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A dual-axis solar tracker rotates a photovoltaic panel in two directions: azimuth, which follows the Sun from east to west, and elevation, which adjusts the panel’s upward tilt. A workable small tracker combines a rigid frame, two independently controlled drives, four light sensors or a solar-position algorithm, limit switches, separate motor and logic power, and a defined night and wind-stow position.
For a tabletop demonstration, servos and an Arduino are sufficient. For an outdoor panel—especially one larger than a miniature cell—use bearings, geared motors or linear actuators, mechanical stops, weatherproof wiring, and a structure designed for wind. A fixed or single-axis mount is often the better practical choice where low cost and reliability matter.
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Elevation axis
/
PV panel -----/
|
Azimuth platform
|
Rotating baseIs a dual-axis tracker worth building?
Tracking can keep a panel better aligned with direct sunlight throughout the day and can improve seasonal alignment compared with a fixed mount. That makes dual-axis systems useful for small experimental systems, remote sensors, solar-concentrator applications, and educational projects.
The trade-off is substantial: two moving axes require more bearings, wiring, controls, calibration, maintenance, waterproofing, and structural work. A raised, movable panel also presents changing wind loads. Motors consume energy, actuators can stall, and a controller failure can drive the frame into a stop.
#1 Best Overall
- Auto Sun Tracking – Tracks the sun's movement both east–west and north–south to keep panels aligned for max power. No more manual adjusting.
- Wind Protection System – Built-in wind sensor auto-adjusts or locks position when wind speed is high, protecting your investment.
- Easy to Set Up – Comes with sunlight sensor, wind sensor, controller, and remote. Clear LCD menu and wiring guide make setup quick.
- Off-Grid Ready – Designed for RVs, farms, remote stations, and DIY solar arrays needing reliable, high-efficiency tracking.
- Global Compatibility – Switch sensor orientation to support either Northern or Southern Hemisphere operation.
Do not assume a universal energy gain. Results depend on latitude, weather, obstructions, tracking accuracy, shading, wind-stow behavior, motor consumption, and how the fixed-panel comparison is made. NREL’s PVWatts system-design documentation models fixed, one-axis, backtracking, and two-axis arrangements separately; two-axis tracking does not automatically remove shading losses.
- Choose dual-axis for learning, experimentation, high-value small panels, or applications where seasonal alignment matters.
- Choose single-axis for larger practical arrays where simplicity and reliability are priorities.
- Choose fixed mounting for the lowest cost and maintenance, particularly where roof space is available.
Choose the mechanical design
| Build level | Typical use | Advantages | Limitations |
|---|---|---|---|
| Tabletop demonstrator | Miniature cells or small panels | Simple, inexpensive, low-voltage | Not suitable for full-size outdoor panels; servos may oscillate or stall |
| Small outdoor actuator tracker | Approximately 50–200 W panel | Good leverage, intermittent motor operation, easy end stops | Requires load calculations, linkage design, battery power, and weather protection |
| Engineered tracker | Permanent or multi-panel installation | Designed structure, foundation, controls, and wind-stow system | Higher cost and usually requires structural and electrical review |
Tabletop servo model
A small Arduino demonstrator can use four LDRs and two servos. Arduino Project Hub shows this educational arrangement with quadrant light sensors and servo motors: Arduino dual-axis tracker example. It is a useful way to learn the control logic, but hobby servos and plastic brackets should not be treated as a full-size outdoor mounting system.
Outdoor actuator model
For a small outdoor panel, use a rotating azimuth base and an elevation frame mounted on that base. A geared motor, worm drive, or linear actuator can drive each axis. Linear actuators are particularly convenient because they can provide leverage, operate only during corrections, and often include end-of-stroke switches. Their stroke, force, duty cycle, weather rating, current draw, and back-driving behavior must match the design.
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A project guide lists a 150 mm actuator and limit switches as examples, but those dimensions are project-specific and must be recalculated for the selected panel and linkage: example tracker materials list.
Calculate loads before buying motors
Do not select a drive from panel weight alone. Wind can create much greater force than gravity, and actuator leverage changes throughout the elevation range.
Weight and balance
Include the panel, frame, cables, counterweights, and any electronics mounted on the moving structure. Place the elevation pivot close to the combined center of gravity. The approximate gravitational torque is:
Tgravity = m × g × rHere, m is moving mass in kilograms, g is approximately 9.81 m/s2, and r is the perpendicular distance from the pivot to the center of gravity in metres.
Wind loading
An initial wind estimate can use:
Fwind = 0.5 × ρ × Cd × A × V2
Twind = Fwind × lever armUse air density of approximately 1.225 kg/m3 near sea level, an engineering estimate for drag coefficient, the projected panel area, and wind speed in metres per second. This is not a substitute for local structural requirements. Apply a substantial safety factor and consider the foundation, fasteners, bearings, frame flex, and the stowed and operating positions.
