Introduction: Magnetic Loop Controller for 4 Antennas
This project is for those ham amateurs who don't have a commercial one . It's easy to build with a soldering iron, a plastic case and a little knowledge of arduino.
This controller doesn't have endstop limit capabilities. In case you'd prefer a model with this feature, I have another design with three motor and endstop capability:
The controller is made with budget components you can find easily in Internet (~20€). The main component is a cnc shield that fits over an Arduino Uno. Both made a compact, small and cheap controller.
- New revision of the software ver 3.0 05/04/2020 fixed some bug. Some improvements in the code
- Added a new version 3.0 capable to tag frequencies to the memories.
- Version 3.1 fixed some bugs (08/04/2020).
- Factory reset function.
- Timer for every function
- Capable up to 4 different antennas.
- Range of 65000 steps for moving every antenna.
- Microstepping capability 1/2 1/4 1/8 1/16 or even more depending on the pololu stepper control.
- 4 memory banks with 14 programmable memories for antenna (56 memories).
- Programmable upper limit for every antenna.
- backlash compensation from 0 to 200
- speed control from 2 (2 miliseconds between step) to 40 (40 miliseconds between step).
-Power supply 12V
The controller is made by budget components you can find easily in Internet. The main component is a cnc shield that fits over an Arduino Uno. Both made a compact, small and cheap controller.
Added STL files por 3d printing at the end of the article.
-the platform for adapting the arduino UNO to whatever case you have
-the nkob por the rotary encoder.
The links I have done are only examples. Needless to say that you can buy wherever you want.
Step 1: Overall View
In this photo you can see the CNC shield over the arduino uno, the optical rotary encoder , the I2C 16x2 display and the five push buttons at the bottom.
Step 2: CNC AND ARDUINO UNO
The arduino board is almost free of wires. The only ones you'll need are the power supply ones. It is necessary to weld some wires into the arduino board and connect them to the cnc shield.The shield comes with 4 pololus a4988 or similar. The pololu has a potentiometer so you can limit the maximum torque of the step motor . My advice is limit the torque to the minimum necessary to move the capacitor. This way prevent for damaging the capacitor
Step 3: OPTICAL ENCODER
The optical rotary encoder is a 100 pulses one. The photo you can see how the wires yellow (A ) and green (B) are welded to the pins 10 and 9. just in case a clockwise rotation makes a descending count, you might swap the wires.
Connect the wires in this order:
Black - GND
red - 5V+
green - digital pin 9
yellow - digital pin 10
Step 4: 16X2 DISPLAY AND PUSH BUTTONS
The five push buttons are welded to the cnc shield In this order:
-UP- 17 (A3)
-DOWN - 11 (digital 11)
-MEM UP -15 (A1)
-MEM DOWN - 16 (A2)
-MENU - 14 (A0)
The I2C 16x2 display is joined this order:
DISPLAY SDA - sda pin ( A4)
DISPLAY SCL - scl pin (A5)
DISPLAY GND - gnd
DISPLAY VCC - 5V+
Step 5: WIRING TO THE MOTOR
I have used ethernet cable for connecting the antenna motor and the control.
Step 6: SCHEMATIC
For a deeper understanding of the cnc shield visit this web page :
Using the fourth stepper control implies using d12 and d13 in the cnc shield.
Step 7: DIFFERENT VERSIONS OF THE CONTROLLER
There are different versions of this controller._
This is the first one. It is capable up to 4 different antennas. It is made for the CNC platform and Arduino uno. It doesn't have end-stop capabilities.
Modification of the 4 antennas controller. It is capable up to 3 different antennas. It is made for the CNC platform and Arduino uno. It have got end-stop capabilities.
This is a modification of my Controlador loop 3 antennas .It is adapted to use an 128x32 OLED display It is fully compatible with it so instructions are the same. The only difference is the display.
This is a modification of my former control of 3 antennas.
It fits with the CNC shield V4 for arduino nano and V3 for arduino uno.
Fits perfectly in two different configurations of hardware:
The red one is usually a defective clone. Black one is my advise.
This is a variation of the former loop controller for 3 antennas this time with only 1 antenna. At the request of Lev OK2PLL. He is making a small loop controller with an Arduino nano and a pololu for portable operation. The power supply is 5Vcc from the micro USB connector. It is enough for a portable operation with a portable mobile charger
It is a modification Just in case you had a TB6600 driver.
Step 8: CODE AND INSTRUCTION MANUAL
Sometimes, the lcd comes with the chip 8574at and the screen doesn't work.The direction is 0x03f instead of 0x27. In that case you have to change the direction of the chip in this line :
LiquidCrystal_I2C lcd(0x27,16,2); // set the LCD address to 0x27
for this one :
LiquidCrystal_I2C lcd(0x03f,16,2); // in I2C chip 8574at set the LCD address to 0x03f
EEPROM.h included into the arduino ide
I have added a new version for those who like tagging every memory with a frequency (ver 3.0).
You have the two version in case you don't like tagging the memories.
