POT with LDR

[stu746]

Hi,

I am trying to use an ldr with the pot command, i tried connecting it in this order - pin-> ldr-> cap -> gnd

and it seems to work, but not very well, if i cover the ldr i get a value of zero from POT, at normal room light i get about 150, if I cover it slightly the vlaue goes down, but if i shine a torch on it it goes down again to about 30!?

I tried connecting the pin to the cap to gnd, and the pin to the ldr to +5v, but could not get it to work at all.

I belive the second way to be the correct way to wire it? I have tried different values from 1 to 255 for pot with no effect.i just get a reading of 0 which will not change.

Thanks for any help, Stu

[Acetronics2]

Hi, Stu

Everything in the manual ; 5k to 50k for LDR resistance ... no less, no more

Have a look to RCTime ... wider possible range !!!

Alain

[stu746]

in the end i connected both the cap and ldr to gnd but still was not right, so used to following code and seems to work fine

aa var word

trisd.7=0
high portd.7
pause 500
trisd.7=1
loop6:
aa=aa+1
if aa=65000 then aa=aa-1
if portd.7 = 1 then loop6



serout portb.0,n2400,[#aa,13,10]

there is probably a better way to do it, but this seems to work for me

[NavMicroSystems]

Stu,

as Alain already mentioned, it's all in the Manual.

POT is a bit of a pain, does your PIC have a spare ADC?

if yes, wire the LDR with an additional resistor as voltage divider and use ADCIN