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Messages - Silvio Klaic

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Programs / Re: Oron Helper - Greasemonkey script
« on: February 10, 2019, 11:41:37 AM »
It is, but doesn't exists any more, so...
Fixed external link.

Other (Public) / Re: Solar cells test (from calculators)
« on: July 01, 2018, 12:29:39 AM »
I find that best alternative is to buy standard (Polycrystalline) solar cells and create your own solar panel.
That way you have control of size, power and some other strange requirements.
One problem can be low production of partially shaded individual cells, in that case you can bypass load on them with diodes for balance.
Can increase production by adding aluminum passive cooler (or active water cooling), sun tracking, etc.

Don't know.
If you have tables for mains transformer, data are related to specific type of iron laminate sheet.
So you need to find out what type of material is used, and if there is defined specific dimension for transformer for this table.

Transformer calculator (Public) / Re: Links to calculation pages
« on: April 19, 2018, 06:49:56 PM »
Equation is: Power=(With * Height)2
With and height of core cross section are in cm, power is in Watts.

Transformer calculator (Public) / Re: TO DO list
« on: December 29, 2017, 01:48:26 PM »
It is alive and I discussing here only about mains transformer design (50/60Hz), not particularly SMPS design.
Main reason is because I didn't work enough with SMPS to need such program to help me.
All programs which I create is to primarily help me in calculations and I publish most of them as free software to help others.

If somebody have knowledge and willing/time to help me I'm open to create calculator for any type of transformer design.

Transformer calculator (Public) / Re: Links to calculation pages
« on: September 23, 2013, 01:21:21 PM »
Yes, given formula is for steel laminated cores at frequency of 50-60Hz.
If you change frequency or core material, that formula no longer apply.

The best solution is to find detailed specification of core material from manufacturer.
You can also test core to see how it behaves, but that is far more expensive.

Transformer calculator (Public) / Re: Links to calculation pages
« on: September 22, 2013, 08:06:33 PM »
Formula for power of core is cross-sectional area squared: P=S2
Where P is power in watts for 50/60 Hz, S is cross-sectional area in cm2

Because many have problem with installation of my calculator on 64bit, here is archived installed version:
Download it and unpack to C:\Program Files
You may run it on compatibility mode for Win XP.

Hope it helps.

I have a lot of unknown ferrite cores mostly salvaged from radio/TV and other devices.
Main problem with this is to how to know their permeability for calculating number of turns I need to make choke or transformer.

So I needed some simple method to test cores and get theirs permeability.
Simplest way to me is to measure inductivity of choke with unknown core when you know how many turns of wire you have on it.
Then calculate from this inductance factor AL and effective permeability μe of core.

Usually you can find formulas for calculating in manufacturer Data Handbook or production guide.
The AL factor is the inductance per turn squared (in nH) for a given core.
Inductance formula is: L = N2*AL (nH)
When transformed, you can calculate AL with next formula: AL=L/N2
Once you have core data, value of AL is calculated from the core factor Σ(l ⁄A) and the effective permeability: AL= (μ0e*106)/ Σ(l ⁄A) (nH)

To get effective permeability, formula is transformed into this: μe = (AL*Σ(l ⁄A))/(μ0*106)
AL is calculated from measured inductance and number of turns.
Σ(l ⁄A) is calculated by measuring and dividing core physical dimensions of effective length le (mm) and effective area Ae (mm2): Σ(l ⁄A) = le/Ae (mm-1)
μ0 is permeability of vacuum - μ0 = 4*π*10-7 (Hm-1)

This formulae works for most core types except for rods and tubes, for them you need this formula: L = (μ0rod*N2*A)/l (in H)
After transforming we get: μrod = (L*l)/(μ0*N2*A)
L is measured inductance
N is number of turns
A is cross sectional area of rod (mm2)
l is length of coil. (mm)

With this solved only thing to do is to determine optimal number of turns for measurement.
By using large number of turns there is problem with rise of loses by wire resistance, coil geometry and core loses.
Therefore best is to use fewer as possible.
With minimal number of turns, wire length is reduced, thus wire resistance is low.
Beside that with few turns we don't have overlapping wire and loses in coil construction.
However when using single or few turns there is problem with covering entire space on coil former to get fully distributed winding to use entire length of core.

