Solar Tracker - Trouble Selecting Light Sensor

Hey Folks,

I bought few LDRs to test things out,but the problem is, even when its exposed to low intensity evening light, the resistance hits zero. So Voltage drop or the LDR exposed to bright light and brighter light says the same, since its resistance is 0 already.

So what do I actually need?

A More Sensitive LDR? Photo Transistor? Photo Diode? Your inputs are much appreciated.

Thanks :slight_smile:

I bought few LDRs to test things out,but the problem is, even when its exposed to low intensity evening light, the resistance hits zero.

Even in bright light an LDR's resistance is not zero. Show us your circuit and a part number/data sheet for the device.

Maybe you can select a different range for measurements, the resistance could never be zero (that would be a superconductor).

If you are using voltage divider sort of circuit for example, reduce your other resistor so that your divider circuit can produce the right range.

A More Sensitive LDR?

Probably, you mean less sensitive? Of course, you always can reduce sensitivity covering LDR surface with insulating tape or semitransparent plastic caps.

[quote author=Papa G link=topic=159036.msg1190845#msg1190845 date=1365362308]

I bought few LDRs to test things out,but the problem is, even when its exposed to low intensity evening light, the resistance hits zero.

Even in bright light an LDR's resistance is not zero. Show us your circuit and a part number/data sheet for the device. [/quote]

Even I thought the same, but my multimeter proved me wrong. Even the evening Sun (4 PM) made the resistance 0.

Am I missing something?

mjkzz: Maybe you can select a different range for measurements, the resistance could never be zero (that would be a superconductor).

If you are using voltage divider sort of circuit for example, reduce your other resistor so that your divider circuit can produce the right range.

With 0, I meant the 0 in my Multimeter readings. So I assume, the resistance offered is negligible. Not saying its perfectly 0.

Magician:

A More Sensitive LDR?

Probably, you mean less sensitive? Of course, you always can reduce sensitivity covering LDR surface with insulating tape or semitransparent plastic caps.

I thought of that as I read that somewhere, but well, for the sake of precision (or maybe just to keep my mind feel so), I thought I would skip biasing it with a tape or covering. :)

Resistance range: 200K? (dark) to 10K? (10 lux brightness)

http://learn.adafruit.com/photocells

Alternative to LDR, Design 15 and 16: http://www.talkingelectronics.com/projects/H-Bridge/H-Bridge-1.html

xkishorx:

[quote author=Papa G link=topic=159036.msg1190845#msg1190845 date=1365362308]

I bought few LDRs to test things out,but the problem is, even when its exposed to low intensity evening light, the resistance hits zero.

Even in bright light an LDR’s resistance is not zero. Show us your circuit and a part number/data sheet for the device.

Even I thought the same, but my multimeter proved me wrong. Even the evening Sun (4 PM) made the resistance 0.

Am I missing something?
[/quote]
Probably. What scale is your multimeter set to? What does the data sheet say the dark resistance is supposed to be? Is it shorted out?

[quote author=Papa G link=topic=159036.msg1192646#msg1192646 date=1365457695]

xkishorx: [quote author=Papa G link=topic=159036.msg1190845#msg1190845 date=1365362308]

I bought few LDRs to test things out,but the problem is, even when its exposed to low intensity evening light, the resistance hits zero.

Even in bright light an LDR's resistance is not zero. Show us your circuit and a part number/data sheet for the device.

Even I thought the same, but my multimeter proved me wrong. Even the evening Sun (4 PM) made the resistance 0.

Am I missing something? [/quote] Probably. What scale is your multimeter set to? What does the data sheet say the dark resistance is supposed to be? Is it shorted out? [/quote]

I checked it with 2K ohms and 200 ohms as well. Says 0 when I point to the sun (evening sun) and like 10 when I turn it away to the other side.

No, its not shorted out :) Since I just bought it from a nearby shop as is,(they are sold loose), I dont have any model no. or datasheet :(