Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search

Author Topic: Is joule thief circuit gets overunity?  (Read 600396 times)

hoptoad

  • Hero Member
  • *****
  • Posts: 1009
Re: Is joule thief circuit gets overunity?
« Reply #705 on: May 01, 2013, 09:46:25 AM »
snip...
I can currently only go 5MHz with 16bit resolution, above that, I have to go analog.
PW

May Anna Log never die ! .... KneeDeep

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Re: Is joule thief circuit gets overunity?
« Reply #706 on: May 02, 2013, 03:04:21 AM »

@poynt99,
 
For Board 80, 0.38V just managed to turn the LED ON - dimly and flickering.
 
I shorted the Probes on CH1 and CH2 and the screen pictures are attached.  Ch2 turned out to be the more quiet channel.
There is something wrong with that noisy channel Lawrence. There shouldn't be such a large difference in noise between the two. I'd suggest you get those probes checked out, and if they are OK, then the scope.

ltseung888

  • Hero Member
  • *****
  • Posts: 4363
Re: Is joule thief circuit gets overunity?
« Reply #707 on: May 02, 2013, 09:53:12 AM »
There is something wrong with that noisy channel Lawrence. There shouldn't be such a large difference in noise between the two. I'd suggest you get those probes checked out, and if they are OK, then the scope.

@poynt99,
 
Thank you for your suggestion.  Mr. Zhou is an ATTEN DSO retailer.  I shall get him to check all my ATTENs sometime next week.  I shall ask him to focus on the "DC Offset" puzzle.
 
I just came back from the Tektronics Dealer in Hong Kong.  He said that there is sudder interest in the high end 4-CH versions.  At least one customer has placed an order.  He does not have these high end versions in stock.  Seeds turning into ......

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Is joule thief circuit gets overunity?
« Reply #708 on: May 02, 2013, 01:52:59 PM »
A rather obvious test would be to swap the probes between channels. If the noise follows the probe to the other channel, then you know the probe is bad. If it doesn't, then you know the scope's noisy channel is bad.

Yet again I ask. How was the large voltage discrepancy noted during the probe compensation discussion resolved? What caused it, how did you correct it, and can we be assured somehow that it is in fact now corrected?



TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Is joule thief circuit gets overunity?
« Reply #709 on: May 02, 2013, 02:15:41 PM »
Is there some reason why the DC offset issue can't be tested right now, at home, using a known low-voltage source?

For a first test, take a 10 megohm resistor and a 100K resistor and connect them in series. Hook both scope probes from one oscilloscope to the junction of the two resistors. Hook up a AA battery,  positive pole to the 10 meg free end and negative pole to the 100K free end. All probe references to the negative pole. Use an accurate DMM to measure the voltage between the junction of the resistors and the negative pole.

Now look at the voltages seen by each probe/channel combination. Obviously they should all be the same, and the same as the DMM measures. If there is an offset problem it should show up as a difference in the readings of the channel vs. the DMM. Mark your probes and swap them around on the scopes and channels..... 4 probes and 2 channels per scope means 12 tests per scope.  This might actually take you half-an-hour to perform the whole series.

(Check all probes are at 10x attenuation and that all channels are also set for 10x attenuation probes. Do not use the "default setup" or "auto" functions of the scope; set each channel for DC coupling, no BW limit, zero baseline on the center graticule (overlap both traces so that you can see any differences) and the appropriate vertical amp setting (20 mV/div if possible). The timebase setting shouldn't matter since you are measuring DC here. Set the trigger at the zero baseline.)

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Re: Is joule thief circuit gets overunity?
« Reply #710 on: May 02, 2013, 03:02:55 PM »
A rather obvious test would be to swap the probes between channels. If the noise follows the probe to the other channel, then you know the probe is bad. If it doesn't, then you know the scope's noisy channel is bad.
Lawrence, very easy to do as per TK's suggestion above.

ltseung888

  • Hero Member
  • *****
  • Posts: 4363
Re: Is joule thief circuit gets overunity?
« Reply #711 on: May 02, 2013, 11:01:56 PM »
A rather obvious test would be to swap the probes between channels. If the noise follows the probe to the other channel, then you know the probe is bad. If it doesn't, then you know the scope's noisy channel is bad.

