Operating relay module

Other Hardware General Electronics
1

So I had a relay module with a built in optocoupler, which I applied in a setup which I don't have anymore. Stupid thing I did was I did not take a picture of the wiring which was working fine.

Now this relay module switches when its input pins are pulled low via a microcontroller.

But, for some reason (possibly EMF considerations) I had externally pulled these pins low too, via a 10K resistor.

But this seems counterintuitive to me now. Why would I pull it low...wouldn't that just cause the switching action?

What am I missing or forgetting?

2

Shouldn't the resistor pull up the input?
The internal pullup is rather weak.
This reduces energy consumption, but increases susceptability to emi.
So an extra pullup may help.
Better go for lower value...4k7?

3

The 10K resistor will not draw enough current in order to activate the relay.
As to why you had a resistor to ground, only you would know.

Which Arduino are you using?

Are you referring to this from your other topic on relay connections

1 Like
4

This is probably the schematic of your relay module.

modulo_rele_2_2_desenho
modulo_rele_2_2_desenho652×313 29.9 KB

5

Which input pins are you referring to? From the module or from the microcontroller.

If it is from the module, this module actually switches when its input pins are pulled down.

6
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7

Yes the two are linked but also not. My previous question was for a different problem, and not making much sense, so I changed the approach and took the more conventional one of driving the relay module directly from the Arduino.

In amy ways, that concern is resolved.

Here, I had pulled the input pins on the relay module down because I had felt that the pins were floating and switching when they shouldn't.

I just didn't understand why they weren't being read as pulled low when external pull down of 10k was soldered there and Arduino was programmed to pull them high.

Thanks for explaining this.

8

  • We cannot know why you did this. :woozy_face:

  • You are ignoring requests for more information.

  • Here is one way of connecting a similar module using a 3V3 controller and a BJT.

image
image1380×690 160 KB

9

You are wellcome.

10

Hi Larry. I am not ignoring the request for more information. I just don't remember more of my design which I had done some time back. All I remembered was that I was pulling the input pins on the module low with 10K resistors because these pins were floating due to emf, and that had seemed counterintuitive to me now. But Jim has explained now why pulling those pins down with 10K resistors did not trigger the switching action (Switching in this module happens when they are pulled down) when Arduino (I am using Nano) was pulling the pins high.

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