Simulate first, build second
Design and debug in the browser, then take a circuit that already works onto real parts. Fewer parts bought, fewer burned out, and less time sorting boxes.
Prices checked September 23, 2026. US list prices at quantity one, before tax, shipping and any education discount.
Hands-on hardware matters. Students remember the thing they held, and some skills only exist in the physical world: seating a jumper properly, reading a real meter, soldering, finding the loose wire. We are not asking you to give that up. We are suggesting you move it to the end of a unit, where it counts, and do the trial and error somewhere trial and error is free.
Why the order matters
- The first attempt at a circuit is where the mistakes happen: an LED without its resistor, a sensor in backwards, a short across the supply. In a simulator that costs a restart. On the bench it costs a part, and sometimes a lesson while you find a spare.
- A class that has already simulated a circuit needs fewer kits. Groups of four can share one kit for the final build because the build is short: they arrive with a wiring plan that works.
- Prep time drops. Kits come out for a few build weeks rather than every lesson, so there is less counting back in and less sorting of loose parts.
- Debugging is easier to teach when you can see everything. In Mokxi a student can put a scope or a logic analyzer on any wire, then do the same check with a real meter when they build.
- It fits the engineering standards. NGSS middle school engineering asks students to develop a model to generate data for iterative testing and modification (MS-ETS1-4), and the high school standard asks them to use a computer simulation to model proposed solutions (HS-ETS1-4). The CSTA K-12 CS standards ask grades 6 to 8 to design projects that combine hardware and software components to collect and exchange data (2-CS-02). Simulate, then build, covers both halves.
Standards text: MS-ETS1-4, HS-ETS1 engineering design, CSTA K-12 CS standards.
A 12-week plan
This follows the twelve-week course week for week. Everything in the middle column runs in Mokxi; the right-hand column is where real hardware comes in.
| Week | In Mokxi | Real hardware |
|---|---|---|
| Week 1 | Current, voltage and the breadboard. Build and measure in Mokxi. | Teacher demo: pass around a real breadboard, an LED and a meter so everyone has held them. |
| Week 2 | Blink: the first program, compiled and run in the browser. | None. |
| Week 3 | Buttons, pull-ups and contact bounce. Watch the bounce on the simulated scope. | None. |
| Week 4 | Timing with a 555. Measure the frequency three ways. | None. |
| Week 5 | Logic gates as real chips, with supply pins and delay. | None. |
| Week 6 | The full adder, built from gates. | None. |
| Week 7 | Flip-flops and counters, read on the logic analyzer. | None. |
| Week 8 | Shift registers: more outputs than pins. | Build week: each group moves its simulated button-and-LED circuit onto a real kit and checks it with a real meter. |
| Week 9 | PWM, and why an LED looks dimmer. | Group kits: the PWM fade on real hardware, compared with the scope trace from Mokxi. |
| Week 10 | Serial: making the board talk. | Group kits: print a real sensor reading over USB. |
| Week 11 | Interrupts. Groups design and simulate their final project. | None. The design is finished and checked in Mokxi before any part is taken out of a box. |
| Week 12 | Project week: two boards, one wire. | Final build on the group kits, from a circuit that already works in simulation. |
For a shorter unit, keep the shape: simulate for the first two thirds, build for the last third, and never take a part out of a box for a circuit that has not worked on screen first.
The shopping list
The minimum we think a class still benefits from touching: one kit for each group of 4 and a meter for each kit. For 30 students that is 8 kits plus a spare. Here is a group kit from loose parts, every line priced:
| Item | Price | Where |
|---|---|---|
| Arduino UNO R4 Minima | $20 | Arduino Store USA |
| USB A to USB C cable, 1 m | $4.95 | Adafruit |
| Full-size breadboard, 830 tie points | $5.95 | Adafruit |
| Male/male jumper wires, 20 x 6 in | $1.95 | Adafruit |
| 220 ohm resistors, 25 pack | $0.75 | Adafruit |
| Diffused red 5 mm LEDs, 25 pack | $4 | Adafruit |
| Tactile buttons (6 mm), 20 pack | $2.50 | Adafruit |
| Breadboard trim potentiometer | $1.25 | Adafruit |
| HC-SR04 ultrasonic distance sensor | $3.95 | Adafruit |
| DHT11 temperature and humidity sensor | $5 | Adafruit |
That comes to $50.30 per kit, or $452.70 for 9 kits. Add a multimeter per kit at $21.50. A boxed starter kit such as the ELEGOO one at $42.99 (ELEGOO US store) is a reasonable alternative, and the SunFounder kit at $49.99 (SunFounder) includes its own meter.
What you can skip at first: the scope, the logic analyzer, the function generator and the bench supply. Students use them in Mokxi on every wire, and a single real scope for teacher demonstrations is a good first instrument to add later if the budget allows ($329 (RIGOL North America)).
What it adds up to
On the calculator’s default guesses, this plan comes to $1,190 over 3 years for 30 students, Mokxi’s Teacher plan included, against $4,216 for a full hardware lab with kits in pairs and 3 instrument benches. The biggest differences are the instruments you do not buy and the kits you need fewer of. Our breakage guesses (15% a year for a full lab, 5% when most mistakes happen on screen) are guesses, not measurements, so put your own in the calculator.
Where Mokxi falls short
It does not teach soldering, and it does not smell like a burned resistor. Its models are good enough for a first course but they are models: noise, temperature and component tolerances are simplified or left out. Test the final circuit on real hardware, which is the point of the build weeks. The limits are listed plainly on the teachers page.