Yet again I ask. How was the large voltage discrepancy noted during the probe compensation discussion resolved? What caused it, how did you correct it, and can we be assured somehow that it is in fact now corrected?
@TK
 
I just followed your advice and swapped the probes.  The result is the same.  So the problem most probably lies with the scope.
 
One of the boards you refered to showed unusual high voltage output and hence high COP.  My mistake was to return it to Mr. Zhou together with the "rejects".  His people "recycled" some components without a thorough investigation.  The rejects were replaced by good ones. 
 
Now I am keeping the rejects.  I do not have the expertise to indentify the problem.  So they are just being stored until I can find the right person to check them out.  If you are interested, I can send you some of these rejects and you can tell us what might be wrong with them.

picowatt

  • Hero Member
  • *****
  • Posts: 2039
Re: Is joule thief circuit gets overunity?
« Reply #712 on: May 02, 2013, 11:16:25 PM »
Is there some reason why the DC offset issue can't be tested right now, at home, using a known low-voltage source?

For a first test, take a 10 megohm resistor and a 100K resistor and connect them in series. Hook both scope probes from one oscilloscope to the junction of the two resistors. Hook up a AA battery,  positive pole to the 10 meg free end and negative pole to the 100K free end. All probe references to the negative pole. Use an accurate DMM to measure the voltage between the junction of the resistors and the negative pole.

Now look at the voltages seen by each probe/channel combination. Obviously they should all be the same, and the same as the DMM measures. If there is an offset problem it should show up as a difference in the readings of the channel vs. the DMM. Mark your probes and swap them around on the scopes and channels..... 4 probes and 2 channels per scope means 12 tests per scope.  This might actually take you half-an-hour to perform the whole series.

(Check all probes are at 10x attenuation and that all channels are also set for 10x attenuation probes. Do not use the "default setup" or "auto" functions of the scope; set each channel for DC coupling, no BW limit, zero baseline on the center graticule (overlap both traces so that you can see any differences) and the appropriate vertical amp setting (20 mV/div if possible). The timebase setting shouldn't matter since you are measuring DC here. Set the trigger at the zero baseline.)

TK,

This is a good idea, however, the divider resistance should be lower to reduce errors.  With 10meg probes (10X probes and 1meg scope input) and using the 10meg/100K dividerstring, probe loading will produce way too much error.  Better to use a 1K and 10R resistor in series with the free ends across the battery to minimize errors due to probe loading.

Better yet, using 100R and 1R would allow his test measurement to be made with the probe connected to a resistance similar to the CSR's and in a similar voltage range.  A fresh AA battery can handle the ca. 15ma load of the 100R/1R string for an time adequate to make the measurement, or he could use his DC supply set to 1.5V.

PW

ltseung888

  • Hero Member
  • *****
  • Posts: 4363
Re: Is joule thief circuit gets overunity?
« Reply #713 on: May 02, 2013, 11:16:41 PM »
Is there some reason why the DC offset issue can't be tested right now, at home, using a known low-voltage source?.......

@TK
 
I do not have an accurate "known low voltage source " at home.  Since the problem appears to be with the Atten Scope and at least one of them is still under warranty, I shall get the manufacturer to check it out with their experts.
 
All my three Atten Scopes showed the crossing 0 reference line behavior.  If it were a bug, the manufacturer would be and should be interested.  They need to fix it or provide a solution for their customers.

poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Re: Is joule thief circuit gets overunity?
« Reply #714 on: May 02, 2013, 11:34:05 PM »
All my three Atten Scopes showed the crossing 0 reference line behavior.  If it were a bug, the manufacturer would be and should be interested.  They need to fix it or provide a solution for their customers.
Can you borrow an analog scope? If so, check your current trace and let us know what you find.

picowatt

  • Hero Member
  • *****
  • Posts: 2039
Re: Is joule thief circuit gets overunity?
« Reply #715 on: May 02, 2013, 11:56:23 PM »
Can you borrow an analog scope? If so, check your current trace and let us know what you find.

.99,

Sorry.  In my previous post I referred to that formula as the "DC offset spec".

I meant to say "DC measurement accuracy".

