Core One – MMU3 Active Filament Indicator

English:
Core One – MMU3 Active Filament Indicator

When working with multiple materials on the MMU3, it’s easy to lose track of which filament channel is currently active. The stock Prusa cover doesn’t allow you to see the MMU3 selector directly from the front – so I designed an LED panel that makes it instantly clear which filament track is in use.

Features

• Clear front-facing display showing the active filament channel (1–5).

• Compact angled LED panel held in place with magnets – designed to match the Core One’s front edge.

• Simple reed switch + magnet system that detects the position of the MMU3 selector.

• Powered by external 5V (e.g. from a Raspberry Pi).

How it works

When the MMU3 selects a filament, a small magnet mounted on the selector arm triggers one of the reed switches. The corresponding diffuse green LED on the front panel lights up, so you can immediately see whether the machine is running on track 1, 2, 3, 4, or 5 – like a simple “light timetable” for your filaments.

https://www.facebook.com/100000655244863/videos/pcb.5114107335481749/1384030599365213

Components required

• 5 × 3 mm diffuse 5V green LEDs (soft light, not clear/sharp)

• 5 × 470 Ω resistors (one per LED)

• 5 × Reed switches (small glass type)

• 1 × 3×2 mm neodymium magnet (mounted on selector arm)

• Wires (thin, flexible)

• 3 × Small neodymium magnets for mounting the LED panel

• Printed parts (front LED plate, angled box, reed switch holder)

• M3 screws (for reed switch sliders)

• External 5V supply (e.g. Raspberry Pi or USB power source)

Electronics links:
Youmile 250-Pack (5 Colours x 50-Pack) 3 mm LED Light Emitting Diode Lamp Diffuse Assorted Kit (White, Red, Green, Blue, Yellow)
https://www.amazon.de/-/da/gp/product/B07Q1813PN/ref=ox_sc_act_title_1?smid=A3BN2T8LLIRB5S&psc=1

Innfeeltech 1/4 W 1% Tolerance 470 Ohm Metal Film Resistor for DIY Project and Experiments, 100 Pieces
https://amazon.de/-/da/gp/product/B0CL6N8JP2/ref=ox_sc_act_title_3?smid=A17GKGMDXTQ2B0&psc=1

Gebildet 30pcs Reed Switches Nearby Magnet - Connect Circuit Magnet Removed - Break Circuit Magnetic Induction Switch, Miniature Reed Contact (2mm x 14mm)
https://www.amazon.de/-/da/gp/product/B07XL5KCKJ/ref=ox_sc_act_title_4?smid=A1DBC97EH2O973&th=1


Video link: https://www.facebook.com/100000655244863/videos/pcb.4982048015354349/1713520545969577

Best regards
Leif Lumby Henriksen
Odense3D Community: https://facebook.com/groups/2911561982402973

Dansk

Core One – MMU3 aktiv filament-indikator

Når man arbejder med flere materialer på MMU3, kan det hurtigt være svært at holde styr på, hvilket filamentspor der er aktivt. Med den originale Prusa-top kan man ikke se vælgeren direkte fra fronten – derfor designede jeg et LED-panel, der viser det med det samme.

Funktioner

• Tydeligt frontdisplay, der viser aktivt filamentspor (1–5).

• Kompakt skråt LED-panel, der holdes fast med magneter – tilpasset Core One’s frontkant.

• Simpelt reed-kontakt + magnet-system, der registrerer MMU3-vælgerens position.

• Får 5V strøm udefra (f.eks. fra en Raspberry Pi).

Sådan virker det

https://www.facebook.com/100000655244863/videos/pcb.5114107335481749/1384030599365213

Når MMU3 vælger et filament, aktiverer en lille magnet på vælgerarmen en af reed-kontakterne. Den tilsvarende diffuse grønne LED på frontpanelet lyser op, så man straks kan se, om maskinen kører på spor 1, 2, 3, 4 eller 5 – lidt som en “lys-togplan” for filament.

