Electronics > Electronics
Beginner question : Connecting relay
h3ro:
I have a few questions about how to connect a relay:
Question 1:
Should the circuit with the low voltage be connected to the long side (8 and 5)?
Question 2:
A friend of mine said that in order to make my relay work correctly I have to connect a diode parallel to the relay. Is this correct? And if it is, is this the right way to do it (where should +/- go)?
Sorry for all the stupid questions I have, but I really want to learn this. Im thinking of getting a book :)
airman00:
Question #1: pins 8 and 5 are for the relay coil and the other pins are for the switch. The way a relay works is that a certain voltage given to the coil will trigger a reed switch. This means that you can have a low voltage control a high voltage without being connected to the high voltage. Pins 8 and 5 are NOT connected to pins 2 and 4 in any way. They are two separate entities. However, the coil can control the switch without touching it. ( tell me if im confusing, i tried to make it simple, i think :P lol )
Question #2: A relay can be given + or - on either pin. You can have pin 8 be + and 5 be - or pin 5 be + and pin 8 be -. Those are the only two setups possible for a relay to work. The diode in parallel will prevent backlash from the electromagnetic coils (i think) and will protect the microcontroller.
A diode blocks positive voltage on the black side of it. This means that positive voltage cannot flowthrough the black part of it. However negative voltage can, so this makes your relay be triggered from only one setup and not the other. This can be useful in R/C.
Hope I helped...
,Eric
HDL_CinC_Dragon:
Hate to just randomly step in here but damn airman, that helped me too and I wasnt even looking for that info lol
We need a Kudos system on here heh
h3ro:
Thank you for you great help Airman00, but I still manged to do something wrong.
Here is my circuit:
The LED does work, and I have tried turning the Diode around. Still dont work.
Does someone have some good ways of solider the relay to the board? I am having big trouble with it, as the legs of the relay is to short to go fully through the holes in the board.
Ro-Bot-X:
Man, you're doing something wrong there...
Take a look at this pdf document, it explains pretty well how relays should be connected to any microcontroller.
http://www.kronosrobotics.com/Anotes/Relays.pdf
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