Here are the specs again:



DC measurement accuracy:

±[3%X(|reading|+|offset|)+1% of |offset|+0.2div+2mv]


DC gain accuracy:

≤±3.0%: 5mv/div to 5V/div in Fixed Gain Ranges
≤±4.0%:typical for 2mv/div and Variable Gain Ranges

There really is no "offset spec" per se, other than inferred by the DC measurement accuracy.

PW



poynt99

  • TPU-Elite
  • Hero Member
  • *******
  • Posts: 3582
Re: Is joule thief circuit gets overunity?
« Reply #716 on: May 03, 2013, 01:50:29 AM »
PW,

For interest sake, the Tek DPO4054 spec sheet states "±1.5%, derated at 0.10%/°C above 30 °C" for DC Gain accuracy.

picowatt

  • Hero Member
  • *****
  • Posts: 2039
Re: Is joule thief circuit gets overunity?
« Reply #717 on: May 03, 2013, 02:13:37 AM »
PW,

For interest sake, the Tek DPO4054 spec sheet states "±1.5%, derated at 0.10%/°C above 30 °C" for DC Gain accuracy.

.99,

I saw that in your scope's manual.

In this spec:

DC measurement accuracy:

±[3%X(|reading|+|offset|)+1% of |offset|+0.2div+2mv]

Assuming the term "offset" is the distance the trace is positioned relative to the graticule center, and the way the above is written, would you read that last part "+0.2div+2mv" as separate from the preceding "1% of [offset]" expression?

That is, with the vert sensitivity set to 20mv/div, does "+0.2div+2mv"  actually, all by itself, add +/-6mv to the accuracy spec? (.2x20mv+2mv).  Possibly they dropped a bracket or two as a typo, but I checked several different manuals for a few models and all were written as above.

If that does indeed add +/-6mv by itself, by the time one adds in the rest of the expression and throws in the DC gain error spec as well, 12-14mv may not be all that far out of spec.

PW

ADDED:  Also, Lawrence should check to see if he has the latest firmware installed.  I read somewhere aout an issue with these scopes llocking up or doing something wierd when the "power on cal" reached the offset portion of that procedure.  A firmware update was issued which was supposed to correct the problem.

ltseung888

  • Hero Member
  • *****
  • Posts: 4363
Re: Is joule thief circuit gets overunity?
« Reply #718 on: May 03, 2013, 05:40:08 AM »
.99,

I saw that in your scope's manual.

In this spec:

DC measurement accuracy:

±[3%X(|reading|+|offset|)+1% of |offset|+0.2div+2mv]

Assuming the term "offset" is the distance the trace is positioned relative to the graticule center, and the way the above is written, would you read that last part "+0.2div+2mv" as separate from the preceding "1% of [offset]" expression?

That is, with the vert sensitivity set to 20mv/div, does "+0.2div+2mv"  actually, all by itself, add +/-6mv to the accuracy spec? (.2x20mv+2mv).  Possibly they dropped a bracket or two as a typo, but I checked several different manuals for a few models and all were written as above.

If that does indeed add +/-6mv by itself, by the time one adds in the rest of the expression and throws in the DC gain error spec as well, 12-14mv may not be all that far out of spec.

PW

ADDED:  Also, Lawrence should check to see if he has the latest firmware installed.  I read somewhere aout an issue with these scopes llocking up or doing something wierd when the "power on cal" reached the offset portion of that procedure.  A firmware update was issued which was supposed to correct the problem.
@PW,
 
Two ADS1062CA were purchased over 3 years ago.  As far as I know, no firmware update was applied.
The ADS1062CAL was purchased in Dec 2012.  It is still under warranty.
***
If that does indeed add +/-6mv by itself, by the time one adds in the rest of the expression and throws in the DC gain error spec as well, 12-14mv may not be all that far out of spec.
***
What does that really mean?  The Atten Scope may be unreliable when voltage drops to that level? :(

picowatt

  • Hero Member
  • *****
  • Posts: 2039
Re: Is joule thief circuit gets overunity?
« Reply #719 on: May 03, 2013, 07:12:34 AM »
@PW,
 
Two ADS1062CA were purchased over 3 years ago.  As far as I know, no firmware update was applied.
The ADS1062CAL was purchase in Dec 2012.  It is still under warranty.
***
If that does indeed add +/-6mv by itself, by the time one adds in the rest of the expression and throws in the DC gain error spec as well, 12-14mv may not be all that far out of spec.
***
What does that really mean?  The Atten Scope may be unreliable when voltage drops to that level? :(

