The Raspberry Pi works on digital signals - one or off. Analogue can be any value and normally the Raspberry Pi requires an Analogue to Digital converter.
I have one connected to a 2m length of cable and one connected to a 20cm length of cable.
Requires a 1uf Capacitor
Resource - http://learn.adafruit.com/basic-resistor-sensor-reading-on-raspberry-pi
Takes a parameter of RCpin. This is the pin where the resistor is connected to. I have 2 connected to the system, one inside, one out. The inside sensor is basically dark all day.
###################################################################
def RCtime(RCpin):
reading = 0
GPIO.setup(RCpin, GPIO.OUT)
GPIO.output(RCpin, GPIO.LOW)
time.sleep(0.1)
GPIO.setup(RCpin, GPIO.IN)
# This takes about 1 millisecond per loop cycle
while (GPIO.input(RCpin) == GPIO.LOW):
reading += 1
if reading > 200:
break
return reading
def pdslight(GPIOPIN):
if debug:
print("Reading light " + str(GPIOPIN))
x=0
loops=5
for y in range(0,loops):
x = x + RCtime(GPIOPIN)
x = x/loops
if debug:
print("Reading light " + str(GPIOPIN) + " " + str(x) )
return x
##################################################################
| 20pcs Photoresistor 5MM GL5537 LDR Photo Resistors Light Dependent Resistor | |
 |
$4.75 End Date: Wednesday Dec-11-2019 7:22:19 PST Buy It Now for only: $4.75 |
| 20 X 5mm Photoresistor GL5528 LDR Photo Resistor Light Dependent Resistor USA | |
 |
$5.49 End Date: Monday Dec-9-2019 11:02:10 PST Buy It Now for only: $5.49 |
| 5 Types 10 Pcs Photoresistor Dependent Light Resistor LDR Pack For Arduino Kit | |
 |
$1.98 End Date: Monday Dec-9-2019 18:45:11 PST Buy It Now for only: $1.98 |
| 20pcs Photo Light Sensitive Resistor Photoresistor GL5516 CA | |
 |
$0.75 End Date: Sunday Dec-22-2019 20:20:22 PST Buy It Now for only: $0.75 |
| Photoresistor 5537 5mm Photoelectric Sensor Silver + Coffee 10 PCS | |
 |
$0.99 (1 Bid) End Date: Friday Dec-6-2019 20:45:41 PST |
| 10Pcs innocuous photoresistor 5mm 5800B LDR resistor light dependent BH | |
 |
$4.99 End Date: Friday Jan-3-2020 21:42:36 PST Buy It Now for only: $4.99 |
| 20Pcs Photo Light Sensitive Resistor Photoresistor Optoresistor 5mm GL5549 CA | |
 |
$0.98 End Date: Wednesday Dec-11-2019 2:41:57 PST Buy It Now for only: $0.98 |
| LDR CDS Resistance Arduino Light Dependent Resistor Sensor GL5516 | |
 |
$1.00 End Date: Thursday Dec-19-2019 19:24:03 PST Buy It Now for only: $1.00 |
| 10 pcs Innocuous Photoresistor 5MM 5800B LDR Resistor Light Dependent | |
 |
$1.58 End Date: Tuesday Dec-24-2019 8:47:05 PST Buy It Now for only: $1.58 |
| 5 PCs Photoresistor GL5537 LDR Photo Resistors Light Dependent Resistor US Selle | |
 |
$2.25 End Date: Saturday Dec-14-2019 8:16:07 PST Buy It Now for only: $2.25 |