Rank #2
- Colour: white
- Material: plastic
Actuator geometry
For a linear actuator:
Factuator = Trequired / mechanical moment armThe moment arm may be large in the middle of travel and very small near the ends. A mechanism that moves easily at midday may stall when the panel is near the horizon. Check the force at low, middle, and high elevation angles, and prevent the linkage from approaching a near-zero-force geometry.
Specify a drive with adequate rated force, startup and stall-current capacity, duty cycle, travel, weather resistance, and holding capability. A 12 V label alone does not establish that an actuator is suitable.
Parts and control architecture
Mechanical parts
- Rigid panel frame and panel-specific mounting hardware
- Azimuth bearing or slewing ring with a rotating post
- Two elevation side pivots for larger panels
- Two geared motors or linear actuators
- Fabricated brackets, hinges, linkage arms, and fasteners
- Mechanical end stops and, where appropriate, a brake or self-locking drive
- Protected cable route, flexible loop, or slip ring if continuous rotation is required
Electronics
- Arduino Uno, Nano, or equivalent microcontroller
- Four LDRs with four fixed resistors for voltage dividers, or a real-time clock and calculated solar-position software
- Two suitable H-bridge drivers or reversing relays
- Two normally closed limit switches per axis
- Separate motor supply and regulated logic supply
- Battery, solar charge controller, and DC-DC converter for an independent outdoor system
- Fuses close to the battery and in each motor branch
- Manual jog controls, emergency stop or master disconnect, and a weatherproof enclosure
- Optional current sensors, encoders, actuator feedback, anemometer, or wind switch
Never power motors or high-current servos from an Arduino 5 V pin. Use a separate motor supply, appropriate suppression, and a regulated logic supply. Share ground where a non-isolated driver requires it. Motor noise can cause resets, so separate motor and sensor wiring, add suitable bulk capacitance and flyback protection, and use a watchdog reset.
Arduino’s Motor Shield Rev3 uses an L298P driver and recommends an external 7–12 V motor supply; its listed absolute limit at the Vin screw terminals is 18 V. It is not automatically suitable for every actuator. Check continuous, startup, and stall current against the driver’s actual limits.
Recommended wiring arrangement
PV panel
|
Charge controller
|
12 V battery
|--------------------> Motor driver / relays ---> Azimuth drive
| |
| +--------> Elevation drive
+--> Fuse --> DC-DC regulator --> Microcontroller
LDRs / RTC / wind input --> Microcontroller
Limit switches ----------> Controller and/or hard motor interlock
Manual jog controls ------> Motor driver controlUse normally closed limit switches where practical. A broken wire can then be detected as a fault or prevent further motion. Software should stop immediately when a limit is active, while the electrical circuit should prevent the controller from driving farther into the stop even if firmware fails. Add direction interlocks and dead time so both directions cannot be energized together and the drive stops before reversing.
Choose the tracking method
Four-LDR feedback
Mount four matched light-dependent resistors on the moving frame, separated by a small vertical and horizontal cross-shaped shade:
LDR-NW | LDR-NE
-------+-------
LDR-SW | LDR-SEWith the exact signs determined by the sensor wiring and orientation, calculate:
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horizontalError = (NW + SW) - (NE + SE)
verticalError = (NW + NE) - (SW + SE)Move an axis only when its error exceeds a deadband. Otherwise stop that axis. Average readings, use short movement pulses, add a settling interval, ignore very low light, and reject impossible readings such as a sensor that remains permanently at zero. Keep the divider symmetrical and clear of shadows from the panel frame.
Rank #3
- This controller can control the dual-degree-of-freedom platform to track the sun in real time, and has the ability to be leveled in case of wind, leveled and centered on cloudy nights, and is applicable to both the northern and southern hemispheres
- The instruction manual is marked for use in the northern hemisphere, if it is used in the southern hemisphere, reverse east-west and north-south
- Button control and infrared wireless manual control functions, and the parameters can be freely adjusted, LCD parameter display and other functions.
- The requirements for the platform are: it must be a platform driven by two brushed DC motors, and the platform must have a limit function (it is recommended to set an external limit, or a controller can be introduced for limit).
LDR control is inexpensive and naturally compensates for some mechanical misalignment, but clouds, reflections, dirt, snow, unequal sensors, and partial shading can cause hunting or false corrections. The sensor head must move with the panel; sensors mounted on a stationary base may measure the wrong reference as the panel rotates.
