RANT CAFFE ASYLUM

[picowatt]

CaptainLoz,

What prompted my initial post to EMJ was with regard to your video #5:

https://www.youtube.com/watch?v=Tk9uSOdj-hE

At around 7:30 in that video, we see the two incandescent lamps, apparently in series, being used as a load.  At that point, the DC supply is providing a total of around 17 watts.  It does not seem probable that those two incandescent lamps could be dissipating 17 watts, let alone more than that, as indicated by the scope.

Thanks to your reply, we now know that the lamps will draw .2 amps when driven by 14VDC.  Therefore, when driven to their rated brightness, each lamp will dissipate 2.8 watts.  The series connected pair, will therefore dissipate 5.6 watts when connected across 28VDC.

The waveform driving the lamps is not DC, but the thermal mass of the lamps tends to do a good job smoothing/averaging a complex AC waveform driving the lamps. 

I suggested that you connect the two lamps directly to the DC supply and adjust the supply's voltage until the lamps are illuminated as bright as they are at 7:30 in the video and compare the watts drawn from the supply to the watts driving the POC circuit at 7:30 in the video.  Although a judgement as to what is "similarly bright" is rather subjective, such a test will, at the least, provide a ballpark number to compare to the scope reading.

Its a fairly simple test and should not have set off a firestorm of insulting replies from EMJ (which he then deletes).

So, to repeat, in video 5, at around 7:30, we see 17watts from the supply being used to light a pair of 2.8 watt rated incandescent lamps.  Even if the lamps were being overdriven to almost three times their rating, the circuit would be less than unity and way more inefficient than what the scope is indicating.

If the scope math is not set correctly, you could be measuring reactive power circulating in the circuit and not real power driving the load.  Performing a quick test with the two lamps, driven to comparable brightness by the DC supply, would provide an "in the ballpark" verification of the scope's measurements.

PW     

       

[partzman]

CaptainLoz,

Respectively, I would recommend you try what Picowatt has suggested and if you find that his test shows you could not be producing the level of output your scope indicates, I have a suggestion.

Remove all the floating grounds.  These are not necessary due to the inherent isolation provided by the transformer windings.  IOW, place the common ground from your signal generating source on the the same ground connection of your circuitry, on the same ground of your scope and ground each secondary at this same point.  Now take your measurements as let's see what the result is.

Regards,
Pm

[picowatt]

Partzman,

A comment to his video #9 suggested he feed two zero to 5 VDC "in phase" 50% duty cycle square waves into the two scope channels for a simulated 25 watts during the square wave on times.

If the scope math is correct, that should read an average of 12.5 watts (25 watts for 50% of the time).  One of the square waves is then phase shifted 180 degrees and the scope should then read close to zero watts.

I think the above is an excellent suggestion as well.

PW

[picowatt]

EMJ,

Apparently you do not grasp the logic of this suggestion.  It is a simple method of verifying that the scope math is programmed and reading correctly.

A function generator is used to simulate a voltage and current signal of known amplitude and duty cycle and fed directly into the two scope channels.

Various amplitudes, waveforms, duty cycles, and phase relationships can be used, but the suggested pair of "in phase", 0-5VDC @50% square waves makes for easy math.

When the pair of square waves are "in phase", the scope should read 12.5 watts (5V X 5A= 25W for 50% of the time = 12.5W).

The phase of one of the square waves is then shifted 180 degrees.  The scope should now read very close to zero watts.  If the scope does not read zero watts, the math is not properly programmed and is not measuring "real power".

Feel free to ask additional questions if you or CaptainLoz do not fully understand this suggestion.

PW

Is anyone reading these moronical Assumptions?

50%? last I checked Loz used 35% or less. What is wrong with these people? Cant they get simple figures right?

How many times do you have to be told the simple stuff?

Why do they all rush in, from years of Slumber, to act like children, when we have a measurement that shows something special?

It is obvious to me!

Best wishes, stay safe and well in these Dire Times,
   Chris Sykes

[partzman]

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