Sensing and 支配（する）／統制する for hobbyists and schools: 軸 Encoders
If you have a 天候 先頭, you will need a 軸 encoder. 軸 encoders tell you how far around a 軸 has been turned. In practice, other techniques are 普通は used for 容積／容量 支配（する）／統制するs, but they could also be "read" using a 軸 encoder. その上の 負かす／撃墜する this page, I will also discuss 手段ing the 速度(を上げる） of a 軸's rotation.
One approach.. not a very good one, on several counts,... but you may 遭遇（する） it, is to stick the 軸 to a potentiometer. Turning the 軸 turns the potentiometer, so the 抵抗 it is showing 暗示するs the position of the 軸, i.e. how far from "home" it has been 回転／交替d.
One of two good approaches, 井戸／弁護士席 ふさわしい to 天候 先頭s:
Attach two transparent レコードs to the 軸, at 権利 angles to it. Divide one into two halves, the other into four ４半期/4分の1s. Paint half of the 2 part レコード 黒人／ボイコット, and 補欠／交替の／交替する ４半期/4分の1s of the other. 開始する a slotted opto detector to look at each レコード. Call the detectors "A" and "B". (A slotted opto detector consists of two small 地位，任命するs. On one you have an LED 向こうずねing light に向かって the light detector 機動力のある on the other.)
With the above, as you 回転／交替 the 軸, at one point both detectors will find the gap between the 地位，任命するs 封鎖するd; at another A is 封鎖するd, B isn't; at another B is 封鎖するd and A isn't; the last 可能性 is that both detectors find nothing 封鎖するing the light. With two レコードs the rotation of the 軸 can be 解決するd to 90 degrees.
If you 追加する another レコード, you can 二塁打 the 決意／決議. If you do decide on three (or more) レコード system, be sure to learn about "Gray codes". By using them, you design problems out of your 装置. Only one bit changes between any two positions of the 軸. If this is not the 事例／患者, 誤った readings can arise as one bit changes わずかに before a different one changes. (To 会社にする／組み込む what I assume was something discovered by a Mr. Gray only 要求するs that you place the opaque 部門s in a pattern that might not have occurred to you.) Use Google to search on "gray code" tutorial and you can find out more. I liked yagni.com/graycode/
For a four レコード encoder, the Gray code numbers are: 0000, 0001, 0011, 0010, 0110, 0111, 0101, 0100, 1100, 1101, 1111, 1110, 1010, 1011, 1001, 1000
A variation on the above:
If you want to 避ける the hassle of the レコードs and using slotted opto detectors, and you can find some 満足な reflective detectors, you can use a different geometry the same way. A reflective detector is like the slotted detector, but instead of 向こうずねing the light across a gap, it 向こうずねs out from the 装置. If something shiny is in 前線 of the detector, the light is bounced 支援する to the sensor, and the thing is "seen".
First, you somehow 増加する the 直径 of part of the 軸 to about 2cm. It also needs to be 十分に shiny that the reflective detectors will "see" the 軸. This section needs to be as high as three of your detectors if you want to 解決する the 軸 position to 45 degrees.
Instead of 部門s of the レコードs 存在 made opaque, you 単に make 類似の 部分s of the 軸 非，不，無-reflective.
I have woefully short-changed gray code 計画／陰謀s here. They are very 冷静な／正味の, and very useful. I'd know those things for years... but it was only 11/21 that I discovered that you can have a six (or いっそう少なく, or more) bit gray code in a SINGLE BAND of "ons" and "offs"! You'll need six detectors, but that's the same as you would need if the 禁止（する）d of ons and offs were "spread", one 禁止（する）d per bit.
What you need is there. I'm afraid I have to 追加する that when I tried to download the .pdf 11/21 very 汚い strange things happened. Be sure you have a good anti-malware 控訴 in place and up to date if you try to download the .pdf. (Let me know how you get on, if you do? 接触する 詳細（に述べる）s below, and please について言及する this page's URI if you 令状... (SheSof/)sc2se.htm
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Another approach... not 井戸／弁護士席 ふさわしい to 天候 先頭s, but the basis of most ball mice, and many 容積／容量 支配（する）／統制するs. A good way to interface a rotary 支配（する）／統制する which will be used to tell your system to turn something up or 負かす／撃墜する.
If you are not so much 利益／興味d in the 絶対の position of a 軸, but you are 利益／興味d in 選ぶing up and 手段ing rotation 今後s or backwards, you can get high 決意／決議 やめる easily from the に引き続いて approach. You can get the mechanical elements by cannibalizing an old ball-type mouse.
