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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.
Erfahren
Unknown
Anweisungen
1
1
Make the housing and measuring shaft
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.
Materialien für diesen Schritt:
Aluminiumrohr1 housing
Unbekanntes Metall1 measuring shaft
Kugellager1 Stück
Unbekanntes Material1 contact headBenötigte Werkzeuge:
Metalldrehmaschine
Handbohrer
Unbekannte Maße2
2
Make the pulse generator
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.
Materialien für diesen Schritt:
Unbekanntes Material1 slotted disk
LED-Sortiment1 light source
Fotodiode (BPW34)1 photodetector
Widerstand1 SetBenötigte Werkzeuge:
Handbohrer3
3
Build the counting circuit
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.
Materialien für diesen Schritt:
Leiterplatte1 Stück
Schwingquarz1 Stück
Logik-IC-Sortiment1 divider, AND gate, counter, latch, reset
Siebensegment-Anzeigetreiber1 Stück
Vierstellige Siebensegmentanzeige1 Stück
Lötdraht1 as neededBenötigte Werkzeuge:
Lötkolben4
4
Power it and measure
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.
Materialien für diesen Schritt:
Batterie1 Stück
Drucktaster1 StückBenötigte Werkzeuge:
LötkolbenMaterialien
15- 1 housingPlatzhalter
- 1 measuring shaftPlatzhalter
- Platzhalter
- 1 slotted diskPlatzhalter
- 1 light sourcePlatzhalter
- 1 photodetectorPlatzhalter
- 1 SetPlatzhalter
- 1 StückPlatzhalter
- 1 StückPlatzhalter
- 1 divider, AND gate, counter, latch, resetPlatzhalter
- 1 StückPlatzhalter
- Platzhalter
- 1 as neededPlatzhalter
- 1 StückPlatzhalter
- Platzhalter
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