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222

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[–] 1 pt

Nice, though the DHT11 isn't very accurate.

My e-peen is getting stoked because I wasted/used a few weeks with no beer on a wifi temperature sensor using thermisters. Two channels so one channel could be used to measure humidity via the wet-bulb technique. They are ESP8266 based and most of the difficult code was writing the temperature compensation and zeroing.

I use them for incubator control, and they are demonstrably accurate.

[–] 1 pt

Yes, the DHT11 is accurate from 22-100F, this thing is built for monitoring my shop temperature. I have a Baytech IIII RPC11A-NC telnet relay with all my lights and a kerosene Monitor 2200 heater wired up. The whole idea for this unit is have my linux box take measurements every 5 or 10 minutes and if temp=40 trigger a telnet script to logon to the control relay and turn on the heater that has a "power failure auto on" setting. I have 20 inch concrete walls 8' high with 3 inch insulation inside so if I can keep the thermal mass above freezing all I have to do is throw 4 logs in the stove and it is 60F in an hour. When the concrete gets cold it takes 2 days of constant heat to get up to an OKish temperature. The ones I am going to build for outside will have the DHT22 and no LCD as well as wireless serial or wifi for communication.

Thermisters are always hard to lock down the relative analog value to reality, I would always throw them in the freezer to get a reading and then measure ambient and do calculations from there.

[–] 1 pt

Use PT100/1000 then zero them with an ice bath, but they are way more expensive to interface with than DHTxx and for no gain in your case.

[–] 1 pt

Very cool! Can you give us some more details on the hardware you used? Does that even have an OS or purely sensor -> screen type rig?

[–] 2 pts

Arduino micro, HR911105A ethernet module, DHT11 temp/humidity analog to digital sensor, a lcd module I got out of a security system, and a bunch of random resistors and diodes. All stuff I had on hand minus the ethernet module. Some custom code, started with the arduino temp sensor example and added to it. The next step is to make a handfull in different locations on my property and pull the data to my server in a textfile and graph temperature differentials using MRTG. The micro-climates on my property are really drastic and I have always wanted to have a visual graph for comparison. Could easily turn one into a full weather station as well I suppose.

[–] 1 pt

Have you played with cacti? I think that would be a better solution for you than MRTG because it can capture damn near any data and display in a graph or just log it for you. It has a pretty steep learning curve, but VERY powerful.

Have never played with that board. Damn! It's really small! What OS / version you using? I've been doing a lot with RPIs and found dietpie to be the meanest / leanest headless distro out there. Worth a look.

[–] 2 pts

There is no OS, you just write a loop of code, flash it, and it runs. Arduino micros are really handy and you can get a 10 pack for like 15 bucks. Also if you are doing anything with pulse width modulation they can't be beat for the price.