Another readadc on 08m2 question

P

PersonX99

New Member
I am using on 08m2 (bear with me as I am new to this) with a simple voltage divider circuit. One side is a 25K pot and the other side is a fixed 10K resistor. In between the two I have connected C.2.

My code is as follows:

main:
readadc C.2,b0
sertxd("Variable b0 = ",#b0,13,10)
pause 200
goto main

When I run this program with the terminal window up, I see the value of 117-119. I adjust the pot and the output remains the same. I check the voltage (+ at input c.2, - at ground) and the voltage varies with the pot adjustment between ~.6 and 3.6V (numbers may be slightly skewed). The 08m2 is powered with 3AA battery pack. The voltage divider circuit is powered from a separate 5V source, but I got the same results from using the Vcc from the 08M2.

All of the other pins on the 08m2 are floating. Will this affect the results?
Which source should I use for the voltage divider circuit (08m2 or seperate source)? Can I use either?

I have done a couple of simple circuits with the 08M2 using simple high,low and PWM commands to light up some leds on the outputs. All of these seemed to work as expected so I believe to 08M2 to be working correctly.

Any thoughts, comments and/or suggestions?

Thanks for any info,
Dave
 
Technical

Technical

Technical Support
Staff member
Welcome to the forum.
Sounds like a simple wiring error somewhere, your code is correct and the floating inputs make no difference.
You have got both 0V lines connected between the two supplies?
 
G

Goeytex

Senior Member
Some things to check.

1. Check your ground from the battery pack to Picaxe Leg 8.
2. Take all voltage measurements using Picaxe Leg 8 as the ground reference.
3. If using a separate supply make sure the grounds are tied together
4. ALWAYS put a 100nf bypass/decoupling capacitor across the +V and 0V Picaxe Pins
5. Try a different Picaxe Pin.
 
M

mrburnette

Senior Member
I am using on 08m2 (bear with me as I am new to this) with a simple voltage divider circuit. One side is a 25K pot and the other side is a fixed 10K resistor. In between the two I have connected C.2.
Click to expand...
Wire the Pot as a Rheostat (2-wire device) ... tie the wiper to the end connecting to the AD of the PICAXE.

If you reverse the 10K resistor (one end to +5V) and put the rheostat (variable resistor) with one end to GND, then you would effectively have something like:
Test-Results-On-AD
where the rheostat would be mimicking the thermistor.


- Ray
 
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