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Complete USB flashlight tutorial with step-by-step guide #616

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272 changes: 271 additions & 1 deletion docs/tutorials/building-a-simple-usb-flashlight.mdx
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Expand Up @@ -6,9 +6,10 @@ description: Learn how to build a simple USB-powered flashlight circuit using ts
## Overview

This tutorial will walk you through building a simple USB flashlight using
tscircuit.
tscircuit. We'll create a circuit that powers an LED from USB-C, controlled by a push button.

import TscircuitIframe from "@site/src/components/TscircuitIframe"
import CircuitPreview from "@site/src/components/CircuitPreview"

<TscircuitIframe defaultView="3d" code={`

Expand Down Expand Up @@ -40,3 +41,272 @@ export default () => {
)
}
`} />

## Objectives

A USB flashlight is a simple but practical project that demonstrates core circuit concepts:

- **Power delivery** - Using USB-C as a power source (5V VBUS)
- **Current limiting** - Protecting the LED with a resistor
- **User interaction** - Adding a push button for control

## Bill of Materials

| Component | Value/Type | Purpose |
|-----------|-----------|---------|
| USB-C Connector | SMD USB-C | Power input (5V) |
| Push Button | Through-hole | On/off control |
| LED | Red, 0603 | Light source |
| Resistor | 1kΩ, 0603 | Current limiting |

## Circuit Design

### Understanding the Circuit

The circuit operates on a simple principle:
1. USB-C provides 5V power on the VBUS pins
2. When the push button is pressed, current flows through the circuit
3. The resistor limits current to protect the LED
4. The LED illuminates when current passes through it

### Step 1: USB-C Power Input

First, let's add the USB-C connector which will provide power to our circuit. The USB-C connector has multiple pins, but we only need VBUS (5V power) and GND.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => (
<board width="12mm" height="30mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS"
}}
/>
</board>
)
`} />

### Step 2: Adding the LED and Current-Limiting Resistor

LEDs require a current-limiting resistor to prevent damage. For a typical red LED with a forward voltage of ~2V and desired current of ~3mA:

**Resistor calculation:**
- USB voltage: 5V
- LED forward voltage: ~2V
- Desired current: ~3mA
- R = (5V - 2V) / 3mA = 1kΩ

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board width="12mm" height="30mm">
<resistor
name="R1"
footprint="0603"
resistance="1k"
/>
<led
name="LED"
color="red"
footprint="0603"
/>
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
`} />

### Step 3: Adding the Push Button

The push button connects VBUS to the resistor when pressed, completing the circuit. When released, the circuit is open and the LED turns off.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board width="12mm" height="30mm">
<pushbutton
name="SW1"
footprint="pushbutton"
layer="top"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS"
}}
/>
<resistor
name="R1"
footprint="0603"
resistance="1k"
/>
<led
name="LED"
color="red"
footprint="0603"
/>
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
`} />

### Step 4: Complete Schematic

Now let's combine all components into the complete circuit:

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => (
<board width="12mm" height="30mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS"
}}
schX={-4}
/>
<pushbutton
name="SW1"
footprint="pushbutton"
layer="top"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS"
}}
/>
<resistor
name="R1"
footprint="0603"
resistance="1k"
/>
<led
name="LED"
color="red"
footprint="0603"
/>
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
`} />

## PCB Layout

With the schematic complete, we can position components on the PCB. The layout is designed for a compact form factor:

- USB-C connector at the bottom for easy cable access
- Push button in the middle for ergonomic use
- LED at the top to project light forward

<CircuitPreview splitView={false} hideSchematicTab hide3DTab defaultView="pcb" code={`
import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => (
<board width="12mm" height="30mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS"
}}
pcbY={-10}
schX={-4}
/>
<pushbutton
name="SW1"
footprint="pushbutton"
layer="top"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS"
}}
pcbX={0}
pcbY={-1}
/>
<resistor
name="R1"
footprint="0603"
resistance="1k"
pcbY={7}
/>
<led
name="LED"
color="red"
footprint="0603"
pcbY={12}
/>
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
`} />

## 3D Preview

Here's the final 3D preview of the assembled board:

<TscircuitIframe defaultView="3d" code={`
import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => (
<board width="12mm" height="30mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS"
}}
pcbY={-10}
schX={-4}
/>
<pushbutton
name="SW1"
footprint="pushbutton"
layer="top"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS"
}}
pcbX={0}
pcbY={-1}
/>
<resistor
name="R1"
footprint="0603"
resistance="1k"
pcbY={7}
/>
<led
name="LED"
color="red"
footprint="0603"
pcbY={12}
/>
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
`} />

## Ordering the PCB

You can order this PCB by exporting the fabrication files and uploading them to JLCPCB. Follow the instructions in [Ordering Prototypes](/building-electronics/ordering-prototypes).

## Modifications and Extensions

Consider these enhancements to customize your flashlight:

- **Brighter LED**: Use a white or high-brightness LED (adjust resistor accordingly)
- **Multiple LEDs**: Add more LEDs in parallel for increased brightness
- **Different button**: Use a latching switch for hands-free operation
- **Battery power**: Add a battery holder instead of USB-C for portable use
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