Calculated solar position
A chronological controller calculates the Sun’s expected azimuth and elevation from latitude, longitude, date, time zone, clock accuracy, and the tracker’s axis geometry. It needs a real-time clock or reliable network time and careful mapping between solar coordinates and motor coordinates.
This approach is predictable through cloud cover and can move every few minutes, but errors in time, location, axis zero, or coordinate conversion produce pointing errors. It also needs explicit sunrise, sunset, night, and stow logic.
Hybrid control
For an outdoor build, a strong arrangement is to use calculated position for the normal path and LDRs for small corrections. Add a wind input or manual stow switch, and treat limit switches as hard safety interlocks. Neither sensor tracking nor astronomical tracking is universally superior; the right choice depends on calibration, weather, hardware, and project scale.
Build the tracker
- Define the panel and travel. Record dimensions, mass, mounting holes, center of gravity, desired azimuth and elevation range, stow position, and local wind or snow exposure. Do not copy another project’s servo angles.
- Build the fixed base. Provide an overturning-resistant foundation and a bearing that keeps the azimuth axis vertical or deliberately aligned. Add mechanical stops, cable management, and a means of preventing unlimited rotation unless a slip ring is installed.
- Build the elevation frame. Use two side pivots for larger panels. Put the pivot near the center of gravity and brace the frame against twisting.
- Install and test the drives. Confirm extension and retraction, measure travel, test each limit switch, check for binding, and verify that the drive cannot force the frame into a hard stop.
- Balance the panel. With power disconnected, move it through the complete range. It should not fall, swing, or require the actuator to fight a large static imbalance.
- Install the sensor head. Center the divider, protect it from rain, keep all quadrants similar, and make it accessible for cleaning and calibration.
- Install wiring. Use outdoor-rated cable, drip loops, cable glands, strain relief, corrosion-resistant fasteners, and physically separated sensor and motor routes.
- Test without the panel. Verify direction, current, limits, manual controls, emergency stop, homing, controller resets, and recovery behavior using a low-risk test load.
- Fit the panel and calibrate. Set azimuth and elevation zero, sensor orientation, travel limits, night behavior, sunrise and sunset positions, and wind-stow position.
Program the controller
The following is a control framework, not a drop-in safety-certified program. Pin assignments, limit logic, motor functions, travel ranges, current limits, and stow behavior must be adapted to the actual hardware.
const int sensorNW = A0;
const int sensorNE = A1;
const int sensorSW = A2;
const int sensorSE = A3;
const int azimuthEastLimit = 2;
const int azimuthWestLimit = 3;
const int elevationLowLimit = 4;
const int elevationHighLimit = 5;
const int horizontalDeadband = 35;
const int verticalDeadband = 35;
const int darkThreshold = 80;
void loop() {
int nw = analogRead(sensorNW);
int ne = analogRead(sensorNE);
int sw = analogRead(sensorSW);
int se = analogRead(sensorSE);
int averageLight = (nw + ne + sw + se) / 4;
if (averageLight < darkThreshold) {
stopAllMotors();
stowOrHomeAtNight();
delay(30000);
return;
}
int horizontalError = (nw + sw) - (ne + se);
int verticalError = (nw + ne) - (sw + se);
if (horizontalError > horizontalDeadband && digitalRead(azimuthWestLimit) == HIGH)
moveAzimuthWest();
else if (horizontalError < -horizontalDeadband && digitalRead(azimuthEastLimit) == HIGH)
moveAzimuthEast();
else
stopAzimuth();
if (verticalError > verticalDeadband && digitalRead(elevationHighLimit) == HIGH)
moveElevationUp();
else if (verticalError < -verticalDeadband && digitalRead(elevationLowLimit) == HIGH)
moveElevationDown();
else
stopElevation();
delay(500);
}Direction names may be reversed by the physical orientation or motor polarity. The limit-switch logic also depends on whether inputs use pull-ups or external resistors. Test one axis at a time with manual jog controls and illuminate one sensor quadrant at a time before enabling automatic movement.
A simple delay() can work in a demonstration, but an outdoor controller should normally use nonblocking timing so it can monitor limits, wind, current, emergency stop, and faults continuously. Use short movement pulses, a deadband, hysteresis, averaging, movement timeouts, and mutual exclusion between directions.
Use a state machine
INIT
HOME_AZIMUTH
HOME_ELEVATION
TRACK
NIGHT_STOW
WIND_STOW
FAULT
MANUALTransition when a limit is reached, a timeout expires, current exceeds a threshold, light falls below the night threshold, wind exceeds its setting, the user selects manual override, or the controller restarts. A stalled actuator must never be allowed to run indefinitely.
Rank #4
- The fuselage is made of all-metal, and the bracket is made of ultra-thick aluminum alloy, with excellent stability!
- Ultra-low-speed worm gear motor, all-metal gear, torque 35KG, with self-locking.