The basic idea is やめる simple: You attach to the 軸 one レコード, 類似の to the ones used in the previous approach to 軸 encoding. However, this レコード has many 禁止（する）d of （疑いを）晴らす and opaque 構成要素.
You fit not one, but two slotted detectors to "watch" the turning of the レコード. Each 移行 from transparent to opaque 暗示するs a slight turn.
The clever thing about using two detectors is that you can tell which way the レコード is turning by looking to see which "sees" the 移行 from （疑いを）晴らす to transparent first. When the レコード 回転／交替s clockwise, it will be one, and when counterclockwise, the other. I'm sure Google can find you good descriptions of this with illustrations.
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And novel approach...
The 見解／翻訳／版 3 Dallas/ AAG 勝利，勝つd direction sensor 器具／実施するs an extraordinarily clever way to encode the 軸's position, as I'll 輪郭（を描く） in a moment. Just before I do, let me について言及する that earlier 見解／翻訳／版s of the 装置 were much いっそう少なく clever. The 軸 had a magnet. There were 8 reed switches. The 見解／翻訳／版 3 装置 uses the same magnet and reed switches. However, the 早期に 装置s were blunt 器具s. The system relied on 8 separate 半導体素子s which were switched on or off by the magnet. One bit of "cleverness" was there, and is still part of the system: When the magnet is half-way between two reed switches, they are both switched on, so 8 switches can 解決する 16 positions.
The 見解／翻訳／版 3 system relies on 4 voltage 手段ing 装置s (ADCs) to sense the 明言する／公表する of the 8 reed switches. No two 隣接する reed switches are on the same ADC. When no magnet is 近づく one of the switches, the ADC it is connected to "sees" 5 volts. When a magnet is 近づく one of the switches, the ADC "sees" either 0 volts or about 2.5 volts. This is how each ADC can "watch" two switches.
Not "important", but maybe 利益／興味ing: If you think about it, you will notice that this system is using a base 3 number system rather than the ありふれた base 2 (binary) system which has made such a difference to what we can do easily, reliably.
手段ing Rotation 速度(を上げる）
.
You can use opto detectors, just as you did in （悪事，秘密などを）発見するing the 軸's degree of rotation.
A better bet is probably to 開始する a magnet on the 軸 and put a reed switch nearby, such that the switch opens and の近くにs once for each time the 軸 回転／交替s.
In place of the reed switch, you might use a 半導体 同等（の） called a Hall 影響 switch.
Once you have a turning-軸-operated switch in place, you 単に count switch 開始s or closings to 決定する rotation 速度(を上げる）. You could, of course, build a system that relied on the computer to look at the 明言する／公表する of the switch. This 証明するs to be messy in practice. Under that シナリオ, you have two choices: You can time how long it is between one 開始 and the next, or you can count the number of 開始s in some constant time interval, e.g. 開始s per second.
A little more work with your soldering アイロンをかける will more than 返す you. You will be able to relieve the computer of a 広大な／多数の／重要な 取引，協定 of 過程ing work.
The extra electronics is a "反対する". One 味方する is connected to your reed switch, the other is connected to the computer. Inside the 反対する is electronics that keep 跡をつける of how many times the switch has been operated, and make that number (count) 利用できる on request to the computer. No longer does the computer have to "watch" the switch continuously, for 恐れる of "行方不明の" an 開始. I have written a separate page about 反対するs for you.
A company called Posital had and 利益／興味ing illustration on the に引き続いて page 利用できる at 7/10. It was more 利益／興味ing 支援する in 2005, if I remember rightly, but is now a pop-up, and "悪賢い" and "glossy". You want message? No, no- medium is the thing these days, isn't it? The link I've given is 深い, the company's main page if the previous link doesn't work.
A 関係のある 事柄
If you are making a 勝利，勝つd 速度(を上げる） or 勝利，勝つd direction sensor, or another 装置 which will be a long way from it's 監視するing computer, a suggestion:
Between the reed switches, Hall 影響 装置s or opto detectors "looking at" your 軸 and the computer, there will be long wires. At the end of the wire 近づく the computer, 追加する an opto-isolator. Most voltage spikes which arise in the long wires will be kept out of your (推定では expensive!) computer.
Optoisolators are simple little 装置s. They consist of an LED and a photo transistor, embedded within a bit of plastic. They are not "connected", but when the LED is on, the phototransistor 行為／行うs.
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