Solar Tracking kit
Price - Stock No
Motors with Gearboxes
Price - Stock No
750 3v Gearbox 2.93RPM - 3000 RPM (6
Price - Stock No 751 12V Gearbox 36
Price - Stock No 752 12V Gearbox 70
Price - Stock No 753 12V Gearbox 160
This kit is designed to follow the sun
or move towards the brightest thing.
This kit monitors the position of the sun using two Light
Dependant Resistors (LDR's), and makes the decision to move towards the
brightest light source adjusting it's path continuously.
IC1 - LM1458
- To make up the Kit, firstly check the PC Board for
any damage. Check continuity of all tracks with a
multimeter or an electronic circuit tester.
- Identify the resistors using a multimeter or the
Resistor Colour Chart
- The three resistors can be bent to shape and fitted,
- Solder in place - see Soldering
- The two diodes are polarised so care needs to be taken to position
and orientate correctly, solder in place.
- The IC socket can be carefully pushed into place. Ensure
all the pins of the socket have come through the PCB and solder in
- The two trimpots are different, identify, push in place
- Pins are provided to terminate the input and output
wires, and the switch. Insert and solder the pins.
- Use the above diagrams to orientate and insert the two
transistors. Solder in place.
- The LDR's need to be offset from one another. This
angle facilitates the direction finding capability. Trim one leg of one
LDR, solder this leg to the other LDR to create the 'LDR offset' above.
Solder the 'LDR offset' in position.
- Cut the figure 8 wire
into three appropriate lengths - one for each motor and one for
power input . Strip and tin the wire - see Tinning
- Solder one wire to the voltage input.
- Note the '+' signs on two of the motor terminals on the
PCB Layout Diagram. Depending on your locomotion method, you need to
determine which way to connect each motor so that it moves in a forward
direction. Using a suitable power source for your motor, connect it so
that it moves in a forward motion, note which terminal you have connected to
positive. With this determined, connect each motor with this
'positive to go forward' to the pin with the '+'. Connect the other
motor terminals to the respective pins.
- You will find that the legs of the IC are spread too wide
to fit into the socket. Place the four legs on one side of the IC
on the table and push gently so they are bent in
slightly. Repeat for the other side. Find the locating DOT on the top
surface of the IC, turn it so it matches the placement diagram and
push it into its socket.
Setup and Testing
- Check the supply voltage, we will call this +V
Adjust both trimpots to
a position of approximatly 1:30. This is the initial setting
With the LDR's pointing to a bright light, connect the supply
voltage. Both Motors should run.
Check for correct operation by shading each LDR in turn -
checking that each motor stops. Shading the right LDR will stop the left
motor and vice versa.
The 100 K trimpot sets the balance point.
The 20K trimpot sets the
If we look at the schematic, and particularly the motor
control, the forward and reverse is achieved when the outputs of IC1a and IC1b
are in different states. A truth table helps explain this:
Right FWD, Left FWD
||Right STOP, Left FWD|
||Right FWD, Left
The transistors enguage each motor when a low signal is outpt from
it's respective operational amplifier. See Transistors.
power diodes protect the transistors from the voltage created by the motor in
the instant(s) after the motor has been stopped. As the motor still has
angular momentum, it will generate a voltage and current (Power). This
power is capable of destroying the transistors and is bled off via the
diodes. See Diodes.
input stage uses two operational amplifiers (contained in IC1) to make a
decision on the direction of light. The op-amps are fed by the
junction of the LDR's. If both LDR's see the same amount of light, their
resistance is equal. The junction of the LDR's would be at input
voltage divided by two ie. 12V input - junction of LDR's at 6V. If
the light on one LDR is greater than the other, than the voltage will move,
higher or lower depending on which LDR has more light.
Limits are set by
the four resistors in series from +V to 0V, and adjusted by the two
trimpots. If the voltage moves outside these limits, the respective op-amp
will activate the motor and move appropriatly.
The 20K trimpot sets
the sensitivity ie. the distance between these limits. The 100K trimpot
adjusts so that these limits are symetrical around +V/2 (balance
For more information on the LM1458 see Datasheet for the LM1458.
Troubleshooting will consist of:
- ensure IC is inserted correctly
- check all components for values and location
- check all polarities
- resolder any or all joints