Hello all,

I've recently completed the design of a circuit schematic and PCB for controlling an RGB LED string using a NodeMCU ESP8266 WiFi module. The circuit operates on a 12V DC input and utilizes three relays to control the red, blue, and green LEDs respectively. The LED string itself draws approximately 14.4W per meter, and I plan to power a 5-meter long string, resulting in a total current draw of 6A.

In order to ensure proper operation, I used an online PCB trace calculator to determine the required trace widths for the PCB. Utilizing a 1oz copper weight, the outer layer traces should be wider than 3.56mm to handle the current load effectively. Therefore, I used 4mm trace widths for powering the LED string. It might be a overkill since each relay powers up one third of the total requirement but ı wanted the power line to be safe.

I used bottom layer as GND.

I am open to receive feedback and suggestions for potential improvements or any oversights.

Thank you all.

 

Hi cool,
It looks OK to me.
When you say you have used the bottom layer as ground, the images show copper tracking pattern on both upper and bottom layers having almost identical tracking.
Which of course would be an advantage in current carrying
E

Update: @coolworm
Can you confirm which image is the component side of the PCB??
You are showing Through Plated Holes on both faces of the PCB, but you say: I used bottom layer as GND.

 

Hi cool,
It looks OK to me.
When you say you have used the bottom layer as ground, the images show copper tracking pattern on both upper and bottom layers having almost identical tracking.
Which of course would be an advantage in current carrying
E

Update: @coolworm
Can you confirm which image is the component side of the PCB??

Hello Eric,
Thank you for the input. Both pictures are from top layer. The bottom layer is empty. One of the pictures shows 2D look, other one shows traces and copper areas.

 

Hi cool,
If the bottom face is only used for ground, how will you be able to solder in the relay pins, which normally project through the PCB.?

Most relay types and PCB connectors cannot be top soldered.

E

 

Hi cool,
If the bottom face is only used for ground, how will you be able to solder in the relay pins, which normally project through the PCB.?

Most relay types and PCB connectors cannot be top soldered.

E

Hello Eric,
Through hole components go through the PCB and they are isolated from the ground plane if not connected to the ground.

I added the bottom side of the PCB as well after your suggestion.

 

Hi cool,
I would increase the clearance of the soldered through holes from the backplane, at the solder pins.
E

 

Hi cool,
I would increase the clearance of the soldered through holes from the backplane, at the solder pins.
E
View attachment 320477

Thank you Eric, that's a great input. I will definetely do that.

 

Where are you using this board? Do you need mounting holes in the corners? If so, leave clearance for a nut driver.

Take a look at this design tip to ensure mounting hole clearance.

 

Where are you using this board? Do you need mounting holes in the corners? If so, leave clearance for a nut driver.

Take a look at this design tip to ensure mounting hole clearance.

Hello John,
Great input. I totally forgot about mounting holes.
What is the difference between versions with and without pad? Shorting the holes to the ground plane is a good thing or not?

 

In some cases, you may want to connect the board ground to a metal enclosure, say for grounding via brass standoffs. Or you may want a plated through-hole for added strength. Some fabs (mostly in the past I think) wouldn't allow non-plated holes.

All that being said, I usually use non-plated holes for mounting.

I really find the clearance being shown in the document layer handy during board layout to ensure enough room around mounting holes – being in the document layer, it doesn't show up on the finished board.