Recent Posts

Pages: 1 ... 3 4 [5] 6 7 ... 10
41
Other (Public) / Low cost tweezers type LCR meter
« Last post by Silvio Klaic on October 18, 2011, 06:43:02 PM »
I started new project; LCR tweezers - impedance measuring instrument, capable of measuring resistance, capacitance or inductance.
One of main reasons is lack of cheap instruments of this type on market.
Other one is that I have pile of SMD components that need testing and sorting out.

My other projects are currently in hibernation, mainly because they started to be too complex for my taste in current state of development.
In battery capacitance tester I replace 8bit ADC0804 with more precise and cheaper ICL7135 which also increase number of ICs for interfacing with parallel port.
At that point I was seriously thinking to use microcontroller with 10 or 12bit ADC, and replace entire circuit.
On pulse charger after numerous experiments I find out that complex charging signal is more effective, especially if contains complex charging/discharging sequences.
But to experiment with that I need to build far more complex hardware with standard ICs, at which point I decide to start working with microcontrollers.

My pile of SMD components is nightmare to sort out with standard multimeter. I have ability to measure capacitance, inductance and resistance on it, but switching between ranges to find out what is component value started to be never ending painfully slow process.
So I start to look for small tweezers type multimeters which can detect and measure components of inductance, capacitance and resistance. Sadly, existing ones are too expensive for my taste as amateur in electronics.
But this gave me idea to determine what exactly I need. Here is specification of tweezers which I want to construct:
  • Low cost – less than 30 euros.
  • Portable and small size, to easily fit into hand as tweezers.
  • Battery powered for easy handling – idle auto power off (bonus for integrated charger).
  • Based on KISS principle – fewer components as possible (single chip with few passive parts would be ideal).
  • DUT (Device Under Test) automatic type detection – L, C or R (bonus for diodes, etc.)
  • Fast type detection – under 1 second.
  • Fast measurement – under 1 second.
  • Low accuracy – 20% or better.
  • Wide measurement range if feasible:
    • Inductance – 1 uH to 1 H
    • Capacitance – 1 pF to 1 mF
    • Resistance 1 ohm to 10 Mohm
As you can see, I need small, cheap and simple sorting tool. I already have other instruments if I want more precisely testing/measuring.
After searching net I find this as possible project which may have something that fit/closely match or can be adapted to my specification:

I. group: Exact or closely matched
There are projects which involve measuring all three components.
They are based on measuring phase shift between voltage and current.
One is Russian version of LCR meter; you can find details at http://kripton2035.free.fr/lcr-repository.html or http://www.pro-radio.ru/measure/6873/ (Russian language).
Other one is at http://www.circuitcellar.com/microchip2007/winners/third.html

Now, these hardware projects are complex, expensive and big. Adopting them to my requirements is not feasible (my estimation).

II. group: Closely matched and can be adapted
Other instruments are mostly based to test LC, RC or only one L/C/R type and do not measure by default all three types.
There are many working principles from measuring charging time to change of frequency.
Here are some of those projects:
Adaptation any of this to my needs will require adding additional switching, some independent test hardware and then some way to determining what DUT it is.
However I find one version closest to my needs at http://members.cox.net/berniekm/super.html there is also changed version at http://benryves.com/journal/3632205

This is simple, small and it can be made to measure all three types.
However measured range is limited and some measurements require up to few seconds or are unreliable, like inductance where entire device can hang and need resetting.

I can recombine these schematics by using more LC components for resonance to increase measurement range and resistors to achieve my specifications.
For switching it will be needed to replace relays with MOSFETs or analog switchers like CD4066.
And all of that must be built with SMD components to be small.
In short: feasible but I put this solution for last resort if all other possibilities are exhausted.

III. group: Create completely new device from available methods
On end I decide to build my own microcontroller based LCR meter using new methods with new approach.
After thinking I came to conclusion that first thing to do is to find a way to determine what type of DUT is.
So I need something what all three types have in common and the answer is resistance.
Not standard DC resistance, but AC resistance or impedance - reactance.

