A circuit simulator for kids: a real breadboard, nothing to break
Mokxi is a free online circuit simulator for kids that runs in the browser, with nothing to install and no account needed. A 5 V supply, a switch, a resistor and an LED on a breadboard: the first circuit, with the whole loop in view. Click the switch and the light goes off; click it again and it comes back. It works on a school Chromebook, and nothing can get hot, short out or be swallowed.
- 455parts on the bench
- 43boards running now
- 1.00xreal time, on every board
What you can do here
In the circuit above, or in the editor it opens.
- Build a first circuit with a switch, a resistor and an LED
- Click parts while the circuit runs and see what changes
- Make mistakes for free: a backwards LED costs a click, not a part
- Blink a light with a 555 timer chip, with no code at all
- Press buttons and watch AND, XOR and NOT light up in the gate lab
- Move on to Arduino code in the same editor when they are ready
What the running circuit shows
One loop, one light.
Electricity needs a complete loop. Here it leaves the 5 V rail, goes through the switch, through a 220 ohm resistor that keeps the current small, through the LED and back to ground. Open the switch and the loop is broken, so the light goes out at once, wherever along the loop the break is.
In the engine the LED takes about 14.9 mA and drops about 1.72 V, and the rest of the 5 V falls across the resistor. Turn the LED round and it stays dark, because an LED only lets current through one way; a child finds that out with a click, not a burnt-out part.
Why a simulator suits first circuits
Real behavior, nothing to lose.
The parts behave like the ones in a kit, because the engine solves the circuit the way the physics does rather than with a cartoon of it. Take the resistor down to almost nothing and the LED’s current shoots far past what a real one survives, which is the lesson of why the resistor is there, learned without the smell.
It runs in Chrome on a school Chromebook or any laptop, with nothing to install. Children can open and run every circuit without an account; saving work needs an account, and a child under 13 needs a parent’s consent first, which we confirm by email. What it leaves out: the feel of pushing a wire into a real breadboard. Many families and classes start here and buy a kit once the interest lasts.
Questions
Is it free?
Yes. The circuit on this page, every part in it and the editor it opens in are on the free plan, with no card.
Does my child need an account?
No. Every circuit opens and runs without one. An account is only for saving work, and for a child under 13 it needs a parent’s consent first.
What age is it for?
Many children enjoy the no-code circuits from about 8 with a grown-up reading along, and typed code tends to suit 11 and up. Go by the child rather than the number.
Is it safe?
Yes. Everything is on screen: no battery to short, nothing hot and no small parts. A mistake costs a click.
Can a class use it?
Yes. It runs on school Chromebooks with nothing to install, and a teacher can hand out a starter circuit and see each student’s work; the teachers page says how.
More simulators
Each one opens on a circuit that is already running.
Build a first circuit
Open the circuit, click the switch and press Run. Nothing to install, and no account needed.