LDmicro Forum - decimal numbers

decimal numbers (by Alex)

Hello, is there any way to use decimal numbers for temperature or values for proximity sensor reading, etc , here is a video where he uses decimal numbers by doing some kind of trick, but i don´t understand:

https://www.youtube.com/watch?...gudatw03c010c.1548017347761422

Tue Jan 22 2019, 01:11:05

(no subject) (by José GILLES)

Hi Alex

There's no way to use decimal numbers in ldmicro, but I think sensors generally return int values to be converted by the user.

In your video, these values are converted in an integer part and a decimal part which are both integers, displayed with a dot '.' inbetween.

What is your sensor model and comnunication protocol ?

JG

Tue Jan 22 2019, 11:13:40

(no subject) (by MGP)

Attached a program you can find in Samples.zip on this forum.

Tue Jan 22 2019, 16:06:03, download attachment DecimalpointLCD.ld

(no subject) (by Alex)

Hello, thanks for your replies, i used DecimalpointLCD.ld with 2.4v it works ok:

https://www.youtube.com/watch?v=LlR1LatUB0E

is like an "ilussion" or trick to set a decimal dot, if there wasn´t decimal dot max value would e 1023 intead of 10.23 ,

i want to test lm35, if somehow with some math functions or some ladder tricks can we managed to visualize temperature with lm35 in decimal values?

here Jonathan Westhues explains a solution using lm35, i tested that before, it works, but only integer number can be shown in lcd

Tue Jan 22 2019, 20:44:36

(no subject) (by José GILLES)

Your LM35 can be connected directly to an ADC input (but should be translated with an offset if Temp <= 0 and may be amplified before because V_out = T/100 is low)

It isn't really designed to deal with decimal values, mainly integer temperatures because of its precision (+/- 0.5 °C) !

If you connect directly a 10 bits ADC (0->1023) with 5V reference you can compute temperature (T >= 0 °C only) simply in ldmicro with:

T ~= ((Adc_in + 1) * 25) / 51

Examples:

30°C => V_out= 300 mv= 0,3 V=> Adc_in= 61.38 -> 61
=> T= (62 * 25) / 51 = 30,3 => 30 °C

100°C => V_out= 1000 mv= 1 V=> Adc_in= 204
=> T= (205 * 25) / 51 = 100,4 => 100 °C

If you want to have some decimals (not reliable), do :

T'= ((Adc_in + 1) * 250) / 51 = 303

And then display (T'/10) '.' (T'%10) to get 30.3

But in this latter case beware that if Temp is too high, Adc_in will be higher than 130 and (Adc_in + 1) * 250 will overtake max signed value of 32767 !
So, for high Temps you must rather do (because 250 / 51 ~= 4.9):

T'= ((Adc_in + 1) * 5) - ((Adc_in + 1) / 10) = 304

JG

Wed Jan 23 2019, 03:45:51

(no subject) (by Ziggy)

What Jose said but with a small addition...

While LM35 accuracy may be 0.5C, Your display may show 0.1C resolution.

To correct for 0.5C accuracy You could calibrate the sensor.

Wed Jan 23 2019, 04:26:25

(no subject) (by Alex)

thanks for yout reply, i am testing :

btw in any ldmicro version i think we can´t use "°" symbol i want to display "°C" but instedad in prints "-C" in ldmicro versions

Wed Jan 23 2019, 14:17:01, download attachment lm35 °C.pdf