Measure light with an LDR
Read the sensor voltage divider on A0, average eight samples and print reading at 115200 baud.
Read the sensor voltage divider on A0, average eight samples and print reading at 115200 baud.
Use the Uno R3 Learning Kit. Build with power disconnected, check the labelled connections, then upload the supplied sketch. Drag or zoom the 3D model to inspect it from any angle.
Step 1 — Watch the complete build
Press Play for the narrated build. You can rotate and zoom the model while it plays, or follow the individual steps below.
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Keep U S B disconnected while you build. On this breadboard, each group of five holes shares a connection; the centre channel separates the two halves. You can drag the 3D view to look around. Connect the Arduino’s five volt output to the positive rail. Connect Arduino ground to the ground rail. Add the Photocell. Its pin 0 lead goes into column 12 row C; the highlights show the remaining holes. Add the 10 kiloohms resistor. Its Pin 0 lead goes into column 15 row E; the highlights show the remaining holes. Connect the sensor’s pin 0 pin to the positive rail. Connect the sensor’s pin 1 pin to Arduino analog input 0. Connect the other end of the resistor to the ground rail. Check all wiring. Connect the square U S B-B plug to the Uno and the U S B-A plug to your computer. Use Verify and Upload in the code editor below.
Step 2 — Understand the breadboard
Keep USB disconnected while you build. On this breadboard, each group of five holes shares a connection; the centre channel separates the two halves. You can drag the 3D view to look around.
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Keep U S B disconnected while you build. On this breadboard, each group of five holes shares a connection; the centre channel separates the two halves. You can drag the 3D view to look around.
Step 3 — Connect Uno 5V → T+ rail 3
Connect the Arduino’s five volt output to the positive rail.
| Connect | To |
|---|---|
| Uno 5V | T+ rail 3 |
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Connect the Arduino’s five volt output to the positive rail.
Step 4 — Connect Uno GND → T- rail 1
Connect Arduino ground to the ground rail.
| Connect | To |
|---|---|
| Uno GND | T- rail 1 |
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Connect Arduino ground to the ground rail.
Step 5 — Place Photocell
Add the Photocell. Its pin 0 lead goes into column 12 row C; the highlights show the remaining holes.
Exact breadboard holes
- sensor · pin 0 → column 12 row C
- sensor · pin 1 → column 15 row C
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Add the Photocell. Its pin 0 lead goes into column 12 row C; the highlights show the remaining holes.
Step 6 — Place 10 kΩ resistor
Add the 10 kΩ resistor. Its Pin 0 lead goes into column 15 row E; the highlights show the remaining holes.
Exact breadboard holes
- r · Pin 0 → column 15 row E
- r · Pin 1 → column 15 row H
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Add the 10 kiloohms resistor. Its Pin 0 lead goes into column 15 row E; the highlights show the remaining holes.
Step 7 — Connect column 12 row A → T+ rail 11
Connect the sensor’s pin 0 pin to the positive rail.
| Connect | To |
|---|---|
| column 12 row A | T+ rail 11 |
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Connect the sensor’s pin 0 pin to the positive rail.
Step 8 — Connect column 15 row A → Uno A0
Connect the sensor’s pin 1 pin to Arduino analog input 0.
| Connect | To |
|---|---|
| column 15 row A | Uno A0 |
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Connect the sensor’s pin 1 pin to Arduino analog input 0.
Step 9 — Connect column 15 row J → T- rail 15
Connect the other end of the resistor to the ground rail.
| Connect | To |
|---|---|
| column 15 row J | T- rail 15 |
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Connect the other end of the resistor to the ground rail.
Step 10 — Place USB-A to USB-B cable · Uno
Check all wiring. Connect the square USB-B plug to the Uno and the USB-A plug to your computer. Use Verify and Upload in the code editor below.
Loading assembly…
Check all wiring. Connect the square U S B-B plug to the Uno and the U S B-A plug to your computer. Use Verify and Upload in the code editor below.
Step 11 — Program your Uno
Choose Arduino Uno. Verify, pair the board and Upload this sketch. Keep USB connected. Read the sensor voltage divider on A0, average eight samples and print reading at 115200 baud.
Step 12 — Explore the live readings
Cover the photocell and then expose it to room light. The reading rises as it gets brighter.
Step 13 — Troubleshooting
Check that the sensor and resistor meet only at the signal node, and that both supply rails are connected.
Parts List
Required Parts (1)
Use the components named in this tutorial. A computer and any additional power supply are not included.
x1
$64.70
In stockProject Summary
1 part total
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