I’m just starting to use KiCad and I’m working on an Arduino powered project that will end up in an enclosure.
I’d like to add one of those Multicomp Stainless Steel Pushbutton Switch to start the device.
However I don’t know how I should lay it out on the schematic. Obviously the pushbutton won’t be mounted on the board, but should I use connectors to plug it into the PCB, or directly solder wires?
Here are my questions : First: Is the SW6 pushbutton the right component ? (It won’t matter since it will be marked as a DNP, it’s just for clear documentation) Second: Is connecting J6 to J7 like this the right move ?
I don’t know the structure of your Multicomp device, but usually “push button” is used for a momentary contact that opens as soon as you remove your finger, and “switch” is used for a contact that stays in one position until some action (such as pushing it again) is taken. But I’m not exactly sure of terminology (Not a native English speaker).
Does your switch / button have a built in series resistor? You may have to add it on your PCB.
I like your second attempt with the 4 contact connector better. You can use the Exclude from Board attribute for SW6 and J6, or else they will be added to the PCB too. You probably do want these in your BOM, but not on the PCB.
Another (and a bit sneaky) method is to assign a connector footprint to your switch. This looks neater on the schematic, but in this case neither the switch nor the mating other connector will show up in the BOM, and you also have to be careful with the pinout. This method would be reasonable if you want to solder wires to the PCB directly. In that case you will still need a footprint on the PCB to solder the wires to.
Yes, the terminology is a bit confusing here, it has a pushbutton action but a switch function.
Your comment made me realize that, so I replaced SW6 with SW7, which I think makes more sense.
I agree that this method would look neater, but I’ll stick with the connector. That way, the PCB will have a more homogeneous look, since in the end I’ll have four different connectors placed on top of it.
Apparently there are latching versions of that PS switch.
If it’s got some electronics to sense your finger, then adding in an extra flipflop inside the switch is trivial.
The flipflop probably gets reset when the power is removed. This is different from a mechanical switch, but can be an advantage too.
The one we use have only 2 wires shorted for a while when pressed (no supply).
In my application pulse from switch switches on P-MOS powering uC from battery then uC sustains this P-MOS. From that moment it is uC that makes decision when to switch power off. Next button presses (our device has only one button) during working are received by uC to change functionality, but if needed can be used to simulate on/off switch.
Good for you that you use the momentary version, but writing down that would be the only available version is not correct.
For the rest: I quite like the soft power switch as implemented around the ubiquitous “transistor tester”. It’s a very popular gadget and available in very many versions. It uses a momentary button that then opens a BJT, which powers a voltage regulator and an ATMEGA328, and the uC then keeps that BJT open with one or two other BJT’s.
I buy them from our local distributor. So to not give link to Polish language page I have just found that page and short look at text you circled told me: “No latching”
