Hi guys,
I want to start a simple experiment using an LDR to turn on a LED. But along the way i have some questions
1) When i read about LDR's they are used for dark/light detection and according their change of resistance. Mainly they are used to switch off lights during day for electricity reduction. But this part is unclear for me ...
- as i understand it during the day the resistance is low and the correct flows trough the LDR and not the Lightbulb/LED , so a current is flowing !!!. If i hook this up to a battery my battery would be drained even during the day. Am i correct or do i miss something ?
2) Calculating the resistance values. I found an article which explained how to calculate the fixed resistance value ... Square root (min value LDR * max Value LDR). In all the formula's i never see the amount of current that is needed in the circuit and based on that the calculation of the resistor.
- If my voltage ranges from for example 0 to 8 volts do i have to put a resistor in front of the LED to limit the amount of current (20MA for LED). Is the series resistor in front of the LED the one that decides how much current flows in the circuit ?
Thanks for the help
Mike
I want to start a simple experiment using an LDR to turn on a LED. But along the way i have some questions
1) When i read about LDR's they are used for dark/light detection and according their change of resistance. Mainly they are used to switch off lights during day for electricity reduction. But this part is unclear for me ...
- as i understand it during the day the resistance is low and the correct flows trough the LDR and not the Lightbulb/LED , so a current is flowing !!!. If i hook this up to a battery my battery would be drained even during the day. Am i correct or do i miss something ?
2) Calculating the resistance values. I found an article which explained how to calculate the fixed resistance value ... Square root (min value LDR * max Value LDR). In all the formula's i never see the amount of current that is needed in the circuit and based on that the calculation of the resistor.
- If my voltage ranges from for example 0 to 8 volts do i have to put a resistor in front of the LED to limit the amount of current (20MA for LED). Is the series resistor in front of the LED the one that decides how much current flows in the circuit ?
Thanks for the help
Mike