How to best change orientation of diode, and other errors?

I dont know if this was the corect thread name, but I will try to explain.

I posted this and got alot of help: Assist with what footprint to use? - #5 by JacobW

In this thread someone pointed out that the diods where in the wrong direction.

How can I in a simple way change them.

Can I change them all at once?

Take a look at the project:
Dimmer (1.4 MB)

What I am most worid about is the amount current threw ground and what route the current will take?

Will this eaven work?

I want about 10A 5V per chanel.

But all together around 32 A, so around 7A per chanel.

Best regards!

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I looked at your pattern and see that you didn’t put the diodes in parallel with the relay coil to avoid voltage peaks when they are used.

What diodes are you referring to?

You also have 5V, 12V, 28V short circuit via fuses!

I’m not really a specialist in high current PCBs, but according to KiCad Calculator 10A would require ~7.5mm trace width. For 7A your 4.7mm are ok. That goes for SW_K1 (longest way).

You have 8 channels, you want 10A each, adding up to 80A. So how are they “all together” 32A? And then 7A: 32/8 is NOT 7.

Take care J10,J11,J12 can support the current you want.

Btw, there is a left-over trace fragment near F11


As far as I see, they are actuated by switches, so spikes won’t matter.


Yes you are right, the logic is at 3v3.
However, it is a good practice to always put diodes in parallel with the coils.
Feeding must absorb such peaks that could cause problems.

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Sure, but it is at least not catastrophic compared to the fuse thing…

[EDIT] Maybe not all fuses are inserted in parallel. Maybe the desired output voltage is selected by inserting the respective fuse.

The Diodes D37, 2, 4 are correct if they are used for the protection from reverse polarity in combination with the fuses (even if they must be well sized) used SMA diodes and for the current values involved they are not good, at least to a first general assessment.
But since the fuses are incorrectly placed I don’t know what to say.

Again, they are not necessarily incorrectly placed if the output voltage to J1, 2, … is selected by inserting the proper fuse ONLY.

In this case, relays must also be changed.

Why so?
20 characters…

look at that:


the thin trace will be vaporized immediately. And the diodes are at the voltage input, not behind the fuses.

I do not understand.
If you are referring you have relays they cannot work well if used at 5V, 12V, 28V .
For the selected relay model it does not exist for a 28V coil operation.

So they don’t serve.

The relais is connected to 5V all the time. The fuse is not involved there.


…or maybe I should doubt my sanity. Forse sono pazzo :slight_smile:

You’re right I have to analyze the circuit better.
The fuses put in that way created confusion for me. :upside_down_face:

Bottom line, the thing will work as far as the logic is concerned.
I am not so sure about the track widths. The data the OP has given is contradictory. If he really wants 7A per channel that adds up to 56A, making the traces glow in a warm light. For a short time…

It’s long past midnight, bed calling.

The fuses are dual function.

Instead of selecting a jumper, with is hard to find that can handle 10 amps or 7.

I also want to be able to select what output voltage to have on each Chanel, so you are only suppose to put one fuse in, at once for each Chanel.

The benefits are that I also can have a fuse on each Chanel.

I was locked at the design of this relay card:

It looks like it only have one diod to protection for all relays. I hade diodes in parallel with all relays but decided to use only one.

At the moment most diods on the pcb are in wrong direction. Only Chanel one on the output is corect. So most of them would create a short circuit.

For example look at the diods after the d-sub. They are corect in the schematics but not correct on the pcb.

I want the board to handel about 150W at 5 volt.

Let’s say 160W, = 32A at 5V

I also would prefer if each output could handel 7,5A per Chanel.
2.5*3=7.5A per Chanel.

So they don’t need to handel 10A per Chanel but it is good with head room.

All chanels should be able to handle 7.5A but all don’t have to do it at once.

But what I am most worried abut is the return current. I don’t have a clear ground path for return current. A lot of tracks in the way of the current on the ground plane.

The relays will be controlled 2 ways. Either with toggle switch or with external GIPO like arduino or Pokeys.

Those inputs need to be protected. That’s why I put the diods in line with the inputs near the d-sub.

That is Corect!

Have not decided if I want a buck converter to feed power to relays and GIPO.

Absolutly but it would regardless of thicken of the trace. Because the diod is in the wrong direction. But not in the schematics?

This diod is only for protection. If you connect something that can produce back emf, but now when I think of it I don’t need on each output. Only on the power input one on each input. I can then remove 7 diodes. Or war do you think?