DIY Greenhouse data logger – update 1 week in.

Electronics, Gardening and Lifestyle

DIY Greenhouse data logger – update 1 week in.

April 8, 2019 DIY Gardening 0
greenhouse data logger update coverimage


It used to be that i’d head to the greenhouse with a pocket full of seeds and cup full of coffee, these days its a laptop and pocket full of cables. It’ll be worth it though just wait!!!

It’d been 4 days since i plugged my little test data logger in and i was excited to see what was waiting on the memory card.

Power Drain

I was a bit worried about how this would drain my small solar set up, but currently it doesn’t appear to be an issue.

Friday morning i got up early before the sun had hit the greenhouse to see what the voltage was like, down to just under 13.5v which was great to see. I’d had this horrible feeling that i’d get back and the batteries would be toast, but the sleep cycle seems to work OK. I’ll need to work on this still no doubt as i start adding in other elements to the system.

Within about 30 minutes the sun although weak was on the panel and it was quickly charging it up showing that the datalogger system was drawing little power.

While i was out  i decided to pull the card out and copy the data so i could have a look and plan ahead for changes and what to do next in the garden.

Looking at the Data

Again to my surprise it had logged perfectly for the 4 days i ran unattended without issue outputting a file size of 124kb.

My maths may be off but i think it could log for nearly 32000 days or 90 years with the 8gb card 😂 it’ll still be logging once i’m pushing up daisy’s.

I encountered a few problems trying to graph this, at 2500+ entries it caused the excel program to crash a few times so i may need to find a work around for that.


I was pleased to see it holds the temp well at around 25*c with a 10-15*c outside temp hopefully this will be one to watch as summer approaches to see how this changes.

Alas night time temps are still low currently down to 1*c so this is going to stop me planting the tomatoes/chillies out for a few weeks longer. I’m hoping as the water storage fills up and i get more pots and soil in for some thermal mass this will help with the temperature drop off overnight.


Not much to say on this currently as i’m not watering in the greenhouse, so its as id expect. Decreasing during the day as the vents are open and increasing during the night as the moisture condensed on the glass.

Noisy data

The cheap DHT11 sensors throw a fair few false readings making for some noisy data but i managed to get some code added to average 3 readers per sensor so try and smooth this out. It adds 6 seconds to the read time over all but that’s nothing in this set up as its only checking every 5 minutes so far.


Whats been done since the Last data logger post

  • Clean up code of ease of trouble shooting/data formatting.
  • Add in some averaging to avoid erroneous data.
  • Work on a way to reduce power usage. (doesn’t seem to be an issue but increased the sleep time from 2 minutes to 5) 
  • still to add in additional sensors (Light, Rain, soil moisture etc)
  • I’m definitely Separate the data in to Day/night or daily logs for analysis and protecting data encase of data logger issues.
  • still to optimise position of sensors or improve covers to avoid radiation heat influencing readings

Well that’s it for now, need to start working in the control’s for the auto watering next as it wont be long until plants are in.

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