Komponentliste

• 5 × 3 mm diffuse 5V grønne LED’er (blødt lys, ikke klare/skinnende)

• 5 × 470 Ω modstande (én pr. LED)

• 5 × Reed-kontakter (små glasrør)

• 1 × 3×2 mm neodym-magnet (monteres på vælgerarm)

• Ledninger (tynde, fleksible)

• 3 × Små neodym-magneter til at fastholde LED-panelet

• Printede dele (frontplade med LED-huller, skrå boks, reed-kontakt holder)

• M3 skruer (til reed-glidere)

• 5V strømforsyning (f.eks. Raspberry Pi eller USB-strøm)

Elektronik links:
Youmile 250-Pack (5 Colours x 50-Pack) 3 mm LED Light Emitting Diode Lamp Diffuse Assorted Kit (White, Red, Green, Blue, Yellow)
https://www.amazon.de/-/da/gp/product/B07Q1813PN/ref=ox_sc_act_title_1?smid=A3BN2T8LLIRB5S&psc=1

Innfeeltech 1/4 W 1% Tolerance 470 Ohm Metal Film Resistor for DIY Project and Experiments, 100 Pieces
https://amazon.de/-/da/gp/product/B0CL6N8JP2/ref=ox_sc_act_title_3?smid=A17GKGMDXTQ2B0&psc=1

Gebildet 30pcs Reed Switches Nearby Magnet - Connect Circuit Magnet Removed - Break Circuit Magnetic Induction Switch, Miniature Reed Contact (2mm x 14mm)
https://www.amazon.de/-/da/gp/product/B07XL5KCKJ/ref=ox_sc_act_title_4?smid=A1DBC97EH2O973&th=1

Video link: https://www.facebook.com/100000655244863/videos/pcb.4982048015354349/1713520545969577

Med venlig hilsen
Leif Lumby Henriksen
Odense3D Community: https://facebook.com/groups/2911561982402973

English: 
Version – Changes in the frame and selector arm (MMU3)

Compared to the original MMU3 setup, some key modifications have been made:

• New subframe under the MMU3
  A redesigned frame has been added beneath the MMU3. It includes an integrated rail with sliders for the reed switches. The sliders can be adjusted forward and backward and locked with an M3 screw, making it easy to fine-tune the exact switch positions for reliable triggering.
• Selector arm with integrated magnet
  On the MMU3 selector, a small arm has been mounted that extends underneath the unit. The arm can be adjusted up and down to ensure the correct distance to the reed switches. At the tip sits a 3×2 mm neodymium magnet, which activates the reed switches and accurately registers which filament track is active.

https://www.facebook.com/100000655244863/videos/pcb.5114107335481749/1384030599365213

These improvements make the indicator system more precise, easier to adjust, and more robust, while keeping the design simple and clean.

Dansk 
Version – Ændringer i stel og vælgerarm (MMU3)

I forhold til den oprindelige MMU3-opsætning er der lavet nogle vigtige ændringer:

• Nyt stel under MMU3
  Der er tilføjet et redesignet understel under MMU3. Det har en indbygget skinne med glidere til reed-kontakterne. Gliderne kan justeres frem og tilbage og låses med en M3-skrue, så det er nemt at finindstille kontakternes placering og få en stabil aktivering.
• Vælgerarm med integreret magnet
  På MMU3-vælgeren er der monteret en lille arm, der går ind under enheden. Armen kan justeres op og ned, så afstanden til reed-kontakterne bliver helt korrekt. I spidsen sidder en 3×2 mm neodym-magnet, som aktiverer reed-kontakterne og registrerer præcist, hvilket filamentspor der er aktivt.

https://www.facebook.com/100000655244863/videos/pcb.5114107335481749/1384030599365213

Disse ændringer gør indikatorsystemet mere præcist, lettere at justere og mere robust – samtidig med at designet forbliver simpelt og brugervenligt.