Schematics for relays

I am a new user of KiCad and wanted to place following relay into my schematic:

However, all relays I can find look quite different. The only “normal looking” schematic I could find is this:

Unfortunately I need it also as dual coil version.

What is the reason the relays in the schematics do look so different?

First, I agree that the Relay library (like a lot of others) is a mess.
But using KiCAD, you’ll need to make your own symbols in many cases. Live with it.
I suggest that you copy the symbol “Relay_DPDT” to a personal library and modify it to your needs.
Check the FAQ section to see how to do this.

you’re looking at my two relays - HUI has One-Coil with two independent channels. you hook-up as needed. if wanting independent coils, keep looking.

Kicad has handfuls of Relays… and includes Dual Coils… you could do some homework to find exactly what you want…


Kicad stock - dual coil Example

I did find the relay you refer to, but why does it look so different from the schematic in the datasheet? The pins are not on the right side.


@BlackCoffee Do you mind uploading the symbol/footprint files for your relay? :slight_smile:

• Symbols and 3D-STEP/WRL are made by people and we ‘people’ like different things so, we make ‘whatever’ it is to our liking unless there’s a company policy about it…
• Symbols are very easy to make so, most Kicad users grab one and hack it or create a new symbol… can be done in 5 minutes…

relay_sw_qianji_jqc-3f(t73).kicad_sym (1.7 KB)
relay_sw_hui-ke.kicad_sym (3.6 KB)
Relay_Qianji-3F.kicad_mod (6.0 KB)
Relay_HUI-KE.kicad_mod (7.0 KB)
Relay_QAINJI-3F.step (530.8 KB)
Relay_HUI-KE.step (93.4 KB)

You may need to re-link the two STEP files to the two Footprint’s…

Thank you so much! :hugs:

Because a symbol is there to show the function of a device, nothing else.
The supplier in this case decided to combine symbol and pinout in one picture. That actually works sometimes. But don’t count on it.

For most applications, I do not like relays shown as a single unit. KiCad does have a few relays which are split into several units such as:

  • FRT5_separated
  • G5V-2_Split
  • COTO_3602_Split

In KiCad it is very easy to create your own “component” by matching one of the default symbols, with another footprint, and make modifications as needed. The mayor concern is to make ensure that the pin mapping between the symbol and the footprint is correct, and that the relay you have fits on the footprint.

I also believe that the ability to modify and create custom symbols and footprints is an essential skill in any EDA package, and there are many who agree with that. Apparently it’s mostly beginners who feel apprehension to learn this part, but in reality, there are literally millions of parts, and it’s not realistic for KiCad to have them all. Websites like SnapEDA and PCBLibraries have much bigger libraries, but those are “generic”, and parts for a specific EDA package are generated on the fly when you download it. Those parts are often usable, but need some modifications.

Why? Can you be more specific?
I do agree that the whole electronics world is a mess, with millions of parts, and with tens of thousands of “different” opamps, while maybe 100 or so is probably enough to fill the whole range from “cheap general purpose” to “high end supper accurate / fast”. There are also many different types of relays, from big contactors to small signal, high frequency, low contact resistance, many contacts, high voltage, etc. But you can’t blame the libraries for that. Another problem with relays is that type numbers do not mean anything. Lots of different manufacturers, and naming conventions, but it’s all random names for most people.

KiCad’s libraries are also not complete, but that is completely different from being a “mess”.

Overall, I’m quite happy with KiCad’s libraries. All relays I’ve looked at have similar style and probably fall within the KLC They even all seem to have direct links to datasheets. I tried a few (towards different manufacturer’s websites) and they all work. I am actually quite impressed by that.

What would be nice is to have an easy way to visually compare footprints of relays.

Usually the reason is the basic drawing and reading convention for schematics. Left to right and top to bottom.

Inputs on one side and outputs on the other side. If you are sending a signal to two different outputs, you’d usually use the left representation of the relay. If you were selecting from two signals to one output, You’d usually mirror the relay as in the right hand relay shown.

More drawing conventions on the right.
With transistors and pots, it is generally similar. In one side and out the other, but these have a control in the middle.

Symbols are an abstract version of a component. They are neither the actual component nor the footprint. Their purpose is to help understand a schematic.


Thanks for the explanations. It is the first time I even draw a schematic, I even started with the PCB first and then realized how important a schematic is, so I have redone all again. Before I’ve used Fritzing but I don’t really understand it, KiCad on the other side is very interesting for me and it makes fun to learn.

I am highly impressed that this is an Open-Source project. The software is so professional :hushed:

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Welcome aboard and have fun :ok_hand:

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The Symbol Library is just that: for symbols.
But that’s not really how it is.
I picked out the “Relay” library in this case, but a lot of others are just like it.

It’s a long list of relays from a handful of manufacturers, each one available as 3 V, 4.5 V, 5 V, 6 V 12 V, 24 V, 48 V, 120 VAC, 230 VAC etc. and each with its own symbol.
Why? One would suffice.

On the other hand, there are only five (5) generic symbols there. Yes, really.
I’ll postulate that with 10…15 generic symbols you’ll have covered 99% of the relay world. Pinouts will need to be modified, but that’s in the personal library space anyway.
Additionally, each supplier could only have one main symbol for each relay series. That would cover footprint, pinout and data sheet.

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One would not suffice due to the amount of different footprints. I for one am very happy with the library because every time that I need to pick a new relay, it is simply there. And it is already pointing to the correct footprint. And there is a link (which mostly work) to the datasheet. So with all this, I think it is a really good library. I can also find my relay by it’s name.

So it takes me almost no time at all, to place the correct symbol which has the matching footprint linked.

This would imo suck really hard. You would have to ‘fix’ the pinout every time that you come across a new relay and you need to pick the correct footprint.

I only add things to my personal library for one of two reasons.
1). If it is about a component I am going to use alot. I need to add a vendor code.
2). What I need is not to be found in the default library.

If however I make some PCB with some component that I need just this one time, than
I am happy that I can find it in a default library.
I am happy if the correct footprint is already linked for me
I am happy that I can that I can duplicate a The correct symbol to my personal library, when I need to add a vendor ID code.

So yeah, KiCad libraries make me a happy person :wink:

:coffee: Bas

I once forgot to ‘feed’ my relay. :joy:

(picked the wrong symbol, was my bad)

One would suffice, as it’s the same relay, same footprint, just different coil voltages. Pure clutter.

I had a look at the results for a search for: “EE2 SNUX” On first sight it has 5 entries, with just different coil voltages. When you look a bit closer, you see they are all others derived from the 3V variant.