I have only been working with LDR's for a short while and had a question regarding measuring light and dark values.
I have measured some LDR's for an effect I want to clone and came up with 6.5K to room light and at least over 20M dark (my meter stops at 20M so I just get "L" on the digital meter screen for over range). The same LDR gives about 39K when exposed to and LED and 1.5M dark (if the LED is driven by an LFO at a moderate rate).
My question is, what is or would be the correct way to measure an LDR for accurate resistance readings? Should there be a waiting period between light and dark before measuring the "Dark" resistance on the LDR? Without a light meter, how much light should I use for the "ON" resistance measurements?
The reason I ask is because I have ordered different LDR's from several suppliers that cover a wide range of values, but when I measure them at room lighting and very dimly lit room for dark, I get almost the same readings from all of them. For example, I have an LDR that says Light resistance 10K - 20K and Dark resistance 10M. When I measure them at normal room lighting and then no lighting at all they measure 2.1K Light and over 20M Dark. Can you see my confusion!!
Any help would be appreciated.
Jim
I have measured some LDR's for an effect I want to clone and came up with 6.5K to room light and at least over 20M dark (my meter stops at 20M so I just get "L" on the digital meter screen for over range). The same LDR gives about 39K when exposed to and LED and 1.5M dark (if the LED is driven by an LFO at a moderate rate).
My question is, what is or would be the correct way to measure an LDR for accurate resistance readings? Should there be a waiting period between light and dark before measuring the "Dark" resistance on the LDR? Without a light meter, how much light should I use for the "ON" resistance measurements?
The reason I ask is because I have ordered different LDR's from several suppliers that cover a wide range of values, but when I measure them at room lighting and very dimly lit room for dark, I get almost the same readings from all of them. For example, I have an LDR that says Light resistance 10K - 20K and Dark resistance 10M. When I measure them at normal room lighting and then no lighting at all they measure 2.1K Light and over 20M Dark. Can you see my confusion!!
Any help would be appreciated.
Jim