SANAA
UREMBO NA USTAWI
UJANJA
UTAMADUNI NA HISTORIA
BURUDANI
MAZINGIRA
CHAKULA NA VINYWAJI
UHANDISI WA KINYUME
SAYANSI
MICHEZO
TEKNOLOJIA
VAZI
Youblob (generated from this blueprint's notebook) · CC0
The Time-Delay Relay: Switching a Set Time Later
Many control jobs need a pause: start the motor, wait until it is up to speed, then load it; stop the burner, then run the fan a little longer to clear the heat; light the stairway, and switch it off a few minutes later. The time-delay relay does it. An on-delay closes its contact a set time after it is energised; an off-delay keeps its contact closed a set time after it is de-energised.
The earliest timed their delay with a dashpot — a piston pushing air or oil through a small adjustable hole — or with a bimetal warmed by a heater. Electronic relays charge a capacitor through a resistor and switch when it reaches a threshold.
This rung works out an RC delay and why capacitor tolerance and leakage limit it, draws on- and off-delay timing, and builds an on-delay relay with a 555 timer.
Mwanzo
About 3 hours
Maagizo
1
1
The RC delay and its limits
The RC delay and its limits
Inapakia daftari la Jupyter…
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Build a 555 on-delay relay
Build a 555 on-delay relay
On a breadboard wire a 555 as a monostable from a 9–12 V supply: pins 4 and 8 to the supply, pin 1 to 0 V, a resistor R from the supply to pins 6 and 7 joined, a capacitor C from pins 6 and 7 to 0 V, 10 nF from pin 5 to 0 V, and pin 2 (trigger) held high through 10 kΩ with a push button to 0 V.
Pin 3 goes high for 1.1 RC after the button is pressed. Drive an NPN transistor from pin 3 through 1 kΩ, with the relay coil between the supply and the collector and a diode across the coil, reversed, to catch the coil's kick. Wire an LED through the relay's contact.
Time the relay with a stopwatch for three values of R. Plot delay against R: a straight line whose slope is 1.1 C. Swap in a second capacitor of the same marked value and watch the delay change — its tolerance.
Vifaa kwa hatua hii:
Saketi iliyounganishwa ya kipima muda NE5551 kipande
Transista ya NPN1 kipande
Rile ya SPDT1 kipande
Dayodi1 kipande
Seti ya Kapasita1 kipande
Seti ya vizuizi vya umeme1 kipande
Kitufe cha kubonyeza1 kipande
LED ya mm 51 kipande
Bao la Majaribio1 kipande
Nyaya za Kuunganisha1 kipande
Rile ya kuchelewesha muda1 kipandeZana zinazohitajika:
Chanzo cha nishati ya mkondo wa moja kwa moja
Kipima-umeme cha aina nyingi
Saa ya kupima muda3
3
The relay it times
The relay it times
A time-delay relay is a relay with a clock in front of it. The embedded blueprint shows the electromagnetic relay it drives.
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A timer that times wrong
A timer that times wrong
Time-delay relay faults.
Flow
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5
Context and honest limits
Context and honest limits
Pneumatic dashpot timers, thermal timers and motor-driven timers served machine and process control for decades; the 555 timer IC, introduced in 1972, made cheap electronic delays universal, and programmable controllers now provide timers in software.
**Honest limits.** An RC delay drifts with temperature and with the capacitor's age. For accurate long delays use a crystal-timed or counting timer. A relay switching mains loads must be wired and enclosed by someone qualified; the bench build stays at low voltage.
Vifaa
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Zana Zinazohitajika
3- Kishikilia Nafasi
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Blueprint zinazohusiana
Blueprint hizi zinashiriki maarifa — mbinu, vifaa au kanuni
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