Automotive battery voltage monitor


[Rajendra’s] car had just about all the bells, whistles, and gauges he could dream of, but he thought it was missing one important item. In an age where cars are heavily reliant on intricate electrical systems, he felt that he should have some way of monitoring the car’s battery and charging system.

To keep tabs on his car’s electrical system, he built a simple device that allows him to monitor the battery’s instantaneous voltage when the car is powered off, as well as the charging voltage across the battery when the car is running. A PIC16F1827 runs the show, using a simple voltage divider network to step the input voltage down to an acceptable level for use with the PIC’s A/D conversion channel. The resultant measurements are output to a four digit 7 segment display, mounted on the front of the device.

He says that the voltage monitor works quite well, and we’re sure he feels a lot better about the health of his car’s charging system. For anyone interested in keeping closer tabs on their car, he has a circuit diagram as well as code available on his site.

Faux LED scroller using phosphorescence


Hackaday reader [BGR] wrote in to share a video he put together showing off a cool “poor man’s LED scroller” that he built. Rather than build a huge array of LEDs, spending tons of time time wiring and programming, he decided to use only a handful of LEDs on a moving display instead.

The scroller is built upon a PIC16F887 microcontroller which resides on an EasyPIC6 dev board he borrowed for the project. The PIC controls a strip of eight bright white LEDs, which are used to write text on a long strip of phosphorescent paper that can be found at many printing supply outfits. The paper’s dispensing mechanism was cobbled together with parts from several sources, including  a laser printer and VCR.

When he wants to display a message, he inputs text into a flash application he wrote. The app sends the LED byte values to his scroller via a separate serial proxy that talks to the pic over his computer’s COM port.

The effect is pretty slick, looking similar to a slow-moving diffused LED scroller. The messages disappear after about 5 minutes in a pitch black room, which is perfect, since he originally intended to use the device for displaying Twitter updates. He is already considering a second revision of the project, which he wants to mount on the wall – sounds great to us!

Be sure to swing by YouTube to see the video, or continue reading to watch it here.

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