How to get data from a circuit board with a microcontroller?

Thread Starter

23himanshu23

Joined Feb 16, 2022
1
Hi, I'm a complete novice in field of electrical circuits and have zero knowledge in this domain. Yet, I wanted to work on IOT but instead of using raspberry pi and similar, I wanted some data out of few devices. For example, I have a very old traditional treadmill which reflects the speed at which it is rotating. So where actually is data stored in circuit board of this treadmill which I can transmit. So, just as a beginner, can someone help me how to start in this kind of knowledge hunt? Thanks in advance.
 

sagor

Joined Mar 10, 2019
695
Data like treadmill speed is not stored anywhere, it is calculated. Most treadmills have a magnetic sensor that goes on/off for every revolution of the motor or main pulley. The micro inside calculates the time between pulses, and that gives an estimated speed, which is displayed.
In some very, very old treadmills, speed could be estimated by inputting average sensed voltage (like each pulse gives a bit of voltage to a capacitor) to a display driver via some analog circuits. I doubt any of those treadmills would still be around. Anything from the past 20 to 30 years would have a small microprocessor chip doing the calculations.
 

Ya’akov

Joined Jan 27, 2019
5,663
Welcome to AAC.

Your question has an enormous scope. There is no one answer to it, not even to the specific case of a treadmill.

The answer is entirely dependent on the particular treadmill and how its designers decided to implement it. For example, the speed could be stored in the memory of a microprocessor. It might be possible to connect to it and read that information through something like a diagnostic serial port, which is a communications interface often including in devices for debugging and testing.

On the other hand, it could be just in RAM inside the microprocessor with no practical way to get to it. Yet still, it could be stored nowhere. If the only control the designers wanted to have was setting a speed, there could be an independent speed controller that simply gets a signal from the MCU (microcontroller unit) ion the form of a PWM pulse train. That is, a signal that is a square wave with varying on time and fixed period which the controller uses to determine the expected speed.

In most of those cases, if you really wanted the information, you could probably get it but it would take a lot of reverse engineering since the details of the circuits and software are unlikely to be available. It would also take a lot of testing and risk potential damage to the treadmill.

This is not to discourage you, rather to possibly refocus your interest. It is my best advice to start with something like an Arduino starter kit that includes teaching materials to get some idea of both MCU programming and circuits. Then, I would pick small projects that stretch your knowledge so you can learn both more theory and importantly, practical concerns about building working devices.

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There are many less expensive options than the official kit but keep in mind when you buy from Arduino you are supporting the development of alol the really great stuff that Arduino produces and others copy. They are the source, and worth supporting from time to time. You can buy clones, that’s not a problem, everything is open source but buying some Arduino products is like donating.

It’s going to take an investment of time and effort but the steep part of the learning curve levels out after a while and each think you learn will help you to learn even more things more easily. AAC is a great resource for help when you get stuck or need more clarification. Just be sure that if you are asking a question it is well thought out, includes photos and/drawings if possible, and probably most importantly, includes first a description of the problem you were trying solve before your potential solution became a new problem. The importance of this last thing is hard to overstate.

Again, welcome, good to have you here—and good luck on your new hobby.
 
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