Patterndo is a web editor where you lay out parts and wiring on a perfboard and check by simulation that the circuit works before you solder. In this article you will build the simplest circuit, "supply → resistor → LED → GND", from start to finish and learn the basic flow of adding parts, entering values, wiring, simulating, and saving. No sign-up is needed, and following along takes 10 minutes. It is convenient to read with the editor open in a new tab.
The circuit you will build
An LED cannot limit its own current, so it is always connected in series with a resistor (LED Current-Limiting Resistors). The circuit runs from the + side of the supply to the resistor, the LED's anode (A), the LED's cathode (K), and then GND.
| Part | Value | Notes |
|---|---|---|
| Supply | 5 V | The app's default power setting |
| Resistor | 330 Ω | When added the default is 10 KΩ, so you have to change the value |
| LED | Red | Red is the default when added |
When you first open the editor, the VCC rail (a red line) on the top row of the board and the GND rail (a blue line) on the bottom row are already drawn as wiring. Connecting to any hole on a rail is the same supply. The default board size is 62×28 holes, and the Inspector panel on the right summarizes the board size, the supply voltage (5.0 V), and the number of parts, wires, and nets. Along the left edge is a vertical toolbar, with a shortcut (G, Q, L, W, D, C, E, A) written under each icon.
Step 1: Add parts
- Press the A key, or use the + button on the left toolbar (or the Add part button below the inspector) to open the add-part window.
- Type
Resistorin the search box and choose Resistor (10KΩ / 5 holes). The part is placed in the middle of the screen and selected automatically, and a small bar with rotate, properties, and delete buttons appears over it. - In the same way, search for
LEDand add an LED (red / 2-pin).
The add-part window is divided into All, IC, Basic components, Switches, and Displays, and you can search by name or model (for example, 74LS02 or FND). A new part is placed in the middle of the visible screen, so it may overlap a part you placed earlier. Drag the body of the overlapping part to an empty spot. While dragging, if it rests over another part, a "Part overlap" warning is shown.
Step 2: Decide positions and values
When you add a part, the tool changes to normal move (Q V S). With this tool, drag parts to move them and press the R key to rotate in 90-degree steps. Parts always snap onto holes.
- Place the resistor horizontally near the top VCC rail. The pins are 4 holes apart, so it takes 5 holes.
- Place the LED vertically below the resistor. The top of the LED is A (anode), and two holes below is K (cathode).
Select a part and press Enter (or the properties button on the bar over the part) to open the Properties panel on the right. The panel has the part number (a name like R1), the value, and the pin list, with the delete, close, and apply buttons below.
- Enter
330in the resistor's Resistance and press Enter or press Apply. Prefixes like1Kand4K7also work. - Choose the LED Color from red, green, blue, yellow, white, and orange. The forward voltage differs by color.
Step 3: Wire it up
Choose the wire tool with the W key. Hold the mouse down at the starting hole, drag, and release at the end hole, and the wire is drawn in one go. Wires are drawn only horizontally, vertically, and at 45 degrees, and if the direction does not line up they bend once to connect.
| Connection | Start | End |
|---|---|---|
| Power connection | A hole on the VCC rail | Pin 1 of the resistor |
| Resistor to LED | Pin 2 of the resistor | A of the LED |
| Ground connection | K of the LED | A hole on the GND rail |
If you draw something wrong, undo with Ctrl+Z or click the wire with the delete tool (E) to erase it. When bare wires cross, like real copper wire, they are calculated as touching at the crossing and the two wires merge into one net, and no separate warning appears. Where you have to cross, use the jumper tool (D) to lay an insulated wire that hops over (Wiring Methods Compared).
Step 4: Check with simulation
Press the Sim button on the top bar and live simulation starts, with the notice "Start live simulation". If enough current flows through the LED, it is shown lit.
The app's LED model uses a forward voltage (red 1.9 V) and a dynamic resistance of 12 Ω. With 330 Ω at 5 V, the current is about 9 mA as follows.
I = (5V − 1.9V) ÷ (330Ω + 12Ω + supply internal resistance 0.2Ω) ≈ 9mA
If the screen is wide, the top bar shows the VCC voltage and the total current. While simulating, lightly click a wire or hole and the net probe opens, showing that wire's voltage and the current flowing. How to read it is explained in Using Patterndo Simulation. If you want to calculate the same values by hand, try the LED resistor calculator.
Step 5: Check diagnostics
Click the E (errors) and W (warnings) numbers in the status bar at the bottom of the screen to open the circuit diagnostics panel. If there is no problem, it shows "No issues detected." If VCC and GND are joined or a part has overcurrent, items appear, and clicking an item moves the view to that location (Reading Diagnostics Messages).
Step 6: Experiment
Changing values and seeing how the result changes speeds up understanding. If you change a value in the Properties panel, the simulation result is recalculated.
| Change | Expected current | Result |
|---|---|---|
| Make the LED blue | about 5.8 mA | The forward voltage is 3.0 V, so it gets dimmer |
| Make the resistor 1K | about 3 mA | Lights dimly |
| Make the resistor 100 | about 28 mA | Exceeds the LED's 20 mA maximum, so a warning appears |
| Swap the LED's A and K connections | 0 | It does not light. No error is shown |
If the current exceeds the rating, diagnostics shows the warning "LED current exceeds the maximum rating". With real parts, under the same conditions the life shortens or it burns out.
Step 7: Save and share
Patterndo has no member accounts, so it does not automatically save boards to a server. Instead, the circuit being edited is continuously reflected in the address bar value, so bookmarking that address lets you reopen the same circuit. You can make a short share link with the Share button on the top bar, or back up to a file with Export RAW in the More menu. The differences and retention periods are explained in Saving, Sharing, and Backing Up Boards.
What to do next
- Learning the shortcuts greatly speeds you up (Patterndo Keyboard Shortcuts).
- Alternate between 2D and 3D and between the component and copper side, and check the side you will solder (2D and 3D Views).
- For the real part placement and wiring order, see Moving a Schematic onto Perfboard in 7 Steps.
Summary
The basic flow of Patterndo is these five: add a part (A), enter a value (Enter), wire (W), simulate (the Sim button), and check diagnostics. Do not leave the resistor at its default value but calculate and enter it, and do not forget to save by address or link when you finish. Simulation is a tool for reviewing values before buying parts and does not guarantee real-part variation, so check with a multimeter after soldering (How to Choose a Multimeter).