Magnetic digital scale

Above you see a solenoid being used as a digital scale. The magnetic field from the coil in the base levitates the platform above, where a load to be measured is place. This floating platform has a permanent magnet in it, hovering above a hall effect sensor in the base. As the distance between that magnet and the sensor changes, the measurable magnetic field changes as well. The hall effect sensor is linear so the measured value can easily be correlated with a weight. In the video after the break [Vsergeev] demonstrates the device using test weights to show off its 0.5 gram resolution. He thinks that with a few hardware improvements he could easily achieve 0.1g accuracy.

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Spinning POV clock done oh-so-right

[Kizo] built¬†an extraordinary persistence of vision clock. The design uses a PC cooling fan to spin the propeller-like PCB. As it goes around, a hall effect sensor synchronizes the illumination of the LEDs to draw the display. Power for the rotating electronics is transferred wirelessly via a transformer on the base and coil on the spinning board. The final version uses an ATmega324 microcontroller running at 20 MHz and has an IR receiver for changing the settings. The 3000 lines of code bring a lot of bells and whistles, including a menu system with a huge amount of settings from tweaking the clock display, to font selection for scrolling messages. Take a look at the demo after the break. The double-sided board looks like it’s pretty difficult to etch at home, but as you can see from the forum post (translated), [Kizo] did a great job on this build from start to finish. [Read more...]

Simple automatic LED lamps


[woody1189] put together some automatic lighting for his closet. Nine LEDs are grouped into three lamps and controlled by a hall effect sensor. He prototyped this on an Arduino and then migrated over to an ATtiny85. Although the current implementation could be accomplished without a microcontroller, we’d love to see some firmware improvements such as an auto shutoff for when you forget to close the closet door. The hall effect sensor seems to pop up in a lot of projects so make sure you get a few of them with your next parts order. Video of this in action after the break.

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