--- title: The Casio F-91W As A Contactless Payment Device. | daily.dev description: A hobbyist named Matteo P embedded a contactless payment NFC chip into a Casio F-91W digital watch, 3D-printing a new front face that positions the chip above... canonical: https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: The Casio F-91W As A Contactless Payment Device. | daily.dev og:description: A hobbyist named Matteo P embedded a contactless payment NFC chip into a Casio F-91W digital watch, 3D-printing a new front face that positions the chip above... og:url: https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy og:image: https://api.daily.dev/og/posts/Lhcpd9LIy.png og:image:alt: The Casio F-91W As A Contactless Payment Device. og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # The Casio F-91W As A Contactless Payment Device. **[Hackaday](https://daily.dev/sources/hackaday)** · 2 min read · 0 upvotes · 0 comments ## Summary A hobbyist named Matteo P embedded a contactless payment NFC chip into a Casio F-91W digital watch, 3D-printing a new front face that positions the chip above the display with a pick-up coil around its perimeter. The write-up focuses less on the build itself and more on the RF engineering challenge of tuning the antenna and coupling coil for resonance at 13.56 MHz, drawing on prior investigations into how NFC card antennas are constructed. The piece also points to a related one-transistor 125kHz NFC reader challenge for those interested in exploring similar RF hacks. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Turning My CASIO F-91W Into a Contactless Payment Device](https://daily.dev/posts/turning-my-casio-f-91w-into-a-contactless-payment-device-maq3ohnmh) · Lobsters · 7 upvotes · 0 comments - [2026 Green Power Challenge: NFC Powers Command Write And Wake Of MCU](https://daily.dev/posts/2026-green-power-challenge-nfc-powers-command-write-and-wake-of-mcu-l6wk7fdso) · Hackaday · 0 upvotes · 0 comments - [Coin-cell powered Nordic nRF54L15 Tag prototyping platform supports Bluetooth Channel Sounding, Matter, Edge AI](https://daily.dev/posts/coin-cell-powered-nordic-nrf54l15-tag-prototyping-platform-supports-bluetooth-channel-sounding-matt-mhj4qbsq1) · CNX Software · 0 upvotes · 0 comments - [Using NFC To Power Devices Instead Of Qi](https://daily.dev/posts/using-nfc-to-power-devices-instead-of-qi-lk79ogxyq) · Hackaday · 0 upvotes · 0 comments - [Someone made an Arduino-powered NFC scanner that treats physical movies like cartridges](https://daily.dev/posts/someone-made-an-arduino-powered-nfc-scanner-that-treats-physical-movies-like-cartridges-blzsod2hj) · XDA Developers · 0 upvotes · 0 comments --- Tags: [#hardware](https://daily.dev/tags/hardware) [View this post on daily.dev](https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"The Casio F-91W As A Contactless Payment Device.","url":"https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy"},"datePublished":"2026-08-24T08:21:14.104Z","dateModified":"2026-08-24T08:21:30.428Z","description":"A hobbyist named Matteo P embedded a contactless payment NFC chip into a Casio F-91W digital watch, 3D-printing a new front face that positions the chip above...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/52cb6d0262345558a929ea924c228d90?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/52cb6d0262345558a929ea924c228d90?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Hackaday","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Hackaday","logo":"https://media.daily.dev/image/upload/s--JhDfhy70--/f_auto,q_auto/v1767541814/logos/hackaday","url":"https://daily.dev/sources/hackaday"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/the-casio-f-91w-as-a-contactless-payment-device--lhcpd9liy","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"hardware","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Hackaday","item":"https://daily.dev/sources/hackaday"},{"@type":"ListItem","position":3,"name":"The Casio F-91W As A Contactless Payment Device."}]} ```