I have a DHT11 temp/humidity sensor which I got as part of a DIY weatherstation kit with LCD. Its now fitted with an additional DS1307 RTC, and SD card reader. I am having some issues with all the components but mainly the DHT11..
Firstly, when the temperature gets to about 16-17 degrees it jumps around, sometimes to 19 degrees and back again. An example log looks something like this (in seconds):
18,18,53
18,18,53
18,18,53
18,18,53
17,16,55 }
16,16,53 }
17,16,53 }
19,16,53
19,16,54
17,16,54
18,16,55
19,16,56
19,17,56
21,17,58
20,18,59
21,18,56
21,18,56
21,18,56
21,18,56
So im heating it up slowly, it should really be at 18 going to 19 but it jumps down to 16/17 and back up, or vica versa. I've tried decoupling and filter capacitors with no change. Sometimes flicks between 16 and 19... is this just an inherent feature of electronics? Do I have a faulty sensor?
I also have a switch to tell it when to write to the SD, its wired in this way: From 5v power rail on breadboard to switch, from switch to breadboard followed by (in series) to digital pin 8 to read input, and resistor to ground.
When the switch is on the temperature jumps up a couple of degrees (17 to 19) and when switched off jumps down again. Someone please explain this??? I thought the DHT was digital how could a switch be interfering? (Note: again, this only seems to happen in the 16-19 range)