Difference between a relay and a transistor?

[daviddoria]

I am putting in a keyless entry system in my car and i thought of this question. Can anyone enlighten me?

also, has anyone ever done this, or care to answer a few questions on the topic?

 

[kinjalgp]

1) Relay provides galvanic isolation between driving circuit and load whereas transistor does not.
2) If something gets short on your load side, your circuit will be protected it ifts relay based otherwise everything will blow up.
3) Transistors have better swithing speed.
4) Transistors does not generate high voltage spikes during switching as relay does across its coil due to falling magnetic field( can be solved using free-wheeling diode).
5) Transistors require less current to operate than relay.

 

[Sebi]

I use the relay only when don't know what kind of voltage will switching (AC or DC).
With optocoupler and transistor i can make also galvanic isolation.

 

[bogdanfirst]

relays are better when having high current, because a 30mA relay/12V can switch 10A, but if you were to use a transistor you will loose lots of power like heat

 

[daviddoria]

ok, so i bought some DF005 relays.

there are 5 pins,
87 & 87a (power to lamps)
30/51 (Fused power from Battery)
86 (to switching means)
85 (to ground)

are those 8* numbers some sort of standard?

also, so i connected my keyless entry output to 86, my +12v to 30/51, my ground to 85, and the actual lock motors to 87. i left 87a empty

does this sound correct?

i can't find ANYTHING about this relay, where is a good relay schematics place?

 

[bogdanfirst]

how are they placed on the relay?
it they are like 4 in the corneres of a rectangle and one wich is closer to 2 of the 4 then that pin in the one that is connected to n.c.(normally closed) swotch
the other 2 near it are to the coil and the last 2 are for n.o. abd n.c.

 

[daviddoria]

i uploaded a picture of the back of the package for you.

http://www.bandtank.com/~calculusap/relay.gif

now what do you mean by the normally open and closed and stuff? i know what the term means, and i heard the guy at the auto store mention it, but in this case, what is it refering to?

 

[Phasor]

also, so i connected my keyless entry output to 86, my +12v to 30/51, my ground to 85, and the actual lock motors to 87. i left 87a empty

From what I can ascertain, you have it correct. 8)

 

[scubasteve261]

there are 5 pins,
87 & 87a (power to lamps)
30/51 (Fused power from Battery)
86 (to switching means)
85 (to ground)


try this:

leave output on 86, leave +12v on 30/51 but also put +12v to 87, leave ground on 85, and put actual lock on 87a... this should fix your problem

 

[SPDCHK]

Yet another DEAD post (2003) revived

 

[crutschow]

So do the newbies go scrounging through old posts to see ones they'd like to answer for some odd reason?