hello all and thank you in advance for any guidance that you can give.
What I am trying to build / learn the feasibility of is I want to make a power supply capable of putting out 24v dc power and take an input of 85v-260v ac OR 24v-120v dc power. This would be off the same input power pins so would be plug and play on either Ac or Dc power.
I am needing to run some external sensors off 24v dc. Hence wanting to use 24v I will use a voltage divider to run down to the correct voltage for the board and other accessories but that I can figure out.
I know this is possible to do as several sensors I know of (banner sensors) are able to take in roughly the range of power I am looking for. Also I have seen in looking on parts website (mouser digikey etc) that you can buy switching power supplies but none that I have seen can take the lower end dc power that I want it to be able to run. 24v dc needs to be an acceptable input.
Also I do not need this to be a large power supply. Probably 300ma and 24v dc is all I would need.
The best, most flexible solution would be to incorporate two supplies, one with a suitable AC input range and one with a suitable DC input range. Wire-or the outputs, such that you have 24VDC for your system regardless of which of the two inputs is powered. You will need two input connectors, granted, but that's the way you should do it. You also need to carefully consider grounding of the various circuits you're describing.
Even if you find a "universal supply" that will take the full range of input, both DC and AC, you'll have boxed yourself into a fairly unique, and likely expensive solution, and (if this is a design you want to market, or repeat-build down the road), you'll be far more vulnerable to product-orphan issues. Two supplies as described above will be far more available and generic.
Your descriptive wording is such that I suspect you haven't the electronics knowledge to pull this off safely and correctly, though of course, I may be misunderstanding you. Frankly, IMHO, if power electronics/electrical isn't your background, you're getting into stuff you really need some technical expertise for.
Oh, and without links to the sensors you reference, it's kinda hard to infer what you're talking about, or what your needs might be. So, links, please.
Voltage dividers are no good for power supply circuits. Use buck converters.
From the above linked tutorial.
[### Application Dont's
As tempting as it may be to use a voltage divider to step down, say, a 12V power supply to 5V, voltage dividers should not be used to supply power to a load.
Any current that the load requires is also going to have to run through R1. The current and voltage across R1 produce power, which is dissipated in the form of heat. If that power exceeds the rating of the resistor (usually between ⅛W and 1W), the heat begins to become a major problem
Consider purchasing a lab power supply, they supply any voltage you want but will also limit the current to whatever level you set it at as long as it is in its range. There are many available under US$40.00. Check your favorite suppliers.
As far as using resistor dividers that is a great idea on paper but it will not work as expected. You also need to take into account the load and what happens to the voltage if the load changes? You could supplement the lab supply with a few SEPIC (Buck/Boost) converters, many under US$5.00. Some time on the internet will save you some money and a lot of time.
In principle this seems easy; use a bridge rectifier and capacitor to make whatever you plug it into into a dc supply - of between 24V (- 1.4V) and 400V
but now you need to provide isolation, (so you need a transformer)
and to get a 24V dc output from what is now a 22V supply you need a buck - boost regulator.
One complicating factor is 24V out (regulated) from 24V in. Simple regulators need Vin to be more than Vout.