Apr 292018
 

This part of the project is to help you understand how we are going to control the motors of the rotator and we are deviating from the 2rpm motor to a higher rpm to be able to quickly move from one location to another at a higher speed then slow down to be able to follow the path of the satellite.

In the previous post I gave links to the parts needed and for this part of the project, we will be using the H Bridge, 2 motors, and the Arduino Nano.

I have found a good video which explains the principle of driving the motors, but before watching it I thought it better to explain a bit about writing code for the Arduino. The code is known as a “Sketch” and contains all the information for the Arduino IDE to compile it and load it into the Nano so that it can run the program.

A variable is a number that can be changed by the sketch and is usually given a “label” that identifies it in the sketch, say for example we define “Int variable1 = 5”, “Int variable2 = 2” (Int tells the compiler the type of variable it is and in this case an integer) and later as the sketch is running we want to perform a mathematical calculation and change “variable1” to another value “variable1 = variable1 + variable2;” (the “;” defines the end of the line) the microcontroller will process this and “variable1” will now = 7 (5+2). Another way to increase the value of the variable is “variable1 ++1” which will increase the variable by +1 and tends to be used in loops. See here for more information about the syntax for arithmetic calculations and more information of the programming syntax can be found here

(For those who want more information,  when the sketch is compiled, the compiler changes the label “variable1” to a fixed memory address which contains the value of the variable so calculations result in the microcontroller changing the value of the fixed memory address.)

The next post will be on the magnetometer and how we use it to control the motors of the rotator.

Apr 262018
 

I had been asked to do a talk on the Arduino for a long time but never did get round to it, but I was influenced by Adrian M0NWK’s excellent talk and decided the best thing to do was to do a series of posts on a project that Ian M0RPD asked me to help him with and at the same time give people an understanding of the power of the Arduino system in microcontrollers and its benefits to our hobby of Amateur Radio.

This should be a good start to your journey into the Arduino, the project that we will be working on can be found here, but remember that I am not following the Arduino side of this project but modifying it in true Amateur Radio style.

At the moment rather than having pretty pictures to look at you will find a lot of links in this article as I prefer to use other people’s work to explain what I am doing rather than repeat it myself. (I am getting lazy in my old age)

For anyone the doesn’t understand microcontrollers they are like a computer with only one job to do, so they are programmed to undertake tasks whether it be a single task or a multi-task they are very good at what they do, like your washing machine which is controlled by a microcontroller.

The rotator project interfaces with the HRD satellite program on your computer and uses ready available modules that can be purchased cheaply on the internet and the system will run on a 12V making it ideal for portable use. Using a regulator like the LM7805 to drop the voltage down to 5V for the Arduino system is not very efficient so I am using a buck converter which has an efficiency of about 80% thus saving battery power. How the Buck Converter works 

Instead of expensive stepper motors or servo motors, this system uses 2 cheap Chinese 12VDC Reversible High Torque Turbo Worm Geared Reduction Motor these have a power rating of 60mA
Interfacing the motor with the Arduino is easy and we are using a dual H Bridge module,  the bridge is rated at 2A so plenty of power to drive the motors. You can find out how the H Bridge works here.

To reduce the size of the project I am using the Arduino Nano which is a smaller format of the UNO but has the same capabilities. Because we wanted this system to be remote you will need to buy 2 Arduino Nanos for this project.

The heart of this project is the GY-273 HMC5883L 3V-5V Triple Axis Compass Magnetometer Sensor Module which will give us the compass direction and inclination of the aerial which is fed back to the Arduino so we know the exact position of the aerial and is fitted to the aerial. More information on the chip.

Finally is the remote control radio module NRF24L01+ 2.4GHz Wireless RF Transceiver and you will notice that there is also a back plate which you plug the module into. The 3.3V supply on the Arduino will not drive this module sufficiently and you had to add capacitors on the module across the input voltage for the module to work properly but with the back plate, this is not needed as it has its own 3.3V regulator on the back plate. Because this module has different variants with external aerials and higher power, I will cover the transceiver in a separate post.

Don’t be put off with computer programming and having to know the C++ language as the code will be provided later. If you are thinking of doing other things with the Arduino, other people could have done something similar to what you want and willing to share their code. On the internet, there are thousands of people using the Arduino system. Make Google your friend for finding the information you seek.

To start with you need to download the Arduino IDE (Integrated Development System) to be able to program your Arduino board. (There is a number of different boards that run the Arduino System) and this link should give you a good idea of how it works.

On a final note to this part of the Arduino project, eBay is a good source of Chinese clones and they are as good as the real ones and I have not had any problem with them in the past, my Scottish genes tend to point me to the cheapest source. 

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Apr 112018
 

Tonight Jason G7KPM gave a 10 minute talk on his home brew J-Pole dual band antenna; the design was taken from the ARRL Manual.   The J-Pole is an effective, low cost antenna made from bits available from Birketts and the local DIY store. This antenna will go well with the new Baofeng dual band radios recently ordered by the club and is a possible project for future candidates on the Intermediate Course.

Other topics in the ’10 minute talk’ category were Potholes – Les G1LQB and Wine and Whisky – everyone.

 Posted by at 11:50 pm