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InstruMod – A Moto Z Mod Measuring Instrument

Posted February 6, 2017

The InstruMod is a multifunctional smartphone based measuring instrument. Attach it onto your Moto Z and you have an entire Laboratory in your pocket. Incorporates a wireless probes design that works with a microcontroller embedded on the probes, responsible for converting analogue to digital. Use the accompanying android app for documenting your project development, making calculations and displaying readings.

The Problem We’re trying to solve

Having worked with the Formula Student Racing team at the Nelson Mandela Metropolitan University (NMMU) as Project lead in the Electric Vehicle, we often witnessed a daily problem of having a shortage of basic measuring tools. We were a large team but not enough basic measuring instruments for all the team members, so we had to take turns completing separate tasks. Problems like this always tend to slow production down to a crawl. Through research we’ve discovered that basic measuring tools are expensive and some students who build projects on a daily basis can’t afford to buy a reliable multi-meter, Vernier Caliper, not to mention a Power Supply, an Oscilloscope, a Function Generator and so many more. Though school laboratories are equipped with these expensive necessities they’re sometimes full, as everybody is busy working on a project. Labs aren’t open every day and are rarely opened during recess when everybody has free time.

How we intend on solving the problem

Introducing the InstruMod, a multi-functional smartphone based measuring instrument, some could rather refer to it as a pocket laboratory. The InstruMod is a Moto Mod, a modular measuring device that attaches onto a Moto Z smartphone and renders the smartphone capabilities of recording mechanical and electronics measurements. The design of the InstruMod focuses on factors such as affordability, convenience and reliability.

It’s that convenient pocket multi-meter, you’ve always wanted. You’ll be able to take measurements such as voltage, current, resistance, continuity and temperature using detachable probes. The design incorporates a wireless approach to eliminate the use of wires on probes.

No need for an external Oscilloscope or Function generator. We’ve identified that students often have to analyse electronics signals on an oscilloscope or regenerate them using a function generator, the InstruMod’s Android Application offers an on-board oscilloscope for analysing signals and an on-board function generator for generating signals.

The wireless probes are versatile in that they can be configured to operate in four modes to measure mechanical and electronics quantities. These modes are namely:

Mode 1 is Ruler mode: when both probes are joined end-to-end linearly they form a 30 cm long ruler which can be used for technical drawing.

Mode 2 is the Goniometer mode: The red probe consists of a rotatory potentiometer that is inserted into a slot on the end of the black probe. The red probe is then allowed to rotate with reference to the black probe, the resulting resistance is converted to an angle by an algorithm in the probe’s microcontroller.

Mode 3 is the Vernier mode: This mode works by placing the two probes against each other, with a linear resistor in between, and sliding one probe against the other to create an increasing resistance that gets converted, with an algorithm in the probe’s microcontroller, to distance.

Mode 4 is the Electronics mode: In this mode the probes are used to measure voltage, current, resistance, continuity and temperature. The probes are wireless, so to complete the circuit when taking electronics measurements, the probes will have to touch each other physically to complete an electrical connection. If measuring a large area, a long wire can be used to link up both probes.

The probes have their own microcontroller that is independent of the InstruMod’s microcontroller. This microcontroller on probes is responsible for converting the analogue data to digital data and sending that data wirelessly to the InstruMod for display and calculations. This also means that the probe’s software and hardware can be updated overtime to include more measuring features.

Other measurements are taken using the InstruMod’s on-board sensors, such as the:

  •  Weight sensor for measuring object weight,
  •  Light sensor used to determine the intensity of the light,
  •  IR sensor used as a tachometer to determine rotational speed
  •  and a distance sensor for measuring Length, Area and Volume.

The InstruMod is equipped with a :

  •   Laser Leveller for keeping DIY projects in a straight accurate line.
  •   The Moto Z’s on-board Gyro and Accelerometer are used for determining inclination angle   and acceleration respectively.
  •  The on board 13MP Moto Z camera is used to document your project as it is being built.
  • Last but not least, the InstruMod can also be used as a 5v regulated power bank to supply development boards such as the Arduino, Raspberry pi and many more.

About the accompanying Android Application

Basic working Android App to control the prototype via Bluetooth

The whole InstruMod package isn’t complete without the accompanying Android application. The accompanying Android application is designed to display readings, do calculations from the recorded values, logs the history of the project and consists of tutorials of how to use basic tools like a Vernier Caliper, Oscilloscope, multi-meter etc. The advantage of using the accompanying Android application is that you are able to build your projects specification sheet as you are busy prototyping your project. All your project documentation is done on the Android application which works seamlessly with the InstruMod for taking measurements. When the project is done you can just simply export your project documentation to a pdf file and if you’re working in a team you can just share all the projects specifics with your team members.

What have we done so far?

To prove our concept, we’ve built a simple working prototype able to measure voltage, current, resistance and test continuity. The prototype also has an on-board IR sensor that’s used as a tachometer for measuring rotational speeds. We’ve also included an ultrasonic distance sensor, Laser leveler and a flash light.

We’ve used a STM32F4 Discovery board as our microcontroller but Prototype 2 will be developed on the Moto Mod Development Kit (MDK). The InstruMod is intended to work seamlessly with a Moto Z smartphone as a Moto Mod. When developing our first prototype we were just focused on proving the basic concept on a small scale, therefore the full product we’ll be developed with the MDK instead of the STM32F4 board and will connect seamlessly with the Moto Z through the Moto Mods interface connectors like all the other Moto Mods out there.

Source: project page on

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