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Homestead 'PanelCam' Project - 2017

PanelCam plan

 

Setting the stage:

Our original solar panels were mounted on or near our house but it soon became apparent that the maple trees south of the house were blocking the sun – especially in the winter when we needed power the most. What we were after was a spot to relocate the panels that had dawn-to-dusk direct sun all year round. The closest spot is over 400’ east of the house, near our water pumping windmill.

Normally it would not be economical to try to transmit low voltage DC that distance without significant voltage drop; the cables would need to be large and expensive. Fortunately we managed to obtain, as salvage ($50), about a quarter mile of 100-pair phone line. This cable is about 1-1/2’ in diameter including its significant shielding and insulation and we had a couple of segments that were well over 400’ long. I stripped each of the 200 ~19 ga. wires a couple of inches, stuffed them into a short section of copper tube, hammered the tube flat and flowed solder into the joint – on each end of two cables – 800 wires to strip, all together. I then drilled a 3/8” hole in each connector and celebrated!

We ran these cables on top of the ground from the new array location to a spot just outside the house. Over several years we buried the cables to protect them from us and our inclination to try to mow too close to them. Over the years, (we installed our first 32 Watt Arco panel in 1981) the array has grown to a bit over 1000 watts and runs at 24 volts DC. Voltage drop is minimal and actually somewhat protects our older 50 Amp MPPT charge controller.

      Solar array
                           Solar array and camera box

Enter the PanelCam:

Every morning in winter we would look out towards the array and try to guess if there was enough snow on the panels to warrant getting dressed for the cold and trekking out clean off the panels. We can see the array from the house but since it is directly east of the house we can only see the edge of the solar panels. We have long considered, half joking, installing a remote camera, aimed at the front of the array but dismissed the idea because of cost and in truth, we didn’t mind those early morning walks all that much.

Before I go any further I should come clean on another point. I have not had a lot of glowing success with electronic projects in the past, having smoked several circuits including a homemade solar panel tracker. But I had been reading about Arduinos. Those small microcontrollers were designed in Italy to help young folks learn about electronics and programming. Since I wouldn’t have to invent my circuits from scratch I figured that I might have a chance with those little guys.

The PanelCam project is made up of two separate systems; 1) inexpensive Wi-Fi ‘security’ camera and 2) a circuit that would switch the camera on when needed and off when not – which is most of the time. The reasons for this are that because of its remote location the camera needs to be battery powered and more importantly, if the camera was on and connected to the Internet all the time it would blow our limited Internet plan into overtime, many times over.

      FunLux Wi-Fi Camera
      FunLux Wi-Fi Camera       

I found a reasonably priced ($35) ‘FunLux’ Wi-Fi camera that has an external antenna and can run on 5 volts DC. I have mounted the camera in a mostly weatherproof enclosure on a fence post out in the garden. To increase the range of the camera I also installed a small, 6” square, parabolic reflector with the antenna right at the focal point of the reflector.

The Cantenna:

      Antennas on house roof
     Two antennas on house roof - 'Cantenna' on right

At the house end, because our router is inside, below the earth-covered roof, I installed a TP-Link Wi-Fi Extender that also has a single external antenna. This unit is connected via 6’ of expensive low-loss cable to a homemade, very directional ‘Cantenna’ that aims right at the camera enclosure – line of sight with no obstructions. Other than constructing the cantenna, phase one of the project went pretty quickly. Here’s a brief rundown on the cantenna construction which is totally borrowed from a couple of web sites.

      Thermos 'Cantenna'
                   Cantenna constructed from old Thermos shell

My research showed that to build this antenna I would need a can about 3-5/8” in diameter and 7” tall but I was unable to find a can that size in the grocery store. I did have the shell of an old thermos bottle that I ended up using. Here are a couple of photos of the first try with the thermos. I subsequently refined the thing by soldering on a new, flat, shiny bottom and moved the placement of the receiver wire a little. A little paint and a cover to keep out the snow and it was ready to go.

The Switch Circuit:

Arduinos (pronounced like: are-‘Dween-ohs) are cool! They’re small microcontrollers capable of handling multiple inputs and outputs, draw very little current and with the addition of battery are totally independent little units. They are programmable, meaning with a few instructions you can have it do your bidding. I began with a common Arduino Uno, about $24 for the original Made in Italy version. The neat thing is that the source code for the microcontroller boards and everything else about them is officially ‘Open Source’. Because of space constraints I chose to use a couple of smaller Arduino Nano clones that cost around $4 each.

