Keypad uses a PIC’s built in capacitance functionality

[Giorgos Lazaridis'] most recent project was to build a capacitive touch pad. Since he’s using a PIC 16F1937 it will be relatively easy. That’s because it has a 16 channel capacitance sensing module built right in. But there are still some design considerations that make the development a bit touching.

This isn’t the first time he’s worked with capacitance sensing. Through past experience he has found that it is very important to position the microcontroller as close to the button pads as possible. Because of this, the chip is soldered on the back of the PCB used for the keypad itself. Because he’s hand soldering vias, he also used some foam tape to raise the button pads just a bit. This way they will be flush with the acrylic overlay, which cannot sit flat on the board due the via solder joints.

Check out the video after the break to hear [Giorgos] walk us through the project.

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Simple clock uses RTC chip and character display

[Giorgos Lazaridis] just finished building a simple clock on a breadboard. It uses a common real time clock chip, the DS1307. This is less expensive that its full-featured older brother, the DS3232. The difference between the two is that the 1307 requires an external 32.768 kHz crystal and it is not temperature compensated. This means it will not be quite as accurate over the long-haul (it may wander as much as one minute per month), but it still blows the accuracy of using a microcontroller as an RTC out of the water and includes a backup battery which will keep time when the rest of the circuit is switched off.

This design uses a PIC 16F1937 to display the time and date on a 16×2 character LCD screen. Six buttons are dedicated to incrementing one specific chunk of data (ie: one button changes the year, another the day, etc.). A seventh button can be held down when using the other six in order to decrement the setting. We’re always interested in how the button code is written. [Giorgos] did share his code, but he wrote it in assembly so it’s of little use to us as we tend to stick to C code.

See the walk through video after the break.

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