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The TK61 at an angle: a black board with a gold border, two tall black towers standing at the top with a 5 mm slot between them, an eight-pin comparator chip below, pairs of small resistors either side of it, a capacitor and an LED, a white speedometer drawing, lonely binary up the left edge, two round LEGO holes, 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/tk61
You have this

Infrared Speed Sensor

A GK105A slotted optical switch on a TinkerBlock board: an infrared beam across a 5 mm slot, judged by an LM393 comparator. Something in the slot reads HIGH; a clear slot reads LOW and lights a red LED. Put a slotted disc through it and count pulses for rpm, up to about 1,900 a second. VCC must be your board's logic voltage.

Something in the slot
HIGHclear reads LOW, LED lit
Slot
5mm wide, 8 mm deep
Counts up to
1,900pulses 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. SIGNAL is an LM393 comparator's output with a 10 kΩ pull-up: HIGH while something blocks the slot, LOW with the red LED lit while it is clear.

Product questions & answers ↓

The whole handbook10 articles · 50 minQuick referencePDF · 430 KBInfrared Speed Sensor model (GLB)GLB · 1.1 MBInfrared Speed Sensor CAD (STEP)ZIP · 1.4 MBGK105A datasheetPDF · sivago.com.cnLM393 datasheetPDF · datasheet.lcsc.comPinout and specsThe pin table, and the questions people ask first
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Infrared Speed Sensor

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Need another

Not on general sale yet. Reply to your order and we will sort out a spare — quote tk61.

Order or missing parts?

Email us or reply to your order, and quote tk61 — 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.