      Arduino Nano
                        Arduino Nano layout - (note size)

Arduinos are programmed using versions of the ‘C’ and ‘C++’ languages and a free, downloadable programming environment (IDE).. Although I have been programming computers starting back in 1975 on an IBM 5100 mini computer and subsequently using a few other programming languages, I had never done anything with ‘C’ before. (As an aside, that IBM 5100 cost my employer about $16,000 with 16 MB of memory. We upgraded it to its maximum of 64 MB (yes, that’s megabytes!) at $1,250 per each of three memory boards. That’s in 1975 dollars.)

Basically what I did was hook up a Wi-Fi transceiver to each of the Arduinos and then configured the circuits so one, the one at the house, is the transmitter, and the other, the one out with the camera, as a receiver.

The Transmitter:

The unit in the house is set up with a simple push button, and a bit of code, to send either an ON or OFF message to the receiver. This unit’s Wi-Fi radio is connected to a 6’ low-loss cable designed to be used with 2.4 GHz devices. On the far end of that cable is the transmitter’s original little ‘rubber duckie’ type antenna with its own parabolic reflector. This is mounted inside a small weatherproof box and aimed at the camera box out in the garden. The transmitter and the Wi-Fi Extender are each powered by their own DC-DC buck converter. The transmitter runs on 7 volts DC and the extender on 9 volts DC. The transmitter also has a small 4-line LCD display that confirms that the signal was sent & received OK and as a bonus, shows the temperature out at the camera box.

      Rceiver circuit board
                    Receiver circuit board

The Receiver:

This unit is mounted in the lower part of the camera box with its own directional parabolic reflector aimed back at the house. When the receiver gets a valid ON or OFF message it confirms this by sending a quick little ‘ack’ message back to the transmitter. And cool enough, I programmed it to tack the temperature onto that message. When it receives an ON message the Arduino activates a small relay that sends power to the camera and simultaneously lights up a pretty bright LED that we can see from the house to confirm that all’s well and the camera is indeed ON. An OFF message does the opposite and the OFF state is confirmed by the LED being OFF.

     Sue cleaning the panels
              View from the PanelCam

Operation:

If there is any chance that the panels might have snow on them I flip a switch at my desk that turns on the power to the Extender and transmitter. I then go over to the ON/OFF button and press it a couple of times so the camera cycles on and off and then ends up ON according to the display. I probably should refine this a bit in the code but for now the temperature only shows correctly if the receiver is cycled on & off & on again. I’d rather it didn’t need to do that but I can live with it for now.

     PanelCam LCD Display
    LCD Display shows camera status and temperature at camera

I wait a minute or so for the extender to boot up and for our router to find it. Then I fire up the FunLux app on my Kindle Fire HDX 8.9 tablet and if all went well I can see a nice HD snapshot of the array. Another click and a live HD video of what’s going on out in the orchard displays. This works well much of the time but sometimes the FunLux app shows “Device Off Line”. I then usually force-close the app and try again and usually the system works as planned. In the app you can turn the infrared night lighting on or off and the images in night darkness are surprisingly clear though of course, colorless.

Summary:

What might I do differently?
1) I might just buy a little TP-Link 9 Db external antenna, about $21, to use in place of the cantenna. It was an interesting sub-project but it took me nearly a month to build and fine-tune it.
2) I might shop around for a different camera. The camera seems to be working fine but the FunLux app is a bit clunky and at times totally unresponsive. Unfortunately, I think I’m stuck with that app but if you know otherwise, let me know, OK?

Cost breakdown for the whole system:
• Camera, FunLux 720p HD … $35
• TP-Link WiFi Extender … $20
• Arduinos Nano Clones (2) … $8
• nRF24L01 (+) wireless Transceivers (2) … $11
• 6’ Low-Loss antenna cables ~ $25 ea. … $50
• 4-Line LCD Display (Frentaly) … $13
• 2-Chanel relay (SunFounder) … $7
• DC- DC converters (4) ~$10 ea … $40
• Waterproof DS18b20 Temperature sensor … $3
• Misc. perf board, wire & solder … ~ $15
Total (Unless I’ve forgotten something) … $ 202


Code for the Transmitter:

// PanelCam Switcher TX using AckPayload - the master or the transmitter //
// By Steve Schmeck 1/27/2017 //

#include <LiquidCrystal_I2C.h>
#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>
#include <Button.h>

#define CE_PIN 9 // Define radio pins
#define CSN_PIN 10 //

LiquidCrystal_I2C lcd(0x3F,20,4); // set the LCD address to 0x3F for a 20 chars and 4 line display

const byte slaveAddress[5] = {'R','x','A','A','A'}; // Set 'slave' or remote address

