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Aneesh Murali Nariyampully , 06-09-2025, 07:39 AM

Do I need to pour the GND on the top layer or not for this pcb layout. I mean in the low voltage side the mcu section.
Please help me... To decide.
It's a dual layer board GND plain on the bottom, signal and power trace on the top.

QDrives , 06-09-2025, 08:29 PM

No.
Even with most copper being on the bottom, it do not think you get a copper balancing problems.

Aneesh Murali Nariyampully , 06-11-2025, 02:58 AM

@QDrives worried about the noise immunity 😔

QDrives , 06-11-2025, 02:44 PM

Yes, for improved EMC / EMI (and safety) you would need to change the layout and schematic.
Functionally, I think SMPS is incorrect with pin numbering.
I assume:
- R2 and R20 are varistors? If so, rename to VR1 and VR2
- U4 and U6 are ULN200x
- U3, U7, U8 and U5 are opto-couplers
- U2 is a microcontroller (programming header??)
- C1, C13 and C14 are X1 or X2 capacitors

Aneesh Murali Nariyampully , 06-12-2025, 01:00 AM

@QDrives that's correct 😁, smps is from Hi link 12v module.
What are the recomanded changes that you prefer?
Is this a bad design? 😞

QDrives , 06-12-2025, 04:30 PM

I see that the Hi-Link module has the high voltage pins close together and low voltage pins far apart. Normally it is the other way round.

"*Is this a bad design?*":
- What should it do?
- Why the 2 relays in series?
- Do you plan to sell it?
- Which parts of the world?
- What are the applicable (safety) standards?

For a commercial product, yes, this would be a bad design.
For both hobby and/or learning I would still go for a much better design.

Aneesh Murali Nariyampully , 06-15-2025, 10:00 AM

@QDrives
Why it's a bad design?
What's the better design?
What are your recomanded changes to make it better?
Which makes you think it's a bad design?

Now answer for your question.

What should it do?
A) It's a power control unit for my new power amplifier.
It do inrush current limit during startup, standby and power on off by a microswitch, temperature based shutt down(over temp protection), over current based shutt down(power amplifier fault).

Why the 2 relays in series?
A) one for the power on and off another one is for the current limit bypass.

Do you plan to sell it?
A) Yes not as boards we sell as the whole amplifier.

Which parts of the world?
A) who ever loved it's performance and quality i mean not this board the whole power amp.

So it's just a rough layout that I just drown so I know there is mistakes, I make mistakes and I learn from it and I learn from others mistakes too. May be the board have problems so that's why I'm asking to the experts to improve and make it better as I can, we can. We have to make it best as possible anyway.

Aneesh Murali Nariyampully , 06-15-2025, 10:16 AM

That's why I put this layout here for confirmation. Honestly I thought I can fix the errors before going to manufacture and someone really going to help me. But it didn't happened anyway. I just ordered the first 5 nos as the test units and I hope we will do better at least in the next Rev if someone really helps.
Means I just lost my time and effort and to design the system and money for the pcb.
Or else it's just trail and error I have to find myself the right way to do it but anyway I will not throw any garbage on the market "do the best or do nothing"
@Drives thanks for your valuable time that you spend with me thankyou.

QDrives , 06-15-2025, 03:08 PM

Now it makes more sense.
The two relays are not so much in series and I see what the big resistors are doing. That is why I asked the first question.
The datasheet of the SMPS also shows a common mode choke. Better add that in you next revision.
As for the filter capacitors -- they need to 'short' the noise and you want them as close a possible to the noise source and with a very short connection between the the two 'powers'.
For creepage and clearance I would see if you can get a copy of IEC 60950 or 60664. From memory for 230Vac you would need 6.4mm clearance and 8mm creepage. Do think of the creepage inside the relays too.
Add programming pins for the MCU.
You have many unused pins on the MCU and all 'prot'(ection?) pins with hard jumpers. Why not have each of those inputs to the MCU and let software handle it?
The opto-couplers do not add anything other than voltage level shift. A lot cheaper and smaller solution is to use pre-biased transistors, like the here https://www.digikey.nl/en/products/filter/transistors/bipolar-bjt/single-pre-biased-bipolar-transistors/292. There are also arrays of them, making it even smaller. The ULN's can also be replaced by them, but make sure that the relay current remains well within the limits of the transistor.
You need to connect R5.

Aneesh Murali Nariyampully , 06-15-2025, 04:38 PM

@QDrives I used ulns to make the routing and soldering simple and to make compined logic from the 7channel amp protection inputs and it's always have the input resistors and flyback diodes built-in. and I used jumpers to enable and disable protection logics of channels because we have to use the same board in 2channel, 3 channel ,4channel , 5channel, 6 channel and 7 channel amps and by the way the uln reduce the distance of mcu pin wiring because I thought it will cause and have chanses for false trigger when the wires are long because especially we have to wire that into the protection boards. I used the optocoupler for two reasons, one is make it as inverted logic active low and use mcu internal pullups and other is to reduce the wire length from the mcu pin keep the loop area small and my input triggers are designed for 12v logics, because we have to wire the inputs to the front panel and temperature sensors placed over different areas inside the power amplifier.
Thanks for your answer 🙂

Aneesh Murali Nariyampully , 06-15-2025, 06:16 PM

Yes check the first image of the 2d model it's the finished view of the layout there you can see R5 was connected and added programming headers.