Source: https://mokxi.com/learn/how-to-use-a-breadboard Updated: 2026-09-27 Learn # How to use a breadboard, one wire at a time Written by the Mokxi team, updated September 27, 2026 Sign up free or see every lesson - 192 parts on the bench - 25 boards running now - 1.00x real time, on every board Hold the button A complete loop with 5 V, a pushbutton, a resistor and an LED. Open the guided build to place every wire yourself. A breadboard lets you build a circuit without soldering. The holes are not all separate, though, and learning which ones are connected underneath is the first skill that makes the board feel predictable instead of mysterious. In each numbered column, the five holes on one side of the middle gap are joined together. The five holes on the other side are another group. The gap keeps those two groups apart, which is why a pushbutton or chip can straddle it without shorting its two sides together. The long red and blue rows are power rails. Red normally carries the positive supply and blue normally carries ground. Some breadboards split a rail in the middle, and the top and bottom rails are always separate until you join them with a wire. A circuit only works when current has a complete path from power, through the parts, and back to ground. The circuit above is that complete path: 5 V, a pushbutton, a 220 ohm resistor, an LED, and ground. Hold the button and current can cross it, flow through the resistor and LED, and return to ground. Release the button and the path opens, so the LED turns off. Open the guided build when you are ready. The same parts start in place with no wires. Mokxi asks you to draw the first power wire, then each connection after it, and finally run the circuit. You can undo any wire and try again without damaging a part. Want the step-by-step version? The lesson "Build your first circuit wire by wire" walks through this with checkpoints. Open the lesson ## Which breadboard holes are connected? Look at one numbered column. Holes a through e form one connected group, and holes f through j form another. A component leg in f17 is electrically connected to a jumper in j17 because both are in the same five-hole group. A jumper in e17 is across the middle gap, so it is not connected. The easiest check is to follow column numbers rather than judging distance on the screen. Parts can look close while sitting on separate groups, and parts can look spread out while a wire joins their groups directly. ## How the power rails work The red rail gives many parts access to the same positive voltage. The blue rail gives them a shared return to ground. The color is a convention, not an electrical rule, so the supply and ground parts still have to be plugged into the correct rails. The first circuit uses a short jumper to join its ground rails. Without that jumper, the ground part at the bottom would not reach an LED returning to the top blue rail. This is one of the most common reasons a breadboard circuit looks correct but does nothing. ## Build the first complete loop Start at 5 V and trace one unbroken route: power rail to button, button to resistor, resistor to the LED anode, and LED cathode back to ground. The resistor limits current so the LED has a safe operating point. The button opens and closes the same route. Press Run only after you can trace that loop. If the LED stays dark while the button is held, start at the red rail and inspect one connection at a time. This is faster than moving several wires at once because each check rules out one small part of the path. ## Put each part across different connected groups A two-legged part only does useful work when its legs land on different groups. Put both resistor legs into the same five-hole group and the breadboard connection goes around the resistor. Put both LED legs into one group and both sides sit at the same voltage, so no useful current passes through it. The guided circuit places each part correctly before you start wiring so you can concentrate on the connections first. A four-legged tactile button is different. The two legs on one side are already connected inside the button, and pressing it joins that side to the other side. Straddling the middle gap puts each pair on its own breadboard group. Turning the button ninety degrees can join the wrong legs through the breadboard before it is ever pressed. ## Read an LED direction before powering it An LED only conducts in one direction. Current enters its anode and leaves its cathode. On a physical LED, the longer leg is usually the anode and the flat edge marks the cathode. In Mokxi the part and its pin labels preserve that direction, so reversing it gives you the same dark circuit you would get on the bench. Direction is separate from current limiting. A correctly oriented LED still needs its series resistor, and a correctly sized resistor cannot make a reversed LED light. Keeping those as two separate checks makes troubleshooting much easier: first trace the loop and direction, then inspect the resistor value. ## Move from the simulator to a physical board Use the same column numbers when you rebuild the circuit on a physical breadboard. Connect the supply only after the parts and jumpers are placed, then trace the route once before switching it on. A 220 ohm resistor is a safe common choice for a small red LED on 5 V, though the exact brightness depends on the LED. The simulator prevents damaged parts, loose jumper wires and weak batteries, but it keeps the connection rules that matter. If the simulated circuit works and the physical copy does not, compare one node at a time. Check that the rails are powered, that any split rail is bridged, that the LED faces the right way, and that every leg uses the intended column. ## Questions Are all holes in a breadboard row connected? No. Each numbered column has one group of five holes on each side of the middle gap. The gap separates the two groups. Are the top and bottom power rails connected? No. Join them with a jumper if both need the same supply or ground. Some physical breadboards also split each long rail in the middle. Why does an LED need a resistor? An LED does not limit its own current. A series resistor sets a safe current and prevents the LED from asking the supply for far more than it can handle. What should I check when the LED does not light? Trace one complete path from positive power through the button, resistor and LED back to ground. Check the LED direction and confirm every wire shares the intended five-hole group. Related ## Keep going Ohm's Law, in a Circuit You Can Run Picking a Resistor for an LED Pull-Up Resistors and the Floating Input They Fix Breadboard connections and pins How an LED behaves in the simulator Start the guided first-wire build ## Build this for real Open the editor, change a value and watch the number move with it. Nothing to install, and no account needed. Start building Open the editor