temperature reading cannot constantly show on LCD dispaly

[freedoms]

Hi, i would like to ask why my temperature reading cannot constant show on the LCD display. normally when temperature increase, it will increase by 0.1,0.2..., right? but my one always change the temperature reading from 23.5C to 23.9C or 24.2C (example) but when i measure the temperature sensor output voltage, it constant. pls advise! thanks!

 

[blueroomelectronics]

The LCD backlight and all the other electronics will put out heat.

 

[freedoms]

but it update very fast within 1sec will change from 23.5C to 23.9C or 24.2C

 

[blueroomelectronics]

Move the sensor away from the electronics.

 

[ndru_w]

Re: temperature reading cannot constantly show on LCD dispal

And what kind of sensor do you have? Maybe its accuracy is more than 0.1 deg? Or maybe you've got some error in the algorithm of calculating the value of temperature?

 

[sau_sol]

Re: temperature reading cannot constantly show on LCD dispal

use lm35 transistor as temperature sensor

it comes in different rating and different resolution
then use a good ADC ic then get this data to the microcontroller for display
i uses this scheme and this works

 

[Abdul Manan]

Re: temperature reading cannot constantly show on LCD dispal

be more practical
use digital temperature sensor

use tmp 124 which supports spi protocol
pros
no adc needed
harware become simple
sense temperature upto 0.25 degrees
high response time
programmable ic
supports interrupts
16 bit spi
when i use it i can see its output on lcd changing 2-3 times pr second
u can free sample it from ti.com

 

[waseem]

Re: temperature reading cannot constantly show on LCD dispal

Hi!
Well i faced a similar problem and the reason was noise in the power supply circuit. That greately effects the stability of the readings. Specially if you are using the ADC refrence as the power supply. The simplest solution is to add one or two 100nf capacitors on the power supply line as close as possible to the microcontroller and the adc results will hopefully stabilize.
Regards.

 

[blueroomelectronics]

Re: temperature reading cannot constantly show on LCD dispal

My thermostat works great because I designed the electronics to not be heating up the sensor.
**broken link removed**

 

[waseem]

Re: temperature reading cannot constantly show on LCD dispal

Hi blueroomelectronics!
Heating of the sensor may also be one of the reasons. By the way how are u driving this LCD. I cannot see any driver IC in the picture. Can u tell me the source of this LCD display from where it can be purchased.
Regards.

 

[salwa ahmed54]

Hi blueroomelectronics , i am working on the same project now , ur cit is very simple can u please upload or send to me the circit diagram

 

[kerur.vardhan]

Re: temperature reading cannot constantly show on LCD dispal

could u pls post the lcd program over here i'm gr8 distress since my program is'nt working. infact any lcd program does not work.
i tried interfacing the lcd to other MCU's and it worked...

 

[blueroomelectronics]

1 the 16F917 has a built in LCD driver
2 see my site "Cricket" for the schematic
3 LCD program for the Cricket?