A Light Dependant Resistor (LDR) is a resistor that changes in value according to the light falling on it. An LDR commonly has a high resistance in the dark, and a low resistance in the light.
By placing the LDR as the top or bottom resistor in a potential divider circuit varying light level can be turned into varying voltages which a PICAXE can read.
The following program will read the LDR light level value and display it as the contents of the 'b1' variable.
main: readadc C.0, b1 ; read the value debug ; show the value read pause 1000 ; wait a short while goto main ; repeatCopy Code Submit an Example
This program will read the LDR value and, depending on that value, will light one of three LEDs to indicate what light level range it is in.
main: readadc C.0, b1 ; read the value if b1 < 100 then light1 ; range 0-100 = 1 if b1 < 145 then light2 ; range 100-145 = 2 if b1 < 175 then light3 ; range 145-175 = 3 goto main light1: high B.1 ; switch on LED 1 low B.2 ; switch off LED 2 low B.3 ; switch off LED 3 goto main ; loop light2: low B.1 ; switch off LED 1 high B.2 ; switch on LED 2 low B.3 ; switch off LED 3 goto main ; loop light3: low B.1 ; switch off LED 1 low B.2 ; switch off LED 2 high B.3 ; switch on LED 3 goto main ; loopCopy Code Submit an Example
The LDR create module provides an analogue input signal to the PICAXE on the motherboard which varies as brightness changes.
| Description | Code | Qty | |
|---|---|---|---|
| Miniature light dependant resistor | SEN002 | 1 | Buy Now |
| 10k resistor (pack 100) | RES10K | 1 | Buy Now |
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