Flux.ai designs PCBs. Soldr builds your RFID door lock from stock
Last post in our five-project series running live prompts through Soldr next to other AI tools. Guest session, unedited screenshots.
What Flux.ai is
Flux is a browser-based PCB design tool with an AI copilot that reads datasheets and helps you route a custom board. It is genuinely clever, and if your project's end state is a manufactured PCB, it belongs in your toolbox. But it lives one layer below this project: an RFID door lock for your room isn't a custom board — it's six modules and the wiring between them, and no PCB tool sources modules, prices them in rupees, or couriers them to Pune.
The prompt
"An RFID door lock that opens for my card and refuses everyone else."
What it got right that generic AI answers usually miss:
- It carded the authorised key fob itself (₹17) — the part every tutorial forgets until the reader has nothing to read.
- It put a driver between the controller and the solenoid, because a 1.5A-peak lock cannot hang off a controller pin.
- It flagged the MFRC522's 3.3V logic against the Uno's 5V — and listed the level shifter as STILL NEEDED rather than pretending the build was complete. Ask it to add one and it does; we're showing the honest state.
The buy list, from that live tray
| Part | Price |
|---|---|
| Arduino Uno R3 CH340G ATmega328P Board | ₹230 |
| MFRC522 RFID Module | ₹180 |
| MIFARE Classic 1K Key Fob | ₹17 |
| 5V Solenoid Lock | ₹240 |
| L298N Motor Driver Module | ₹180 |
| 5mm LED Assorted Pack | ₹120 |
| Dupont Jumper Wire Kit | ₹60 |
| 9V 1A Power Supply Adapter | ₹240 |
| Total | ₹1,267 |
When to use which
Designing a product around an RFID chip? Flux. Wanting your door to open for your card by the weekend? Soldr: ₹1,267 of live stock, pin-by-pin wiring for the exact modules in the box, and firmware billed per generation — first one free, never more than ₹150 — with no subscription.
Flux description from its public product pages at time of writing. Screenshot from a signed-out guest session on app.soldr.ai. Soldr numbers are the live values in our deployed billing code.