Problems with RFM69 and DHT11

Using Arduino LEDs and Multiplexing
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Hello!

I'm very new to all this so please be kind!

I've 2 ardunio Uno's wired to rfm69's with a level converter in between.
Also attached is a DHT11 to gather temp data and send it back to a pi which updates a Google sheet.

All was working perfectly!

However I wanted to create another node, this time using a 5v nano.

They only has two grounds instead of 3. Whilst waiting for it to be delivered I soldered the ground pin from the DHT11 onto the ground from level converter on the 3v side. (see attached picture, I've taken out the other connections as I know they work for simplicity).

It is still all connected to the Uno but now it doesn't work.
The code runs once and then stops, it doesn't send anything. It is reading the correct temperature from the DHT11.

Why is this happening? I think it must have something to do with the ground pin connection from the DHT11... where should I connect it if it in the wrong place?

Any help would be much appreciated.

Thanks,

Ben

rfm69.jpg
rfm69.jpg929×521 32.9 KB

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They only has two grounds instead of 3.

This is no problem just chain the ground from one device to the other. Or solder two wires to the one pin.

All grounds must be connected together.

I am not clear what changes their have been between the setup that works and the one that doesn't. What does the schematic show the one that works?

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Hello!

Thanks for your help.

So the schematic is the one that doesn't work. The one that does work, the ground from the DHT11 (s1 on schematic) goes to the available ground on the Arduino.

So it doesn't matter chaining grounds together of devices that have different voltage?

Thanks very much for your help.

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So it doesn't matter chaining grounds together of devices that have different voltage?

Correct. Not only does it not matter, it is essential for things to work.

5

Thanks for your help, I realized that in all my connecting and disconnecting of the RFM69, I'd gotten two wires the wrong way round. Doh!

Now they are correct is has stopped behaving wierdly, but I have a new problem but I'll make a new post for that!

Thanks again

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