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Author Topic: LDR trigger  (Read 410 times)

Offline chicobulilit

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LDR trigger
« on: February 17, 2011, 09:31:58 PM »
mga kuya pwede po diba gawing parang trigger ang ldr papunta sa pic

thie circuit goes like:

VCC(5V)--LDR--Resistor(still unknown)--gnd

then ung junction po bet LDR and resistor is ikakabit po sa PIC16f877a

mga anong value po ng resistor ang gagamitin ko enough na para matrigger ung PIC.... salamat...
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LDR trigger
« on: February 17, 2011, 09:31:58 PM »

Offline Mayalin22

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Re: LDR trigger
« Reply #1 on: February 17, 2011, 09:48:03 PM »
kung gagawing analog input ang pic16f877 pwede. kung digital dapat gumamit ka ng comparator.
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Re: LDR trigger
« Reply #1 on: February 17, 2011, 09:48:03 PM »

Offline chicobulilit

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Re: LDR trigger
« Reply #2 on: February 17, 2011, 09:52:40 PM »
Quote from: c0♂Lәt♥ on February 17, 2011, 09:48:03 PM
kung gagawing analog input ang pic16f877 pwede. kung digital dapat gumamit ka ng comparator.

analog input(nosebleed).... how po? might have slept when this was discussed
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Re: LDR trigger
« Reply #2 on: February 17, 2011, 09:52:40 PM »

Offline Mayalin22

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Re: LDR trigger
« Reply #3 on: February 17, 2011, 09:57:07 PM »
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Re: LDR trigger
« Reply #3 on: February 17, 2011, 09:57:07 PM »

Offline chicobulilit

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Re: LDR trigger
« Reply #4 on: February 17, 2011, 10:15:43 PM »
Quote from: c0♂Lәt♥ on February 17, 2011, 09:57:07 PM
http://home.cogeco.ca/~rpaisley4/Comparators.html

http://www.allaboutcircuits.com/vol_6/chpt_6/2.html

thanks po.... uhm....

so i guess ill put the LDR on the inverting input of the comparator para negative ung output nung comparator then connecti it sa PIC.....?

kasi po ganito ung scenario...

once na naputol ung ilaw na nakatutok sa LDR magttriger ung PIC....

reffering to the second link

ung sinabi ko po sa taas ung pwede ko gawin?.....
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Re: LDR trigger
« Reply #4 on: February 17, 2011, 10:15:43 PM »

Offline Mayalin22

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Re: LDR trigger
« Reply #5 on: February 17, 2011, 10:24:17 PM »
kahit anong input sa pic galing ng comparator ok lang... halimbawa

lights on = comparator output is high
lights off = comparator output is low

o kaya baliktad

lights on = comparator output is low
lights off = comparator output is high


bali sa program na ang bahala don...

kung active high kung may ilaw then ang trigger mo ay LOW
kung active low kung may ilaw then ang trigger mo ay HIGH
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Offline Mayalin22

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Re: LDR trigger
« Reply #6 on: February 17, 2011, 10:30:02 PM »
yong link na comparator equivalent ok na ok yon sa ldr.
don mo ilalagay sa negative input yong ldr... what value ba ng LDR mo?
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Offline Mayalin22

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Re: LDR trigger
« Reply #7 on: February 17, 2011, 10:31:09 PM »
computation ng resistor

                    LDR                 R1
 V+ --------^^^^-----+---^^^^----gnd
                                 |
                                 |
                                out


out=  v+  (  r1  )
                ---
              ldr + r1
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Offline chicobulilit

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Re: LDR trigger
« Reply #8 on: February 17, 2011, 10:45:39 PM »
Quote from: c0♂Lәt♥ on February 17, 2011, 10:31:09 PM
yong link na comparator equivalent ok na ok yon sa ldr.
don mo ilalagay sa negative input ang junction ng ldr/resistor devider... what value ba ng LDR mo?




hmmm... i assume 1M siguro... kasi ung reading nya pumapalo ng .8++ Mohms eh
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Offline Mayalin22

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Re: LDR trigger
« Reply #9 on: February 17, 2011, 10:49:03 PM »
ang taas naman hehehe

ano yan pag me ilaw?

pag walang ilaw, ilan ang value
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Offline chicobulilit

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Re: LDR trigger
« Reply #10 on: February 17, 2011, 11:00:20 PM »
Quote from: c0♂Lәt♥ on February 17, 2011, 10:49:03 PM
ang taas naman hehehe

ano yan pag me ilaw?

pag walang ilaw, ilan ang value

xenxa naman... :P

pag walang ilaw po ung as in medjo pitch black... umaabot ng 12.++M ohms
pag may ilaw (ung tutok) nasa 0.275 k ohms po
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Re: LDR trigger
« Reply #10 on: February 17, 2011, 11:00:20 PM »
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