Using 9V to capture 5V.
I turned 50. Yay! My thoughtful colleagues at Elemental Cognition got me this very cool kit as a gift.
My kids and I built the kit according to the instructions we found on the product website. Like any good project, it was not straightforward. First, the pieces in the kit did not match those in the instructions. For one, the side pieces of the top platform did not match those in the pictures; they had different numbers of tabs and the holes drilled for the servo coupler were on the wrong side. Our solution was to do some drilling.
Another issue seemed to be with the design. When we rotated the top platform, it got blocked by its mount. What did we do? We got a saw and literally hacked it!
Finally, our kit did not have a bracket to hold the light sensitive resistors but a plastic tie on all the wires right at the base held them in place well enough.
The instructions were written fairly well. At least there were a lot of pictures. When we were done with them, it was time to test things out. We downloaded the tracker software and uploaded it to the Arduino and ran it. Bing, bang, zoop! The top platform spun wildly and made a horrible sound while the bottom platform did nothing! Time to debug.
I started by isolating the servos to see if they were working. After brushing up on my C a bit, I wrote this code to help me. It sweeps the servos between some range of degrees as well as prints out the readings from the 4 light sensitive resistors.
#include <Servo.h> // include Servo library
int servoPort[] = {9, 10};
int servoCt = sizeof(servoPort) / sizeof(servoPort[0]);
int minPos[] = {0, 0};
int maxPos[] = {80, 120};
int absDelta = 1;
Servo servo[2];
int delta[2];
int pos[2];
// LDR pin connections
// name = analogpin;
int ain[] = {0, 1, 2, 3};
int ainCt = sizeof(ain) / sizeof(ain[0]);
void setup()
{
Serial.begin(9600);
for (int i = 0; i < servoCt; i++) {
servo[i].attach(servoPort[i]);
delta[i] = absDelta;
pos[i] = minPos[i];
}
}
void loop()
{
Serial.print("analog in ");
for (int i = 0; i < ainCt; i++) {
int v = analogRead(ain[i]);
Serial.print(v);
Serial.print(" ");
}
Serial.println("");
for (int i = 0; i < servoCt; i++) {
servo[i].write(pos[i]);
// Serial.print(servo[i].read());
// Serial.print(" ");
pos[i] += delta[i];
if (pos[i] > maxPos[i] || pos[i] < minPos[i]) {
delta[i] = -delta[i];
pos[i] += 2 * delta[i];
}
}
Serial.println(" ");
delay(10);
}
My tests with this code showed me a few things. First they showed me that the USB connection to the Arduino doesn't provide enough power for it and the servos. Digging through my collection of old electronics, I found a 9V power supply that fixed that.
Next my tests showed me that we got a bad servo with the kit! We ordered a bag of servos from Amazon to fix this problem.
Next my tests showed me that the cable constructed with chunky terminal blocks kept getting hooked on the Arduino preventing the platforms from moving. We broke out the soldering iron to fix that issue. At the same time, we made the wires longer than we originally had them.
As a note to those new to Arduino, I learned a few things about uploading software to it. First, the upload process is very prone to failure. If the Arduino is doing anything, it is unlikely to succeed. Also if the USB connection is not dedicated then there might be failures. So, have one instance of the Arduino IDE open. Close the serial monitors. Hold down the reset button on the Arduino. Click the upload button in the Arduino IDE. When the status reads "Uploading..." release the reset button. If it fails then try again.
After I was confident that the servos and light sensors were working properly, we went back to the software that we downloaded for the project and uploaded it to the Arduino. Blurp. More badness. I started debugging the code and realized it was quite wacky. I won't go into the details. I ended up rewriting it. Here is the result.
#include <Servo.h> // include Servo library
Servo horizontal; // horizontal servo
int servoH = 60; // stand horizontal servo
int servoHMax = 120;
int servoHMin = 0;
Servo vertical; // vertical servo
int servoV = 30; // stand vertical servo
int servoVMax = 80;
int servoVMin = 15;
// LDR pin connections
// name = analogpin;
int ldrbl = 0; // BOTTOM LEFT
int ldrbr = 1; // BOTTOM RIGHT
int ldrtl = 2; // TOP LEFT
int ldrtr = 3; // TOP RIGHT
int dtime = 10;
int tol = 50;
int servoDelta = 2;
void setup()
{
Serial.begin(9600);
horizontal.attach(10);
horizontal.write(servoH);
vertical.attach(9);
vertical.write(servoV);
delay(1000);
}
int setServo(Servo servo, int minPos, int maxPos, int currPos, int sensorDelta) {
// Darkness is pos
// Dark top and light bottom => positive delta => turn down => increase servo
// increase servov to turn down
if (abs(sensorDelta) > tol) {
currPos += (sensorDelta > 0 ? 1 : -1) * servoDelta;
currPos = min(currPos, maxPos);
currPos = max(currPos, minPos);
servo.write(currPos);
}
return currPos;
}
void loop()
{
int tl = analogRead(ldrtl);
int tr = analogRead(ldrtr);
int bl = analogRead(ldrbl);
int br = analogRead(ldrbr);
// dtime = analogRead(4)/20; // read potentiometers
// tol = analogRead(5)/4;
int avt = (tl + tr) / 2; // average value top
int avb = (bl + br) / 2; // average value bottom
int avl = (tl + bl) / 2; // average value left
int avr = (tr + br) / 2; // average value right
int dvert = avt - avb;
int dhoriz = avl - avr;
servoV = setServo(vertical, servoVMin, servoVMax, servoV, dvert);
servoH = setServo(horizontal, servoHMin, servoHMax, servoH, dhoriz);
Serial.print(dvert);
Serial.print(" ");
Serial.print(dhoriz);
Serial.print(" ");
Serial.print(vertical.read());
Serial.print(" ");
Serial.print(horizontal.read());
Serial.println(" ");
delay(dtime);
}
The idea is quite straightforward. The light sensors are isolated from one another by the wood. The software then calculates deltas between the signals from the top sensors and the bottom sensors and from the left sensors and the right sensors. It then uses these deltas to determine in which direction the light is; up or down, to the left or right. It then turns the vertical and horizontal servos such that the light sensors turn into the light.
Finally we added the solar panel and voltmeter. I had hoped that the solar panel would provide enough power for the tracker such that it would be a standlone device but that was not the case. Perhaps we can do a project like this to add that feature.
This was a really fun project. My favorite part was being introduced to the Arduino. I'm looking forward to using it in our other projects!