16F876A Pulsin issues

[Bobbo_ZA]

Hi Melanie,

Firstly, wow, thank you, :-) all the reading up I was doing last night and I cant believe I missed that, :-), makes sense and I'm sure it will work (will have to wait till I get home from work to test it - note to self, bring board to work)

Another probably small issue I have is the pic does not seem to be driving the servo correctly, in the 12F I could simply do a pulsin on one pin and pulsout to another pin which would control the servo no problem (Planing to use this as a failsafe - want to read in a switch channel and depending on the position I'll output either direct to the servo or via another pic or Arduino for navigation), however now with the 16F the servo moves in one direction but extremely slowly, like 1mm every 5 minutes, its almost as if the resolution is so high its moving in tiny steps, could this be caused by the 20Mhz osc?

Thanks again
Rob

[Melanie]

The value of P (or other timing) may well reveal why.

[Acetronics2]

Hi, Bobbo

Try this

...

PAUSE 2000
LCDOUT $FE, 1, "Pulse"," "

Main:
    PulsIn Rx,1,P                    'Read in Rx input
    LOW servo
    pulsout servo, P                 'output to a servo connected on B.1
    Toggle PORTB.5
    LCDOUT $FE, $80+7,  # P    'Output to LCD
    LCDOUT $FE, $C0+1,# P           'Testing on the second line
goto main:

...

Servo will follow the input signal ...

Alain

[Bobbo_ZA]

I feel like such a rookie, :-) I should have look at more of my previous code, :-)

pulsin gr,1,g	
pulsin rx,1,P          
low throttle
pulsout throttle, P

Thanks exactly what I had in a previous project, :-)

Can't wait to get home now, :-)

Will post pics once I have it programed and working, hope to build up a nice multi function test unit - once thing im still investigating is how to measure the battery voltage of a 4 cell flight pack (nicad or nimh) with a 250ma load, im using the units 5.02V regulated supply as a reference but not quite sure if I could just give the flight pack's V to the ADC through a resistor and work from there? 4 Cell fully charged will give me 5.6V and I dont know what the ADC does when the voltage is higher than the reference V, also could the pic handle the extra .6V?

On a side note I'm still hunting down a case for my LM35 project, finally got some ally tubing to house the sensor, just need to find a nice case for the PIC and water proof it, :-) (will post pics etc as well once complete)

Kind Regards
rob

[Acetronics2]

Hi, Rob

Consider all inputs are clamped to Vcc + .6 v ... ( take care: clamps diodes are very Weeeeeeak ! )

so, the best is not to have more than Vcc ... or use strong external clamp diodes ( 1 N4148 i.e )

but analog inputs can rise to Vref + 2v ... not forgetting Vcc+.6v is an absolute maximum ...

Alain

[Bobbo_ZA]

Would adding a bigger load to the pack solve the problem? A bigger load should pull the cells down to 1.2v per cell to give me a max of 4.8V on a fully charged pack? perhaps a 500ma load?

[Acetronics2]

Bad Idea ...

just use a voltage divider in the input ...

1/2 is the easiest to find ( 2 equal 1% resistors ) ...
2/3 is still easy ( 1 k and 2k resistors @ 1%)

Installing a load that can draw 300 - 400 mA on demand is rather a good thing ...

But think regulator doesn't output EXACT 5.000 v ... so measure it and enter value as a parameter for calculations ...

Alain