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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.
高级
Unknown
说明
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.
此步骤所需材料：
铝管1 housing
未知金属1 measuring shaft
滚珠轴承1 个
未知材料1 contact head所需工具：
金属车床
手摇钻
未知尺寸2
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.
此步骤所需材料：
未知材料1 slotted disk
LED 灯珠组合1 light source
光电二极管（BPW34）1 photodetector
电阻1 套所需工具：
手摇钻3
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.
此步骤所需材料：
印制电路板1 个
石英晶体1 个
逻辑集成电路组合1 divider, AND gate, counter, latch, reset
七段显示驱动器1 个
四位七段数码显示器1 个
焊锡丝1 as needed所需工具：
电烙铁4
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.
此步骤所需材料：
电池1 个
按钮1 个所需工具：
电烙铁材料
15- 1 housing占位符
- 1 measuring shaft占位符
- 占位符
- 1 slotted disk占位符
- 1 light source占位符
- 1 photodetector占位符
- 1 套占位符
- 1 个占位符
- 1 个占位符
- 1 divider, AND gate, counter, latch, reset占位符
- 1 个占位符
- 1 个占位符
- 1 as needed占位符
- 1 个占位符
- 占位符
此蓝图制作
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