AC/DC adapter regulated?

[bignateyk]

Is there a way to tell, just by looking at any old AC/DC adapter whether or not the voltage is regulated?

I'm thinking of reusing some of my old adapters for other purposes...

 

[brentkiosk]

Do you mean the "wall wart" type? I belive most, if not all, are unregulated.

 

[bignateyk]

yeah thats what I figured...

 

[HippyWarlock]

You'll find out when you put it on load <g>

If it's cheap as hell - Guess it as unregulated

If it costs a couple of quid more, and especially if it says 'Regulated' then it's a fair bet it's regulated.


Tech moment:

Unregulated supplies are analogous to the mains supply.

UK: EU law and some foul up in harmonising UK and EUominal Voltages ended up as
230V +/-10% i.e. 207-253V

USA: is governed by the ANSI C84.1 = 114 - 126V or Nominally @ 120V
With the exception of California who set tighter tolerances.

Canada: 240V nominal
228 - 252V

Ozzies: 240V +/-6%

So if your Item needs spot on 5v - Don't take the risk that it 'should' be regulated.

 

[zephyrprime]

They're almost all unregulated. I have some regulated ones but I bought them mail order from an electronics surplus store and they were advertised as regulated. It's easy to tell with a volt-meter because the unregulated ones have higher than advertised voltages. (a 12V will put out 14V)

 

[bignateyk]

hmm.. ok, I have an old 486 power supply with the usual +-5, +-12V. Would it be possible to use this for general electronic stuff (like microcontrollers?)

It isnt like modern day power supplies where it has to be plugged into the motherboard to turn on...

 

[HippyWarlock]

PC PSU's are pretty accurate but again a cheapo one will have tolerance fluctuations or over/under volts, and some have better smoothing than others.

Voltmeter/Oscie-scope to clarify but in general yeh.

I think the 486 had a 3.3V rail too? Or was it pure TTL 5v stuff? I may be wrong. Got one behind me - can't be arsed to look 🙂

 

[HippyWarlock]

You can always trick the PSU into turning on - make a switch of it.

Anyhow this link may be usefull if you get an ATX PSU at anytime:
http://answers.google.com/answers/threadview?id=52126

 

[bignateyk]

ok, 3 more questions:

1) most opamps take +- 15V, but ive heard that +-12V will work fine for them. Is this true for most, if not all opamps?

2) Also, i've noticed that some AC/DC adapters are extremely heavy, while others are very light. The lightest one i have is switching. Are the lighter ones most likely regulated?

3) if I take an unregulated power supply (or even a regulated one jsut to be safe), and add my own 78xx series voltage regulator to it, would it be just as good as a regulated power supply?