Software Status (02/19/14)

Our release software is done.  It's been in final test for the past week now.  Here is the list of  issues and latest additions.

As of today (02/19/14), the current state of the software in Project Curacao is as follows:

- Arduino Battery Watchdog:  

1. Control of the wind turbine (selection between solar and turbine).   The Battery Watchdog turns the solar off and the wind turbine on at sunset and turns the solar on at sunrise.  This is time based and not luminosity based.  We will add more smarts to the Pi to look at cloudy days (via luminosity and color sensors) after the system is deployed to Curacao (to be deployed in early March, 2014).

RasPiConnect Screen modified for Wind/Solar Selection

- Project Curacao Pi main program:  The main program is generating all the graphs, camera pictures, environment sensing as required.  It is also regulating the Fan automatically now.    Reading log files from the Arduino Watchdog.  Next  things to be implemented:

1. Improving sensor error detection (Vastly improved, but still needs more).  We still have an issue with the DHT22 sensor (Humidity Spike as shown below from RasPiConnect).  We believe that we will have to buckle down and figure out the checksum to detect these.  This is a Pi software problem, so we can do it after deployment.

- RasPiConnect:  Complete.  We use this all the time now to monitor what is going on in the project remotely.   

Here's the newest main screen (1 of 6 at this point):

50W Wind Turbine Loaded Results

Update (03/26/14):  The Wind Turbine was deployed down in Curacao two weeks ago.  The actual data from the Turbine matched this article quite well.  About 60-90ma at 15 MPH.  Not much (and not nearly enough to run the box - takes about 300ma) but it did provide a trickle charge at night.  A windstorm took out the turbine about a week later.  See the blog posting about Project Curacao Operational.


We have now completed the 50W Wind Turbine characterization.  During the test of three weeks ago, we blew out the DC/DC voltage regulator with an over voltage condition. The damage was limited to the regulator.

Why did this happen?

The open loop voltage measurement on the 50W Turbine gives us a clue. The regulator is specified as a maximum 19V input. When the turbine hits more than about 25MPH, we started to generate more than 22V, even loaded. This eventually fried the regulator.

What did we miss in our test setup?

The 50W Wind Turbine very minimal specifications say in perfect conditions we can get 2A at 25V which is 50W. However, if we aren't taking 2A (which is 2X to 4X our maximum), the voltage goes up. Eventually, it killed our regulator. We did not think that one through.

How to fix it?

We added an over voltage circuit on the Wind Turbine side of the DC/DC regulator. The wind turbine is rated at 50W, but we aren't going to trust the number. We built one using TVS diodes and made sure we sized it for about 4A@25V (100W) to cover hurricanes (although in a hurricane, that will be the least of our problems - We would expect the Turbine to be halfway to Aruba by then). We did this by getting a 50W 5 Ohm resistor and putting 10-5W TVS diodes in parallel. TVS diodes operate by shunting excess current when the induced voltage exceeds the avalanche breakdown potential. It is a clamping device, suppressing all over voltages above its breakdown voltage. Like all diodes of this type, it automatically resets when the over voltage goes away.

We set the over voltage protection at 20V to avoid this problem in the future.

A good link for a diode based over voltage protection circuit is http://www.electronics-tutorials.ws/diode/diode_7.html

Completed Overvoltage Circuit

We ran another set of loaded tests for the 50W Turbine after the over voltage circuit was added and got the following curve (without generating any smoke).

Conclusion

We are going to go with the 50W wind turbine for this project down in the Caribbean. Our curve shows some power generation at 15 MPH and it gets really good at about 25 MPH. When we get the box down to Curacao, we are going to further characterize both the 50W and 15W wind turbines.

Our control system takes the weather into account on cloudy days (low luminosity and solar voltage) and turn the wind turbine on. Of course, we will turn the wind turbine on at night all the time. As our curves show, generating even 10W on an ongoing basis from the wind poses a set of special problems. Our next wind powered system will use better (and more expensive) turbines but as this is a secondary source of energy, the chosen 50W turbine will work for Project Curacao.

BM017 / TCS34725 Color Sensor I2C Python driver

We have made one more addition to the hardware on Project Curacao.  We have added a BM017 / TCS34725 RGBC color sensor to the device.  Here is the device attached to the back of the top of the box and then a picture of it peeking through (with the LED turned on for emphasis - it normally operates with the LED off).

This device was purchased from solutions-cubed.com (excellent service and documentation).  Another version (compatible) can be had from Adafruit.

We wrote a Python driver for the BM017 / TCS34725 as we could not find one on the net that met our needs.

It has been posted on github under https://github.com/projectcuracao/PC_BM017CS for anyone who needs such a driver.

We connected the INT line to the LEDON pin (and the VDD_LED to VDD) and now we can switch the interrupt on and off and turn the white LED on and off without burning another GPIO pin.


The example code to test the library and the TCS34725 is below:

#!/usr/bin/python



# example driver for BM017 and TCS34725



import time

import smbus

from Adafruit_I2C import Adafruit_I2C

from PC_BM017CS import BM017



bm017 = BM017(True)

bm017.debug = True



bm017.readStatus()

bm017.isBM017There()



bm017.getColors()

bm017.readStatus()



bm017.disableDevice()

bm017.setIntegrationTimeAndGain(0x00, 0x03)



bm017.getColors()

bm017.readStatus()



bm017.readStatus()



# this will turn on the LED if LEDON is connected to INT and LEDVDD is connected to VDD_LED



bm017.setInterrupt(True)

time.sleep(5.0)

bm017.setInterrupt(False)



And the results:





pi@projectCur ~/PC_BM107CS $ sudo python example.py

BM017 initialized

('BM017 Status=', 17)

BM017 / TCS34725 is present

('ColorList = ', [2, 0, 1, 0, 1, 0, 0, 0])

('clear_color= ', 2)

('red_color= ', 1)

('green_color= ', 1)

('blue_color= ', 0)

('BM017 Status=', 17)

('IT set to:', 0)

('Gain set to:', 3)

('ColorList = ', [8, 15, 157, 7, 105, 5, 151, 3])

('clear_color= ', 3848)

('red_color= ', 1949)

('green_color= ', 1385)

('blue_color= ', 919)

('BM017 Status=', 17)

('BM017 Status=', 17)

Interrupt On

Interrupt Off


We pointed the sensor at a spool of red wire.  That's why the "red_color" is higher than the green and blue.

Final Box for Project Curacao

As we ramp up to the last few weeks before deployment, our last task is to put Project Curacao in the final box.  Here is the NEMA enclosure purchased on Amazon (BUD Industries NBB-15253 Style B Plastic Outdoor NEMA Box with Solid Door).  I highly recommend this type of enclosure.  The plastic is easy to work with and the dimensions of the box are given in multiple forms and CAD files.

We are giving a talk at Spokane Create on February 19th so we have to get to work on finishing the box conversion and write a presentation.