lloydi12345
Member
I have successfully made my temperature controller but there's a problem. With a 320°F setup using a temperature calibrator machine. While my thermistor probe placed in the machine my controller detects it quite well with a maximum error of 1°F. Sometimes it is 321°F sometimes it is 320°F. Now the problem is that randomly in 15 mins, 30 mins, 40 mins, 1 hour or even two (no particular time really), the temperature display changes to values higher or lower than the real temperature values by 10 values(numbers between 310°F and 330°F). What I'm doing to fix this is to turn off the circuit and turn it on again then everything will go back to normal. I don't think this is right. I think the cause of this problem is the noise but I can't figure out what type or value of capacitor I should use. Maybe it's not the noise. I might missed something. I attached my schematic below. C5 is the ceramic cap near the microcontroller.
I measured the value of the ADC voltage fed to the microcontroller and it's a stable voltage. It doesn't change even a millivolt.
I tried a trial and error approach just hoping this as my lucky day. I waited for the values to fluctuate then I tried plugging at 7805's output pin capacitors like 10uF. The temperature value slowly crawled to the actual temperature. So I soldered it thinking it's the right value but after again some random time the temperature value jumped again. I even tried 22uF and 220uF all rating 25v. Does the voltage rating affect the circuit?
I badly need some helping hand![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Regards,
lloyd
I measured the value of the ADC voltage fed to the microcontroller and it's a stable voltage. It doesn't change even a millivolt.
I tried a trial and error approach just hoping this as my lucky day. I waited for the values to fluctuate then I tried plugging at 7805's output pin capacitors like 10uF. The temperature value slowly crawled to the actual temperature. So I soldered it thinking it's the right value but after again some random time the temperature value jumped again. I even tried 22uF and 220uF all rating 25v. Does the voltage rating affect the circuit?
I badly need some helping hand
Regards,
lloyd
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