A bridge rectifier simulator with a scope on it
Mokxi is a free online rectifier circuit simulator that runs in your browser, with nothing to install and no account needed. A 50 Hz sine, 9 V at its peak, into a full-wave bridge of four 1N4007 diodes, a 1 k load and a 100 µF smoothing capacitor, with the output on an oscilloscope.
- 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.
- See full-wave rectified DC and its ripple on a two-channel scope
- Change the capacitor and watch the ripple grow or shrink
- Change the load and see it drain the capacitor faster
- Take a diode out and turn it into a half-wave rectifier
- Swap the 1N4007s for 1N5817 Schottkys and get more volts out
- Add a zener or a regulator after it to make a power supply
What the running circuit shows
Two diode drops, 100 humps a second, and a capacitor that fills the gaps.
The generator stands in for a transformer’s secondary and floats, neither end tied to ground. The bridge steers both halves of every cycle the same way through the load, so the output gets a hump every 10 ms, 100 a second. The current always passes through two of the four diodes, so each hump is the 9 V peak less two drops of about 0.65 V: without the capacitor the engine’s output peaks at 7.70 V and falls to 0 V between humps.
With the 100 µF capacitor across the 1 k load, the engine’s output sits between about 7.03 V and 7.61 V, a ripple of about 0.6 V. The rule of thumb I / (2fC) says 0.75 V, a little more, because it assumes the capacitor drains for the whole 10 ms when the next hump starts topping it up early. Make the capacitor 1000 µF and the ripple drops to about 0.06 V; make the load 220 ohm and it grows past 2 V.
How the diodes are simulated
Real diode models, solved with the whole circuit.
Every diode is a device model solved by Newton-Raphson with the rest of the circuit, with a forward drop that grows with current and the junction capacitance on its card. Pick a 1N4148, a 1N4007 rectifier, a 1N5817 or 1N5819 Schottky or a BAT54 in the properties panel. A zener part and a voltage regulator are in the bin for the next stage of a power supply.
What it leaves out: there is no transformer part, so the generator stands in for one, and the diodes do not heat up. The analog circuit exports as an ngspice deck for anything the canvas does not show.
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.
Do I need an account?
No. The circuit runs the moment the page does, and the editor opens without one. A free account is only for saving a project to the cloud and sharing it by link.
Can I simulate a half-wave rectifier?
Yes. Delete one diode from the bridge, or build it from one diode and the load, and the output gets a hump every 20 ms instead of every 10.
How do I calculate the ripple?
A rule of thumb is ripple = load current / (2 × frequency × capacitance) for a full-wave rectifier. It slightly overestimates; the scope here shows about 0.6 V where the rule gives 0.75 V.
Can I put the input on the scope too?
Not directly: the input floats, so a scope channel measured to ground does not show it. Ground one end of the generator and build a half-wave rectifier from one diode, and then both traces share a ground.
More simulators
Each one opens on a circuit that is already running.
Build a power supply
Open the circuit, change the capacitor and press Run. Nothing to install, and no account needed.