# Using a relay

Discussion in 'Electronic Basics' started by Jan Nielsen, Apr 24, 2007.

1. ### Jan NielsenGuest

I got a relay I cant figure out how to use, it as 5 connectors.

Its a finder 36.11.9.005.0000 5V(dc) 10A 250V(ac), I dont have a
datasheet for it.

The legs are like this
O_O 1_2
OOO 345

1=NO (Normally open?)
2=NC (Normally closed?)
3=no label
4=COM
5=no label

Anyone know how to use this, if its even something I can use

/Jan

2. ### John PopelishGuest

It looks like the 5 volt DC coil is connected between pins 3
and 5.

When unpowered, there should be a (normally) closed contact
between pins 4 and 2.

When 5 volts is connected to the coil, there should be a
contact closure between pins 4 and 1.

Check the resistance between pins 3 and 5, to see if it is a
reasonable resistance for a 5 volt coil. I would expect a
resistance between 25 and 100 ohms.

3. ### Doug MillerGuest

What you have is a single pole double throw (SPDT) relay. The coil is rated
for 5 VDC, and the contacts are rated for up to 10A at 250VAC.

NO and NC are, as you surmised, normally open and normally closed. Pins 3 and
5 would be the relay coil. Pin 4 (COM) is the common terminal, connected
(internally) to pin 2 (NC) when the relay coil is not powered, and to pin 1
(NO) when the coil is powered.

Specifically:
- no current across pins 3 & 5: pin 4 is connected to pin 2, and not to pin 1
- 5VDC across pins 3 & 5: pin 4 is connected to pin 1, and not to pin 2

Whether this is something you can use, depends on what your application for it
might be.

4. ### Jan NielsenGuest

Doug Miller skrev:
It works, thanks

seems wierd to have the com so close to the 5vdc, since it can be
dangerous voltage ?

/Jan

5. ### John PopelishGuest

I agree. I would not use this relay to switch line voltage,
unless the 5 volt supply was completely and safely isolated
from any chance of being touched, and was referenced to the
voltage applied to the common.

6. ### Jan NielsenGuest

John Popelish skrev:
Some time in the future I plan to switch line, but probaly with another
relay, its a jungle

I just need a Normally Open relay rated for a few amp 230V, and
triggered by 5vdc so I can do it from a logic circuit.

This one is rated for 24VDC too, so I will find some uses for it

Is that a Single Pole Single Throw - Normally Open then ?

/Jan

7. ### Doug MillerGuest

That's correct. Of course, a double-throw relay can be used in place of either
a single-throw NO or a single-throw NC -- you just leave the other terminal
open.

8. ### Pete DGuest

You cannot generally switch a relay from a logic circuit, logic circuit
will not provide enough mA, you will need a transistor between the
output and the relay

9. ### Jan NielsenGuest

Pete D skrev:
Ok, the pics I use can handle 20mA current draw on the out pins.
Still waiting for a new fuse to be able to measure amp, oops

/Jan

10. ### Pete DGuest

You have a point, I was thinking logic gates not MPU, just thought it
worth mentioning, as the original poster didn't know how to wire a
relay, i suspect not using a MPU.
Of course I could be wrong, I usually am ;-)

11. ### Jan NielsenGuest

Pete D skrev:
I am the OP
I started playing with electronics a few months ago, so even after a lot
of reading, its still pretty basic.

I am using the picaxe, not a "real" pic but a lot faster to code on
(mostly because I dont know c, cpp or assembly).

but yes its worth mentioning, I already killed one of their medium range
chips, not sure how, but resistors and making sure not to draw much more
than a relay, transistor or led from the pins could be a start

/Jan

12. ### Pete DGuest

Oh mine is pretty basic, after a mere 30 years, sokeep plugging away at it
If you want to program 'real' PIC's but want to stick to Basic, have a
look at www.crownhill.co.uk their Proton basic is very powerfull, there
is a free sample version with a limited no of lines of code.

13. ### Ross HerbertGuest

The Finder website isn't working so trying to get data is hopeless.
Nevertheless, The Relays-R-Us website in the UK does have some info on
the 36 series
http://www.relays-r-us.co.uk/webpages/products/finder_cat/36.htm