Make a moisture sensor

What can we use instead of a wire stripper or nails if those are hard to find?

If you don't have a wire stripper you can carefully use scissors to strip about 1 centimeter of insulation as in step 3, and if you don't have nails you can straighten metal paperclips, wrap the stripped wire around them, and push them into the soil instead of nails.

My LED won't light — what parts of the setup should I check first?

If the LED doesn't glow, check that the resistor is taped to the battery positive terminal, the LED's long leg is connected to that resistor, the short leg is connected to the wire from the first nail, the second nail's wire is taped to the battery negative, each wire has about 1 cm stripped, and the soil is moist so the circuit can complete.

How can I change the activity for different ages?

For younger kids have an adult pre-strip wires, wrap the resistor to the LED and insert the nails while the child watches pouring water and observing the LED, and for older kids let them strip wires, twist or tape connections themselves and use a multimeter to measure how LED brightness changes with soil moisture.

How can we extend or personalize the moisture sensor project?

You can add a small toggle switch between the resistor and the battery, use multiple nails at different depths to compare LED brightness as the soil dries, decorate the pot, and then share photos or a video of the finished sensor on DIY.org.