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Digital Tachometer: Hand-Held Contact Type That Holds Its Reading (Sugiyama, Shimpo, US 4,000,465, 1976)

Yasumichi Sugiyama · Public domain (US patent drawing)

أنشأه

3. نوفمبر 2026

Digital Tachometer: Hand-Held Contact Type That Holds Its Reading (Sugiyama, Shimpo, US 4,000,465, 1976)

A hand-held digital tachometer. You press the contact head on its shaft against the end of a turning shaft and push the thumb button; a slotted disk inside chops a light beam into pulses, and the pulses counted in a fixed time, set by a quartz clock, appear in the window as the speed. A latch holds the reading after you take the tachometer away, so you can read it even where you could not see the window while measuring. Result: a contact tachometer that shows revolutions per unit time and keeps the last reading. Source: Y. Sugiyama (Shimpo Kogyo), US 4,000,465 (1976). Unknown: the number of holes, the clock, the gate time and the circuit details. Picture: the patent drawing.

متقدم

Unknown

التعليمات

Make the housing and measuring shaft

Make a cylindrical housing to hold in one hand, with a window in its side for the reading and a push button for the power switch where the thumb falls. Run a measuring shaft out of the front end in bearings and fit a contact head on its tip to press against the shaft being measured. Not given: materials, sizes. Ours: aluminium tube, a ball bearing.

المواد لهذه الخطوة:

أنبوب ألومنيوم1 housing

معدن غير معروف1 measuring shaft

محمل كُريّ1 قطعة

مادة غير معروفة1 contact head

الأدوات المطلوبة:

مخرطة معادن

مثقب يدوي

أبعاد غير معروفة

Make the pulse generator

Fix a disk on the measuring shaft with a ring of small holes evenly spaced near its edge. Put a light source on one side of the disk and a photodetector on the other: each hole passing makes one pulse. Shape and amplify the pulses. Not given: the number of holes. Ours: an LED and a photodiode.

المواد لهذه الخطوة:

مادة غير معروفة1 slotted disk

تشكيلة مصابيح LED1 light source

ثنائي ضوئي (BPW34)1 photodetector

المقاومة1 طقم

الأدوات المطلوبة:

مثقب يدوي

Build the counting circuit

Divide a quartz oscillator's clock down to gate pulses one unit of time long. Pass the measurement pulses through an AND gate during each gate pulse into a counter. At the start of each gate pulse a reset pulse clears the counter. After the gate pulse ends, the first measurement pulse that arrives triggers a latch pulse that loads the new count into the display. If the head has been taken off the shaft, no pulse arrives, no latch pulse is made, and the display keeps the last reading until the next measurement or until the power is switched off. Not given: the clock frequency and gate time. Ours: logic ICs and a seven-segment display.

المواد لهذه الخطوة:

لوح دارة مطبوعة1 قطعة

بلورة كوارتز1 قطعة

تشكيلة دوائر منطقية متكاملة1 divider, AND gate, counter, latch, reset

مشغل الشاشة سباعية المقاطع1 قطعة

شاشة سباعية المقاطع بأربعة أرقام1 قطعة

سلك لحام1 as needed

الأدوات المطلوبة:

كاوية لحام

Power it and measure

Fit the battery and the thumb button as the power switch. Press the contact head against the end of the turning shaft so it turns with it, push the button, and read the revolutions in the window, now or after you take the tachometer away.

المواد لهذه الخطوة: