Sensors in the projects

Programming hobbyists are facing different kinds of sensors which are necessary for their projects.  Sometimes distance sensors are used for curiosity, just for gathering and checking some physical parameters, but other makers use sensors and their parameters for practical reasons – to solve problems in their projects.


Sensors in Totem system

Variety of possible hardware is astonishing. Major amount of products in the market are user friendly, so almost anyone can set up different kinds of sensors on Raspberry Pi or Arduino platforms.

Distance, or echo, sensor isn’t something new that can amaze, but anyway it is very handful for various projects, especially in robotics. Totem has developed its own distance sensor, but let me explain the whole idea behind. Totem is introducing not only different hardware and software solutions for handy makers. Our team works on the whole system, which has more than just software and hardware. Our main goal is to lift up makers into new dimension where they will be able to materialize their projects in proficient and joyful way.


To do this we have introduced variety of mechanical parts, which lets you to accomplish major mechanical problems in DIY, hobbyists and robotics projects. And it is just the beginning!  We also partly introduced our electronics and software and our TotemBus. All this makes a complete building system where you are free to build your own very customizable projects without big quest of searching for mechanical and/or electronic parts in various shops. Our team goal is to provide freedom for builders.

Distance sensor in TotemBus

Now lets go back to distance sensor.  I’ll show how it works in TotemBus perspective. Firstly we need  hardware and brain (Raspberry Pi) which can run TotemBus with intelligent broker.

We already introduced TotemBus conception on bluetooth and smartphones. In this case TotemBus runs on bluetooth baseboards and broker runs on smartphone. This approach is very user friendly, so definitely it can be managed easily. TotemBus is very flexible and lets me show another approach with Raspberry Pi.

We are running TotemBus and broker on Raspberry Pi.  Each function board  has it’s own message list. We have already introduced TotemBus and it is just the first steps of it into the wide world. Echo sensor board is one of many function boards. Base board gets sensible data from echo sensor board, read-write pins and etc. Then baseboard throws data into TotemBus and later broker manages it. From this video you can see data flow into broker. Thrown result – distance from obstacle, measured in centimeters. This is a useful data for various projects. Broker can manage up to 250+ devices in the system! So just imagine what complex systems you can build with Totem mechanics, electronics and TotemBus.


How Totem distance sensor works

Actually simple physics are hidden behind this device. Principle is simple and  works the same way as bats find their way in the nature – by ultrasound waves.

Board generating pulse width modulation signal into transceiver and it transmits ultrasound just before generating ultrasound one of timers begins to count. Transceiver pins are read on receiver in a short time. As ultrasound signal echoes back into receiver ear, electrical signal from transceiver pin rapidly soars. So when program finds peak, timer halts and than program getting time difference T diff. It’s time between transmission beginning and peak. T diff parameter can be used in calculations to get distance from nearest obstacle. Distance parameter relies on T diff, sound speed and temperature, but don’t forget that sound speed has dependency on temperature.


This is how it looks on oscilloscope:

Oscilloscope view, used to sense the distance

Yellow graph illustrates generated PWM and blue graph shows electrical signal of receiver when ultrasound hits it. That’s how echo sensor works.


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