Simply put I need to measure impedance at two or more different frequencies.
If DUT maintain identical reactance on all frequencies, then DUT is resistor and measured reactance value is actually resistance.
On other hand if DUT reactance becomes higher at higher frequencies then it is inductor.
To find out inductance, we can use formula to calculate it:


And at last if DUT reactance becomes smaller at higher frequencies then it is capacitor.
To calculate capacitance from reactance we can use this formula:


So this is simple method to automatically detect what type of DUT it is and do measurement.
Now all that I have to do is construct impedance meter, which actually work similar as classical DC ohmmeter with addition of using AC with changing frequency and made calculations for capacitance and inductance from measured reactance.

Searching web for this type of instrument did yield some results.
There is solution based on the same method but using computer soundcard and PC software – ZRLC meter.
See details at http://www.sillanumsoft.org/ZRLC.htm
This software solution is nice and it’s worth using it, but it is not mobile and has limited measurement range because it uses max 40 kHz from soundcard with single resistor.
By my calculations for my range I’ll need selectable resistance and frequencies up to few MHz.
Nevertheless this is proof that this method works. Here is another example for this method:

Surprisingly I didn’t find any other complete projects which will be using solution like this.
All other projects are about special functions like ESR etc.
However I find some other useful information:

So that is idea, now I have to do more detailed research, crunch some data and make calculations to find out how to build it.
Guessing these would be primary key points:
  • Cheap digitally controllable frequency generator in range of 100 Hz up to 2 MHz
  • Digitally fast selectable resistance for range
  • Accurate measuring AC voltage with ADC
42
Programs / Oron Helper - Greasemonkey script
« Last post by Silvio Klaic on September 11, 2011, 01:37:32 PM »
I didn’t find useful existing helper scripts for Oron, like ones for RapidShare or MegaUpload.
So I wrote my own.
You can download it from here: oron_helper.user.js
or from: http://userscripts.org/scripts/show/112760
http://userscripts-mirror.org/scripts/show/112760

Script does next stuff:
  • Automatically click on Free download button (can be disabled in script options).
  • Removes download delay.
  • Automatically reload page after waiting time for next download elapsed.
  • Showing countdown of waiting time in title (can be disabled in script options).
  • Alerts you when captcha is ready (can be disabled in script options).
  • Automatically starts to download (can be disabled in script options).
For changing script options, you must edit script.
43
LARP (Public) / Re: Popis velikih LARP dogadanja 2011
« Last post by Silvio Klaic on July 18, 2011, 08:40:26 PM »
Obavijest za sve one koji imaju novac na Rajskim Vrhovima:

Zbog interesa i razvoja situacije ingame odluceno je da ce se pustiti odredena kolicina novca van za upotrebu na drugim dogadanjima.
Serije novca su:
  • crno-sive boje
  • u apoenima od 1 i 2 vepra
  • datuma 21-24.07.2011
  • priznati ce se na svim dogadanjima Rajskih Vrhova
Svi igraci koji imaju i zele preuzeti novac za svog karaktera mogu sukladno pravilima novca za Rajske Vrhove ih preuzeti u utorak 19.7.2011 (vjerojatno i ostale utorke)  u Tomislavcu izmedu 20 i 22 sata.
Ako niste u mogucnosti u ovom terminu preuzeti novac, slobodno me kontaktirajte ili nekoga od organizatora sa Rajskih Vrhova.
44
LARP (Public) / Popis velikih LARP dogadanja 2011
« Last post by Silvio Klaic on June 20, 2011, 12:07:52 AM »
Evo kratki popis velikih LARP dogadanja:

Fantasy LARP:
21-23.6.2011 Rajski Vrhovi XIV
lokacija: Zumberak, vise...
21-24.7.2011 Jaska 8
lokcija: kraj Jastrebarskog, vise..
13-15.8.2011 Rajski Vrhovi XV
lokacija: Zumberak
26-28.8.2011 Majcin Gaj
lokacija: kraj Vrbovca

FALLOUT LARP:
Event je trenutno odgoden do daljnjega.

Za ostale detalje pogedajte na larphr webu.
45
Transformer calculator (Public) / TO DO list
« Last post by Silvio Klaic on May 09, 2011, 12:23:50 AM »
This is additional TO DO list for future upgrade of Transformer program.
However, for making any update I’ll need data about any transformer coils and formulas.
So if anyone is willing to help, I appreciate it.