So to solve that problem I did some testing. For my test I chose RM6S/I ferrite core.
I was using three different core materials 3H3, 3C90 and 3E5 and I make coils with different number of turns, form 1 to 31.
For measuring inductance I was using Agilent U1731C LCR meter (resolution 1-100nH, accuracy 1%) with 100 Hz and 1 kHz setup.

Wire thickness is another important part, if it is too thick you can get losses from skin effect.
On another hand if you use too thin wire you can get losses in wire resistance.
For my setup maximal measuring frequency is 1 kHz and on that frequency skin depth is 2.088 mm, thus wire must not be larger than AWG 6.
I choose to use SWG 25 (diameter 0.5 mm) with max frequency of about 80 kHz. Using this wire I can fit 9 turns on former in single row.

One set of measuring was done from 1 to 31 turns with all cores exchanged on that turn. I repeat that set three times.
At end after several hundreds core swapping I compare readings from beginning and end.
Difference in data is from -4.62% to 43.37% which is primary result of loosening mounting clip after so many reassembling.
Most difference (higher than 10%) I got after 22nd turn which just confirms that less turns are far better for precision even in loose clip mounting.

Comparing 100 Hz vs. 1 kHz measurement data gave me difference from -7.51% to 0.98% which is not that bad.
Data from 1 kHz are much more close to datasheet values so it confirms that higher frequencies are better for measuring lower inductivity.

All processed data are from measurement at 1 kHz setup. Those values are used to calculate AL and compared with value from datasheet.

Here on this graph you can see difference for each core material.
For 3H3 material stable results is between 5th and 20th turn, for 3C90 is from 3rd and 31st turn and for 3E5 it looks there aren't stable results however after 21st turn difference are gone totally wild.
So it is safe to say that measuring from 5 to 20 turns gives best results.
To get and calculate permeability the best method is:
  • if possible, use high measuring frequency but close to working frequency of core
  • use 5 to 20 turns (closer to 5 turns for high amplification cores)
  • use thickest wire possible depend on measuring frequency and space on former
  • fill up equally entire length of former in single row

Other (Public) / Magnets
« on: February 18, 2013, 03:48:04 PM »
It's difficult to find good information about magnets and how they behave.
So here I will put some info about them which I found over the years.

The best start is to look K&J Magnetics FAQ. On their site you have also other useful stuff like magnetic calculators etc.
Here are my expanded data from theirs FAQ which I have done thru measurements and experiments:

  • Both poles of magnet are equally strong, but only when measuring in magnetic neutral environment. If you don't measure in magnetic neutral environment results will differ from pole to pole.
    For example if you measure poles of magnets in nature on earth northern hemisphere where is south magnetic pole, you will get data with stronger south pole than north.

  • Stacking magnets will get you slightly higher magnetic field, but there is limit how much magnets you can stack.
    Magnetic conductivity of used material is not that good; therefore there will be resistance to magnetic field.
    You can look values of permeability for different materials:
    MaterialRelative permeability
    Neodymium magnet1.05
    So as you can see neodymium magnet has slightly higher permeability than air, but only small fraction than regular steel/iron.

    Here are some measurements which I was performed on cylindrical neodymium magnets stacked together on top of each other (in series).
    Diameter of magnet 5 mm, length 5 mm, grade N35, maximum strength 3900 gauss.
    Measured only on magnet south pole with gauss meter HGM0200 (resolution 10 G, accuracy +/-2%):
    Number of magnetsField strength (gauss)Strength increaseLength (mm)Max strengthMax strength increase
    6401010,47%304400   11,36%
    Stacking magnets together does not give you too much more power and stacking more than 9 magnets is a total waste.
    So no, you can not get more than 25% of initial (single magnet) field strength in any combination. Therefore combining magnets to get stronger field have no sense.

