They went down.

The amps draw also went down, but this is the wrong direction. strange bird this jt!

with 40 turns on the secondary instead of 18 and the same 5T one way connected to 8 T the other way, the amps draw for 3 leds off the secondary was 12.7mA (22.9mA before)
The rectified voltage as shown through the bridge was no longer 11.25 volts but 6.7V rectified. The scope said 0.485v this time I found a symbol meaning rms maybe. Anyway they both went down. I guess I happened on a good resonance in the earlier wind. Maybe I will take one turn out at a time.

ugh!

jeanna

[xee2]

@ jeanna

RMS is only meaningful if input is a perfect sine wave. Don't use it.

[jeanna]

@ jeanna

It would seem that you have a 100:1 scope probe. On a good scope with and a good probe the display will automatically adjust for this. But not all scopes and probes do this. Most likely you are getting 75 volts peak to peak which would be about 37 volts DC out of a full wave rectifier for a perfect sine wave. Try using the probe on a 1.5 volt battery and see what shows up on the display - don't forget to zero the scope first - short out probe and adjust vertical trace position to 0 volts. It sounds like you got a good scope for the price.

OH good some help!! Thanks xee2!

The manual calls it x1 and x10 probe, so I am not sure.
There is an automatic display, but it goes by too fast to understand. I used it on my skin yesterday to be sure the machine was working.  (THAT was interesting.)

Then I found a way to make the screen show timed divisions on the x axis and voltage on the y axis. I can change the resolution of these. But I don't understand (or maybe can't see well enough) the symbols for the voltage.

I will read the manual and try to figure out how to do what you just described. There is a dc function and somehow a way to move the trace lines. I saw them both a couple of times..

Remember when digital wristwatches first came out? there were 2 max 3 buttons and depending on how long you pushed them the buttons did different things. This is what is going on here to add to my total newbyness.

I will try to quickly re read the part you refer to

thank you,

jeanna

[jeanna]

I wonder if it is the decibels readings.

I recognize the initials, but that is it.

dB= measured signal (ac+dc) is converted to dB (0dB=dBref which is user defined !!)
dBV= measured signal (ac+dc) is converted to dBV (0dB=1 V)
dBm=measured signal (ac+dc) is converted to dBm (0dB=0.77fV)

I assume ac+dc means for either and both. there is also a list for just ac.

jeanna

[xee2]

@ jeanna

0 DBm is one milliwatt. DB are log measurements. I suggest you avoid theses. They really have no use for what you are doing.