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Topic: Troubleshooting: I can hear relay clicking, but load doesn't transfer? (Read 4098 times) previous topic - next topic

tinman13kup

@tinman13kup

You have better eyes than mine.


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That's the new progressive bifocals at work. I can see the computer screen great (24"lcd), but as soon as I stand up and walk, I fall on my face....
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

larryd

Is this the pinout of the relay?

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tinman13kup

NO, NC, and C are the switching part of the relay. It's the reason you used the relay. C= Common pin, which is the 'common' pin regardless of the relay being on or off. With the relay off, the common pin connects to the NC (normally closed) pin. If you had 5v on the C pin, and the led attached to the NC pin, the led would stay lit until the relay is energized, which then connects the C pin to the NO (normally open) pin. If you had a different led on the NO pin, it would remain lit as long as the relay was energized.

The relay is energized with the coil. Placing 5V on one pin, and ground on the other causes the relay coil to become energized, and magnetic forces physically move contacts between the NO and NC pins.
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

tinman13kup

That's the pinout I was looking at. The rest was in Chinese. Seems the pin numbers are a bit goofy
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

larryd

If that is the pinout, the breadboard wiring does not look even close.


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rockorsmthn

Hmmm...the relay in the diagram is a DPDT type, and the one that came with my kit has only 5 pins.  Maybe that's the problem?  My kit doesn't match diagram?  I'm going to try to self smart myself on how a 5 pin relay works, and maybe figure it out.

larryd

Pin 1 and 12 may be combined as one pin.
This shows a SPDT relay.


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tinman13kup

Quote
I'm going to try to self smart myself on how a 5 pin relay works, and maybe figure it out.
It shouldn't be too hard with a multimeter. You would still have a NO,NC,C, and 2 coil pins
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

rockorsmthn

OK, I got the system to work...by eliminating the transistor/diode components.  I just put the pin from the Arduino to the + of the coil, grounded the -, and it worked fine.

I guess I need to learn more about how transistors work...the relay wasn't getting the signal from the transistor.  The middle "base" pin was getting .7v due to the 2.2k resistor, but only .01v was coming out of the "collector" pin.  Even when I lowered the resistance, and then bypassed the resistor entirely, the collector pin wasn't putting out enough voltage to activate the relay's coil.

I thought transistors were supposed to switch *and* amplify?  I must be doing something wrong.  What was the point of the transistor in this circuit anyway?

 

larryd

Quote
I just put the pin from the Arduino to the + of the coil, grounded the -, and it worked fine.
Glad you got things working.

However, if you power the relay from an Arduino output, there is a good chance you will damage your controller.

It is only safe to source/sink ~20mA on a output pin.

I believe the coil is 125 Ω therefore: 5V / 125 = 40mA


Learn how to use a transistor.


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rockorsmthn

Yep, learning how to use stuff like transistors and relays is precisely why I'm here!  I don't have a formal education in these areas (I studied, and now work in the foreign relations field) so I'm trying to catch up.  I get the reason for needing a transistor now; in addition to limits of Arduino pins for this test application, I'm going to need this skill to employ larger loads. 

I guess I need to figure out why this transistor isn't providing enough voltage (or amperage?) to activate the coil.  Now that I know what a coil trip sounds like...the sound I heard before was weak by comparison. 

The link I provided earlier has a different breadboard layout than the printed version that came with the kit.  I took a picture, and also a picture of everything hooked up before connecting transistor/diode to the relay.  If I were to just take the yellow signal wire and put it in breadboard row 10, and ground to row 9, that is what I had last night when it was working without a transistor.



https://imgur.com/a/3QKTQ


larryd

Oh my, that pinout for the relay is completely different.

Some transistors have different layouts for the same part number :(



You should strive to have nice neat wiring:


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rockorsmthn

SOLVED?!  I decided to just remove the 2.2k resistor that impeded the signal input to the transistor.  I replaced it with a 560 ohm resistor, and it works fine.  I also put a potentiometer in there instead of the resistor, and found there was a spot just past the failing point where I could hear the coil trying to move but not getting enough energy...just like with the 2.2k resistor.

Thanks for the help!  I learned a lot from this project.  I'm kinda bummed that there are no more in this kit.  I guess I'll look around for things to start building, freestyle.

sdturner

removed as redundant.

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