Connecting a relay?

Ok so I connected my relay to a transistor and all and it produces a clicking noise whenever the base is HIGH. But now I need to know which pins to connect an LED or motor to. Just tell me the names not locations, I know where they are but not what to connect to them. Com, NC, or NO and such.

polishdude20: Ok so I connected my relay to a transistor and all and it produces a clicking noise whenever the base is HIGH. But now I need to know which pins to connect an LED or motor to. Just tell me the names not locations, I know where they are but not what to connect to them. Com, NC, or NO and such.

Com (common) and NO (normally open) are the relay switch contacts that one normally wires the load to be controlled to. That way when the arduino output pin goes HIGH the relay coil energizes and that causes the the Com and NO contacts to close, allowing current to flow in your controlled circuit.

Normally open means the state of the contact when no power is applied to the relay coil, it's so called 'shelf condition'.

That enough information?

Lefty

like here.

hookup_examples.jpg

There is a led on a board connected to pin 13. Just insert digitalwrite(13, high), whenever you need it

retrolefty:

polishdude20: Ok so I connected my relay to a transistor and all and it produces a clicking noise whenever the base is HIGH. But now I need to know which pins to connect an LED or motor to. Just tell me the names not locations, I know where they are but not what to connect to them. Com, NC, or NO and such.

Com (common) and NO (normally open) are the relay switch contacts that one normally wires the load to be controlled to. That way when the arduino output pin goes HIGH the relay coil energizes and that causes the the Com and NO contacts to close, allowing current to flow in your controlled circuit.

Normally open means the state of the contact when no power is applied to the relay coil, it's so called 'shelf condition'.

That enough information?

Lefty

so with the LED I connect the negative pin to com and positive to NO?

How about this?

motor_drive.jpg

so with the LED I connect the negative pin to com and positive to NO?

Of course not. Doesn't a LED need a voltage source to work? Doesn't an LED need a series current limiting resistor to set the LED current to a proper value for the voltage you are using to power it? Relay contacts can not provide voltage or current. Relay contacts act just like a simple on off switch, they are a passive component.

I assume the LED you are using is just an example load for the relay? I ask because you can drive most standard LEDs directly from a arduino digital output pin using a series resistor to set the current draw to 20ma or less. The transistor stage you are using could also drive a LED/resistor string without needing to use a relay at all. Relays are usually used where you need the higher voltage and current ratings that some relays contacts can provide.

CrossRoads posted you a nice schematic drawing (reply #5) showing a typical relay circuit including the load it switches on or off. Maybe you need to be more detailed on what you want to do and why you want to use a relay to do it>

Lefty

retrolefty:

so with the LED I connect the negative pin to com and positive to NO?

Of course not. Doesn't a LED need a voltage source to work? Doesn't an LED need a series current limiting resistor to set the LED current to a proper value for the voltage you are using to power it? Relay contacts can not provide voltage or current. Relay contacts act just like a simple on off switch, they are a passive component.

I assume the LED you are using is just an example load for the relay? I ask because you can drive most standard LEDs directly from a arduino digital output pin using a series resistor to set the current draw to 20ma or less. The transistor stage you are using could also drive a LED/resistor string without needing to use a relay at all. Relays are usually used where you need the higher voltage and current ratings that some relays contacts can provide.

CrossRoads posted you a nice schematic drawing (reply #5) showing a typical relay circuit including the load it switches on or off. Maybe you need to be more detailed on what you want to do and why you want to use a relay to do it>

Lefty

Ok crossroad's schematic helps but when I connect the LED to the comm pin and then to +5 v , and the NO pin to ground then the LED doesn't turn on even when I hear clicking. but, when I switch the ground from NO to NC then the LED ALWAYS stays on. Shouldn't it stay on only when the relay is off and not clicking? I basically want to connect a motor to the relay and such but I'm starting with an LED for basics

Ok crossroad's schematic helps but when I connect the LED to the comm pin and then to +5 v , and the NO pin to ground then the LED doesn't turn on even when I hear clicking. but, when I switch the ground from NO to NC then the LED ALWAYS stays on. Shouldn't it stay on only when the relay is off and not clicking? I basically want to connect a motor to the relay and such but I'm starting with an LED for basics

If your symptoms are accurate, something is wrong somewhere and it's difficult to troubleshoot over the net. Can you draw out a schematic of how you actually have everything (arduino, transistor, relay, led, resistor, external power)? Also a link to your relay datasheet might be helpful.

retrolefty:

Ok crossroad’s schematic helps but when I connect the LED to the comm pin and then to +5 v , and the NO pin to ground then the LED doesn’t turn on even when I hear clicking. but, when I switch the ground from NO to NC then the LED ALWAYS stays on. Shouldn’t it stay on only when the relay is off and not clicking? I basically want to connect a motor to the relay and such but I’m starting with an LED for basics

If your symptoms are accurate, something is wrong somewhere and it’s difficult to troubleshoot over the net. Can you draw out a schematic of how you actually have everything (arduino, transistor, relay, led, resistor, external power)? Also a link to your relay datasheet might be helpful.

ok I drew out a schematic sort of but I don’t think I have a datasheet for the relay.

untitled.JPG

ok I drew out a schematic sort of but I don't think I have a datasheet for the relay.

Then the relay manufacture name and model number of the relay?

Lefty

retrolefty:

ok I drew out a schematic sort of but I don't think I have a datasheet for the relay.

Then the relay manufacture name and model number of the relay?

Lefty

Midland Ross, Midtex Division, coil 24vdc , 190-22C100, B8211 .....thats all there is written on it.

KE7GKP:
If the coil is “24VDC” then it will almost certainly not operate with 5VDC.

so i guess that means it switches at 24vdc…

Pretty much a show stopper unless you can test with a 24vdc power source. If you do test at 24vdc be sure to remember to recalculate the LED's resistor size for the higher voltage.

Lefty

polishdude20:

KE7GKP:
If the coil is “24VDC” then it will almost certainly not operate with 5VDC.

so i guess that means it switches at 24vdc…

Yes, and at 5vdc, you are hearing a small click but the relay coil has not enough power to actually pull the armature and contacts closed.

Lefty

retrolefty: Pretty much a show stopper unless you can test with a 24vdc power source. If you do test at 24vdc be sure to remember to recalculate the LED's resistor size for the higher voltage.

Lefty

hmm well that's a bummer cause I don't have 24v to test with, oh well./

Back home after long day of coaching fencing ...

Yep, 24V coil relay not going to turn on with 5V across it. Surprised it even clicks.

CrossRoads: Back home after long day of coaching fencing ...

Yep, 24V coil relay not going to turn on with 5V across it. Surprised it even clicks.

ok thx anyways

Try a relay like this http://www.dipmicro.com/store/842A-1C-S-5VDC even get 10-20% discount on it if you can order now & be patient on delivery. (stock up a little - can get a ton of stuff for $20 with these guys). inexpensive shipping too, like $2.50 in the US.

CrossRoads: Try a relay like this http://www.dipmicro.com/store/842A-1C-S-5VDC even get 10-20% discount on it if you can order now & be patient on delivery. (stock up a little - can get a ton of stuff for $20 with these guys). inexpensive shipping too, like $2.50 in the US.

LOL, you might want to stay away from their 'bargain priced" 741 op-amp offering:

http://www.dipmicro.com/store/LM741CH