Buy an emonPi without the USB power supply?

Is it possible to buy either the emonPi or emonTX from the store, without having to select a 5V USB power supply? I don’t get the option to continue without selecting one. The AC adaptor IS showing as optional, just not the DC. You can’t even get just the emonPi board on it’s own without a PSU either.
EDIT: emonTX allows a -none- selection. I was mixing it up for the emonPi basic board.

With so many USB adaptors already floating around, and ever more being replaced by USB-C, it seems somewhat unnecessary and just adds to the mountain of ewaste by forcing people to select one.

I would have thought so, but it does appear not. Might be an error. There is an issue in that the connection is a mini not a micro USB connection, but as a minimum just a cable should be available I’d have thought. @TrystanLea?

Looks like an emonTx can be ordered w/o a PSU. Viz:

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Had a bit of a derp moment there! I’ve amended the original post accordingly.

It looks to me as if it IS possible. On opening the shop page
the Power Supply section has no choice selected:


Each toggles on and off when clicked, and when on, the price increases appropriately.

I did notice that, but unless one of those options is selected I get a pop message when trying to add to cart saying it’s a required option.

I didn’t go that far. In that case, it’s an email to [email protected]

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Hi guys,

Sorry for the inconvenience, for the recent change we made to the shop to require a USB power supply be purchased with the emonPi / emonBase. This was a very painful decision, I’ll try an explain:

I totally agree, I hate it. The issue is the Raspberry Pi foundation keep increasing the power requirement for the RaspberryPi. The current Pi3B+ that we ship requires a 2A min power supply to run stable, the Pi4 requires 3A. The emonPi has a mini-B power socket therefore a USB-A to Mini-B cable is required with 20AWG conductors to handle the current, this cable was difficult to source. The vast majority of USB-A to Mini-B adaptors ‘in the wild’ have much smaller conductors 28/24AWG is typical, this cable cannot meet the peak current requirement. Previously we had had lots of issues with users using sub-standard cable and power supplies resulting in unstable systems.

If you have a good quality 2A USB-A power supply we would be more than happy to just include the 20AWG Mini-B USB-A and a £5 discount.

I suspected something like this.

Might I suggest you add this to the shop page (if you haven’t) and add something to the error message as well.

Might I also suggest you could modify the options to offer just the cable but selecting this triggers a popup telling users that it is their responsibility to source a good 2A supply. You could then add a note to the order stating that the user has accepted their responsibility for a 2A supply (which most phone chargers are not).

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Thanks for the response Glyn. It’s a good point about the Mini-B cables - as they’re an older design from before when phones and tablets charged at the rates they did, it’s no surprise most of them are pretty thin gauge wire!
Happy to test out any changes in the shop that’s needed - ready to place an order whenever!

@glyn.hudson the other option could be one of these