  • field for selecting the core shape (toroid, U, E, I, W)
  • the input Amps should be user defined;
  • wire thicknes in P1 should be user defined + a field with optimum calculated for both P1 and S1 (maybe S2) wire thickness;
  • if it is feasible, due to the S1 wire thickness (in the stepdown type) to put an area cross section field (maybe different shapes for the wire);
  • possibility of using transformer taps on S1 to regulate the output voltage
News 26.Jan 2013
  • simplify user input fields and program handling
  • improve corrections on core/wire specification
  • add option to calculate with unknown core/ferrite by inputting few simple measurements
  • calculate bare essential data to match wide range of cores/materials – if you need more precise or detailed calculation, then you need professional program or manual calculations
46
Other (Public) / Re: Pulse charger...
« Last post by Silvio Klaic on March 27, 2011, 03:46:19 PM »
There is error in previous schematic; MOSFET must be P-type to work properly.
I was originally made on test board with P-type and it didn’t work as expected, probably because used MOSFET was too weak.
After that I rearrange parts and made N-type version which worked. Here is modified version:


In here capacitor C8 was placed to reduce load on MOSFET and add better spike output.
When used without C9 it produces 3-4 spikes in short duration and acts like desulfator.
C9 was closed loop with primary coil and significantly increase power output.
Charging in this configuration is much faster, but output spikes are reduced to about 50V.
Running frequency is set to 6.4kHz.


Here is shown coil with only primary (upper left) and prototype device with completed coil.
There is 766 turns in both coils, primary one uses copper wire of 1.4mm diameter, and secondary of 0.6mm.
Inductance in primary is 0.994mH, resistance 0.99 ohm, in secondary is 1.89mH with resistance of 6.22 ohms.
As you can see this coil is big, 500mm in length and 43mm in diameter, but it does job done. :)

However I was not happy with this, because I want bigger pulses and smaller charger, so I started from beginning with new direction.
After searching thru other project with pulsed chargers I find these two most interesting:
http://www.freepatentsonline.com/5633574.html
http://www.wipo.int/pctdb/en/wo.jsp?WO=2003088447

And so I create list of what my charger must have:
  • Go on directly at AC line
  • Generating short high voltage spikes (100V+)
  • Pulses must be strong to do actual charging not only desulfation
  • Made in KISS principle
  • Smaller dimensions
So after thinking I decide to try with something like this:


This schematic should fulfill all listed must haves.
CD4060 with potentiometer will provide frequency range from 760Hz to 3.5kHz.
Switch provides selection of duty cycle from 50%, 25%, 12.5%, 6.25%, 3.125% and 1.5625%.
IC3 with two transistors make driver for MOSFET.
Entire device get current from AC line thru C2/D1-2 and power for spikes goes form rectified power AC line.
This should provide powerful and stable 250-300V spikes.

Anyway this is idea, after testing and building prototype I’ll post results.
WARNING: Do not attempt to do this at home, this uses live AC current and it can easily kill you!
Remember, I’m trained amateur and I know what I’m doing. ;)
47
Other (Public) / Re: Pulse charger...
« Last post by Silvio Klaic on March 11, 2011, 08:36:10 PM »
Here is update on restoring sealed battery; in short I gave up.
After breaking seal and examining internal plate status, there was no point in repair attempt.
There was crystal structure which deformed and at multiply points shortened opposite plates.
So even if I remove that crystal form, there is question; will I have enough plate material to be able to restore it in normal working condition?
I’m thinking at best to quarter capacity, but amount of work and price of chemicals equals more expensive than new one.

One another observation; while performing tests with measuring internal resistance I found that my method form Wikipedia isn’t good.
So I have to find something else for reliably test internal resistance of battery.

Next, about tests with charger, my initial setting was excellent for small batteries up to 2Ah, in range from 1.2V to 24V.
There is only need to adjust DC output voltage with duty cycle.
My first test was on 70Ah battery and after 2 days of charging voltage raises to 12.4V, so I decide to do testing on smaller battery to see result more quickly.

Next test was done on 4.5Ah battery, and after 4 hours I didn’t notice significant improvements.
Charger consumption with battery was 0.38A and I need to get more power to charge it faster.


This is new setting; on left are out pulses with only light bulb connected.
In middle are pulses for MOSFET gate and on right you can see brightness of light bulb at this setting.
Frequency is 1.2 kHz, with 65% duty cycle on, voltage output 10.6V/23.9V (DC/AC scale at multimeter), consumes 0.29A with only light bulb and 1.12A when charging battery.
With this I was able to fully charge 4.5Ah battery in about 3:30 hours.
Coil was very hot, so I rearrange ventilator from blowing out of casing to in at coil to make it more temperature stable.

