Wednesday, November 1, 2017

Valve Audio Amplifier

Magnetic Loop Antenna For Transmitting

After the success of my receiving magnetic loop, i wanted to give a try on transmitting loop. It has both good and bad results.

One fine evening my friend OM Prem VU2RPC and myself started fabricating the magnetic loop to transmit on 40meter.

Used 3/4" copper tube used for air conditioner with a length of 9 feet.
Wide spaced variable capacitor 30-300pF salvaged from old valve transmitter
2.5SQm wire for inner loop.
Construction is as simple as possible. Just used 3/4" PVC pipes.
Just maintained the outer loop dia as 3feet, and inner loop 0.5feet.

We had about 10 contacts within 15 mins, it was sunday. The tough part is to keep the SWR.
The loop is very narrow bandwidth, even 10KHz change is frequency will affect the SWR to 3:1. Really bad, so maintain power level not more than 50 watts.
The RF from the antenna was also very severe, we can feel the radiation.

Result :
The overall result is,
It is definitely compromised antenna for receiving. There is no doubt, we had no noise pick up, and very good gain also.

For transmitting it not a good antenna. Unless we want to use just for only one frequency, like beacon. Because the bandwidth is too narrow. We have to adjust the variable capacitor for every change on frequency.

Magnetic Loop for Shortwave Receiving

DRM AIR +6100 KHz Shortwave receiving Magnetic loop antenna for 80m to 20m band

This is my trial during year 2015 to receive All India Radio DRM signal from Delhi, India. I'm located south India which is 3600Km far. The actual DRM on 6100KHz is transmit to cover 80Km surrounding Delhi. I made a simple Magnetic loop to get signal from that far. It was a huge seccess. Since i'm using magnetic loop the noise level was very low, and i can null alomost to zero. Below you can find the pictures of my AIR DRM 6100KHz.

I used old Oats container filled with sand on it as a post support. 3/4" PVC pipe, inside is a house electric wiring wire (3-20swg wire). Its about 3feet diameter. The outer loop is connected with a 365pF broadcast set variable capacitor. Inner loop is 1/2 feet dia. I used the same wire.

The radio Redsun (Kaito) RP-2100 comes with a IF out. I made a small converter to convert the RF to AF. Its inside the small black color box.

Saturday, January 7, 2017

VU3XVR Software Defined Radio SDR Using Si5351 DDS VFO and ATMega8 Microcontroller

This is a demonstration on Software Defined Radio Using Si5351 DDS VFO. Original designer is Burkard Kainka, Author of Elektor  SDR-2007. I Just modified VFO by using my own Si5351 based VFO, For more details please chek my blog vu3xvr dot blogspot dot in

Specification :

Frequency Range : 3 to 30 MHz
Mode  : AM - SSB - CW - DRM
Hardware Used :
Software Used : SDRadio by I2PHD available from this website

Thursday, January 5, 2017

VU3XVR Si5351 DDS VFO to Use BITX40

Click here for the video demo of sending CW using BITX (real carrier !!! not modified tone)

Friday, March 11, 2016

Washing Machine Controller Using AVR ATMEL ATmega8 Microcontroller Using Assembly Language (NOT Arduino)

Washing Machine Controller Using  AVR ATMEL ATmega8 Microcontroller Using Assembly Language (NOT Arduino)

A brief history about why I decided to make my own controller :-

I have a washing machine, with control board problems. I did changed the control board from OEM 2 times, each time it cost Rs.3900 + 300 for service charges. So, I spent Rs.8200/- since 2008. Actual machine cost is Rs.12,000/- Now in year 2016 the same control board SMPS failure . The washing machine model is Whirlpool Splash 55. Seems the designer of the board is a beer addict during design ! Very sad that not only for me for those having this model is having the same issue!!!. But this time I'm decided to design my own control board with my experiences. My control board costs less than Rs.500 and all of the components are from my junk box. not spent a paisa but time.


 Basic operation sequence of a washing machine :-

There is just 4 relays to be controlled in a regular sequence, not a rocket science either. The basic operation sequence is like this
  1. Water filling (at actual time)
  2. Agitronic soak (15mins)
  3. First wash    (15mins)
  4. First drain (4mins)
  5. Second wash or call it as first rinse (10mins)
  6. Second drain (4mins)
  7. Spin (5mins)
  8. Buzzer chim (15sec)
There are lot of  information available about the time taken for each operation from several washing machine manufacturer. But i referred Whirlpools manual and it recommends as below
Program Time / Cycle time for each mode
                     All values in minutes
                 Agitronic    Normal    Speedy    R+S    S only
 Soak            20            -                  -         -            -
 Wash           20          20                 9          -            -  
 Rinse           16          16               16         8             -
 Spin              8           8                  6         6             6
And there is a very nice recommendation from Bureau Of Energy Efficiency
Energy Labeling Scheme For Washing Machines by Bureau Of Energy Efficiency

From the above given recommendation i choose  following timings
   soakTime     = 15 mins
   washTime     = 15 mins (For one wash cycle)
   rinseTime     =  8 mins
   spinTime     =  5 mins
At this point of time, there is no selector / program selector available on the controller. But it's on my wish list.

Why decided to use AVR Assembly language and not to use Arduino C

For this washing machine controller i decided to use assembly language, and it'll be my first AVR assembly language project. I'm using AVR Studio 4.19 and ProgISP to compile and upload.
I personally do not recommend higher version of AVR Studio. V 4.19 is lite and there is not much improvement on ASM compiler between V4.19 and V6.2. (Both IDE's assembler version is 2.1.xx)
Since 2006 i'm using Arduino, now i'm feeling limited with arduino resources when there is really a lot of things can be done with AVRs other line of products like ATtiny13, 2313, etc....Arduino will not help to develop codes for this. The size of HEX code for LedBlink in arduino is 890 bytes, the same LedBlink in assembly will be just 34 bytes !!!! Wow ahh.. Excess  856 bytes of code dumped inside my ATmega8 for nothing. When comes to industrial application the unwanted junk of code will generate lot of issues. That's why the Arduino's liquidCrystal library is not recommended by most of developers as it collide with interrupt cycle or millis() library.
Arduino is for kids and new comers. For real time application Arduino is not the right tool to write my code. Best to go for ASM Assembly language for AVR.

Hardware setup

I had my own ATmega8 break out board with 6 inputs and 4 outputs. I'm using this pcbs for most of my project. Here is the schematic diagram of controller.


Water level pressure switch
Loading door open / close switch. (in my project, i'm not using this sensor)


Motor forward
Motor reverse
Water inlet solenoid
Water drain traction motor
           ( In my model Whirlpool Splash 55, Its single motor for slow spin and fast spin, it's the drain traction motor change the gear wheel between slow and fast spin )
Wish list : heartbeat LED, sequence indication LEDs, start / pause button, EEPROM storage of electricity failure recovery, etc...

Here is my complete source code in ASM language  for ATMEL ATmega8 controlled Washing Machine
 AVR-ATMEL-ATmega8-Microcontroller-controllerd-washing-machine- Using-Assembly-Language.asm

Complete project file in zip file (asm, HEX, etc..)
AVR-ATMEL-ATmega8-Microcontroller-controllerd-washing-machine- Using-Assembly-Language