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327 changes: 285 additions & 42 deletions docs/tutorials/building-a-simple-usb-flashlight.mdx
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Original file line number Diff line number Diff line change
@@ -1,42 +1,285 @@
---
title: Building a Simple USB Flashlight
description: Learn how to build a simple USB-powered flashlight circuit using tscircuit with a push button, LED, and USB-C connector.
---

## Overview

This tutorial will walk you through building a simple USB flashlight using
tscircuit.

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

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

import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => {
return (
<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}
/>
<led name="LED" color="red" footprint="0603" pcbY={12} />

<resistor name="R1" footprint="0603" resistance="1k" pcbY={7} />
<trace from=".R1 .neg" to=".LED .pos" />
<trace from=".LED .neg" to="net.GND" />
</board>
)
}
`} />
---
title: Building a Simple USB Flashlight
description: Build a tiny USB-powered flashlight with a USB-C connector, pushbutton, LED, and current-limiting resistor.
---

## Overview

This tutorial walks through a tiny flashlight circuit that turns on when you
press a momentary pushbutton.

The design is intentionally small:

1. USB-C provides 5V power
2. A pushbutton acts as the on/off control
3. An LED provides the light source
4. A resistor limits LED current

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

## 1. Start with the full circuit

The complete circuit is shown below so you can see the end result first.

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

export default () => {
return (
<board width="18mm" height="32mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS",
}}
pcbY={-11}
schX={-7}
/>

<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"
schX={4}
schY={0}
pcbX={4}
pcbY={7}
/>

<led
name="LED1"
color="red"
footprint="0603"
schX={8}
schY={0}
pcbX={0}
pcbY={12}
/>

<trace from=".R1 .neg" to=".LED1 .pos" />
<trace from=".LED1 .neg" to="net.GND" />
</board>
)
}
`} />

## 2. Add the power input

USB-C gives us a simple 5V source. In this board, we only use `VBUS` and `GND`.
That keeps the example focused on the flashlight path instead of USB data.

If you want the flashlight to be more robust, keep the USB-C connector close to
the edge of the board and give it enough mechanical support in the final layout.

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

export default () => (
<board width="18mm" height="18mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS",
}}
schX={0}
schY={0}
/>
</board>
)
`} />

## 3. Add the pushbutton

The button connects `VBUS` to the resistor path only while it is pressed. That
means the LED stays off until you actively hold the switch.

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

export default () => (
<board width="26mm" height="18mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS",
}}
schX={-8}
schY={0}
/>

<pushbutton
name="SW1"
footprint="pushbutton"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS",
}}
schX={7}
schY={0}
/>
</board>
)
`} />

## 4. Limit the LED current

The resistor keeps the LED from drawing too much current. A `1k` resistor is a
safe, beginner-friendly value that produces a visible but gentle light output.

The exact value is not sacred here. If you want a brighter light, you can lower
the resistor, but you should keep an eye on LED current and heat.

## 5. Add the LED

The LED sits after the resistor so current flows through it only when the button
is pressed.

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

export default () => (
<board width="36mm" height="22mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS",
}}
schX={-13}
schY={0}
/>

<pushbutton
name="SW1"
footprint="pushbutton"
connections={{
pin1: ".R1 > .pos",
pin2: "net.VBUS",
}}
schX={-2}
schY={0}
/>

<resistor
name="R1"
footprint="0603"
resistance="1k"
schX={8}
schY={0}
/>

<led
name="LED1"
color="red"
footprint="0603"
schX={18}
schY={0}
/>

<trace from=".R1 .neg" to=".LED1 .pos" />
<trace from=".LED1 .neg" to="net.GND" />
</board>
)
`} />

## 6. Place the parts on the PCB

This layout keeps the USB-C connector at the bottom, the button near the top
center, and the LED near the top edge so the light is easy to see.

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

export default () => (
<board width="18mm" height="32mm">
<SmdUsbC
name="J1"
connections={{
GND1: "net.GND",
GND2: "net.GND",
VBUS1: "net.VBUS",
VBUS2: "net.VBUS",
}}
pcbY={-11}
schX={-7}
/>

<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"
pcbX={4}
pcbY={7}
/>

<led
name="LED1"
color="red"
footprint="0603"
pcbX={0}
pcbY={12}
/>

<trace from=".R1 .neg" to=".LED1 .pos" />
<trace from=".LED1 .neg" to="net.GND" />
</board>
)
`} />

## 7. Bill of materials

| Reference | Part | Notes |
| --- | --- | --- |
| J1 | USB-C connector | Brings in 5V power |
| SW1 | Pushbutton | Momentary on/off control |
| R1 | 1k resistor, 0603 | Limits LED current |
| LED1 | Red LED, 0603 | Light source |

## 8. How it works

When the button is not pressed, the LED path stays open and no current flows.
When you press the button, `VBUS` reaches the resistor, then the LED, then
ground. The resistor keeps the current in a safe range so the LED does not get
overdriven.

## 9. Next steps

- Change `LED1` to green or blue if you want a different look
- Try a different resistor value if you want more or less brightness
- Add a tiny enclosure or mounting holes if you want it to feel like a real
product
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