Monday, March 7, 2016

More on the dsPIC-EL

OK, so a few months down the road we can give a progress report on the dsPIC-EL and the high school club.

Solderless Breadboard
First of all, the members of the high school Electronics and Wireless Communications Club are wicked smart.  These kids are just unbelievable.  Before building the dsPIC-EL boards we gave them a handful of parts, a solderless breadboard, a schematic, and asked them to make the LED blink.  Your standard first PIC project, but the guidance they got was very limited.  All of the students had little problem accomplishing the task (for that one we used the PIC24FV16KM202 because at the time we didn't have enough of an inventory of dsPICs for all the club members.)

We felt it was useful to start with a "from scratch" sort of build so the club members understood that they don't need to buy an Arduino or some prepared kit to do something interesting.  They are prefectly capable of doing whatever they want.

After they had the LED blinking we gave them a few more LEDs and resistors and told them to play.  Interesting results, and I think it is useful for them to go off with little guidance and explore on their own.

They then built the dsPIC-EL.  The provided dsPIC33EV32GM002 contained an acceptance test so they could see right away that they were successful. (Refer to the construction instructions link on the previous post.) A provided library for the LCD allowed the club members to experiment with the buttons and LEDs and display what they were doing.
Shield with DS1821 annotated

Next up was to add sensing. The ultimate goal is to do a high altitude balloon launch in the spring.  This balloon is to carry a payload containing sensors for those measurements of interest to the club members.  A shield was built for the dsPIC-EL containing a DS1821 digital thermostat.  Again, a library was provided to ease the handling of the Dallas One Wire protocol.

LDR voltage divider
For sensing, analog input will be a must, so next the students added a light dependent resistor to their shield and learned how to read voltage.

The final, sort of "directed" experiment was to add a serial EEPROM to the shield.  In the spring launch, this will be needed to store the measurements for analysis after the payload is recovered.

The club members then split into small teams of two or three members.  One team was responsible for the control processor, one for the storage processor, and the remainder for each sensor module.  The plan is for each sensor to take commands from the control processor, report the measurement, and then have the storage processor store the result.  K8VFO guided the teams in preparing functional specifications and then designs for each of the modules.  Students did Internet research to select sensors and are currently working on firmware for each module.

Initial testing and development is being done on the dsPIC-EL, but the launch payload will use a dsPIC-EL for the control processor, and purpose-built shields for the measurement modules.

K8VFO is also walking the club members through the process of converting their schematics to a PCB layout, sending the design out to manufacture, and testing the resulting board.

Of course, some of our stronger club members will be graduating about the time we do the launch.  We hope the remaining members will return in the fall when we plan to build on this year's progress and address telemetry from the balloon to an earth station.

As I said, these kids are wicked smart.

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