Introduction: Radar With Arduino, HB100 and MAX4466
This article is going to introduce you to the Dobbler Radar principle. I will show you how to make your own radar using the HB100 module, the Adafruit 1063 module and any Arduino.
You will also need some soldering skills, a fine tipped soldering iron, a 1Mohm resistor, a breadboard and the wires to go with it.
The diagram shows the principle you will experience with this exercise. All the fine technical details is given in this article, so I will not go into these details here, except to say that you should not expect a highly sensitive radar using this setup, but it will work good enough for you to see it in effect.
The article states that the signal coming out of the radar HB100 module is very very small. The signal is smaller than anything you probably have ever dealt with before.
Therefore the signal needs to be amplified. The optimal solution is to custom build an amplifier for this specific purpose. But I just want to show that standard components can do it without special built hardware.
For this purpose I have studied the MAX4466 amplifier and its nice features allows us to get enough gain and noise suppression for this setup. The Adafruit 1063 module contains a MAX4466 chip, but its tuned for a microphone, that is extremely loud, and therefore cannot even hear the radar modules signal. So the module just needs some tweaking to amplify even more.
Instead of a super duper amplifier, we just use a simple set of signal processing's in the Arduino to help us extract the signal features we want to see.
Let's get started...
Step 1: Prepare MAX4466
The Adafruit 1063 module is a microphone amplifier, so its amplifications is not nearly strong enough. The module is set for a specific amplification, but the MAX4466 amplifier can do even better. So we just need to modify the module for our purpose.
You can read about the modules technical details here.
The picture with red circles, shows what must first be removed. Microphone, R2 and R6a.
The picture with the green circles shows what must be added. A wire and a 1Mohm resistor.
And the remaining pictures show the final board.
With these modifications we remove the feedback resistor (R6a) and solder in a 10 times bigger resistor. This gives us 10 times more gain. The new resistor goes onto the two R6a terminals close to R6b,
We remove the microphone and add a wire instead, so we can feed the radar modules output directly info the place where the microphone was.
The resistor (R2) is there to charge the microphone and must also be removed, so the dobler radar module is not disturbed by DC going back from the amplifier to the radar.
The module is now set up for the radar signal.
Step 2: Build and Setup
Now you need to add wires to the dobler radar. Cut some wires for the breadboard in halves and solder the cut ends to the corner terminals of the radar.
+5V should be red
GND should be black
IF is the output, and should be any other color.
Now build the diagram. The power supply unit (PSU) shown can be eliminated. Some Arduino's has a built 5V power regulator and this could be used, so the battery could go into the power plug of the Arduino.
Otherwise make your own setup regarding power with 5V.
Try to not use ground connected equipment, even the PC should be running off battery, so a laptop is best.
The mains hum causes very large signals that does disturb the signals we want to see, but it would still work just about. But for this reason alone, it is best to use equipment not connected to mains in any way.
Step 3: Program Arduino
You must connect the output from the amplifier to an analog input, and you should edit the program to fit the input you choose. You edit the line #define RADAR A7, since not all Arduinos have the pin named A7.
Othervise than that, you should try experiment with making even better filter algorithms for your dobbler radar, when you see the initial program work.
Step 4: See Results Using Serial Plotter
When you upload the program and everything is set correctly up, you can start the serial plotter that is available with the Arduino IDE, from the tools menu.
Notice that some radar modules has a shield cover on one side. If this is the case for your module, it is the unshielded side that is most sensitive to motion.
You should see two lines being drawn. They both jump only a little while the radar sees nothing. When you wave your hand to and from the radar module, the lines should show some extreme peaks to indicate the received signal is changing. If you just hold your hand still over the radar, it does not change the radar wavelength and no signal is generated by this type of module. Only movements generate signals and are therefore detectable.
This Arduino program does not show direction, ie. if you are moving your hand to or from the radar. This is your task to find a algorithm to show this.
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