LEDs are tiny light bulbs that use very little energy.
When the LED blinks, you will know your plant needs watering.
Can you see the long leg of the LED?
This means it's important which way around you place the LED.
This is called polarity.
All components where the legs have different sizes have polarity.
The current enters the long leg (+), lights the LED and leaves through the short leg (-).
Place it on the board
Match the long leg with the + sign.
Bend the legs out
This keeps the LED in place
Find the resistor
A resistor slows down the flow of electricity, giving just enough to light the LED.
Too much electricity would make the LED pop!
Did you notice the colours on the resistor?
If you go to an electronics shop, you'll find tons of different resistors. The colours indicate how much energy they let through. Different circuits, different resistors!
Make the resistor’s legs look like the letter n.
Place it on the board
It doesn’t matter which way round you put the resistor in.
It does not have polarity. We know this because its legs are the same length.
Twist the legs together
Pinch and twist the resistor leg with the long LED leg.
Find the solar panel and peel off the plastic
This is the power source for your circuit. It turns light into electricity. It makes about as much electricity as small AA battery in bright light.
In low light, the circuit will not work, so don't expect the Thirsty Plant sensor to blink at night!
Solar panel wire
Twist and pull the ends off.
Push the wires through the acrylic
The colours of your acrylics might be slightly different.
Push the red wire through the + sun hole
Pinch and twist the red solar panel cable around the already twisted resistor leg and long LED leg.
Find the sensor wires
The metal inside wires carry electricity from one place to the other. They can be different kinds of wires, short, long, fat and thin. The plastic coating protects the wire and does NOT conduct electricity.
These are the same as you might find connecting some older speakers.
If you have one at home, check it out!
Pull off the tips, then pinch and pull the cables apart with your finger nails.
Push the wires through the two sensor holes
Turn the board over and twist with the resistor leg
Push the black solar panel wire through sun (-) hole
Turn board over twist
Twist black solar panel wire with other sensor wire
Find the mosfet
A mosfet works like a gate:
When the sensor is wet, it stops electricity getting to the LED, so it doesn't blink
When the sensor is dry, it lets electricity through to the LED—making it light up
Place the mosfet with the metal side pointing up
Turn the board over and bend the legs
Wrap the twisted resistor/sensor wire around the right mosfet leg
Wrap bottom (-) led leg around the middle mosfet leg.
Wrap the twisted black solar panel/sensor wire around the left mosfet leg
Test your circuit
Let's make sure the circuit is working before attaching the sensor.
Check that there's enough light hitting the solar panel
Make sure the wires are well wrapped to the mosfet
The metal side of the mosfet should be facing the LED
Remove the mould
Pull apart at the slit down the side.
If you haven't yet, follow the steps to create your sensor here.
Snap the sensor
It will naturally break in the right place below the nails — like a stick of asparagus.
Tightly wrap the sensor wires
Your LED may stop blinking now if your plaster sensor is damp. That shows that it's working!
Find the side acrylics
Their colours might be slightly different from these ones.
Hook the side acrylics onto the board
Gently squeeze the hooks to slot the top acrylic into place
Acrylic is strong, but snaps easily if forced. Be gentle.
Use tape to stick the solar panel in place
Push sensor well into the soil
Find a plant that needs a little love.
Is the LED blinking?
Time to get the watering can out and stop that plant being Thirsty!
Yeah! You built your kit!
But we’re just getting started. To complete your kit, we’re going to teach you how to make the most out of your kit.