Post 2, Week 4 (June 15 – June 21) « Ernesto's AMA GLOVE Blog

Post 2, Week 4 (June 15 – June 21)

Sunday, 6/21/09

PROGRESS

The final components for the microcontroller circuit finally came in, so I was able to finish soldering them tonight. In the pictures, you will see the small blue capacitors and the silver crystal oscillator on the left side of the PIC socket. The oscillator serves as an external clock for the PIC. The clock is a periodic waveform, which means that it repeats the exact same shape again and again. This clock is used as a synchronizing signal that is used to execute the instructions and commands of the program code. Think of it as the heartbeat to the microcontroller, so without it, the system would cease to function.

The PIC has a built-in oscillator, but the external oscillator lets you achieve much higher frequencies, which results in faster operation. The external oscillator frequency is 10 MHz, which means there is 10 million cycles per second. The PIC also has a 8x PLL, or phase locked loop circuit, which multiplies the external oscillator frequency by 8. This means that my PIC will be running at a total of 80 MHz, or 80 million cycles per second. Fast, right?

I posted another link in the Electrical/Electronics Theory Links Page as well. It is to a pdf called Microcontroller Programming – The Microchip PIC. It should help to understand anything you might want to know about electronics, circuits, microcontrollers, etc.

This coming week I will finish soldering the connections of the components that I have so far, and will give the PIC a test run to make sure everything is correct.

In the pictures, you will see that I set up a circuit on my breadboard just to make sure that the PIC and sensors work. The green LED on the right will be lit up whenever there is power being delivered to the PIC, so it serves as a reminder that the circuit is on. The next picture shows that when the flex sensor is hardly bent, the resistance is large, shown by the multi-meter as 57.5 kΩ, which is 57,500 ohms. The second picture shows the resistance measured as 9.7 kΩ when the sensor is bent almost 90 degrees.

I also posted two videos on youtube to show the sensors in action. Please forgive me on the poor video quality, I had to use the camera on my phone…

The first video shows the flex sensor controlling the brightness of the red LED. When the sensor is not bent, the resistance is very large, so there is not enough power being delivered to light up the LED. As I bend the sensor, the resistance goes down, turns on the LED, and increases the brightness correspondingly.