Malay sa Relay na Yan

Malay sa relay na yan. =( A BIG NO NO. (part 2)

We can say that a relay is A SPECIAL KIND of switch.

Here are two examples kung bakit kailangan natin ng relay.


On the upper part is a diagram for automobile circuit.

Pag naka-on ang ignition key ng sasakyan, it allows electricity to flow to the starter solenoid ( yun ang relay) which then connects the battery to the starter motor.
So why do we need the "middle man" relay? Pwede ba nating e-eliminate na lang ito at iconnect ang ignition wires sa +battery terminal at yung isang wire sa motor starter naman?
The important point here is that the electromagmet is using a small amount of current to control a large amount of current to the starter motor. (Remember that the electromagnet and the switch areNOT connected electrically).

Have you noticed that all of the wires (except the ignition wires) are purposely drawn with thick lines? That's because some circuits (like the starter) require tremendous amount of current. (kaya kailangan din ng mas malaking kable).

(If you look at an automobile's battery cables, you will notice they are quite thick.)
Pag maliliit na wire ang ginamit natin, di nito kakayanin ng insulation nya ang mataas na current, kaya masusunog ito, at uusok.
We do have a second choice. Pwede tayong gumamit ng malalaking kable mula sa battery gamit
ang heavy duty ignition switch. However, do you think it would be easy to squeeze cables into thesteering column and squeeze in a heavy duty switch too?
BURGLAR ALARM SYSTEM

Referring to the diagram, let's trace theelectrical flow. 

Kung makikita nyo, mula pt. V2, pupunta sa "C". Mula sa negative battery terminal, pupunta sa V1, tapos sa V2, at dahil tuloy tuloy ang alarm loop, pupunta sa "C" at pagkatapos ay sa positive battery terminal na. Sa circuit loop na 'to, dadaloy ang current sa electromagnet causing the common terminal to switch contact mula "C" patungo sa "B" At dahil walang contact sa A, the siren will not make any SOUND.

Pwedeng lagyan ng isa o mas maraming magnetic switch in series sa alarm loop para magkaroon ng warning signal o alarm sound. Kaya lang, ang mangyayari dito, tuloy-tuloy nga ang kuryente mula pt "C" to pt. "A" hanggang sa siren, NGUNIT HINDI sa electromagnet.

Alarm Circuit 1 does suffer from one serious flaw. Can you see what it is? Pag nareconnect ulit ang alarm loop, madidisconnect lang ang siren. This is a VERY IMPRACTICAL WAY AND NOT RECOMMENDED TO ANY ALARM SYSTEM. The siren goes off! Kung nabuksan ng isang magnanakaw ang pintong me magnetic switch nang pwersahan, sasarhan lang nito ulit ang pinto at di na tutunog ang siren.

Para maging efficient sa tao, kinakailangan natin ng isang device na pagproprovide ng additional contacts na mag-aallow ng isang circuit na gumana habang ang isang circuit ay putol. At yun ang nagagawa ng transfer mechanism ng common contact ng isang relay. =)