Sensor adapter!

[einet]

Hi,

I´m a beginner in PIC OR AVR programing and i wont to now how i begin with my problem!

So my problem is that i wont to adapt a automobile speedodometer with diffrent resistence! to my in car sensors.
My old fuel sensor have 283-ohm for (Low fuel) and (full fuel) 40-ohm and my new automobile indicator
response to the this values (Low Fuel) 60-ohm and (full fuel) 330-ohm.

How cann i adapt this, how i begin with the bascom code or other?
Or is on the forum that is so nice and make me a exemple how to?!

The principe is, ADC voltage in and convert the adc to PWM output.

From Portugal

[demon]

Hi einet
   It depends how your new sensor works as to how you can drive it.

PWM will give you a variable voltage output.

How is the sensor wired?

[mcr]

Please provide the sensor model and if possible, a .com

[einet]

Hi

thanks for help.

So the sensor is on ground connect and the another side from the instrument cluster is
connectet to the intern +10v regulator.

I make a mesure, 2V is 0 LOW fuel and 9.2v is Full Fuel from my Fuel instrument cluster.

thanks

[Parmin]

I think first you need to make sure that the input to your uC is less than 5v.

try to use voltage divider (a couple of resistors would do) to bring the 9V full signal to 4.5V and this would bring the low 2V to 1 V.

By using this, you can straight away use the Uc comparator and measure directly off the output of the cluster.

Goodluck

[einet]

Hallo,

So i tray this exemple on Proton but the input ist 5v and the output is propocional to 5v.

------------------------------------
Device = 12F675
XTAL 4        ' Using internal 4Mhz osc. 
Config BODEN_ON,PWRTE_ON,WDT_OFF,CPD_OFF,CP_OFF,INTRC_OSC_NOCLKOUT,MCLRE_OFF
      
' *** Set configuration registers ***      
TRISIO = %00111111        'all ports inputs
'Note: the PWM command will change it's pin to an output when required
ANSEL = %00001000         'AN3 (GP4) is analog input
CMCON = %00000111         'Shut down the comparator
ADCON0 = %10000000        'right justify the A/D result      
      
' *** Define variables ***      
Dim MyVAR As Word                 
               
'Main program starts here
loop:
 MyVAR = ADIn 3        'load the result of the A/D conversion into our variable       
 PWM PORTB.5, MyVAR, 5 'output the result on GPIO 5
 GoTo loop
       
 End
----------------------------------------------------------------



But i won´t that the voltage make this range!

1v input -> 1.75v output
1.5v -> 2v
2v -> 2.25v
2.5v -> 2.75v
3v -> 3.45v
3.5v -> 3.75v
4v -> 4.25v
4.5v -> 4.75v
5V -> 4.90v

einet
from Portugal

[GreenGiant]

The first step to this type of problem is to come up with the formula.
Ie. The mathematical formula for converting X input into Y output.

You noted:
"283-ohm for (Low fuel) and (full fuel) 40-ohm and my new automobile indicator
response to the this values (Low Fuel) 60-ohm and (full fuel) 330-ohm"

Since the two ranges are very close, simple normalization will be sufficient.
So its more or less an reverse. Theres different methods,  you can use a lookup table in which case you will get exact results (given voltage X it will output voltage Y).
You can use a mathematical formula, something along the lines of abs(X-XMAX) = Y

Once you know the exact method/approach you want to then worry about getting the input.

Since you are using 2-9v you cant feed that directly into your PIC/AVR.
You will want to use an external ADC that can handle 9v, or you can use a simple circuit to scale down your voltage levels to 0-5v.

For the output, it depends on the voltage reference being used, but a simple means if its MAX 5v, use the DAC on most pics, otherwise use an external DAC (microchip makes some very good DAC's).

Enjoy

[einet]

Hi,

Ok i make more results.
so 9v is not the problem, the new instrument need 0-5v is digital dash board.

@GreenGiant
can you demontrate in the code above how i make the voltage tabel .."When x_in then y_out"

thanks

einet

[einet]

Hallo,

Nobody cann help!?

einet

[mcr]

Use a CAS to condition the signal:

http://www.microladder.com/page.php?n=an1_pt100_es