smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Bad readings from wind vane (direction)

Tue Aug 29, 2023 6:00 pm

Hi all,

I have set up my weather station following the official tutorial and all was functioning well on the breadboard, but after soldering onto the perma-proto HAT, the wind direction vane is giving strange readings. I have attached pictures: https://imgur.com/a/bZBsu7d

With the wind vane connected and rotating, the code

Code: Select all

adc.value * 3.3
returns very small values in all orientations (0.001...V), although there are very slight variations. The wind speed on the same RJ11 connector works just fine!

After checking the circuit what feels like a hundred times, I came to the conclusion that the MCP3008 was broken. However, running a cable from the 3.3V rail to the channel returns 3.3V!! (green annotation on this image: https://imgur.com/a/OzUpm3N )

After trying to fix this for the last few days, I am stumped on what to try next... Any help would be greatly appreciated.

Many thanks :D
Last edited by smtuk on Tue Aug 29, 2023 6:32 pm, edited 2 times in total.

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neilgl
Posts: 6879
Joined: Sun Jan 26, 2014 8:36 pm
Location: Near The National Museum of Computing

Re: Bad readings from wind vane (direction)

Tue Aug 29, 2023 7:21 pm

Using a multimeter, check the resistance of the wind vane in various (move by hand) directions.
It should be similar to that in the (official) data sheet https://www.argentdata.com/files/80422_datasheet.pdf but at 3V3 not 5V.
688 ohms up to 33k ohms?
I am looking here https://projects.raspberrypi.org/en/pr ... -station/7

trejan
Posts: 6636
Joined: Tue Jul 02, 2019 2:28 pm

Re: Bad readings from wind vane (direction)

Tue Aug 29, 2023 7:29 pm

Something is wrong with R1. It is probably not connected properly. You'll have to carefully trace out how you've wired your board.

smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Re: Bad readings from wind vane (direction)

Tue Aug 29, 2023 8:16 pm

trejan wrote:
Tue Aug 29, 2023 7:29 pm
Something is wrong with R1. It is probably not connected properly. You'll have to carefully trace out how you've wired your board.
Please could you explain what R1 is - is it the resistor? I’m not sure what I’m looking for.

Apologies

trejan
Posts: 6636
Joined: Tue Jul 02, 2019 2:28 pm

Re: Bad readings from wind vane (direction)

Tue Aug 29, 2023 10:26 pm

smtuk wrote:
Tue Aug 29, 2023 8:16 pm
Please could you explain what R1 is - is it the resistor? I’m not sure what I’m looking for.
Yes. The resistor. The one talked about on https://projects.raspberrypi.org/en/pro ... -station/7

smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Re: Bad readings from wind vane (direction)

Wed Aug 30, 2023 3:05 pm

trejan wrote:
Tue Aug 29, 2023 10:26 pm
smtuk wrote:
Tue Aug 29, 2023 8:16 pm
Please could you explain what R1 is - is it the resistor? I’m not sure what I’m looking for.
Yes. The resistor. The one talked about on https://projects.raspberrypi.org/en/pro ... -station/7
I've taken off the resistor and replaced it with a new one, checked the wiring around this area again (to match the final circuit diagram).

Still reading miniscule voltages with adc.value*3.3 :oops:

Code: Select all

$ python3 wind_direction_byo.py
0.030630190522715893
0.011284807034684995
0.0016121152906691805
0.014509037616023356
0.014509037616023356
0.014509037616023356

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neilgl
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Joined: Sun Jan 26, 2014 8:36 pm
Location: Near The National Museum of Computing

Re: Bad readings from wind vane (direction)

Wed Aug 30, 2023 10:35 pm

What are the resistance readings from the multimeter with the vane in various directions?

smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Re: Bad readings from wind vane (direction)

Thu Aug 31, 2023 7:05 am

neilgl wrote:
Wed Aug 30, 2023 10:35 pm
What are the resistance readings from the multimeter with the vane in various directions?
I’ve got a multimeter coming in the post later today. I’ll post the results here when it arrives :D

smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Re: Bad readings from wind vane (direction)

Thu Aug 31, 2023 4:48 pm

neilgl wrote:
Wed Aug 30, 2023 10:35 pm
What are the resistance readings from the multimeter with the vane in various directions?
I was trying to fix the weather station again this afternoon, and managed to fix readings for the wind direction. 🎉

Unfortunately, I've got another problem... when it was raining this afternoon, I realised that I'm not getting any readings from the rain bucket either. :cry: Is there any way I can test this in a similar way to the wind direction?

Thanks again for the help!

trejan
Posts: 6636
Joined: Tue Jul 02, 2019 2:28 pm

Re: Bad readings from wind vane (direction)

Thu Aug 31, 2023 4:56 pm

smtuk wrote:
Thu Aug 31, 2023 4:48 pm
I was trying to fix the weather station again this afternoon, and managed to fix readings for the wind direction. 🎉
What was the problem?
smtuk wrote:
Thu Aug 31, 2023 4:48 pm
Unfortunately, I've got another problem... when it was raining this afternoon, I realised that I'm not getting any readings from the rain bucket either. :cry: Is there any way I can test this in a similar way to the wind direction?
The rain sensor is just switch inside that closes then opens again when the bucket fills up and tips over. If you take off the top then you can move the bucket. Your multimeter on continuity mode across the output should beep when it tips over.

The guide says it is connected between GPIO6 and ground.

smtuk
Posts: 6
Joined: Tue Aug 29, 2023 5:38 pm
Location: Coventry, UK

Re: Bad readings from wind vane (direction)

Sat Sep 02, 2023 1:15 pm

What was the problem?
Just poor soldering, started working after re-soldering some components and adding some insulating tape in places.


Turns out the rain meter wasn’t broken, it just wasn’t raining enough! 0.27mm of rain is more than it sounds


Thanks for the help everyone - I have my weather station installed in a pretty good location now!
https://pasteboard.co/jWVjSET1Wabt.jpg

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