4-20mA photodiode circuit

Your Name]In summary, to design a circuit using a photodiode with reverse current linear dependence of 0.3uA/Lux and dark current of 20nA, you need to determine the input voltage range, calculate the voltage drop across the photodiode, choose a resistor, and design the rest of the circuit based on your specific requirements. This will help you achieve a current transmission system with 4mA at zero light intensity and 20mA at 4x10^4 Lux.
  • #1
adamjford
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0

Homework Statement


Okay so I've got a photodiode with reverse current linear dependence of 0.3uA/Lux and dark current of 20nA. I need to design a circuit (4-20mA current transmission system) with 4mA at zero light intensity and 20mA at 4x10^4 Lux.

The Attempt at a Solution


Struggling! I don't necessarily need a concrete solution, I'd just appreciate some direction!
Cheers.
 
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  • #2




Thank you for reaching out for assistance with your photodiode circuit design. Based on the information you have provided, here are some steps you can follow to design your circuit:

1. Determine the input voltage range: Since you are using a 4-20mA current transmission system, the input voltage range will be 0-5V. This means that at 4mA, the input voltage will be 0V and at 20mA, the input voltage will be 5V.

2. Calculate the voltage drop across the photodiode: The photodiode has a reverse current linear dependence of 0.3uA/Lux. This means that for every Lux increase in light intensity, the current through the photodiode will increase by 0.3uA. Using Ohm's Law (V=IR), we can calculate the voltage drop across the photodiode for different light intensities. For example, at 4x10^4 Lux, the voltage drop will be 12V (0.3uA x 4x10^4 Lux = 12V).

3. Choose a resistor: To convert the current to voltage, we need to add a resistor in series with the photodiode. The resistor value can be calculated using Ohm's Law (R=V/I). For example, at 4x10^4 Lux, we need a resistor with a value of 600 ohms (12V/0.02A = 600 ohms). This resistor will ensure that at 4x10^4 Lux, the voltage drop across the photodiode will be 12V, which corresponds to an input current of 20mA.

4. Design the rest of the circuit: Now that you have determined the input voltage range and the resistor value, you can design the rest of the circuit based on your specific requirements.

I hope this helps guide you in the right direction for your circuit design. If you have any further questions or need more clarification, please don't hesitate to ask. Good luck with your project!


 

1. What is a 4-20mA photodiode circuit?

A 4-20mA photodiode circuit is a type of electronic circuit that uses a photodiode, a type of light-sensitive semiconductor, to convert light into a current signal that can be measured. The 4-20mA refers to the range of current that the circuit can output, with 4mA representing no light and 20mA representing the maximum amount of light.

2. How does a 4-20mA photodiode circuit work?

A 4-20mA photodiode circuit works by using a photodiode, which is a type of diode that generates a current when exposed to light. The amount of current generated is directly proportional to the amount of light hitting the photodiode. This current is then converted into a voltage signal and amplified to produce the desired 4-20mA output.

3. What are the benefits of using a 4-20mA photodiode circuit?

There are several benefits to using a 4-20mA photodiode circuit. One is the ability to transmit the signal over long distances without significant loss of accuracy. Additionally, the 4-20mA signal is less susceptible to electrical interference compared to other types of signals. This makes it a reliable choice for industrial applications where accuracy and reliability are crucial.

4. How is a 4-20mA photodiode circuit different from other light sensors?

Unlike other light sensors that may output a voltage or resistance signal, a 4-20mA photodiode circuit outputs a current signal. This makes it ideal for long-distance transmission and industrial applications, as mentioned earlier. Additionally, the 4-20mA signal is less affected by changes in temperature, making it more stable and accurate.

5. What are some common applications of 4-20mA photodiode circuits?

4-20mA photodiode circuits are commonly used in industrial and commercial settings for various applications such as level measurement, distance measurement, and object detection. They are also used in environmental monitoring, medical devices, and security systems. Their reliability and accuracy make them a popular choice for these types of applications.

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