Heliospherev1.1

[toadj32]

changes to schematic!

[IsaacNeideffer15]

I would make sure to get someone other than me to review since I am a novice electrical engineer, however I want to give my input for the sake of learning and experience.

The first thing I noticed is that your opamps power supplies are flipped on two of them with ground on the + and 3.3v on the - terminal:

Secondly I was curious what the purpose of having two LEDs in series here is. You may have a reason, but would they not both play the same role?

This may be a result of my lack of understanding of the overall system, however it is unclear what the VDDs are and where they come from. I think the project could benefit from some confluence documentation. I would like to see your research and your decision making steps so I can fully understand the project and give you better feedback.

Another note is that while somewhat more difficult to implement, a switching based regulator would likely be more efficient than a FET based regulator. You may have a good reason for doing it with FETs though, however I would still like to see this reason.

[KnockbackNemo]

Nice work so far! I'm also not too experienced with schematic reviews nor familiar with the Heliosphere, so reading more about the project requirements would help me leave better feedback too, but my understanding so far is that the nucleo is using pwm to connect the lights to the power supply (separate from the nucleo's power supply). Is this correct? Are the LEDs representative of the sun-simulating lights? What are the functions of the regulator, op-amps, and PA0, 2, and 3?

[KnockbackNemo]

Where is the power coming in from or out of your board? The PWR_FLAG marks VDD1-3 and PA_1 as being powered, but how does the power come in to the circuit and connect to them? Will there be connectors on the board provide input voltage for +3.3V and VDD1-3 to power the nucleo and lights?

[KnockbackNemo]

Is there a reason for shorting the output pins of the optocoupler together? I wasn't able to get to the datasheet (Lunainc is redirecting me to the main website for some reason- does that happen to you too?), but I think powering the optocoupler will just connect pins 4 and 3 but not drive any current through the resistor. If the goal is to switch on the mosfet, you'll probably need to add a voltage source on pin 4 to put current into the mosfet gate as well as a pulldown resistor to make sure the gate is low otherwise.

[KnockbackNemo]

What is the purpose of this part of the circuit? It looks like the current through the shunt resistor is being used to amplify the voltage and then send it back to the nucleo. Are the pins trying to sense something?

[KnockbackNemo]

Those are my main questions so far. I think once I know the function of the components, I'll be able to leave a better review. Keep it up! :)

[toadj32]

I would make sure to get someone other than me to review since I am a novice electrical engineer, however I want to give my input for the sake of learning and experience.

The first thing I noticed is that your opamps power supplies are flipped on two of them with ground on the + and 3.3v on the - terminal:

Secondly I was curious what the purpose of having two LEDs in series here is. You may have a reason, but would they not both play the same role?

This may be a result of my lack of understanding of the overall system, however it is unclear what the VDDs are and where they come from. I think the project could benefit from some confluence documentation. I would like to see your research and your decision making steps so I can fully understand the project and give you better feedback.

Another note is that while somewhat more difficult to implement, a switching based regulator would likely be more efficient than a FET based regulator. You may have a good reason for doing it with FETs though, however I would still like to see this reason.

Oops I did not notice the opamps were flipped, thanks!

I'm using two LEDs in series because a major consideration for solar simulators is light intensity, which has to reach 1kW/m^2 to mimic the sun. If I want to reach that requirement, I wanted to use more LEDs so that I can place the light source at a slightly greater distance away from the solar cells so there can be space for the lenses to manipulate the light into a more uniform beam, which is another major requirement for good solar simulators---light uniformity.

The VDDs come from the power supplies. I'll make sure to update my confluence documentation!

I looked into FET-based regulators and switching-based regulators. A FET-based regulator is more stable and has less noise than a switch-based regulator because it has a smooth, continuous feedback loop rather than suddenly switching back and forth, which could generate high-frequency noise.

[IsaacNeideffer15]

Another thought I had is that there are ICs out there that can provide the constant current that this circuit seeks to provide. You may have considered this already, and I am not sure how high power your application is, so it may be hard to find, but something like this may work: https://www.st.com/en/power-management/stcs05.html#documentation (prob not this one, but something similar)

Another small thing is that in your schematic it's probably a good idea to add bypass capacitors to the opamps.