I’ve been working on a thermostat and I’ve got it all functional now. One thing that bugs me tough is that the LM35 I’m using keeps fluctuating around +/- 2 degrees. Now I know I can add a low pass RC filter, add a heat sink and average readouts over time, however I’d rather have a more ‘final’ solution.
Hence the question in the subject:
does anyone know whether the ‘off the shelve’ TH22 sensors do not fluctuate so much? Or are there variants that have build in filters? Or better solutions?
The temperature readings are quite stable and precise. Humidity is a totally different story and a nightmare on DHT’s
AFAIK, the LM35 is a good sensor, but most errors are from not precise ADC (poor reference, noisy VCC, etc)
thnx. how bad is it?
Humidity readings is lottery: Out of six sensors I have one, which is in pair with the three others, that I trust (where readings are consistent with 2% of direct readout) The BME280 are far better.
which brings the obvious questions:
Of course. There are few, my favourite is the one from Sparkfun, but pick yourself 
Hard to tell, as here the DHT’s are good. The only problem I see is not returning values from time to time.
well, they don’t have to be better, they have to be stable so I should have asked that
So look at a day long readings, where a finest steps are 0,1°C. Both are good and “stable” (I don’t know how many read errors they caught in that time, but it doesn’t influenced the overall)
The DHT is read twice a minute, the BME once.
First is DHT. Ignore the spikes at rising edge. They are true.
The BME280 is one of the newer generation of sensors and the people who know about these thinkgs say that they’re much more stable and accurate. If you do a bit of googling you’ll find lots of comparative tests.
They’re very easy to use with an Arduino or ESP8266. I tend to use the Adafruit libraries.
The BME280 also incorporates an atmospheric pressure sensor.
As with most sensors of this type, the absolute accuracy of the temperature, humidity and pressure sensors can’t be fully relied on, without calibrating them against a known reference sensor. However, for most applications that isn’t an issue. If you’re doing room temperature control and the ‘comfortable’ temperature is what you think of as being 20°C, but the sensor says that this is 22.3°C then you can either deduct 2.3° from the reading in your code, or learn to set your thermostat to 22.3° to get the result you want.
Pete.
Thanks, boot look great! Do you connect it over so spi or i2c?
Also another thing I realise: does any of the connectors interfere with the oled shield of the wemos d1? That is does so spi or i2c uses any.connectors also used for the oled?
The BME is connected through I2C in my case.
I don’t know 
You can define any of the useable GPIO pinsa as I2C on the D1 Mini, so it shouldn’t be a problem.
Pete.
thanks again! Just ordered 8 of them.
