Any time after Band 0
Invent Idea bank
52 things you could build, grouped by the band that gives you everything they need. Each one has a person with a problem, a rule in one sentence, and parts from your own box.
Want to see a part working before you choose it? The video library has short videos of every sensor and motor in the course, and a few more.
How to pick one
A list of ideas is a menu, not a muse. Every idea below gets better the moment you find a real person who has that problem and ask them about it. So use the list like this.
- Start from the last band you finished, and read up the list from there. Everything at or below your band, you already have the parts and the ideas for.
- Pick the one where you can name the person. Your aunt with the chop bar beats a perfect idea for nobody.
- Go and ask them what goes wrong now. Write it down in their words. You will almost always change the rule after you hear them.
- Run it through the four questions on Invent a project: who is it for, is there really a rule in it, can you tell whether it worked, and does it fit in 18 pins and your actual box.
- Fill in the one-sheet plan from the same page before you touch a wire.
Every device on this page has the same shape you met on the Invent page: something it notices, a rule it applies, something it does. The rule is the part that makes it a device and not a switch. If you can change the rule and make it better for your person, do.
Stars, and what they mean
★☆☆ an afternoon, mostly one new idea. ★★☆ an evening or two, with something to measure. ★★★ a few evenings, several ideas at once, and a pin budget worth doing on paper first.
The rules that come with every idea
Nothing here touches mains electricity: never a socket, a plug, a mains cable, a pump, a bell or a lamp that plugs into the wall. Every device will lose power one day, so decide what it does when the power comes back. Keep boards and batteries dry, and keep fingers out of anything that moves. A device that helps with health, food or safety is a helper to a person who stays in charge, never a replacement for them.
After Bench Ready
New in this band: sending a program, and timing with digitalWrite and delay on the board's own L light. See these ideas in full on the Band 0 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Choir metronome | Flash once on every beat, forever, at the speed the leader asks for: 1000 ms is 60 beats a minute, 500 ms is 120. | ★☆☆ |
| Heartbeat light | Two quick flashes close together, then a rest, about once a second, so it looks like a real “du-dum”. | ★☆☆ |
| Hand-washing count | One flash every second for twenty seconds, then a long dark rest of five seconds, so you can see where the twenty starts. | ★☆☆ |
| Race-start countdown | Slow flashes that get faster and faster, then one long flash that means go. | ★★☆ |
| Number flasher | Show each digit as that many quick flashes, with a long gap between digits and a longer gap before it starts again. Pick a way to show zero. | ★★☆ |
After Signal Tower
New in this band: wiring your own lights on a breadboard, and holding every pin and timing in a name at the top of the sketch. See these ideas in full on the Band 1 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Lighthouse model | Light the three LEDs one after another round a ring, over and over, so it looks like a beam turning. | ★☆☆ |
| Fire-drill exit arrow | Light the three LEDs left to right, one at a time, then all off, and repeat, so they run towards the door. | ★☆☆ |
| Kundum drum lights | One light for each of three drums, flashing in the rhythm the master drummer taught you, with the rest at the end held longer. | ★★☆ |
| Chop bar menu board chaser | Three lights along the edge of the board chase round fast, then all three flash together twice, then pause. | ★☆☆ |
| Standpipe turn timer | Green for two minutes (fill), yellow for thirty seconds (finish up), red for ten seconds (change over), then green again. | ★★☆ |
After Mood Lamp
New in this band: fading with analogWrite on the ~ pins, mixing colour from three numbers, and repeating with a for loop. See these ideas in full on the Band 2 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Sleep-time fade light | Start at a soft warm colour, then fade very slowly down to off over ten minutes, so the dark arrives too slowly to notice. | ★☆☆ |
| Breathing guide | Fade up for four seconds (breathe in), hold for four, fade down for six (breathe out), and repeat. | ★☆☆ |
| “We are open” kiosk sign | Breathe slowly in the kiosk's own colour all evening, never snapping on or off. | ★☆☆ |
| Black Stars match lamp | Fade between red, gold and green, holding each for a moment, and repeat until the final whistle. | ★★☆ |
| Nursery activity colours | Each activity has its own colour. Hold it for that activity's length, then fade slowly to the next one. | ★★☆ |
| Campfire glow for a drama | Fade between deep red, orange and a little yellow at uneven speeds, so it never looks like it is repeating. | ★★☆ |
After Combination Lock
New in this band: reading buttons, deciding with if and else, remembering between rounds, counting one press as one, and keeping a list in an array. See these ideas in full on the Band 3 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Whose turn? light for Ludo and oware | Each press moves the light to the next player, and after the last player it goes back to the first. | ★☆☆ |
| Shared bathroom sign | Each press swaps between green (free) and red (in use), and it stays that way until somebody presses again. | ★☆☆ |
| Class election counter | Each candidate has a button; every press adds one vote and beeps once; the totals appear on the serial monitor only when the teacher holds two buttons together. | ★★☆ |
| Clinic room call light | When a nurse presses her room's button, that room's light comes on and the buzzer beeps twice; the light stays on until the patient presses “coming”. | ★★☆ |
| Chop bar plate counter | One button for each dish; each press counts one plate and blinks that dish's light once; a fourth button prints the day's totals on the serial monitor. | ★★☆ |
| Penalty shoot-out | The keeper secretly presses left, middle or right; then the kicker presses one; if they match it is saved (red and a buzz), if not it is a goal (green). | ★★☆ |
After Night Guard
New in this band: reading a sensor as a number with analogRead, map, a threshold, and calibration in the place the device will live. See these ideas in full on the Band 4 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Dawn alarm | When the light rises above your measured dawn number, buzz until the button is pressed, then stay quiet until it has been properly dark again. | ★★☆ |