Step 9: EXPLANATION VIDEO
Step 10: Torque Limiting
The shield comes with 4 pololus a4988 or similar. The pololu has a potentiometer so you can limit the maximum torque of the step motor . My advice is limit the torque to the minimum necessary to move the capacitor. This way prevent for damaging the capacitor.
Finally, pololus might be damaged if don't have any motor connected. Please, install only the same number of pololus than motors.
Step 11: BACKLASH COMPENSATION
Step 12: DOWNLOADABLE STUFF
This control is designed for managing 4
different loops antennas. You can manage every antenna without interfere in the rest. The power supply is 12v. This is not a commercial design it is made for a ham amateur only for the enjoy of the rest of the community.
The controller can manage 4 different loops antennas independently.
It has 64000 step for every antenna
14 memories for antenna.
You can define up limit and down limit.
!!!! VERY IMPORTANT!!!
The controller has 4 memory banks (1 memory bank for antenna). If you want to erase a memory bank push UP & DOWN buttons simultaneously.
Just in case you need to erase the whole data push DOWN & MENU buttons simultaneously.
The controller has five push buttons:
MENU –this button selects between MEM/ANT/SAVE/ADJUST/BACKLASH/SPEED/DISABLE POLOLU AND MICROSTEP functions.
UP/DOWN – used for the next functions:
-Increase and decrease manually the stepper motor (normal and adjust functions).
-Save memory in the save memory function
-Modify backlash/speed/micro step and disable pololu functions.
MEM UP/ MEM DOWN – used to select the memories and to change the antennas.
All the functions return to MEM function after 3 or 8 seconds.
In this position you can select the desired memory. If you don’t have any number stored, NO DATA will be shown in the display. Remember that MEM14 is the upper limit. You need to store in this position the maximum step you want to move your capacitor. For select a memory push MEM UP / MEM DOWN.
In this position you can select the antenna between 1 and 3. For choosing an antenna push MEM UP / MEM DOWN.
Once SAVE is shown in the left corner, you must select the desired number of memory (between 1 and 14) and push UP or DOWN buttons to save.
After this will appear a new screen in which you can save the frequency. Introduce the frequency this way:
-Buttons UP & DOWN to select MHZ (1000 KHz) Up to 59 MHZ
- Buttons MEMP & MEMDOWN to select KHZx100 Up to 59 MHZ
-Rotary encoder to select KHZ.
-Push MENU button to save the frequency or wait 4 seconds.
Remember that this is only a tag not a real frequency.
Remember that in position 14 you must save the upper limit.
ADJUST function allows to move the stepper motor without increasing or decreasing any number in the display. It is useful when we need to find the 0 position manually. Sometimes it is necessary for calibrating stored memories. Once adjusted one of them, the rest are calibrated too.
Backlash compensation from 0 to 200. In this position you select the value you consider effective in your system. In order to not to complicate the software, I have decided to compensate only when decreasing. So If you want to as more accurate as possible, before storing a position:
1) increase a bit more the value ---1765
2) decrease the value to the desired position --1750
3) save it --1750 save
Remember to do this if you want to be accurate in the recorded positions.
Just in case you don’t need backlash compensation put the value in 0.
This function stablishes the maximum speed in automatic movement (memories ). 3 is the max speed (3milisecons pause in every step) 20 is the min speed (20 milliseconds pause in every step). You must adjust the speed in order not to broke your capacitor. I could have used 1 millisecond but the speed was dangerous for almost every system.
Pololu is the driver that is in charge to move the step motor. During its work, pololu introduces a lot of rf noise in the antenna. Some people has designed its system in order to not to be affected by this noise. In case you can’t deal with the noise you can disable the pololu after every movement. This happens automatically if you choose “Y“. In case we chose “N” the pololu never disables. Don’t disable the pololu is more accurate but noisier.
On the cnc shield you’ll find three jumpers you can set to modify the Microstep.
Microstep menu uses a compensation to be more accurate when we use micro stepping in the pololu. For no compensation or no micro stepping you can use 0 compensation.
I have added a brochure of the old blackbox I have used as enclosure. It is useful for the dimensions. As you can imagine, you can use whatever box you want.
Step 13: 3D PRINTED CASE
I have made a 3d printed case to install properly all the components.
You need to buy some aditional parts that fit properly in the case :
Step 14: ASSEMBLY
Fix the arduino in the base.
Intall the rj45 sockets and wire them to the dupont conector like in picture nº 3
Probably you will neeed some glue to fix the rj 45 to the rear panel.
There are some holes to pass the wires just in case you don't have the rj45 sockets.
The feet lock the case .
You can add some silicone feet to add some grip .
Step 15: STL FOR 3D PRINTED CASE
Step 16: ADVICE FOR BUTTERFLY AND AIR CAPACITORS
So far I have used a nema 17 motor because y have a 116/12 gearbox to drive my capacitor. In case you had either a butterfly capacitor or an air capacitor, you can't drive ir directly. This is because you'd only have 100 steps to tune your antenna.
My advice is using a modified 12v 28BYJ step motor. This motor is the cheapest on the market . It has a gear box 2000 step per revolution. It is enough to tune your capacitor precisely.
An example from Lev Kohút :