One important part of my IOT project will be to have a small robot that can move around in my house and stream video/pictures with an acceptable delay.
I spotted a platform/robot car that I can start with at a Swedish electronics store and I've spent a couple of evenings with my four year old son building the basic design. In the original setup, the robot uses an ultrasound sensor to determine in what direction it will move.
The robot car consists of:
- An Arduino board (a very limited computer)
- A H bridge that controls the engines
- A pair of simple analog engines that takes 5-10 volts as input.
- An ultra sound sensor
- A servo motor that moves the sensor in different directions.
- A battery pack of 6 AA/LR6 batteries that gives 9 volts.
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I've disconnected the original battery pack and replaced it with a power bank. |
Connecting a Raspberry PI Computer.
The original setup feeds 9 volts both to the engines and to the Arduino board via the DC jack. However, I want to use a Raspberry PI computer with a camera module.
With the Raspberry PI computer, I can connect to the internet over Wi-Fi, setup a video stream or a web server and do some imaging. An USB/Serial connection can handle the interface between the Arduino and the Raspberry PI.
However, it is not that straightforward to connect a Raspberry PI to the Arduino in this setup. The manufacturer recommends that the battery pack is disconnected before connecting to the USB port on the Arduino. There are two options to communicate between the Arduino and another computer:
- Keep the batteries and connect a cable to GPIO pins on the Arduino and Raspberry PI. Since the boards are operating on different voltages (5 V and 3.3 V respectively), I would need a level shifter in between.
- Remove the battery pack and connect the Arduino to the Raspberry PI. That would mean that the motors will get only 5 V. This is the easiest solution, I'll maybe explore the other solution later. Another advantage is that I'll reduce the weight of the vehicle.
I've replaced the battery pack with a LEGO rig for the Raspberry PI computer.
In the next blog post, I'll modify the code of the Arduino so that I can send commands to it via the Raspberry PI.
