Hi All

I am working on a design that will require 24V AC and 5V DC from a 240V AC source.

Therefore my PCB will use the following transformers.

24VAC transfomer
And
5V DC Transformer
And
Terminal Block

I have used a copper pour that is identical across all my 4 layers, instead of just track so that my my overall thickness of the copper is much more then a signal layer or i do not have use a thicker copper PCB process.

Is this a correct way of doing this?
This is my layout

Top:


Bottom:


Mid1:


Mid2:


Regards

DJ

 

I wouldn't do it that way. I'd use a two layer board and spec 2 oz copper, most commercially made boards come with 1 oz or less. Much much less expensive then a 4 layer board with lots of feed through holes to interconnect the traces or layers. Then I'd make the current carrying traces as large as possible with the necessary gap between legs. It's more important to know what the expected output current is going to be, and the expect shorted output current so that the traces are spec'ed the right width. I use a PCB trace width and thickness calculator to find that.

How many amps are you talking? I always spec a fuse or CB to do most of the protecting unless it's a uC or some such circuit, then I get all elegant with foldback current limiting or some such. Depends on how highly I value the circuit.

Now that I've checked the transformers, I definitely wouldn't bother with 4 layers. Don't even need 2 oz copper. The current is so low, that just standard practices would be fine. Make the pads 2X to 3X the pins diameters of the transformers or connectors pins and the traces 1/2 the pads diameter and you'll be fine.

 

Hi Jim

Thank You for your reply.

I am powering a solenoid that has a max current of 300mA. I will be having 16 relays( Relay)on my PCB. They are unlikely to operate all at the same time. The 5V will be charging a Li-Poly Battery via a charge circuit @400mA max.

As I aim to be having 16 relays, I found that it would be necessary to have 4 layers, so that I can keep the 24VAC on one layer so it is simple to route. Otherwise, I would route a 24VAC between my connector pads. This is shown below. Please note this design is working progress and not yet completed. As you can see there is 16 strip terminal connector in middle with 8 relays on each side. Each relay has a copper pad via going to the 24VAC layer. And I can not increase the width of my PCB unless I move a set relays to make another row.


Yes, I will increase the pads for both the transformers and my connectors. I think the standard library has not done it correctly.

 

Can you post a schematic?

 

Here it is.

The relays are repeated 16 times.



Driver

Connector

 

Sorry I took so long to respond, family member had a car accident...they are okay, but it was a mess trying to get them back on the road.

Anyway, after seeing the schematic, the answer to your original posted question, "Is this a correct way of doing this?", in my opinion, is: Sure. That'll work fine. It's one of thousands of ways of doing it limited only by your imagination and budget.

 

Hi Jim

Thank You for your reply.

I hope the accident was not bad and that your family are well.

I had a review and found that i need change the 1.5K resistor to about 450-470ohms to achieve the 2mA for the LED in the relay.

I will go ahead and have this PCB made.

 

Please don't forget to make a drilled slot on PCB to physically separate phase-neutral-other DC lines

 

No need for more than 2 layers, 2oz copper nor routed slots. All that is necessary is to ensure that the creepage between live parts (which includes neutral) and low-voltage parts is greater than the specification in the standard. The highest figure is likely to be 5mm. The largest transformer looks no more than 20VA, so the mains current is <0.1A, so no need for tracks wider than 1mm either.
Don't forget that the 5mm creepage applies to the ground plane - the ground plane should be nowhere near live parts.
And where's the fuse?

 

Unfortunately I will need to use 4 layers, as my PCB and connector dimensions are restricted, therefore it hard to route the 24VAC to the relays on the other side, other wise it would routed between the connector pin which I want to avoid.

I am not really routing the 240VAC anywhere so do i need to create slots, the mains power is being inputted into the 240VAC transformer.

I do not have a GND plane as such, but do have copper below the driver IC and its passive that is connect to GND from the 5VDC transformer. There is no other component that needs GND. And the spacing between GND and 240VAC is 10mm.

Thank You, i will add a small fuse, any recommendations? Preferable something that can be replaced without soldering

This my final layout so far

Top Layer

Mid 1

Mid2
Bottom