- To achieve all-round dual-axis tracking, two horizontal limit switches, and two vertical limit switches to prevent winding wires.
Home, position, and recovery
A commanded motor position is not necessarily the panel’s actual position after a power failure, stall, skipped step, manual movement, gear backlash, actuator replacement, or limit-switch failure.
At startup, move slowly toward a known home limit, stop immediately when it activates, back off slightly, set the software position to the calibrated home angle, and then move to the calculated or sensor-derived position. Limit switches establish endpoints but do not provide continuous position. For more reliable systems, add a potentiometer, Hall sensor, rotary encoder, actuator feedback, or absolute position sensor.
If normal tracking fails, stop both drives, record the fault, retry only a limited number of times, and do not repeatedly drive into a limit. Permit manual jog operation and require inspection after repeated faults.
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Wind and stow
A tracker is a movable sail. Define a stow position that reduces projected area and leverage for your particular structure; there is no universal safe stow angle. Consider an anemometer or wind switch, an independent stow input, a mechanical lock or self-locking drive, controller-failure behavior, and an engineered foundation.
Weather and corrosion
Use outdoor-rated enclosures and UV-resistant cable, provide drip loops and drainage, use corrosion-resistant fasteners, and seal cable entries with proper glands. Condensation can damage electronics even inside a nominally sealed box, so enclosure ventilation or pressure equalization may be necessary.
Electrical and construction requirements
Outdoor PV systems can involve hazardous DC voltage and substantial fault current. Follow applicable local electrical and structural requirements for grounding and bonding, overcurrent protection, disconnects, foundations, wind loads, and mounting hardware. Obtain qualified electrical or structural help where required. Do not connect an Arduino prototype directly to a household inverter or utility-connected system without a compliant design and professional review.
Calibrate and test it
- Jog each axis manually and confirm the direction labels.
- Verify every normally closed limit switch with a meter and through the controller.
- Set mechanical and software travel limits below the physical stops.
- Home the tracker and record the azimuth and elevation zero positions.
- Illuminate each LDR quadrant separately and correct sensor order or motor polarity.
- Log raw sensor values in bright, dim, cloudy, and shaded conditions.
- Test night detection, sunrise initialization, sunset stow, wind stow, emergency stop, and power recovery.
- Run the mechanism through its complete range with the panel installed while checking current, flex, binding, and actuator temperature.
Measure whether tracking works
Compare a tracked panel with the same panel fixed at a defined angle, under the same weather and load conditions. Measure voltage and current at the same point and integrate power over time. A single midday voltage reading is not an energy test.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesLog at least:
timestamp
panel voltage
panel current
panel power
battery voltage
azimuth position
elevation position
sensor readings
weather or irradiance notesFor sampled data:
energy_Wh += power_W × elapsed_hoursInclude the tracker’s own energy use. Compare matched days or, better, use matched panels operating simultaneously. For a preliminary site estimate, use NREL PVWatts V8; array type 4 represents two-axis tracking. PVWatts is an estimate, not a substitute for structural design or measured site performance.
Troubleshooting
| Symptom | Likely causes | Corrections |
|---|---|---|
| Oscillation | Deadband too small, noisy sensors, excessive movement, backlash, clouds | Average readings, increase deadband, use short pulses, add settling time and hysteresis |
| Wrong direction | Swapped sensors, reversed motor polarity, incorrect error sign | Test quadrants and axes independently; print raw readings |
| Repeated end-stop contact | Bad limit wiring, sensor bias, no software limit, wrong home position | Stop and fault, test switches, recalibrate, add a mechanical backup stop |
| Controller resets | Voltage sag, shared supply, motor noise, inadequate suppression | Separate supplies, improve grounding, add capacitance and flyback protection |
| Movement in clouds | LDRs measuring brightness changes rather than direction | Use a light threshold, larger deadband, calculated tracking, or hybrid correction |
| Actuator stalls | Insufficient force, poor linkage angle, binding, wind, low battery, duty-cycle violation | Measure current, inspect geometry, rebalance, increase rating, add timeout protection |
| Position lost after outage | Reliance on timed movement or software position alone | Home at startup and add absolute or continuous position feedback |
| Wind damage | No stow system, weak frame or foundation, high-drag operating angle | Add wind stow, a lock or brake, and engineering review of the complete structure |
When not to build dual-axis
Choose a fixed or single-axis mount when the main objective is dependable, low-maintenance energy production. Two-axis tracking is mechanically and electrically more complicated, and precise pointing is not always worth additional motor energy, wear, and wind exposure. A commercial tracker may be appropriate for a permanent multi-panel installation, while a small actuator build is best treated as an engineered experiment rather than a casual rooftop modification.
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