Light Measuring Circuit

Thread Starter


Joined Jul 30, 2010
Help.. we're making a light measuring circuit as part of our thesis project.

I need a circuit which can convert the amount of light received into a voltage level.

I tried using light dependent resistors but it lacks sensitivity because we are measuring underwater in dark conditions and we are using an optical filter which only lets light around 680 nm wavelength pass..

I'm out of ideas.. :(


Joined Dec 26, 2010
If your light levels are very low, you may find that photo-diode dark current may be significant. The effect of this can be minimised by operating the device at zero bias, providing that you have a device which will operate in this condition.

As suggested by a previous poster, a transimpedance amplifier is useful - it will keep the detector voltage constant.

Really low light levels may lead you to use some kind of shutter to cal out the dark condition.
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Joined Mar 3, 2011
Thank you Dick for sharing your simple but interesting idea.

Off topic, may I ask you how (or when) one can add on a new solution the expression "Copyright 20xx”? Sorry if it sounds a silly question :)