RF24 radio(CE_PIN, CSN_PIN); // Create an instance of 'radio'

char dataToSend[2]; // Data to be sent to remote unit
int ackData[2]; // Holds the value coming from the remote unit
bool newData = false;

char onOffMsg[12]{"Camera: OFF"}; // ON or OFF message to be sent initially to display
int temperature;
int sendTemp = 1; // Ask for temp from slave? 1 = yes, 0 = no
int justPressedButton = 0; // Indicator of just-pressed button; 1 or 2
int lastSentButton = 2; // Indicator of most recently pressed button; 1 or 2 = ON or OFF

Button buttonOn2 = Button(2,PULLUP); // ON/OFF button on pin 2; PULLUP so pin 2 does not 'float'

//===============

void setup() {
Serial.begin(9600);
Serial.println("PanelCam TX starting ...");

lcd.init(); // initialize the lcd
lcd.backlight(); // turn on backlight

initializeDisplay(); // Display the opening screen (function)

radio.begin(); // Turn radio on
radio.setChannel(108); // Above most Wifi Channels
radio.setDataRate( RF24_250KBPS );

// Set the PA Level to prevent power supply related issues and/or overpowering units
// in close proximity. RF24_PA_MAX is default.
// radio.setPALevel(RF24_PA_MIN); // Uncomment for minimum power
// radio.setPALevel(RF24_PA_LOW); // Uncomment for low power
radio.setPALevel(RF24_PA_HIGH); // Uncomment for high power
// radio.setPALevel(RF24_PA_MAX); // Uncomment for maximum power

radio.enableAckPayload();
radio.setRetries(3,5); // delay, count
radio.openWritingPipe(slaveAddress);

// Initialize temperature on display //
send();
temperature = ackData[0];
showData();

} // End of setup

//=============
void loop() {

getButtonPress(); // get button press

} // End of void loop //

//================
void send() {
bool rslt;
rslt = radio.write( &dataToSend, sizeof(dataToSend) );
// Using sizeof() as it gives the size as the number of bytes.
if (rslt) {
if ( radio.isAckPayloadAvailable() ) {
radio.read(&ackData, sizeof(ackData));
newData = true;
}
else {
Serial.println(" Acknowledge but no data ");
}
}
else {
Serial.println(" Tx failed");
}
} // End of send function

//=================
void getButtonPress(){
// Get button press data and assign it to 'dataToSend' variable

// test for button press on pin 2 (ON/OFF button) //
if(buttonOn2.isPressed()){
Serial.print("lastSentButton = ");
Serial.println(lastSentButton);

if(lastSentButton == 2){ // If OFF sent last then ...
strcpy (dataToSend, "1"); // Switch as though ON button has been pressed
strcpy (onOffMsg, "Camera: ON ");
send();
showData();
Serial.print("dataToSend = ");
Serial.println(dataToSend);
Serial.print("onOffMsg = ");
Serial.println(onOffMsg);
}
if(lastSentButton == 1){ // If ON sent last then ...
strcpy (dataToSend, "2"); // Switch as though OFF button has been pressed
strcpy (onOffMsg, "Camera: OFF");
send();
showData();
Serial.print("dataToSend = ");
Serial.println(dataToSend);
Serial.print("onOffMsg = ");
Serial.println(onOffMsg);

}

if(onOffMsg[9] == 'N'){
lastSentButton = 1;
}
if(onOffMsg[9] == 'F'){
lastSentButton = 2;
}
Serial.print("New LastSentButton = ");
Serial.println(lastSentButton);
Serial.println("------------------------");
}
delay(200);

} // end of getButtonPress function

//=================
void showData() {
if (newData == true) {
temperature = ackData[0];
updateDisplay(); // Display temperature on LED display
newData = false;
}
} // End of showData function

//=================
void updateDisplay(){ // Updates the data shown on the LCD display

lcd.setCursor(0,0); // Line 1 - Header
lcd.print("Switch Status ...");

lcd.setCursor(0,1); // Line 2 - switch state
lcd.print(onOffMsg);

lcd.setCursor(0,3); // Line 4 - Temperature
lcd.print("Temp: ");
lcd.print(temperature);
lcd.print(" F");

} // End of updateDisplay function

//=================
void initializeDisplay(){ // Initializes the LED display with openinf screen at startup

lcd.setCursor(0,0); // Line 1 - Header
lcd.print("PanelCam Switcher");
// Line 2 - Blank - for future use
// Line 3 - Blank - for future use
// Line 4 - Blank - for future use
delay(1000);
} // End of initializeDisplay function

