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Monday, July 30, 2012

Wednesday, July 25, 2012

Arduino & LM393 Inductance-meter!

Lately I have been working allot with inductors, ex: DC/DC converters and had a problem not knowing the inductance of most coils I worked with so I decided to build an inductance meter using Arduino and LM393 Comparator. I found the AVR  LC meter with frequency measurement  project by Kerry D. Wong very helpful, it made me understand the concept behind the measurement . The schematic and Arduino code based on similar project by  ReiBot.orgThis meter is not very accurate compared with profesional ones but it does the job.
Update: A better Arduino sketch by ultimoistante:  code here

Using iCircuit App for iPhone

Using a buck converter (AX3003) in an inverting buck-boost topology!

In my previous post I showed an adjustable step-down configuration of AX3003 (SMD buck converter salvaged from old electronic equipment ) and i was wondering what would it take to turn it into a boost converter when I found this paper
It shows how to use a buck converter in an inverting buck-boost topology.
Important note: The paper calls for connecting the Vss pin of the buck device to Vout but if i keep the Vss pin floating (not connected) and connect the Feedback network to Vin instead of Vout, the output voltage goes over -50V !!! (serious boost)!

Monday, July 23, 2012

AX3003 150KHz PWM Buck DC/DC converter

SMD buck converter from AXELITE in TO252-5l package was salvaged from 
some old electronic equipment. Its capabel of taking up to 22V input and 
outputting adjustable voltage from 1.23V to 19.5V / Up to 3 Amps! 
It has 80% efficiency (12 to 5V (2A) ) and 75% (12 to 3.3V (2A) ) See datasheet 

Saturday, July 21, 2012

Running a 12V PC fan using a single AA battery (0.8-1.5V)

THe circuit is for learning purpose only and is far from being
 a practical DC converter... look at the input and output measurements..
very very not efficient :-)
* Replace the 1N4007 diode with a Schottky diode !
Vin = 0.8 - 1.5V, Vout = 65V (no load) /
Load : 12V / 0.15A PC Fan (Vload ≈3.6V, Iout ≈ 20mA)

After adding 2 Zener diodes (5.1V and 15V) and a toggle switch and putting it all 
in a nice tiny little box, here is the End-Product ;-)

Important notice: experimental circuit only!

Sunday, July 15, 2012

Very simple 5v to 65v DC boost converter!

The circuit is derived from the well known DC boost converter circuit using 2 transistors to switch the MOSFET (PNP and NPN). The RC (10nF and 1K) decides the frequency. Higher capacitance gives lower frequency and lower resistance gives higher frequency. The circuit works but im not sure if its the best way to build a DC boost converter. However its the simplest i could think of.

Using iCircuit App for iPhone (Shadi Soundation 2012)

Sunday, July 8, 2012

Internet of Things (IoT) workshop, 7.7.2012 MechArtLab, Zürich

The workshop covered techniques needed to interface internet-connected computers with the real world (sensors, actuators) for clients like Arduino, Netduino and BeagleBone. 
With Thomas Amberg (Software engineer and founder of Yaler) and Thomas Brühlmann (Writer of Arduino Praxiseinstieg)

Thursday, July 5, 2012

Flyback converter (12v to 60v - No Load) and ≈5.5A (max)

I tried to build a flyback converter (or what i think should be called a Flyback converter) using the KHB4D5N60F MOSFET but had a problem with current draw! So i decided to use a Power Transistor E13009 then it worked fine. I used the 74HC14 PWM circuit (previous post) to switch the transistor. The converter has a couple of flaws (the 12V input comes from a 90W power Supply),  .. one of them is the heat dissipation!! Although it can deliver allot of power it heats up fast (BBJ vs MOSFET stuff ... mmmm ) 

Input: 12V, Output: ~60V without load. About 5.5 Amps with 24V DC Motor
Transistor: E13009, Diode: UF3003, Transformer from an old SMPS ,PWM with 74HC14

Important notice: Circuit is not efficient and it was built for experimental reasons only.

Wednesday, July 4, 2012

PWM using CMOS 74HC14 !

The 10nF capacitor between the diodes and GND determines the frequency, higher capacitance means lower frequency. The 10K Pot sets the duty cycle of the pulse.

Schematic using iCircuit App for. iPhone
The original circuit is from, check it out for more info. 

Monday, July 2, 2012

Update1: DC boost converter: MOSFET switching method?

In my previous post i showed a modest 12v to ≈70V boost converter. I used the signal generator of my DSO Quad to switch the MOSFET and was about going the popular way of using a 555 timer chip in astable configuration to do the switching when I had the idea of using the famous astable multivibrator/oscillator circuit (pair of NPN transistors, 4 resistors, 2 capacitors).
I was concerned about the calculations of resistors and capacitors values to set the frequency and duty cycle, so i decided for 50% duty cycle which simplifies the calculation process. 

Schematic using iCircuit App. for iPhone

Normally you would determine the frequency using:  F = (1 / 0.693*(R2C1 + R3C2))
But in case of 50% duty cycle: F ≈ 0.721 / RC  (while R2 = R3 and C1 = C2)

I did choose 10K for R and 1nF for C so I have approximately 72 KHz 

The multivibrator circuit on breadboard

Important notice: everything here is experimental .. 
and such a DC converter and switching method are not a suitable for application!!

Sunday, July 1, 2012

12V to 70V DC to DC converter (Boost converter)

This is my first boost converter (12v to ~70v)  
using A MOSFET (KHB4D5N60F), self-built coil, a fast Diode (B10A45VI - by the way its the wrong diode, click here to see why) and a 47uF/400v capacitor 
Switching Freq. is about 50KHz, 50% DUT

In video: I used a small NPN transistor to switch the MOSFET because the pulse from my handy function generator did not provide enough current to do so.
Loads: 24V DC motor and 12V (20W) Halogen bulb! connected once in series and then in parallel. The converter can handle about 4A current

Schematic using iCircuit  - This circuit is experimental  only and not suitable for application-