Electron power from switching power supply

Hi I got a dilemma regarding power supply selection for the electron.
My app require a PS to feed the Vin pin with the requirements of 100 to 240 v AC line.
One can find lot of switching PS and inexpensive alternatives but I am not sure how it can impact on Electron operation when they are rail din mounted and outside the Electron enclosure.
Some inside on that?

Does the existing panel have a Transformer in it already?
It’s common to have a 24V DC Din rail.

If it doesn’t, could you add a 12VDC Supply in the panel ? That gets you closer.

If you don’t want to make the final step down to 3.3V yourself, you can use an Electron board like this with an input range of 5V-32VDC.

Thank you for your answer.
The enclosure is mounted inside of a A/C package unit. Those unit have a 120/ 208 v step down transformer to 24 vac which feed the contactor for compressor and other fans.
Generally they are very tight in power around 40 a 70 VA.
I would take power from them but I do not want to impact the A/C unit’s contactor with the Electron peak power. Also there are available 120 Vac or 208 V ac single phase.
It is does not recommend using using switching PS for communication.
I also take a look to Mean Well like you showed me but they are Switching PS.
On the other hand linear PS are pretty expensive for my protect summing that I do not want to use the battery.

Which Electron variant? Even with the 2G which pulls the most current (something like 2A peak), when you are pulling from a 24v supply, you will use about 7 times less current due to Ohms law (assuming a step down to 3.3V). So you’re pulling like 300mA max from the 24V supply (just electron, not accounting for external circuitry.) Is there not 300mA available on your 24V supply? You still need a bridge rectifier and a step down converter to the 3.3V but should be easier that finding the right HV supply. Just a though…

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Yes, I would need a step down converter to 12V or 5V to supply the VIN pin of a Electron 2G/3G.

The question is : Can I use a switching power supply inside or next to the enclosure that contain the electron ?

Yes, a properly designed switching power supply can be used.

You can just send your 24V to the terminal board I linked to, or something similar with on-board power supply.


As you suggest the Mean Well brand, do you know about those regarding a good design ?

The Electron can be powered by +12VDC from the Vin pin. There is no reason to step down to 5V in your application unless you have supporting circuitry that requires 5V. The Electron has a 3.3V switching regulator on board that can supply some supporting circuitry (up to 800 mA).

Meanwell power supplies are not well made, and I would not recommend them. They use cheap components and you’ll spend more on warranty repairs than a quality power supply ever cost. I don’t know if your solution is a one-off or there are many units that require a power supply.

If you want a quality power supply that will not die in the field, catch on fire, etc., look at Phoenix Contact, Sola, Allen Bradley, etc. Automation Direct also is a source of budget power supplies. You can generally use anything from 100-240VAC as an input to these.

DO NOT UNDER ANY CIRCUMSTANCES connect your electron to the 24VAC supply noted above, nor try to use a DC-DC converter on that source. It is unrectified AC and is actually 34V peak. It will flat out destroy your electron on contact and won’t do much better for a DC-DC converter. I am noting this as someone above indicated it could be used.

eBay can also be a source for used power supplies from quality manufacturers. I would much prefer to have a used Phoenix than a new Meanwell.

Linear vs switching power supplies is not a black and white issue. The electron is powered by a switching power supply. The issue is noise from the power supply and a quality switcher has very low noise these days. As long as the ripple voltage is within a reasonable range, there will be no problem. I see no prohibitions on the Electron data sheet precluding the use of switching supplies.


No, I was referring to using the existing 24V with the NCD board below:
You posted to have access to an existing 24V transformer.

This (or similar) would be all you need.
[EDIT] Nevermind: I misread, you said the PS is 24VAC.... Scratch my recommendation

What you have listed is DC-DC switching converter. The 24VAC supply is not compatible with this. What the original poster needs is an AC-DC power supply with nominally a 12VDC output and 2A of supply (i.e. 24W).

Sorry, I missed the 24VAC

Thank for your answer.
This is prototype project .
I need to look at the future, and look for a not so expensive brand new PS, those you mentioned can be pretty expensive in relation to the device I am trying to design.
On the other hand as you mentioned I can use input voltage from 120 to 240 v which are
ready available on those HVAC units.
My fist design constraint is to be the less invasive possible regarding the HVAC electrical circuits because my design is about monitoring some parameters.

OK, if you’re building a proto, most anything will do. If you intend to build a product, the time to start testing power supplies is three years ago Thursday with production power supplies in an environmental chamber.

Electrolytics are the weak link as they have always been, and HVAC installations generally have heat involved one way or another. If you’re going to stuff this in an external enclosure, then you can require a utility outlet and use a class 2 wall wart or buy a pre-approved open frame power supply that will be far less expensive than a DIN rail version. As with most things, prices are negotiable when you have volume and a manufacturer’s rep across the table.

Awesome :rofl: this is the answer I was looking for .You pointed at I had doubt: a service outlets and a wall wart 12 vdc @2A or 3A…
Just one old question remain: those wall wart being outside of the enclosure can they be switching type.?. Because they are cheaper.

You need to get a scope and check voltage ripples as well as conducted noise into the device. There’s no way to really know without checking.

And I know someone will say “check the datasheet.” Well, there is no standard for what to write on a datasheet. Some will be very conservative and what you measure will be well within what’s written. Some datasheets will represent exactly what the device does. And others will simply be copies of competitors datasheets with absolutely no relation to the device’s actual performance. I won’t mention who might offer such a datasheet, but I can assure you, they meant well.


@LabSpokane :smile: great, you have a great sense of humor. Yes, I understand what you mean. Thanks.