Then I calculate that for charging 70Ah battery I’ll need more than two continuous days, which is too long.
So I decide to push charger to limit (and beyond).


This is more powerful setting; 1.6 kHz, 75% duty cycle on, voltage output 12.8V/28.9V (DC/AC scale), it consumes 0.34A with only light and 2.2A with battery.
On bottom left picture are out pulses when battery is charging.
As you can see HV spike is completely absorbed and charging is done only 23% in cycles during coil discharge.
Notice on bottom right how 24V light bulb is now much brighter.
At this point I was not sure if ventilator can keep coil cooled enough. Anyway I decide to push forward and see what happens.


This is end result (I remove pieces of melted plastic casing to get better picture of PCB).
In about 6 hours of charging, coil is gradually heating plastic casing and ventilator to a point of melting.
Ventilator at this point becomes working slower allowing coil to become hotter.
After that, everything gone in runaway effect, ventilator casing was deformed and stops working.
Third of casing was melted away and nearby screw fell on PCB making short connection in which MOSFET blocks in on state and starts heating until breakdown occurs.

So for more powerful version I need to make some heavy duty coil.
However I also need more current at output for faster charging.
There is also problem of HV spikes if there is no load present.
Therefore I think to make new approach, something like this:


This will solve HV spikes problem in primary side by capturing it in capacitor.
Frequency must be tuned in capacitor - coil resonation, therefore each new pulse will go with capacitor discharge and reduce collisions/current waste.
Transformer model will produce more current at output for faster charging and hopefully solve problem if no load is connected (yeah I know this won’t work, let me dream a little bit ;)).
48
Other (Public) / Re: Battery capacitance tester...
« Last post by Silvio Klaic on March 11, 2011, 02:53:54 PM »
After intense testing I wasn’t happy with some results and decide to do some changes/upgrades to tester.


Here is new improved schematic.
  • Voltage reading at and beyond 15V shows some nonlinearity, probably because leakage current through 6.2V Zener diode.
    So I remove it and place regular diode to VCC for input overvoltage protection. Input impedance of ADC0804 is 5k (as is stated in datasheet), so I reduced input voltage divider to 19k.
    Now at 15V consumes about 0.23mA, but reading is more accurate. I also have to change base voltage in program from 8.925 to 8.88V.
  • There was some significant difference in voltage at halogen lamp and battery terminals.
    I was hoping this won’t affect calculation, but it does. So I add sense wire which is connected at clamp as +12V wire and all voltage reading are now done at battery terminals.
  • I originally placed halogen bulb inside casing, but that will melt casing if left too long working. There is also problem of changing bulb. So I add PTR connector and mount halogen bulb in it.


Here is how prototype now looks like.

However I’m thinking to add resistor + OP amp for current measure up to 2.5A at halogen load.
To switch between voltage and amperage I’m planning to use MOSFET transistors.
This would eliminate calculation of how much halogen light bulb consumes (which only gives estimate value) and add options to easy replace it with more powerful version.
49
Other (Public) / Re: Pulse charger...
« Last post by Silvio Klaic on March 01, 2011, 05:06:00 PM »
I made some modification to original schematics.
After testing I decide to remove two driver transistors, because 555 IC have enough pull-up to GND for driving MOSFET alone. However I placed 1uF capacitor to stabilize raise-fall gate voltage.
I was also experimenting with different frequencies and came to conclusion that original setting of about 600Hz is optimal. Higher frequencies have lover voltage peak and I need pulses beyond 100V for battery sulfation problem. So to work with higher frequencies I need high voltage transformer (better solution) or coil with lower inductance - higher consumption (worst solution).


Here is new schematic. I place small incandescent light bulb as control and ballast at output. Without load, coil transfer all HV spikes to MOSFET which can burn out in short time. I also added small ventilator to cool down coil.


Here is prototype board and test casing for it.
Frequency is set up to 600Hz, out voltage on DC scale is 5.8V and 12.7V at AC scale of multimeter. Power consumption of electronics (without coil/MOSFET/ventilator) is about 40mA, and without ventilator it consumes 200mA. Ventilator is from old TNT graphic card and consumes 90mA at 12V.

