arduinomaster @ instructables.com has build an EMF detector based on ATtiny85 mcu able to detect signals from 0-999Hz. He writes:
An EMF meter can measure AC electromagnetic fields, which are usually emitted from manmade sources such as electrical wiring, while gaussmeters or magnetometers measure DC fields, which occur naturally in Earth’s geomagnetic field and are emitted from other sources where direct current is present.
This sensor is very sensitive and can pick up electrical signals from anything that uses power. It displays the amount of interference it picks up by sequentially lighting 4 led’s one after the other. I have tested it all around the house and its been kinda fun to see how different things compare. It can also be used to follow house electrical wiring inside the walls, yes its that sensitive.
There’s something fascinating about electromagnetic fields. Thanks to the modern world and the prevalence of electronics and electricity, they’re all around us these days. But because of the extremely limited array of senses that we humans have, we spend most of the time completely oblivious of them. Wouldn’t it be cool to make something simple that could not just detect them, but would allow you look at the waveforms on an oscilloscope. An EMF probe in other words.
Adam Outler wanted to isolate a problem with an ECG (electrocardiograph) so he decided to build this EMF meter to find the cause of the electromagnetic disturbance. The meter is based on Arduino and source code is included on the link below. [via]
Motors are everywhere! From robots to remote-controlled cars, any DIY hobbyist will very quickly find themselves trying to control a motor with a microcontroller. Luckily, simple control of a brushed DC motor is easy, and only requires a few components. Have you ever tried spinning a motor with the contacts connected together? Or seen sparks as you connect and disconnect your motor? What consequences do those things have on how you control the motor and protect your other circuitry? There are instructions out there that allow you to build a complicated motor controller that might work, however in this video tutorial we take a step back and go over some of the very basic things you need to think about when using motors, because so much is dependent on understanding the details of your specific situation. From stall current, to back-EMF, we present 9 small experiments you should try to get a better sense of how the motor is going to behave in your circuit. The tutorial also goes over how to connect a simple motor to a microcontroller, and turn it on and off using a 2N7000 n-channel MOSFET and a few other parts. The topic of power electronics goes much, much deeper. Often times, it is necessary to consider power dissipation, switching frequencies, gate capacitance, and when trying to drive a motor in both directions, an H-bridge is required. However, we have to start somewhere, and there is nowhere better to start than with experimentation!