| Drying-sun meter | Light one, two or three LEDs for weak, fair and strong sun, using three numbers you measured outside on different days. | ★★☆ |
| Torch telegraph | When a torch shines on the sensor, light the lamp and beep, and stop as soon as the torch goes away. | ★☆☆ |
| Tank tap drip alarm | When the rain plate under the tap reads wet, light red and beep; clear only when it reads properly dry again. | ★★☆ |
| Grain store damp warning | Green when the air is dry, yellow when the humidity is creeping up, red when it has passed the number the farmer says is too damp. | ★★☆ |
| Knob safe-cracker | A secret number is hidden in the code; as the knob gets nearer to it the RGB light goes from blue to red, and when it is within 10 the buzzer sounds. | ★★☆ |
After Simon Says
New in this band: writing your own functions, making notes with tone, using random, and timing with millis so the board keeps listening. See these ideas in full on the Band 5 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Hand-washing song timer | Press to start a twenty-second tune with four lights going out one by one; pressing again during the tune starts it over. | ★★☆ |
| Order-ready caller | Each table has its own short tune; when the cook presses that table's button, its tune plays twice and its light stays on until pressed again. | ★★☆ |
| Hot potato | Press to start; tick faster and faster for a random time between ten and thirty seconds; then a long low buzz. | ★☆☆ |
| Cooking timer with a knob | Turn the knob to set 1 to 30 minutes, press to start, see the time left as lights going out, and hear a beep that repeats until the button is pressed. | ★★★ |
| Park football referee timer | Press to start a half; a short whistle at one minute left, a long whistle at the end; a second button pauses and restarts the clock. | ★★☆ |
| Whack-a-light | Light one of four lights at random; hit its button before it goes out to score; each hit makes the next window a little shorter. | ★★★ |
After Things That Move
New in this band: moving a servo with a library, stopping a shivering reading with a deadband, and giving a moving part its own battery with one shared ground. See these ideas in full on the Band 6 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Seats-left dial for a trotro | Each press moves a card needle one seat towards “full”; at full a light comes on and stays on until the second button sends the needle back to empty. | ★★☆ |
| Kiosk OPEN / CLOSED flag | Each press turns a card sign slowly from OPEN to CLOSED or back, one degree at a time, so it does not slap. | ★☆☆ |
| Seedling tray rain cover | When the rain plate is wet, swing a light card lid over the tray; open it again only when the plate has been dry for ten minutes. | ★★★ |
| Bird scarer flag | In daylight, wave a bright flag at a random moment every twenty to ninety seconds; at night stay still to save the battery. | ★★★ |
| Stall turntable | Turn the display slowly and forever; a press stops it for ten seconds so a customer can look, then it carries on. | ★★☆ |
| Fly chaser for the fish table | Spin paper streamers for ten seconds every minute, faster when the knob is turned up; a button stops it at once. | ★★★ |
After Distance and Display
New in this band: measuring distance by echo with the HC-SR04, handling “I heard nothing”, and writing to a screen without flicker. See these ideas in full on the Band 7 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Height measurer for weighing day | Fixed at a measured height and pointing down, it shows the child's height once the reading has held steady for two seconds, and “Stand under me” when it hears nothing. | ★★☆ |
| Chop bar welcome screen | When somebody stands within a metre, show “Akwaaba!” and then today's dishes one at a time, until nobody has been there for thirty seconds. | ★★☆ |
| Hand on the mark | Show a random target distance; the player holds a hand still at that distance; score when they are within 2 cm for one second. | ★★☆ |
| Speech and debate timer | Show minutes and seconds left; flash “ONE MINUTE” with one minute left; show “TIME” and beep at zero; the chair can pause with a button. | ★★☆ |
| Park football scoreboard | Home score on the left two digits, away on the right, the colon between; a press adds a goal and a long press takes one back. | ★★☆ |
| Morning rain gauge | Each morning bring the straight-sided rain bucket under the sensor; it shows the depth of water in centimetres and keeps showing it until the next morning's reading. | ★★★ |
After Build for Nzemaland
New in this band: writing a device as states, writing criteria before you build, choosing what it does when the power comes back, and judging it honestly. See these ideas in full on the Band 8 page, with who each one is for, the parts, and the honest notes.
| The idea | The rule in one sentence | How hard |
|---|---|---|
| Clinic “now serving” number | Show the number being served; when the nurse presses Next, flash the new number and beep twice; Break shows a message (dashes on a TM1637, a word on the LCD) until it is pressed again. | ★★★ |
| Coop night guard | Only when it is dark, sound the alarm when something comes close to the coop door; a button snoozes it for five minutes; it re-arms by itself. | ★★★ |
| Seedling watering reminder | Press when you water; after the time you chose the light turns yellow, and later red with a short beep every minute until it is pressed again. | ★★☆ |
| Fish cool-box warning | When the air inside the box has been above your threshold for ten minutes, light red and beep; clear only when it is well below again. | ★★☆ |
| Chop bar order board | Each table has a light and a button; each press moves that table from ordered (slow blink) to cooking (fast blink) to ready (on, with a beep) to served (off). | ★★★ |
| Medicine time helper | Light and beep when twelve hours have passed since the last press; she presses to say taken; if it is not pressed within an hour, it changes to a different light the family can see. | ★★★ |
The best one is not on this page
Walk round the hub, the compound or the market for an hour and ask three people what goes wrong in their day that nobody has fixed. That idea is worth more than all 52 of these, because somebody is waiting for it. When you have it, take it to Invent a project and fill in the plan.