Robotics & Arduino

Lesson 2 · Refinement

Voltage divider.

How to “choke” a pipe to get a reading.

A water loop with an LDR restriction before the A0 measuring junction and a fixed 10 kilo-ohm restriction between that junction and the GND return. The gauge has a single sensing branch, with no flow through it. — The fixed resistor goes between A0 and GND. A0 measures at the junction between the two resistors.

5V → LDR → A0 junction → 10 kΩ → GND

See the choke in motion

Before: a direct wire from A0 to GND gives 0V and 0.5 milliamps. Adding a 10 kilo-ohm return resistor narrows the passage: current falls to 0.25 milliamps and A0 rises to 2.5V, with the LDR held at 10 kilo-ohms in this example.

Example only: LDR = 10 kΩ, fixed resistor = 10 kΩ, so A0 = 2.5V. Real LDR readings change with light. The added resistor stays fixed once connected.

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