//====== END ==========

Code for the Receiver:

// PanelCam Switcher RX using AckPayload - the slave or the receiver //
// By Steve Schmeck 1-22-2017 //

#include <SPI.h> // radio interface
#include <nRF24L01.h> // for radio
#include <RF24.h> // for radio
#include <OneWire.h> // for temp sensor
#include <DallasTemperature.h> // for temp sensor
#include "LowPower.h" // power-saving

#define CE_PIN 9
#define CSN_PIN 10

const byte thisSlaveAddress[5] = {'R','x','A','A','A'};

RF24 radio(CE_PIN, CSN_PIN); // Create an instance of 'radio'

char dataReceived[10]; // this must match dataToSend in the TX
int ackData[2] = {109, -4000}; // the two values to be sent to the master (placeholder numbers)
bool newData = false;

#define ONE_WIRE_BUS 3 // sensor data line connected to Pin 3
OneWire ourWire(ONE_WIRE_BUS); // Set up a oneWire instance to communicate with any OneWire device
DallasTemperature sensors(&ourWire); // Tell Dallas Temperature Library to use oneWire Library
int remTemp; // int variable for sending temperature (remote temperature)

//==============

void setup() {

Serial.begin(9600);

Serial.println("PanelCam RxAckPayload Starting");
radio.begin(); // Turn radio on
radio.setChannel(108); // Above most Wifi Channels
radio.setDataRate( RF24_250KBPS ); // RF24_250KBPS for 250kbs, RF24_1MBPS for 1Mbps, or RF24_2MBPS for 2Mbps
// Set slow to assure reliability

// Set the PA Level to prevent power supply related issues and/or overpowering units
// in close proximity. RF24_PA_MAX is default.
// radio.setPALevel(RF24_PA_MIN); // Uncomment for minimum power
// radio.setPALevel(RF24_PA_LOW); // Uncomment for low power
radio.setPALevel(RF24_PA_HIGH); // Uncomment for high power
// radio.setPALevel(RF24_PA_MAX); // Uncomment for maximum power

radio.openReadingPipe(1, thisSlaveAddress);
radio.enableAckPayload();

getTempFromSensor(); // get initial temp from sensor & assign it to ackData
radio.writeAckPayload(1, &ackData, sizeof(ackData)); // pre-load temperature data

radio.startListening(); // Power Note: this uses ~ 50 mA

pinMode(2,OUTPUT); // set pin 2 to activate relay
digitalWrite(2,LOW); // set pin 2 LOW (camera is OFF)
}
// END of setup
//==========

void loop() {
getTempFromSensor();

LowPower.idle(SLEEP_2S, ADC_OFF, TIMER2_OFF, TIMER1_OFF, TIMER0_OFF, SPI_OFF, USART0_OFF, TWI_OFF);

// Enter power down state for 4 seconds with ADC and BOD module disabled - not currently enabled
// LowPower.powerDown(SLEEP_4S, ADC_OFF, BOD_OFF);

getData();
showData();

Serial.println(dataReceived);

// DO something with the data

if(dataReceived[0] == '1'){
Serial.println("got to dataReseived");
digitalWrite(2,HIGH); // set pin 2 HIGH (camera is ON)
}

if(dataReceived[0] == '2'){
digitalWrite(2,LOW); // set pin 2 LOW (camera is OFF)
}

// END of Do Something
}

// END of void
//============

void getData() {
if ( radio.available() ) {
radio.read( &dataReceived, sizeof(dataReceived) );
// updateReplyData();
newData = true;
}
}
// END of getData
//================

void showData() {
if (newData == true) {
Serial.print("Data received ");
Serial.println(dataReceived);
Serial.print(" ackPayload sent ");
Serial.print(ackData[0]);
Serial.print(", ");
Serial.println(ackData[1]);
newData = false;
}
}
// END of showData
//================

void getTempFromSensor() {
// Get temperature from sensor
sensors.begin(); // Start up the DallasTemperature library
sensors.requestTemperatures(); // Send the command to get temperatures
remTemp = sensors.getTempFByIndex(0);
ackData[0] =remTemp;

radio.writeAckPayload(1, &ackData, sizeof(ackData)); // load the payload for the next time

} // END of getTempFromSensor


This has been a somewhat abbreviated description of our PanelCam project. I have tried to cover the overall design and construction process but obviously left out a lot of details. If you think you might like to build your own PanelCam or similar project and have any questions or comments please e-mail me using the 'Contact' link below.


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