  • The bigger the better? Not really, but it depends for what you need them.
    If you are interested in building magnetic motor, holding weight or something where magnetic force is important, then this doesn't apply.
    Bigger magnets have much less force per volume/surface than bunch of small ones.
    Here is calculation for square magnets grade N35. Each is 10mm thick, with magnetization thru thickness.
    Price and all data are from company that sells them in my country, so price can be variable to other places, but point here is to show difference in strength.
    Pull force is calculated using The Original K&J Magnet Calculator.
    height (mm)width (mm)max strength (gauss)pricepull force (lb)surface (mm2)pull force/surfacepieces for 3600 mm2 total force (lb)diff total forcetotal pricediff total price
    10543000,56 €4,9500,09872352,8314,04%40,55 €8,30%
    401040004,34 €27,674000,0691759249,03192,25%39,03 €4,25%
    501043005,33 €31,95000,06387,2229,68169,55%38,40 €2,55%
    601042006,36 €35,796000,059656214,74152,01%38,13 €1,85%
    402038008,43 €42,18000,0526254,5189,45122,33%37,92 €1,29%
    5025400012,64 €52,6112500,0420882,88151,516877,82%36,41 €-2,76%
    4040400015,34 €59,5416000,03721252,25133,96557,22%34,50 €-7,84%
    6030390018,51 €63,2718000,035152126,5448,50%37,03 €-1,11%
    10020390022,80 €67,7720000,0338851,8121,98643,16%41,03 €9,59%
    5050360024,39 €73,9625000,0295841,44106,502424,99%35,12 €-6,21%
    6060360037,44 €85,2136000,0236694444185,210,00%37,44 €0,00%
    This data can be easily tested and some of my tests confirms that this is close to real thing.
    So what it shows is that single big magnet is several times weaker than bunch small ones for same volume and surface.
    Also you can see that price of single big magnet vs. smaller ones for same amount volume/surface is very close (10% difference).
    However if you compare forces, then you need 3 times less smaller magnets to replace big one, thus total price, volume and surface is 3 times smaller for same amount of force.
    Conclusion: smaller is better!

Further tests which are currently in progress, result will be posted upon completion:
  • Magnetic force between two magnets at different angels passing by each other on rails.
  • Suppression of magnetic field on one side by redirecting it using different materials aka "magnetic shield".
  • Forces between magnets in linear motor with "shielded" magnets.

Transformer calculator (Public) / Re: Links to calculation pages
« on: February 12, 2013, 10:18:08 PM »
Original program is 32bit and there is no 64bit version.
New program will work on any operating system.
silvio, where can you buy the lamination iron to make the cores for a transformer?
Usually you can buy from transformer manufacturer or you can dismantle some old/burnout transformer and use core from it.

Transformer calculator (Public) / Links to calculation pages
« on: February 02, 2013, 02:07:39 PM »
Here is the list of other useful pages with information on transformer calculation which I collected over the years.
So if you want go in depth looking in calculations, try with these ones:


Laminated-iron core

Ferrite ceramic core,locale=en.html

Air core

Other (Public) / Solar cells test (from calculators)
« on: January 27, 2013, 02:11:52 AM »
During years I collected several solar cells from malfunction calculators and now I'm thinking to combine and use them to make solar charger for single AA or AAA NiMh batteries.
I have two AM-1417 and one SA-3515 cells from Sanyo, one unknown marked KSC08B and 3 newish HP-3012DS.
Only data that I was able to find are for AM and HP cells: at 200 lux they produce 1.5V and 5-20 uA.
Now 200 lux is common lighting at desk level from indoor light source, but I planning to use them outside where light levels are 10 to 1000 times greater.

For charging NiMh battery, produced voltage of 1.5V is sufficient, but the question is whether these cells can produce enough power for reasonably fast charging. My term of reasonably fast charging is up to 8 sunlight hours to charge single AA 2500 mAh battery.
That is constant current of at least 312 mA per hour.

Test preparation

As you can see on image above old cells was electrically connected with conductive tape, which I didn't have. So I connected it with conductive glue. Process is simple; place wires and hold it fixed with some type (top center on image).
Then apply 2-3 thin layers of conductive glue in 20-30 min interval (bottom center on image). After 12 hours of drying apply hot glue on top of wires to fixate and isolate them (top right).
After cleaning up excessive glue, all is set to do testing (bottom right).

