ac or dc voltade detection without oscilloscope

[ali_ali]

ac or dc

Hello all.
Is there any way to find that if a circuit is having Ac or dc Voltage at any point (let's say at output), when one does not have an oscilloscope?
Thanks

 

[karesz]

ac or dc

You can indicate it with a DMM too
Must switch it in a modus of AC-V after than in DC-V....
K.

 

[ali_ali]

Re: ac or dc

what is your reply i didn't understand.do you want to say that first i should check it in D.c And then in A.c.? then how would i know that which value (D.c one or A.c one) is correct.? please explain.
And I've got a better solution.
if i connect 2 leds in parallel reverse to each other. then see if both come glow,it's A.c but if only one glows it's D.c. Am i right.?

 

[2:43AM]

Re: ac or dc

what is your reply i didn't understand.do you want to say that first i should check it in D.c And then in A.c.? then how would i know that which value (D.c one or A.c one) is correct.? please explain.
And I've got a better solution.
if i connect 2 leds in parallel reverse to each other. then see if both come glow,it's A.c but if only one glows it's D.c. Am i right.?

What the previous guy was saying is to use a digital multimeter to test if either a DC or AC voltage is present. That would be the safest way, especially if you don't know the voltage at the output. Connecting two reverse LEDs may work, but you risk either burning them out in a heartbeat, not getting an accurate reading, and possibly risking electrocution if it's a high-power amp or AC/DC source. Best to buy a DMM and go from there.

 

[sakhan]

ac or dc

I have one idea to do this simple task.
One can use a simple voltage follower and two LEDs to do that.
Hope you will have got my idea.
If you need further assistance then tell me

 

[ali_ali]

Re: ac or dc

yes yr please briefly explain it. Thanks

 

[karesz]

ac or dc

@ali-ali!
you did forget to tell us whats your desired voltage range to check!:-(...
If you like the double LEDs apply, you need a seriel resistor as "current limiter"_or better: current generator.
In all cases you must plane some voltage range to test for calculating the resistor value, or as I told it to first: check it per DMM...
If you wish test some voltages you can not do it with "bare finger" or a screwdriver, you need some corresponding tools/instruments to that job...
K.

 

[s_cihan_tek]

Re: ac or dc

As karesz stated, using a DMM twice (Both in AC and DC modes) is better and safer. The LED method will not work in a wide voltage range, unless you use different LEDs and/or current limiting resistors for different voltage ranges.

 

[suru]

ac or dc

FIND RECTIFIER SECTION. IF YES THEN IT'LL BE DC OETHERWISE AC.
USE MULTIMETER IN DC MODE AND THEN AC MODE.

Do not use "Caps" unless otherwise required. Next time, you'll be warned.

 

[pranam77]

ac or dc

If you know the voltage atleast, use a Analogue multimeter in DC range to measure the potential across. If the source is DC, the needle will move forward in forward bias and reverse in reverse Bias. For AC it will give forward deflection in any position but the redaings will not be accurate. Now you know its AC and put the MM in AC position to get accurate reading. Cheers

 

[agbey]

Re: ac or dc

look for the presence of a rectifier. if there is then; its a dc if not ac.

 

[pranam77]

Re: ac or dc

look for the presence of a rectifier. if there is then; its a dc if not ac.

The rectifier will not be always located in the main board. The supply is also supplied from a dedicated power section away from the target baord, in many of the industrial equipments.

 

[sakhan]

Here is the circuit i was talking about.
If one LED glow it means its a DC.
If both LEDs glow then it will be AC.
But before using this circuit you must your input to +-15V or less.
Hope it will be useful to you

 

[sakhan]

Does the solution solve your problem?

 

[ali_ali]

yes thanks a lot every one