Build a high-side PNP switch
Use D8 to control a BC557 high-side LED switch. LOW turns it on; HIGH turns it off.
Use D8 to control a BC557 high-side LED switch. LOW turns it on; HIGH turns it off.
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 BC557 PNP transistor. Its C lead goes into column 12 row E; the highlights show the remaining holes. Add the Red L E D · 5 millimetres. Its cathode lead goes into column 12 row H; the highlights show the remaining holes. Add the 1 kiloohm resistor. Its Pin 0 lead goes into column 3 row A; the highlights show the remaining holes. Add the 10 kiloohms resistor. Its Pin 0 lead goes into column 20 row C; the highlights show the remaining holes. Add the 330 ohms resistor. Its Pin 0 lead goes into column 20 row J; the highlights show the remaining holes. Connect the BC557 PNP transistor’s E pin to the positive rail. Connect the BC557 PNP transistor’s C pin to one end of the resistor. Connect the other end of the resistor to the L E D’s anode lead. Connect the L E D’s cathode lead to the ground rail. Connect the BC557 PNP transistor’s B pin to one end of the resistor. Connect the other end of the resistor to the BC557 PNP transistor’s E pin. Connect Arduino digital pin 8 to one end of the resistor. Connect the other end of the resistor to the BC557 PNP transistor’s B pin. 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 BC557 PNP transistor
Add the BC557 PNP transistor. Its C lead goes into column 12 row E; the highlights show the remaining holes.
Exact breadboard holes
- q · C → column 12 row E
- q · B → column 13 row E
- q · E → column 14 row E
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Add the BC557 PNP transistor. Its C lead goes into column 12 row E; the highlights show the remaining holes.
Step 6 — Place Red LED · 5 mm
Add the Red LED · 5 mm. Its cathode lead goes into column 12 row H; the highlights show the remaining holes.
Exact breadboard holes
- led · cathode → column 12 row H
- led · anode → column 13 row H
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Add the Red L E D · 5 millimetres. Its cathode lead goes into column 12 row H; the highlights show the remaining holes.
Step 7 — Place 1 kΩ resistor
Add the 1 kΩ resistor. Its Pin 0 lead goes into column 3 row A; the highlights show the remaining holes.
Exact breadboard holes
- base · Pin 0 → column 3 row A
- base · Pin 1 → column 7 row A
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Add the 1 kiloohm resistor. Its Pin 0 lead goes into column 3 row A; the highlights show the remaining holes.
Step 8 — Place 10 kΩ resistor
Add the 10 kΩ resistor. Its Pin 0 lead goes into column 20 row C; the highlights show the remaining holes.
Exact breadboard holes
- pull · Pin 0 → column 20 row C
- pull · Pin 1 → column 24 row C
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Add the 10 kiloohms resistor. Its Pin 0 lead goes into column 20 row C; the highlights show the remaining holes.
Step 9 — Place 330 Ω resistor
Add the 330 Ω resistor. Its Pin 0 lead goes into column 20 row J; the highlights show the remaining holes.
Exact breadboard holes
- load · Pin 0 → column 20 row J
- load · Pin 1 → column 24 row J
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Add the 330 ohms resistor. Its Pin 0 lead goes into column 20 row J; the highlights show the remaining holes.
Step 10 — Connect column 14 row A → T+ rail 14
Connect the BC557 PNP transistor’s E pin to the positive rail.
| Connect | To |
|---|---|
| column 14 row A | T+ rail 14 |
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Connect the BC557 PNP transistor’s E pin to the positive rail.
Step 11 — Connect column 12 row A → column 20 row I
Connect the BC557 PNP transistor’s C pin to one end of the resistor.
| Connect | To |
|---|---|
| column 12 row A | column 20 row I |
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Connect the BC557 PNP transistor’s C pin to one end of the resistor.
Step 12 — Connect column 24 row I → column 13 row J
Connect the other end of the resistor to the LED’s anode lead.
| Connect | To |
|---|---|
| column 24 row I | column 13 row J |
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Connect the other end of the resistor to the L E D’s anode lead.
Step 13 — Connect column 12 row J → T- rail 11
Connect the LED’s cathode lead to the ground rail.
| Connect | To |
|---|---|
| column 12 row J | T- rail 11 |
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Connect the L E D’s cathode lead to the ground rail.
Step 14 — Connect column 13 row A → column 20 row A
Connect the BC557 PNP transistor’s B pin to one end of the resistor.
| Connect | To |
|---|---|
| column 13 row A | column 20 row A |
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Connect the BC557 PNP transistor’s B pin to one end of the resistor.
Step 15 — Connect column 24 row A → column 14 row B
Connect the other end of the resistor to the BC557 PNP transistor’s E pin.
| Connect | To |
|---|---|
| column 24 row A | column 14 row B |
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Connect the other end of the resistor to the BC557 PNP transistor’s E pin.
Step 16 — Connect Uno D8 → column 3 row B
Connect Arduino digital pin 8 to one end of the resistor.
| Connect | To |
|---|---|
| Uno D8 | column 3 row B |
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Connect Arduino digital pin 8 to one end of the resistor.
Step 17 — Connect column 7 row B → column 13 row B
Connect the other end of the resistor to the BC557 PNP transistor’s B pin.
| Connect | To |
|---|---|
| column 7 row B | column 13 row B |
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Connect the other end of the resistor to the BC557 PNP transistor’s B pin.
Step 18 — 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.
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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 19 — Program your Uno
Choose Arduino Uno. Verify, pair the board and Upload this sketch. Keep USB connected. Use D8 to control a BC557 high-side LED switch. LOW turns it on; HIGH turns it off.
Step 20 — Try it and troubleshoot
The LED lights when D8 is LOW. Compare this with the NPN lesson, where HIGH turns the load on.
If it does not work
Use only the shared 5V supply in this circuit. Check BC557 orientation and the base pull-up.
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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