NEED: Any thoughts of step-down transformers from US 120vAC mains to Omega?



  • Need a transformer interface between the Onion Expansion Dock (and Omega) and a 120VAC bus coming from my Mains. Any thoughts?



  • I did this in a two-stage approach.

    #1) Decent laptop brick. This brings the voltage down to 12V XXXAmps DC. Cut the laptop-end off and expose the wires.
    #2) https://www.amazon.ca/dp/B01IAOM640/ref=olp_product_details?_encoding=UTF8&me=

    Item #2 I know is now unavailable however the principal is the same. 12V line in and you get USB 5V out in a convenient factor.

    I also took apart an old car charger cable and used its guts. Worked like a charm but it was too bulky.

    These are just my personal opinion and I provide no guarantee of UL/CSA or FCC compliance in any way. Use it at your own risk, you bare sole responsibility for your own actions.

    Regards,
    Stephen



  • Thanks!

    Here is what I am looking at:

    1. Run wire from an existing 120 VAC bus from my main under the house making sure I properly terminate it.
    2. Along the way, create an intersection or vampire connection of the transformer on this wire.
    3. Connect the Onion to the transformer.

    If the Onion dies, I can always unplug/unsnap the Onion and replace it. If the transformer dies, I can replace it pretty easily.



  • @TheMonkey-King You could consider something like:



  • @TheMonkey-King said in NEED: Any thoughts of step-down transformers from US 120vAC mains to Omega?:

    1. Along the way, create an intersection or vampire connection of the transformer on this wire.

    Why does it have to be so complicated? Are you hiding the Omega in some way?

    Anyway, I like this 5V phone charger idea if you are using a dock, or a similar device generating 3.3V if you are powering the Omega directly (or the 5V one with appropriate resistors/diodes). These devices are already proven and tested. All you need is a standard wall plug (or a hidden standard floor plug).

    Why risk a house fire because of an improvised setup?



  • Why does it have to be so complicated? Are you hiding the Omega in some way?

    Yes, in a way. I want a bunch of Omegas in the house to act as nodes. This way I ensure a "mesh" of them for the idea I have. Also, being under the house I don't have wall sockets to plug in wall-wart transformers (ala phone chargers). One of the requirements is that the Omegas receive a steady, regulated supply of electricity with, perhaps, a battery backup. The tasks these Omegas will perform are under the house.

    Why risk a house fire because of an improvised setup?

    That's why I am looking at something not improvised. If I can find something either cuts into (safely) or attaches or clamps to the line safely then all I have to worry about then is a safe power connection (like the USB idea above) between the transformer and the Omega.

    I will ask on the Adafruit forum too. When I find what I am looking for, I report back.



  • I've been using these round 3W 3.3V PSUs from Recom for a few projects a while ago. A bit expensive but very easy to connect and mount, especially within a flush socket housing.

    There's also a less expensive 2W mini-brick shaped version.

    2 or 3 Watts are way enough for the Omega (it consumes about 1W), but of course you need to take your peripherals (sensors, relays, etc,) into account.



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