Universal voltage inputs

[suncq]

I find a industrial product that Universal voltage inputs are polarity independent. Connect to any range voltage in your control panel - from +/- 12 VAC/VDC to 120 VAC/VDC. Does anybody know how to realize this function ?
thanks in advance!
suncq@126.com

[SherpaDoug]

I have never noticed anything that can take 12VDC to 120VAC on the same input pins. 100VAC to 240VAC is common, but that is only a 2.4:1 range. Some "wide range" industrial converters will do 4:1. 12VDC to 120VAC is a 14:1 range! That would be a LOT harder. Can you give a link to a product with such an input?
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Ttelmah]

It depends massively on what he 'means'. There are plenty of input systems, that can 'detect' such a range. A simple AC input opto coupler, with a suitable input resistor.

Best Wishes

[treitmey]

[suncq]

hi:
SherpaDoug,please see :
http://www.omni-site.net/html/products.html

[asmboy]

the 12V dc inlet and 120V AC inlet are mains power connections - correspondent confused by is - and of course the same connector they are not- by language most tortured - so language problems plus slim perhaps electronics comprehension of issues most basic have we not here all together placed in one message , gathered together the experience of , please?

[Ttelmah]

Yes, he appears to be confusing the power requirements, with inputs. These units, have exactly the sort of 'inputs' for signal detection, I was talking about. Probably AC input opto couplers, so they can detect the presence/absence of signals over a huge range. This is distinct from the power supply, which is a 12v _or_ 120v 'option'. Look at the ordering 'part number' sheets, where the last digits have to be '12' for 12v versions, and '120' for 120v versions.

Best Wishes

[suncq]

I think Ttelmah is right. But How to detect the presence/absence of signals over such huge range?

[Ttelmah]

As I said, and AC input opto coupler, and resistor.
If you have a typical opto, the CTR, will probably be something between 50%, and 200%, over an input current range of perhaps 0.2mA, to 20mA. You just have a resistor to give close to the maximum current at your maximum input voltage (say 10KR), and have a 'pull up' resistor on the output to 5v, of perhaps 100KR. Connect this into a logic input on a PIC, and it'll pull down over a range of typically 200v, to only perhaps 6v (depends on the forward voltage of the LED in the opto).
Circuits like this are nice, since they are 'safe' (opto isolated), and can detect signals over a huge range. They are used on millions of bits of industrial kit.
Remember though that you need a couple of watt rating on the resistor.

Best Wishes

[suncq]

I see. thanks for Ttelmah detaill description.