Lawrence,

DC measurement accuracy:

±[3%X(|reading|+|offset|)+1% of |offset|+0.2div+2mv]

The above formula from the ADS1000 series manual specifies the accuracy of the scope when performing DC measurements.  I am assuming that the expression [offset] means the distance in volts that the trace is set above or below the center of the graticule.  Let's assume the scope is set to 20mv per division and the trace is offset from the center of the graticule by 20mv (one full division.  Let us also assume the reading at a given point is 6mv.

The first part of the formula is [3%X(reading+offset), or .03X(6mv+20mv) whivh equals .78mv.  To that we are to add 1% of the offset, which is .01X20mv or another .2mv.  At this point we are at +/-.8mv, which is quite reasonable.

However, I am concerned with the manner in which the last expression is written.  If it was written with additional brackets as "+1% of [offset+(0.2div+2mv)]", that last part would only bring the total error up to +/-1.04mv, which would be useable.

However, the way it is written, the expression "+0.2div+2mv" could amount to adding an additional 6mv to the total error, which would make the spec +/-6.78mv, which is pretty bad considering we would be measuring 6mv with an accuracy of +/-6.78mv.  That would mean the measurement could be anywhere in between 12.78mv and -.78mv.  That's pretty bad and also very difficult to believe.

It is very likely that a typo was made when this specification was printed and they did indeed mean to place additional brackets, which would make the DC measurement error of the 6mv in this example +/-1.04mv, that, while not great, is much better than the case where the brackets are eliminated (+/-6.78mv).  It is just a bit strange that they did actually include similar brackets () in the first part of the formula to remove all ambiguity, yet did not do so in the second part.  Also note that in the first part of the expression they use "+/-3%X()" as opposed to the second part that uses "+1%of [offset]+".

It might be worth emailing the factory to see if they did indeed mean to add the additional brackets into the formula.  After looking at it a bit further, this specification would make way more sense if the additional brackets were indeed meant to be there, or at least if they intended the formua to be used as if they were there, so I would not yet "panick" regarding this until receiving further clarification from the factory.     

DC gain accuracy:

≤±3.0%: 5mv/div to 5V/div in Fixed Gain Ranges
≤±4.0%:typical for 2mv/div and Variable Gain Ranges

DC gain error is basically how accurate the volts per division settings are, i.e., when at 20mv per division fixed gain, a division is somewhere between 19.4 and 20.6mv, which is pretty good.

Firmware:

I would get on the factory website and search for "firmware updates" and your model number to see what the latest rev. number is.  Also, there is likely a way to poll your scopes to see what their current firmware versions are (possibly they display that as it boots).  If yours is not the latest version, consider updating the firmware.

As I said, I read somewhere that there was an issue with the automatic "power on" calibration procedure during boot up regarding the offset correcting portion of that procedure.  But, as I recall, it had more to do with the unit hanging up at that point.  Still, the latest firmware is likely advisable.

In your recent shorted probe captures, your offset looked much better than it appeared in previous captures.  You might try an input current measurement with CH2 (the CSR channel) positioned to the center of the graticule as it is in those shorted probe captures and after having pressed the "default settings" button as you said you did (I assume you adjusted Vert sensitivity, etc after you did that).  It is possible you had something set strangely that may have looked like offset.


On that noisey channel, what happens if you turn off the bandwidth limit?  Does it get worse or better?


To check measurement error and offst, as TK suggested, you could use a resistive divider. Solder one end of a 100ohm resistor to one end of a 1 ohm resistor.  Connect the free end of the 100R to the battery plus terminal and the free end of the 1R to the battery minus terminal.  Connect scope probe grounds to battery minus and the probe tips to the junction of the two resistors.  Use !% resistors and a fresh AA battery.  With exactly 1.5V at the battery, the junction of the two resistors should measure 14.8mv.

You can use a DMM to measure across at the resistors' junction as well to double check against what the scope reads.  Use the DMM to measure the battery voltage, the junction of the resistors will measure (Vbatt divided by 101), or 14.8mv with 1.5V at the battery.

PW