Lego ESP32 Sun Tracker

This is a simple sun tracker, made using Lego Technic pieces for the structural components, and using Lego-compatible servos to control azimuth and altitude.
Control will use the standard Horizontal coordinate system.

Libraries

PubSubClient by Nick O’Leary

ESP32 Servo - Documentation

A servo library tutorial is described here

Arduino JSON by Benoît Blanchon

Green Servo Specifications:

Characteristic	Value
Color:	green
Torsion:	0.7kg
Operating voltage	4.8-6V
Use Angle:	360 degrees, continuous
Limit angle:	None
Operating travel:	360° ±10° (in 500 → 2500 μsec)
PWM signal:	500-2500
Product speed	160/min @ 6V
Gear reduction ratio	1:140
Wire length:	25 cm
Terminal type:	DuPont terminal

Gray Servo Specifications:

Electrical Specification (Function of the Performance)：

Characteristic	4.8V	6.0V
Operating speed (at no load)	0.14 ±0.01 sec/60°	0.12 ±0.01 sec/60°
Running current (at no load)	70 ±20 mA	90 ±20 mA
Stall torque (at locked)	1.8 ±0.2 kg-cm	2 ±0.2 kg-cm
Stall current (at locked)	0.8 ±0.1 A	0.9 ±0.1 A
Idle current (at stopped)	7 ±1 mA	7 ±1 mA
Running life(at no load)	> 50,000 times	> 40,000 times
Temperature drift(at 25°C)	≤ 1°	≤ 1°

Mechanical Specification：

Characteristic	value
Limit angle:	360°
Weight	20 ±1g
Horn gear spline:	Cross hole double output (1 Lego unit deep)
Reduction ratio:	1/300
excessive play:	≤ 1°
Control system:	Change the pulse width
Amplifier type:	Digital controller
Operating travel:	360° ±10° (in 500 → 2500 μsec)
Left&Right travelling:	≤ 10°
Centering deviation:	≤ 2°
Neutral position:	1500 μsec
Dead bandwidth:	≤ 4 μsec
Rotating direction:	counter-clockwise (1500 → 500 μsec)
Pulse width range:	500 → 2500 μsec
Maximum travel	360°(500 → 2500 μsec)
Shock resistance:	250 ±30g
Storage Temperature	-20°C - 60°C
Operating Temperature	-10°C - 50°C

Standard Test Environment

Every test at temperature: 25 ±5° C and relative humidity: 65 ±10％.

MQTT messages

Move servo examples:

{
	"command":   "moveServo",
	"servoName": "altitude",
	"value":     42
}


{
	"command":   "moveServo",
	"servoName": "azimuth",
	"value":     -42
}

Topic: sunTracker/commands
Valid "servoName" values are "azimuth" and "altitude".
For altitude, valid values are integers from 0 to 'altitudeMaxAngle', where those values represent the angle. The servo is capable of rotation between 0° and 360°, but this is being constrained in this program to prevent mechanical interference with other structures. If values outside that range are provided, they will be constrained to the nearest valid value before passed to the servo.
For azimuth, valid values are integers from -100 to 100, where those values represent percentages of maximum speed. Positive values will rotate clockwise when viewed from above. Negative values will rotate counterclockwise when viewed from above. If values outside that range are provided, they will be constrained to the nearest valid value before passed to the servo.

LED

The LED now indicates the status of the Wi-Fi and MQTT connections. It has three states:

• An extinguished LED means Wi-Fi is not connected.
• A blinking LED means Wi-Fi is connected, but there is no connection to the MQTT broker.
• An illuminated LED means both Wi-Fi and MQTT are connected.

ToDo:

• Modify the Wi-Fi connection code to use callbacks, so it no longer blocks.
• Modify the MQTT connection code to not block.