{"product_id":"magnetic-reed-switch-4x28mm-normally-open-no-glass-tube-diy-5pack","title":"Magnetic Reed Switch — 4×28mm, Normally Open (NO), Glass Tube, DIY Electronics (5-Pack)","description":"\u003ch2\u003eMagnetic Reed Switch — 4×28mm, Normally Open (NO), Glass Tube (5-Pack)\u003c\/h2\u003e\u003cp\u003eThese 4×28mm glass-encapsulated normally open (NO) reed switches close their contacts when a magnet is brought within proximity, and open again when the magnet is removed. With no moving parts exposed to the environment, they provide reliable, bounce-free switching for door\/window sensors, flow meters, proximity detection, and position sensing applications. The hermetically sealed glass tube protects the contacts from contamination, making them suitable for both indoor and outdoor use.\u003c\/p\u003e\u003ch3\u003eKey Specifications\u003c\/h3\u003e\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions\u003c\/td\u003e\n\u003ctd\u003e4mm diameter × 28mm length\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eContact Type\u003c\/td\u003e\n\u003ctd\u003eNormally Open (NO) — closes on magnet proximity\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEnclosure\u003c\/td\u003e\n\u003ctd\u003eHermetically sealed glass tube\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eContact Rating\u003c\/td\u003e\n\u003ctd\u003e10W max (typical)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMax Switching Voltage\u003c\/td\u003e\n\u003ctd\u003e100V DC \/ 100V AC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMax Switching Current\u003c\/td\u003e\n\u003ctd\u003e0.5A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperate Distance\u003c\/td\u003e\n\u003ctd\u003e~10–20mm (magnet dependent)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Temperature\u003c\/td\u003e\n\u003ctd\u003e-40°C to +70°C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eQuantity\u003c\/td\u003e\n\u003ctd\u003e5 pieces\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003ch3\u003eReed Switch Types Comparison\u003c\/h3\u003e\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eType\u003c\/th\u003e\n\u003cth\u003eDefault State\u003c\/th\u003e\n\u003cth\u003eOn Magnet\u003c\/th\u003e\n\u003cth\u003eBest For\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNO (this listing)\u003c\/td\u003e\n\u003ctd\u003eOpen (circuit off)\u003c\/td\u003e\n\u003ctd\u003eCloses (circuit on)\u003c\/td\u003e\n\u003ctd\u003eDoor open detection, flow meter pulse\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNC (Normally Closed)\u003c\/td\u003e\n\u003ctd\u003eClosed (circuit on)\u003c\/td\u003e\n\u003ctd\u003eOpens (circuit off)\u003c\/td\u003e\n\u003ctd\u003eSecurity alarm (tamper detection)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSPDT (changeover)\u003c\/td\u003e\n\u003ctd\u003eOne contact closed\u003c\/td\u003e\n\u003ctd\u003eSwitches contact\u003c\/td\u003e\n\u003ctd\u003eSelector, changeover switching\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003ch3\u003eWhy Choose Reed Switches?\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eNo external power needed\u003c\/strong\u003e — passive switch, no power consumption when idle\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHermetically sealed\u003c\/strong\u003e — contacts protected from dust, moisture, and corrosive gases\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLong mechanical life\u003c\/strong\u003e — rated for millions of operations with no contact wear\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast switching\u003c\/strong\u003e — operates in \u0026lt;1ms, suitable for flow meter pulse counting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e5-pack value\u003c\/strong\u003e — sufficient for multiple door\/window sensors or flow meter builds\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eCompatible With \/ Common Use Cases\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eArduino door\/window sensor\u003c\/strong\u003e: Connect reed switch between GPIO and GND with INPUT_PULLUP — LOW = magnet present (door closed), HIGH = door open\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHome Assistant door sensor\u003c\/strong\u003e: Reed switch + ESP8266 (ESPHome) for wireless door\/window state reporting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWater flow meter\u003c\/strong\u003e: Reed switch triggered by rotating magnet on flow meter paddle wheel — count pulses for flow rate\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBicycle speedometer\u003c\/strong\u003e: Reed switch + magnet on wheel spoke for speed pulse counting\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLimit switch replacement\u003c\/strong\u003e: Contactless position detection for 3D printer or CNC machine end-stop\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eQ: How do I connect a reed switch to Arduino?\u003c\/strong\u003e\u003cbr\u003eA: Connect one lead to a digital pin (e.g., D2), the other lead to GND. In code: \u003ccode\u003epinMode(2, INPUT_PULLUP);\u003c\/code\u003e When the magnet is near, the switch closes and the pin reads LOW. When the magnet is removed, the internal pull-up holds the pin HIGH. No external resistor needed with INPUT_PULLUP.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eQ: What magnet should I use with this reed switch?\u003c\/strong\u003e\u003cbr\u003eA: Use a neodymium (NdFeB) magnet for reliable operation at distances up to 20mm. Ceramic (ferrite) magnets work at shorter distances (~5–10mm). For door sensors, a standard door sensor magnet (included in most alarm kits) works well. The magnet must be oriented with its pole facing the reed switch for maximum operate distance.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eQ: Can reed switches be used for AC circuits?\u003c\/strong\u003e\u003cbr\u003eA: Yes — this reed switch is rated for 100V AC \/ 0.5A. For AC switching, ensure the load is within the contact rating (10W max). For higher AC loads, use the reed switch to trigger a relay or optocoupler rather than switching the load directly.\u003c\/p\u003e\u003ch3\u003ePackage Contents\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e5× Magnetic Reed Switch (4×28mm, normally open, glass tube)\u003c\/li\u003e\u003c\/ul\u003e","brand":"Keszoox","offers":[{"title":"Default Title","offer_id":46991465742571,"sku":"\u003cnone\u003e","price":7.36,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0677\/1005\/8731\/files\/4x28mm-magnetic-reed-switch-normally-open-diy-sensor.webp?v=1761719698","url":"https:\/\/keszoox.com\/products\/magnetic-reed-switch-4x28mm-normally-open-no-glass-tube-diy-5pack","provider":"Keszoox","version":"1.0","type":"link"}