Lonely Binary
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The TK41 at an angle: a black board with a gold border, lonely binary across the top, a thin pale green glass tube lying across the board under it with a lead bent down into a pad at each end, two small resistors and an LED under the tube, two round LEGO holes, a white magnet drawing, REED SWITCH and ACTIVE HIGH up the two long edges, and a right-angle four-pin header.
VR

View it in VR

This board opens in a VR headset: life-size, or big enough to stand beside, with every pin and every part named where it sits. Open this address in the browser on a headset such as Apple Vision Pro or Meta Quest.

learn.lonelybinary.com/vr/tk41
You have this

Reed Switch

A glass reed switch on a TinkerBlock board: two blades that a magnet pulls shut, from either pole, with no power needed to sense. It sits between VCC and SIGNAL with a 10 kΩ pull-down, so a magnet reads HIGH, and a red LED lights while it is closed. It draws nothing while open, and VCC must be your board's logic voltage.

Closes at
15 to 18AT, either pole
Draws while open
0mA; about 1.6 mA closed
Up to
100operations a second
VCC
3V3 or 5Vyour board's logic voltage
Start here · 01 The four pinsOpen the board in 3D

Turn it over and see the three holes to wire: GND, VCC and SIGNAL. VCC reaches only the reed switch, which joins it to SIGNAL when a magnet is near; a 10 kΩ pull-down holds SIGNAL LOW otherwise.

Product questions & answers ↓

The whole handbook9 articles · 40 minQuick referencePDF · 420 KBReed Switch model (GLB)GLB · 1013 KBReed Switch CAD (STEP)ZIP · 944 KBMKA-14103 datasheetPDF · rmcip.comPinout and specsThe pin table, and the questions people ask first
Community

Product questions

See what other owners have asked, and read their solutions.

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Reed Switch

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Need another

Not on general sale yet. Reply to your order and we will sort out a spare — quote tk41.

Order or missing parts?

Email us or reply to your order, and quote tk41 — that identifies the product. If something is missing from the bag, your order is the record of what shipped.

Take it with you

Point a phone camera at the code and this page opens there. It is the same address as the one printed on your box, so it is also what to show someone you are passing the board to.