AC Power supply in a Particle-based product

Hello wonderful people at Particle community,

In the past, I have used a USB adapter to power our Particle-based product. However, customers desire the ability to plug our product directly into a wall outlet. Hence, I have started exploring options to integrate an AC-to-DC converter.

While I have been able to find numerous resources for the circuit design and even a few board-mount module options, I am yet to find a reliable NEMA connector that could be soldered on the board. Specifically, I am looking for the plugs shown here in the white circle.

Does anyone know what they are called? I checked with Digikey tech engineer and they couldn’t help. I have seen them on numerous products like USB adapters, smart outlets, so they cannot be custom-made I feel.

In addition, as can be seen in the picture, the power connectors are on a separate PCB (black rectangle) than the digital part of the board and it may be a common practice for scaling reasons. If anyone has gone done this path, could you share good practices for power supply design (EE, regulatory, scaling) in a connected product?

Your inputs and help are much appreciated.

Thanks
Rahil

I’m looking at your question and then your picture but to me the two things don’t match.
You say you want to be able to dispense with an external power brick and have a single unit that simply plugs into the wall. in your picture you appear to have board mounted tines that would grip the prongs of a plug- making it a socket.

I think the easiest way to get what I think you want is to find a “Plug Case”, this would be a nice enclosure with the plug bits integrated into the moulding. Here’s a nice european one https://www.okwenclosures.com/en/Plastic-enclosures/Plug-Cases.htm and some much uglier but cheaper US ones https://www.polycase.com/plug-in-wall-plug. My personaI would be to buy a PCB mopunted switchmode module and then follow the module manufacturers design guidelines. If designing your own you need to look at things like spark gap slots, maintaining good seperation of the AC and DC and low/high voltage circuits. Theres plenty of advice about that online already. For an informative giggle you can also look at Youtube videos where people take apart chinese electronics, they frequently put terrible PSUs in cheap devices that don’t follow the rules.

2 Likes

Have you thought about incorporating a simple 5.5 x 2.1mm barrel jack? Doing this would allow you to “hide” your usb connector. You want to prevent people from getting ideas about connecting the device to a computer and futzing with the MCU.

If you bring in mains voltage, would your customers then ask you to carry a UL/ETL/CSA or some other certification for a high voltage appliance?

It is difficult to understand the benefit to your end users bringing mains power inside your device if it is not needed and creates more complexity.

1 Like

As others have said, the parts you circled are the receptacle part of the device where other things can plugged in. Mouser carries parts like this:

http://www.mouser.com/ProductDetail/Qualtek/738W-CX2-01/?qs=sGAEpiMZZMtiRBiUbHlRZTjFVyTGswEWCxhQ%2FEl9uIA%3D

You can get it in 2 prong and 3 prong configurations.

If you want the other side, the plug part, I think the advice above to get Plug case is good. You are going to get at least an enclosure that meets the flammability standard so your job is made easier.

1 Like

Hello everyone,

Thanks for the replies. I truly appreciate the advice.
I see the error in my post. I was using a picture from a smart plug teardown without realizing that I highlighted the receptacles (which I do not need in my product) instead of the plug.

Plug case is a solid advice, but I do not see a lot of options out there including on Alibaba. The existing ones are certainly not easy on the eye. In addition, I also need the setup button and the status LED provisioned in the case, which might make off the shelf difficult to adopt. A custom injection molded case is not out of the question, however, I am yet to find the plugs that would go in the front of the case.

I have seen at least two implementations of these plugs. In one case, like in the USB adapter shown below, the plugs are part of the plastic case with wires leading to the board. I think this is what would be required if I choose to go down the plug case route. But this implementation would require an extra assembly step and may be less reliable.

I would prefer plugs that can be soldered directly to the board (below). In this implementation, the case has provision (holes) for these plugs and the board is screwed into the case. The product is not intended to plugged in and out frequently, so we can compromise somewhat on the mechanical strength if need be with this embodiment. Any suggestions on where to find such plugs? Any thing obvious that I am missing by choosing this over the first (more common) usage?

@BulldogLowell - Good question. Yes, a barrel jack would not be too different than the microUSB (that we currently have) expect that latter gives the idea of being able to tinker (we are ok with that). But, there is value to be had beyond aesthetics and novelty in being able to plug the device directly into the wall socket. We have some features (nightlight, doorbell receiver) that need plugging directly into the wall socket. Yes, UL/ETL will be needed. We intend to incorporate an already certified power supply to ease the regulatory process.

Thanks
Rahil

I understand. We’d rather just buy a certified adaptor and save the cost of meeting all those rules regarding clearances, materials…etc. UL is now requiring all components do be listed or tested.

Too much money for us!

:stuck_out_tongue_winking_eye:

1 Like

We didn’t want to get involved in the AC messy stuff too, but customers have been pretty clear in what they desire next.