Author Topic: Meyer-Photogrammetry VIC replication  (Read 1810 times)

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Meyer-Photogrammetry VIC replication
« on: February 22, 2011, 04:09:57 am »
This is where the explanation of the inductor backengineering from photo goes.
By running the observed ratios through a ratio relational matrix  the realtive dimensions of the
inductor are obtained.
Because the thickness of the windings is preserved regardless of the shape of the.core.
Example an inductor wound on a thin paper core when flattenend would be twice the thickness of the core in height but when wound aound a paper tube, the thickness of the winding is still the same even though the core is a tube
Thus, if the ratio of the dimensions of the core vs. the core with windings can be determined, the relative thickness of the winding can be determined. Then if a relational string is linked to a known real world value the number of windings can be estimated in the following way. Let's  say the length of the inductor is  20 caliper units, and that the core is round and 10 units in diameter, If the wound diameter is 15 units, then the area of the winding is  20 times 2.5 units square units. 
Because a packing factor for uniformly wound wire is .907 (Steinhaus packing factor) ,the cross sectional area of the wound layer is .907(75) square units. If an actual measurement can be linked to the
length and therefore width of the inductor, the number of square inches of  the winding area (before packing correction can be determined.
If the gauge of the wire can be determined by directly counting the number of winds on the outer layer of winding and with a known length of the inductor wind in inches a gauge from the AWG tables can be estimated. ( Example:For a rough estimation if the area of the winding is one square inch and 18 gauge AWG is being used for the coil (25 winds per inch), there would be 25 by 25 windings per square inch  or aboutr 625  Now take the reciprocal the the packing factor  1/.907 (1/steinhaus) and multiply and this will give you the wirewind count/inch squared  aprox  1.103 x 625 ior about 689)
 Now divide the cross-sectional area of the winding(after, correcting for the packing) by the cross sectional
area of a single strand of wire of the estimated gauge and then the result will be the total number of windings. In cases where the view of the windings are obscured by vinyl tape, glare lines or ridges may still be apparent and give a reasonable wind counts per inch.
After the number of winds a determined, you consider the total length of the wire (for factory winding) to be a series of large rings on top of smaller rings with each layer of rings shifted over and lying  in the crevices formed by two adjacent wires. (another approach for the packing factor) The total number of  concentric rings is not the diameter of the wire divided into the thickness of the wind , but instead  the number of layers of wire is actually greater in number due to packing factor. For each subsequent layer, the effective diameter of each set of rings is smaller than the full diameter by a set constant, so once this is factored in the number of winds for the coil is determined as well as the length of the wire, which in turn gives the resistance.  Application of standard inductor design (open core, iron core etc) now gives you an estimate for the mH of the inductor. Of course , honey comb or random windings will have different packing factors, which  sometimes can be estimated by making similar sized inductors and counting the wraps needed to obtain a given inductor wrap thickness.
This is the search for known scalable component dimensions
imgsearch mousercat:all dim:rtn val desc
smrt search on
2n3055 RCA ST <val>
Dim <vaL> width mounting bracket   25.00 -  26.00 mm
               length mounting bracket  38.50-   39.30 mm
               distance between center of mounting holes 30.00 -30.30 mm


This is the search for AWg wire dimensions

imgsearch wiki awg
smrt search on
<val> 29
search wire gauge 29 AWG
88.8 turns per inch
0.0113 diameter

argument 137:128
Ratio 1.07
argument 64:<val>
argument 149:<val>::39::25.4::loop
1.29 <val>L 2n3055 string 1
argument 137(32)(.907)
This is the winds per inch and reported length of inductor.
argument 88.8(1.312)
<val> 116
These are caliper readings of the y axis of the coil comparied to caliper reading of y axis of coil base
It is being divided by 2 to get the y axis units for thickness of the winding.

argument 128:64::2:<val>
« Last Edit: February 22, 2011, 21:45:10 pm by jim miller »

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Re: Meyer-Photogrammetry VIC replication
« Reply #1 on: February 22, 2011, 15:16:09 pm »
I have some measurements to give you for the coils.
Using the above pictures as a referance the dementions are as followed.
The length of the large coils(left to right) 1.312 inches.
The width of the coils (top to bottom) 1.5 inches
The height of the coils(table up) 1.16 inches.
Coil base size measures .360 x .675 inches.
Length of small feedback coil (green) is.380 inches.
Wire size was 29 gauge .0115 inches.
My calculations for the primary wire is between 600-650 turns, wire resistance measured 10.5 ohms
Secondary 3000-3200 turns, wire resistance measured between 70-75 ohms between the three coils (2 chokes and secondary)
Now get busy