hall effect sensor

37 Articles

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Raspberry Pi Opens Doors

September 28, 2015 by 29 Comments

The Raspberry Pi is a cheap credit card sized computer that has opened the doors of embedded Linux to millions of people. But in this case, it’s literally opening a door. The Computer Club at Western Michigan University had to move to a different room which brought with it a new challenge. The door handle was more difficult to turn than the old one. Nothing that a NEMA 17 stepper couldn’t handle, however.

After printing a few gears and wiring up an Easy Driver board between the Raspi and stepper motor, they had the basics of a door opener in place. A 5v relay is used to keep the power off the stepper when not in use, and a limit switch is used to monitor the position of the door handle while a Hall Effect sensor tells when the door is open and shut.

Be sure to check out the project as all source, parts list and schematics are available in case you have a simliar door that needs amending.

Firing Blanks With Laser Tag

June 2, 2014 by 37 Comments

glockLast year, [Tony] was asked to develop a lasertag system with ultimate realism. This meant a system that used a blank firing replica gun, and a system to detect blank rounds being fired. Very cool, and the way he went about it includes some interesting electronics.

Because the system requires a blank to be fired before shooting a laser at a target, the entire system must be able to detect a blank being fired. [Tony]’s first attempt used a piezo sensor to detect the shock from being fired. This system had a lot of noise and was ditched for a much better solution: a magnet mounted to the slide, and a hall effect sensor mounted to a 3D printed frame that turns this replica into a carbine.

A little bit of tweaking in software was required to inhibit the laser when the operator cocks the gun, but it looks – and sounds – really good. It’s also very, very realistic: the only way to shoot an opponent is to physically reload. Video below.

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Adding An RPM Readout For A Home Made CNC Mill

February 8, 2014 by 5 Comments

rpm_lcd

[Rui] recently put the finishing touches on his homemade CNC mill, which utilizes a dremel-like rotary tool. The problem with using rotary tools for this kind of application is you don’t really have an accurate speed readout… so he designed his own RPM gauge.

The sensor is in itself very simple. He’s using a TLE4935L hall effect sensor, a spare 16FE88 microcontroller, a Nokia LCD, and one tiny neodymium magnet. The magnet has been carefully epoxied onto the motor fan, with the hall effect sensor close by. He’s also built a guard around it, just in case the magnet decides to fly off at high speeds.

During testing he hooked up the hall effect sensor to both his home-made circuit, and an oscilloscope to confirm his findings. Once he was assured everything was working properly he sealed it off and mounted the LCD above the spindle as a nice digital readout.

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Ride, Captain, Ride Aboard Your Arduino-Controlled Autopiloted Sailboat

January 8, 2014 by 22 Comments

[Jack], a mechanical engineer, loom builder, and avid sailor wanted an autopilot system for his 1983 Robert Perry Nordic 40 sailboat with more modern capabilities than the one it came with. He knew a PC-based solution would work, but it was a bit out of reach. Once his son showed him an Arduino, though, he was on his way. He sallied forth and built this Arduino-based autopilot system for his sloop, the Wile E. Coyote.

He’s using two Arduino Megas. One is solely for the GPS, and the other controls everything else. [Jack]’s autopilot has three modes. In the one he calls knob steering, a potentiometer drives the existing hydraulic pump, which he controls with a Polulu Qik serial DC motor controller. In compass steering mode, a Pololu IMU locks in the heading to steer (HTS).  GPS mode uses a predetermined waypoint, and sets the course to steer (CTS) to the same bearing as the waypoint.

[Jack]’s system also uses cross track error (XTE) correction to calculate a new HTS when necessary. He has fantastic documentation and several Fritzing and Arduino files available on Dropbox.

Autopilot sailboat rigs must be all the rage right now. We just saw a different one back in November.

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AVR Atmega Based PID Magnetic Levitator

December 5, 2013 by 33 Comments

[Davide] saw our recent post on magnetic levitation and quickly sent in his own project, which has a great explanation of how it works — he’s also included the code to try yourself!

His setup uses an Atmega8 micro-controller which controls a small 12V 50N coil using pulse-width-modulation (PWM). A hall effect sensor (Allegro A1302) mounted inside the coil detects the distance to the magnet and that data is used by a PID controller to automatically adjust the PWM of the coil to keep the magnet in place. The Atmega8 runs at 8Mhz and the hall effect sensor is polled every 1ms to provide an updated value for the PWM. He’s also thrown in an RGB LED that lights up when an object is being levitated!

So why is there a kid with a floating balloon? [Davide] actually built the setup for his friend [Paolo] to display at an art fair called InverART 2013!

After the break check out the circuit diagram and a short demonstration video of the device in action!

Oh yeah, those of you not impressed by magnetic levitation will probably appreciate acoustic levitation.

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Hacking Grandfather Clock Accuracy While It’s Still Ticking

January 15, 2013 by 36 Comments

grandfather-clock-tweaking

[Keith] got his hands on a few grandfather clocks. Apparently the price tag is greatly reduced if you are able to get them second-hand. The mechanical timepieces require weekly winding, which is a good thing since you’ll also need to correct the time at least that often. But this drift got [Keith] thinking about improving the accuracy of these clocks. He figured out a high-tech way to adjust the timepiece while it’s ticking.

The first thing he needed was a source of super-accurate time. He could have used a temperature compensated RTC chip, but instead went the more traditional route of using the frequency of mains power as a reference. The next part of the puzzle is to figure out how to both monitor the grandfather clock and make small tweaks to its pendulum.

The answer is magnets. By adding a magnet to the bottom of the pendulum, and adjusting the proximity of a metal plate positioned below it, he can speed up or slow down the ticking. The addition of a hall effect sensor lets the Arduino measure the rate of each swing and calculate the accuracy compared to the high voltage frequency reference.

Theremin Takes The Touch Out Of Multitouch

June 9, 2012 by 11 Comments

Multitouch builds are all the rage now, so it’s not surprising someone would come up with a multi-touchless interface sooner or later. [Hanspeter] did just that; his Multi-touchless ribbon controller, a.k.a. Polymagnetophonic Theremin is multi-touch without the touch.

[Hanspeter]’s touchless ribbon controller uses an array of 24 Hall effect sensors that activate whenever a magnet mounted on a thimble is placed near a build. These sensors go to an ARM-equipped Maple Mini to record multitouch events and send them out over Ethernet.

Even though [Hanspeter] is only using his “multi-touchless ribbon sensor” as a theremin, there’s no reason why it couldn’t be put to other uses. It’s entirely possible to place several of these magnetic sensors in an array and build a real Minority Report interface where the user interacts with a computer without touching anything.

After the break is a video demo showing off how much control [Hanspeter] can get with the thimble/magnet setup. There’s also a few demo songs made with SuperCollider showing off a trio of sitar/Moog/harpsichord synths.

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