In theory this charger should never overcharge battery and can be place forever to charge battery (something like trickle charger). But those theories I’m planning to test.
My sealed battery during testing didn’t show any changes. I have recorded internal resistance of battery. In entire time it didn’t change at all, it’s constantly about 257 kohms (yes, kilo ohms).
For measuring (calculating) I use method from Wikipedia:
http://en.wikipedia.org/wiki/Internal_resistance
There are also other methods, like:
http://www.buchmann.ca/Chap9-page2.asp
http://madsci.org/posts/archives/2003-11/1067871870.Ph.r.html

Conclusion is; my sealed lead battery is sulfated beyond repair with charge or/and have some structural damage... My plan now is to open it and try with magnesium sulfate to restore it back to life. If someone interested how, here some links:
http://www.ehow.com/how_5152330_fix-dead-motorcycle-battery.html
http://ysuusy.com/Lead_Acid_Car_Battery_Repair.html

I’ll test my charger with other batteries, and I’ll report back how things going... :)
50
Other (Public) / Pulse charger...
« Last post by Silvio Klaic on February 21, 2011, 12:34:15 AM »
I decide to start new project, pulse charger...
In my last project with battery capacitance tester I stuck with trying to recover battery by draining it to 8V and recharging in several cycles.
This however didn't produce any result and I have feeling that my old charger is not suitable in recovering process.
This 30 years old charger have transformer with 4 power diodes for rectifier and small light bulb for control...
So I decide to build add-on for this charger to transform it into pulse charger.

After searching web for some useful schematic, I found only these sites:
http://electronics-lab.com/projects/power/008/index.html
http://www.freewebs.com/acselectronics/batterypulser.html
http://www3.telus.net/sail/sj23/e_electrical_tips/e04.html
http://sites.google.com/site/johnbediniresearcharchive/radiant-100

None of this fits my needs, so I decide to build my own version based on John Bedini principle.
I use 555 timer, set it up for frequency range from 500Hz to 3kHz, then with two out transistors set driver for MOSFET IRF640.
Then I test how this works with different coils and at end I find that 6mH toroid choke coil is optimal for this configuration.
I didn't want to use my test coil so I made one using parts from dead PC ATX power supply.


Here you can see on left desoldered coil, in middle core without wires (inner diameter is 13.5mm, outer 23.5mm and width 9.7mm).
On right picture is my new coil of 6mH, to make it I use wire with diameter of 0.3mm (with insulation) and 8.5m long.
I use instrument to measure inductance, but I think there are 294 turns unless I miscount somewhere. :)


Here is schematic for prototype. I used small light bulb (24V, 4W) as battery for calibrating device. Input voltage from my test transformer is 20V so I need to add resistor R5 of 47 ohm to drop down voltage to about 17V before 12V regulator to avoid heating.
R3 is for adjusting frequency form 500Hz to 3kHz and R8 for length of positive out pulse (duty cycle).

For testing device I decide to use another dead battery, it is 12V sealed lead battery with 7.2 Ah from 1993. It is originally used 5 years in UPS and then collected dust without charging. Using classical charger I fill it up under minute and drain less than 30 seconds to 2V.

Initial test charging with pulse charger is set as 1.4kHz, 60% duty cycle and last about 21 hours. After resting it holds voltage of 2.9V, and connecting 24V/4W light bulb will drop voltage to 0.2-0.3V. During this test charging, MOSFET become hot and there was no progress on battery, so I decide to reduce duty cycle below 50%.
After calibrating again with 24V light bulb I got this:


On left side is signal which produce 555 IC and it reaches 6V with 46% duty cycle. In center image is signal which drive MOSFET, for start it uses +2.4V and after -1.4V to block gate (without MOSFET out is +/- 4V). On right picture you can see out spike, it reaches 200+V and quick drops to 0V (under 46% of duty cycle). With this I solve heating MOSFET, and now only coil become warm.

During calibrating device to 700Hz I found that light bulb becomes bright, even brighter than connected directly to 20V. So I measure current and I detected some interesting phenomena. This 24V light bulb, directly on 20V, drains 3.6A current, but when connected to charger it drains only 230mA. Less than 15 times!
I think I should do another project involving DC pulse currents and regular light bulb of 100W. I'll try to use current directly from mains power to se if I can get same brightness on 100W bulb and to consume only 10W... :)
Pages: 1 ... 3 4 [5] 6 7 ... 10