Test setup and testing
I was using 22W fluorescent lamp on mechanical arm as light source. With this I was able to precisely adjust height to testing surface. I measure wanted luminosity with lux meter LX-101.
Testing cell was done by connected it to voltmeter and precise trimmer potentiometer in parallel with voltmeter. Then I adjust trimmer to get exactly 1.5V and disconnect cell to measure resistance of trimmer. Measured resistance is then compensated for voltmeter impedance and by ohms law calculated to current at that luminosity level.
Description of my precise trimmer potentiometer which I use in this measuring can be found here.

As you can see from test results, data given from datasheet matches my results. However I notice some difference, mainly between two AM-1417 cells. Second cell (not shown in table) have almost identical response as SA-3515 cell.
This means that older cells have bigger differences than new ones. Not sure if this is to fact that they are used more or/and aging influences.

You may notice that new cells (HP-3012) have better sensitivity at lower light levels, but are weaker at high luminosity. Which is shame because technology of solar cells is much improved? Or there is some other reason for making these bad cells...
I was measure up to 10k lux which is max for my 22W fluorescent lamp. 10k lux is luminosity outside at cloudy day and on sunny day without clouds can reach over 100k lux.

To compare efficiency of these cells to standard outdoor solar panels, this data need to be converted to standard test irradiance (normally at 1000W/m2).
I don't have data how exactly my fluorescent lamp have luminous efficacy, so I assume to be about 70 lux/W, with this irradiance of 7 klux is 100W/m2. To convert data, I'm dividing lux measurements points with 70 to get W/m2.
As you can see from graph current is almost linear and I presume that test at 75 klux will give about 10 times more current than on 7.5 klux.
So using max readings of 10 klux and multiplying calculated power with 7 will get me approximately results for irradiance of 1kW/m2.
Then dividing these results with surface is close enough data for comparing power per cm2 with standard solar panels.
Cells/panelsdimensionSurfacePower per surface @ Irradiance 1 kW/m2
SES 440J655x537mm3517,35cm211,372mW/cm2
Sole SL-40P669x500mm3345cm211,958mW/cm2
In this table I compared result with some standard solar panels.

Anyhow, making charger from 7 cells which I have is not good idea. These cells are too weak, about 10 times worse compared to standard solar panels at same surface levels.
To build charger I'll need to have 100 times more of these cells. There is no way I could find that amount old cells and with new I'll need minimum 500 of them.
Calculation for charging single AA NiMh 2.5 Ah battery at 1.5V with irradiance at 1kW/m2:
1922 cells of HP-3012DS: 5386.4 cm2, 1.272 A/h = 1.907 W/h, 1.967 hours.
For same price solar panel Maxcell 40 Poly: 3345cm2, 3.555A/h = 5.33W/h, 33.8 minutes.

So these cells are no go.
I'll use them as light sensors instead LDR in my project for tracking sun movement across sky.
Another good use is irradiance meter, however I need to find precise and know light source to calibrate meter. The best I can think of it now is summer sun at noon without clouds, but this is only calibration for range above 100W/m2.
If you know other method for calibrating irradiance meter, let me know.

I'll conduct further testing in summer to confirm these calculations.
Another testing at that time would be with standard solar panels.
I found that they work only at high luminosity (no, indoor lighting can't be used for power source).
Another test is efficiency at different angles and with solar tracker.
There is also thermal test to see if they really lose power during higher temperatures.

Transformer calculator (Public) / Re: TO DO list
« on: January 26, 2013, 11:49:00 PM »
Update news
I'm working for some time now on new transformer calculator.
Currently I do tests on different calculations for different coils, mainly ferrite ones at wide frequency range.
In next month or so I'll post result of testing and future updates on program.

Program will be under GPL license and open sourced.
I'm planning to create it as dynamic HTML using java script, this way can be run on any platform, either online or offline.
I am planning to put first beta release in March.

Alternative / Alternative and essential links
« on: February 25, 2012, 01:32:11 PM »
Now and then people ask me for links to other pages for alternative information.
So I decide to place here list of links which I find useful and I hope that this helps.



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