Friday, February 8, 2019

Push button ON/OFF + Soft start v.3

This is a revamping of an old project: "Two versions of soft sart". There were reports in the comments that the circuit doesn't always work. I have tried myself on a breadboard and indeed - the schematic works with chips from Nexperia and doesn't work with chips from other manufacturers. The problem is in the input stage of the schematic - the push button.  There is a capacitor in parallel to smooth the bouncing of the contacts but the pulse gets too long and is registered by 4027 clock input as more than 1 impulse. Without the capacitor schematic will work if the push button is high quality, otherwise, again the 4027 will detect more than 1 input signals. To combat this problem I tried different methods an here I present two of them.

Saturday, April 8, 2017

Download links problem

Hi there,

From some time now the links for downloading project files in my blog are not working. This is because most of them are from dropbox and they for some reason changed their sharing policy and now all public links has been disabled and I must edit all the links one by one. Things get further complicated because I use URL shortening service (, and long story short  - it will take some time to fix all the links.

UPDATE: September 08, 2017
Most of the links are now fixed.

UPDATE: 29.01.2019
Fixed some more dead links and for some of the projects I also added Gerber files.
If there are still dead links, let me know.


Wednesday, September 23, 2015

100MHz frequency counter with LCD display

Update November 26, 2015:
I made a full project with preamp/signal conditioning and power supply with soft on/of switch. It is published here.

This is the same as the previous frequency counter but the output is on the 16x2 LCD display.
For more details about how it work look here:

Wednesday, August 5, 2015

100MHz frequency counter

Couple of weeks ago I purchased from eBay one of these amazingly cheap an useful modules with MAX7219 LED driver and 8 digit LED display. It is ideal for frequency counter project. The problem was the absence of library for PIC microcontrolers. Luckily, I found a great library for Arduino and I reworked it to be compatible with PIC. The schematic of the frequency counter is actually almost the same as the previous . It uses PIC16F628A microcontroller with external 32.768kHz watch crystal attached to Timer1 to generate 1 second time base. Measured signal is fed to pin3 (RA4) which is counted by Timer0.

Sunday, August 2, 2015

Simple and small temperature fan controll

I published this schematic long ago in this article: Adjustable power supply and since then I made some improvements in PCB to make the board as small as possible. The idea is to be easy to attach the whole board to the heat sink which we want to monitor. The board is only 27mm x 27mm.

Thursday, May 14, 2015

Thermal controlled fans

Since many years I am fan of quiet computing, but I also like power computers and videocards because I like do play games from time to time. That's why I have tried number of different solutions to control the fans in my computer.