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1  Using Arduino / Programming Questions / Re: MQ-135 Value Conversion on: December 02, 2013, 08:09:26 am
i'm comparing it against a mh-z14 (using a xively datastrem).
it seams to words good also for Co2 (from 300 to 2000ppm)
results will be published soon on my blog (as soon as i will have time to write the post, and analyze graph).
2  Using Arduino / Sensors / Re: MPU-6050 gyro calibration on: June 17, 2013, 01:39:18 pm
pictures here are taken from processing.org (there is a mac version too).

for calibration, you can find the python script i've built here:
http://davidegironi.blogspot.it/2013/01/gyroscope-calibration-helper-01-for-avr.html
it should works on mac too smiley-wink
3  Using Arduino / Storage / Re: An eeprom config library for arduino on: March 18, 2013, 04:06:56 pm
on attiny85 you have to implement software uart, it could work but you have to try.
4  Using Arduino / Storage / An eeprom config library for arduino on: March 13, 2013, 06:03:58 am
Hello, i've just published this library, i hope it can help your developing.

AVR uartConfig is a small footprint library you can use to config your arduino eeprom through uart communication.
AVR uartConfig is a set of tools running on Windows, Linux and Mac, made up or:
* a avrgcc firmware library
* a commandline utility
* a gui tool

This library prevent you to wire up a disply and buttons to configure your micro eeprom. For example is it usefull to setup PID parameters of your robot by uart/bluetooth uart, or for other small devices that doesn't came with an output/input interface.

more information and download here: http://davidegironi.blogspot.it/2013/03/avr-uartconfig-atmega-and-arduino.html
5  Using Arduino / General Electronics / Re: Circuit check for noob on: January 31, 2013, 08:58:58 am
I think the best option is to run that detector (both the amplifier side and the LED side) from a regulated 5V supply. However, the readings you are getting appear to be roughly ratiometric with the supply voltage. Therefore, if you feed the output into in analog input of an Arduino that is powered from the same 5V supply, then the ADC will approximately compensate for supply voltage variation.

thank for reply,
my readings are taken from arduino, and checked with multimeter, to get voltage i use bandgap for the adc ref voltage, so it does not compensate reading. to check adc i try the compensation why different voltage using other sensor, or using a simple resistor, and it works!, but this times not; i think is the output of this sensor that change with voltage supply changing, but datasheet unfortunately do not tell anything about sensitivity over voltage.
anyway, i suppose you are right, best option is to run it over regulated 5v power.
6  Using Arduino / General Electronics / Re: Circuit check for noob on: January 31, 2013, 05:36:24 am
hello,
i’m experimenting too with GP2Y1010AU0F, but i’ve found a strange behaviour.
my sensor is conncted like datasheet explain, pin 3 direct to atmega (i’ve also try using a mosfet but it do not change)
if i run GP2Y1010AU0F with 5.330 voltage i read an output voltage between 0.800 and 0.850
if i run GP2Y1010AU0F with 5.080 voltage i read an output voltage between 0.770 and 0.830
if i run GP2Y1010AU0F with 4.670 voltage i read an output voltage between 0.700 to 0.770
so there’s a small drift when supply voltage change.
i suppose the fig 3 of datasheet, from which we can extract slope and offset to find dust sensity, it’s 5.0v supply voltage, so reading an “incorrect” voltage would bring to incorrect mg/m^3 conversion.
have you also find this behevior?
have you find a way to balance the supply voltage drift?

thanks all
7  Using Arduino / Programming Questions / Re: MQ-135 Value Conversion on: January 16, 2013, 01:24:42 pm
Quote
so i can obtain Ro value for the chip in open air.
can this be right?
Assuming you're not in Bejing with the current smog levels the answer is yes.

i hope here near milan is not so high smiley
even if i can know it with precision i will approximate it to 394
8  Using Arduino / Programming Questions / Re: MQ-135 Value Conversion on: January 16, 2013, 10:55:59 am
i've made a mistake before, i consider Rs/Ro = ppm, but from fig.2 of datasheet is not so.
it seems that it is a power function (see attached).
so i made some power regression based on the values, and i obtain a scaling factor and an exponent
given those values
a = scaling factor obtained by datasheet figure, for the gas you need
b = exponent obtained by datasheet figure, for the gas you need
ppm = a*(Rs/Ro)^b
now, to obtain a valid Ro value, we have to know the ppm of a gas, for C02, we know the CO2 value for atmosphere,
http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo
so i can obtain Ro value for the chip in open air.

can this be right?
9  Using Arduino / Programming Questions / Re: MQ-135 Value Conversion on: January 16, 2013, 09:47:29 am
yes, i've read the information you link.
but the key point is to find a valid Ro, i do not have a calibrated sensor, so i ask you if someone can tell me a valid Ro values for this chip.

thanks
10  Using Arduino / Sensors / A gyroscope calibration helper in python on: January 14, 2013, 07:22:18 am
hello,
this is my gyroscope calibration python script, hope it helps.
if something wronk in this method please let me know.

http://davidegironi.blogspot.it/2013/01/gyroscope-calibration-helper-01-for-avr.html

11  Using Arduino / Programming Questions / MQ-135 Value Conversion on: December 27, 2012, 01:55:59 pm
i've a mq135 - http://www.futurlec.com/Datasheet/Sensor/MQ-135.pdf

please anyone correct me if i'm wrong:

what i've undestand from datasheet is that

ppm  = Rs/Ro

Rs = mq135 readed resistence
Ro = sensor resistance at 100ppm of NH3 in the clean air (according to datasheet 30Kto200K)

i wire the sensor according to datasheet (see attached image, downloaded is from http://www.staceyk.org)
set RL = pulldown resistor (in the example 39K, according to datasheet any between 10KΩ to 47 KΩ)

so Rs = 1024*RL/adc - RL

the point here is to setup Ro, which means calibrate the sensor.
any help?


thank you,
davide
12  International / Hardware / Re: Amperometro con Sensore ACS758 on: December 06, 2012, 07:56:26 am
per quanto riguarda il settaggio di sensitività avete riscontrato i miei stessi problemi? (vedi post sopra)
tks
13  Using Arduino / General Electronics / Re: ac current meter using acs758 hall sensor on: November 22, 2012, 09:30:15 am
i've made further test
it seems that with a sensitivity of 0.034/2 it works from 4A to 12A quite well.
0.034 seems ok, because my supply is 4.7V, sensitivity should be 0.03824 +- 5mV (Electrical offset voltage from datasheet)
but i've to use half of it.

p.s checked also my multimeter and it has no problem.

have you  any suggestion, or anyone here that can test my code on other chip?

tks!
14  International / Hardware / Re: Amperometro con Sensore ACS758 on: November 21, 2012, 04:56:20 am
ciao,
se qualcuno fosse interessato, ne parlo in questo post, abbiamo "quasi" risolto, ci sono dei problemi con il settaggio della sensitività
http://arduino.cc/forum/index.php/topic,133144.0.html
15  International / Generale / Re: Presentazioni nuovi iscritti, fatevi conoscere da tutti! on: November 20, 2012, 09:03:16 am
ciao a tutti, sono un informatico, appassionato da qualche anno di elettronica... per questo mi ritrovo spesso su questo forum.  smiley-grin
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