Class Notes from 2-16-11

We got through a little over half of the 2 min class presentations today. We'll complete the remainder on Friday. Everyone is given just 2 minutes for their presentation. It's tough getting everything in you would like to say in that time frame. I put together a few power point slides to add to my presentation. I figured that if a picture is worth a thousand words, then the slides gave me the equivalent of about 10 to 15 minutes more speaking time. So far I have not seen anything that makes me change my mind about the placing of the proposals. I only got time for one question about how I would implement the hardware platform for the t-stat. I've not addressed this issue much to this date as I realize this is not a electrical engineering class. I plan on keeping the hardware practical, useful but minimal in nature.I'd also not expect any of the other student to be heavily involved in that part of the project unless they want to. I thought I'd lay out the requirements for the hardware here so that it could be used for input into the software requirements later:

The t-stat will be based o a Microchip PIC16F877a chip which has on board the following:

1. Multi-channel, 10 bit analog to digital converter
2. A USART for serial communications
3. 8K of Program memory
4. 382 Bytes of RAM
5. 256 Bytes of EEPROM
6. Multiple on board timers with interrupt capability
7. Up to 33 general purpose IO lines

The chip has several other on board features, but the ones listed above are the ones need for this project.One other key feature is that it has internal hardware support for the Microchip ICD (in circuit debugger) interface which makes troubleshooting and programming easy. I all ready have the ICD3 interface modual and the programming software to support this function.

Other requirements of the t-stat are

1. LED 7 segement, 4 digit LED display for time and temperature
2. Pushbuttons for user input
3. Other LEDs to indicate mode
4. Two temperature inputs (will be simulated by pots for now)
5. An RS-485 com port
6. A relay output for heat control
7. A 5V power supply to power the unit
8. Crystal oscillator for precision timing for RTC (Real time clock)
9. An ICD connection port for debugging/programming
10. A dip switch to set the units network address (4 place for 16 possible addresses)

Tonight I also spent some time laying out the t-stats hardware interface and some of the hardware. I'm not going to touch the software until the project gets the green light and the other classmates get involved. I'm trying to get some of the hardware design out of the way so that we can hit the software part without delay when and if we go forward with this project. If the project doesn't go, well, I enjoyed the hardware design effort anyway.