Joule Thief 101

[picowatt]

No-this is a different JT i was testing at the time of your request,so rather than swap back to the other JT,i simply did the same thing on this JT to give you examples of what i can and cannot do with the scope as quickly as i could.

No they cannot-the math trace switches off as soon as you switch of one channel.

Brad

Tinman,

Please do not consider any of my posts as "requests".  I am only trying to offer measurement suggestions.

If someone wants to argue about whether changing Ib also changes Vce or Ic, it would only seem logical to figure out how to accurately measure those values with minimal disturbance to the operating conditions. 

I have no dog in the hunt one way or the other. 

Did everyone see where LIGO recently announced the detection of gravity waves using a measurement accuracy of 1 part in 10²¹?  I believe I read where that is equivalent to being able to detect the width of the Milky Way changing by the width of a pencil eraser.

Talk about measurement precision, amazing...

PW

[picowatt]

Why can we not simply do it by subtracting the value of one channel from the value of the other to obtain our voltage drop across the CVR ?

That is what I said when I stated:

"If you can display the math trace, forget about inverting one of the channels and just display a math trace of CH1-CH2..."

It would be a bit easier if you would stick to one set of measurements/operating conditions/circuits until we can figure out what the problem is.

Which circuit is this that you are measuring?

I like how you dimmed the CH1&2 traces.  Try increasing the VPD for both channels.  You'll want as much signal displayed for each channel as possible without clipping the scope's front end.  As I said earlier, increase the 10R to 100R if necessary.

I think you are getting close...

PW

ADDED:  What does the math trace look like with the channels set at 2V/div?

[tinman]

That is what I said when I stated:

"



Which circuit is this that you are measuring?



I think you are getting close...

PW

ADDED:  What does the math trace look like with the channels set at 2V/div?

If you can display the math trace, forget about inverting one of the channels and just display a math trace of CH1-CH2..."

That is(as i stated) what the last scope shot was showing,and the configurations used.

It would be a bit easier if you would stick to one set of measurements/operating conditions/circuits until we can figure out what the problem is.

That was from the original circuit--sorry i forgot to mention that.
I will stick with this circuit from now on-the one the rest of the testing has been done on so far.

I like how you dimmed the CH1&2 traces.  Try increasing the VPD for both channels.  You'll want as much signal displayed for each channel as possible without clipping the scope's front end.  As I said earlier, increase the 10R to 100R if necessary.

As stated in my last post with the scope shot of the noisy math trace-that is across a 100 ohm resistor.. If i raise the VPD to 5v,the wave forms are clipped at the top of the screen-they go out of screen capture.

What i meant by obtaining the voltage drop without using the math trace,is to calculate the values manually,as the math function on this scope is just junk with very limited function.
No one has been able to work it out yet--even Poynt spent some time with me on skype via video,and still no luck.


Brad

[picowatt]

That is(as i stated) what the last scope shot was showing,and the configurations used.

That was from the original circuit--sorry i forgot to mention that.
I will stick with this circuit from now on-the one the rest of the testing has been done on so far.

As stated in my last post with the scope shot of the noisy math trace-that is across a 100 ohm resistor.. If i raise the VPD to 5v,the wave forms are clipped at the top of the screen-they go out of screen capture.

What i meant by obtaining the voltage drop without using the math trace,is to calculate the values manually,as the math function on this scope is just junk with very limited function.
No one has been able to work it out yet--even Poynt spent some time with me on skype via video,and still no luck.


Brad

In your reply 1181, the capture posted there looks like you could easily increase the VPD to 2V/div.

In that capture, are you using a 100R resistor at the base?

Have you returned to the original circuit as per post 1168?

Keep in mind that other than the leading edge of the negative going signal at the base during turn off, where I would expect to see a significant spike as capacitance is charged, you are only looking at around a 20mv signal for 2ma of base current with a 10R resistor.

You could try measuring across the 1K resistor instead of the added CSR for more difference signal.

Your scope was a pretty popular model, have you searched out forums looking for math trace related discussions?

I do now recall you, Poynt, and TK as well, discussing this issue in the past.

PW

[tinman]

You could try measuring across the 1K resistor instead of the added CSR for more difference signal.



I do now recall you, Poynt, and TK as well, discussing this issue in the past.

PW

In your reply 1181, the capture posted there looks like you could easily increase the VPD to 2V/div.

Yes-i guess i could fit the whole waveform in the screen if i drop each channel down a few divisions.

In that capture, are you using a 100R resistor at the base?

Yes

Have you returned to the original circuit as per post 1168?

Yes

Keep in mind that other than the leading edge of the negative going signal at the base during turn off, where I would expect to see a significant spike as capacitance is charged, you are only looking at around a 20mv signal for 2ma of base current with a 10R resistor.

Thank you PW.
I hope MH reads this,as he thinks this is some sort of death spike,and is not normal in a JT circuit operation. To what capacitance are you referring to?. Is the junction capacitance enough in the 2n3055 to allow(carry the current) for this spike to appear ?.

Your scope was a pretty popular model, have you searched out forums looking for math trace related discussions?

Indeed i have--many,and all are having the same issue.
Some have upgraded there firmware to the rigal firmware,but if it dose not take the first time,then it's bye bye scope-there is no returning to the original firmware. A few have lost there scopes trying this upgrade,so i am not taking the chance.