Author Topic: AC-AC Adapter has incorrect sticker?  (Read 178 times)

0 Members and 1 Guest are viewing this topic.

Offline Mp3

  • Regular Contributor
  • *
  • Posts: 137
  • Country: us
AC-AC Adapter has incorrect sticker?
« on: September 19, 2019, 10:11:12 pm »
Hi everyone, I bought an ac adapter from the internet and it got here today. The label is so strange. The part number and label seems to indicate it's an AC-AC adapter, but the diagram indicates the plug has polarity which implies it's DC.

If i measure the plug with my my multimeter on AC mode, either way i measure with the prongs gives me ~16V AC

If I measure the plug with my multimeter on DC mode, i got 0v either way, so its safe to assume this is an AC-AC supply?

Just wanted to be safe. I blew up an op-amp last time i thought i knew what was what so i wanted to ask...
 

Offline Yansi

  • Super Contributor
  • ***
  • Posts: 2608
  • Country: 00
  • STM32, STM8, AVR, 8051
Re: AC-AC Adapter has incorrect sticker?
« Reply #1 on: September 19, 2019, 10:14:53 pm »
Pictures of the label would really help here. "Strange label" is not enough description.

However, if you have measured 16Vac there, then probably it is just a trafo in a case.
 

Offline ledtester

  • Frequent Contributor
  • **
  • Posts: 535
  • Country: us
Re: AC-AC Adapter has incorrect sticker?
« Reply #2 on: September 19, 2019, 10:21:33 pm »
Sounds like just a transformer.

You can always test with an LED and a 1K resistor. If the LED lights up no matter which way it is plugged in you have AC current.
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 13044
  • Country: gb
  • 0999
Re: AC-AC Adapter has incorrect sticker?
« Reply #3 on: September 20, 2019, 02:05:14 pm »
Sounds like just a transformer.

You can always test with an LED and a 1K resistor. If the LED lights up no matter which way it is plugged in you have AC current.
That will work but beware most LEDs are only rated to 5V or so in the reverse direction, but I think some of that is just arse covering on the data sheets.

In my experience, red, orange, yellow and greenish yellow will non-destructively breakdown at around 20V or so and conduct in the reverse direction,  but pure green, cyan, blue and white LEDs can be damaged by too higher reverse voltage.

The safest thing to do is to use two LEDs connected back-to-back. If it's AC they'll both light, otherwise only one connected in the correct polarity will light.

In this case, it's definitely AC, because the meter measures 0V on the DC settling and the expected voltage when set to AC. It can be used to power an op-amp circuit with a bridge rectifier and smoothing capacitor.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf