Ligth Sensitive Alarm - Electronic Circuits Projects Diagrams Free

deadend · 12th May 2003, 07:41 PM

Hey everyone, I'm new to the board and needing some help getting started on this electronics project. So here goes.

I need to design a circuit that responds to light intensity using op-amps, transistors, and photodiodes. The circuit needs to include an oscillator, using a transistor op-amp.

Here are the device requirements:
Output in sunlight: 1 W 500 Hz sinusoid into an 8-ohm speaker load
Dark output: Silence
Linear output voltage increase between extremes

I think I can figure out the correct component values, but what I really need help with is the schematic for the circuit.

Any thoughts, opinions, or ideas are greatly appreciated. Thanks.

Scubasteve · 13th May 2003, 04:54 AM

What do you want to increase, the volume or the frequency of the output?

In both cases, you will need to convert the light intensity to a variable frequency or gain. You will need to use a 'transimpedance' amplifier to change the variable current from the photodiode to a variable voltage. This variable voltage will then need to vary the frequency of a voltage controlled oscillator, or it can vary the gain of an amplifier. Which photodiode are you using?

I do not have much time right now to help with a schematic, but when you answer your questions, I should be able to work something out.

Steve

deadend · 13th May 2003, 09:33 PM

Thanks for the reply.

I want the volume of the output to increase, not the frequency.
For the transimpedance amplifier I want my variable voltage to then vary the gain of an amplifier.
As far as the photodiode goes, I have no constraints on what kind I can use. This is a theoretical design problem so I do not need to find a specific photodiode, I can make up the components of it as long as they are reasonable.

What will the transimpedance amplifier consist of?
Thanks

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12th May 2003, 07:41 PM	#1
deadend	Ligth Sensitive Alarm Hey everyone, I'm new to the board and needing some help getting started on this electronics project. So here goes. I need to design a circuit that responds to light intensity using op-amps, transistors, and photodiodes. The circuit needs to include an oscillator, using a transistor op-amp. Here are the device requirements: Output in sunlight: 1 W 500 Hz sinusoid into an 8-ohm speaker load Dark output: Silence Linear output voltage increase between extremes I think I can figure out the correct component values, but what I really need help with is the schematic for the circuit. Any thoughts, opinions, or ideas are greatly appreciated. Thanks. __________________ I know this, becasue Tyler knows this...

13th May 2003, 04:54 AM	#2
Scubasteve	What do you want to increase, the volume or the frequency of the output? In both cases, you will need to convert the light intensity to a variable frequency or gain. You will need to use a 'transimpedance' amplifier to change the variable current from the photodiode to a variable voltage. This variable voltage will then need to vary the frequency of a voltage controlled oscillator, or it can vary the gain of an amplifier. Which photodiode are you using? I do not have much time right now to help with a schematic, but when you answer your questions, I should be able to work something out. Steve

13th May 2003, 09:33 PM	#3
deadend	Thanks for the reply. I want the volume of the output to increase, not the frequency. For the transimpedance amplifier I want my variable voltage to then vary the gain of an amplifier. As far as the photodiode goes, I have no constraints on what kind I can use. This is a theoretical design problem so I do not need to find a specific photodiode, I can make up the components of it as long as they are reasonable. What will the transimpedance amplifier consist of? Thanks __________________ I know this, becasue Tyler knows this...