Can i connect 15V ac supply to pins of AVR32 or AVR 128

Go To Last Post
22 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hello Friends,

I have this question in mind that whether we can give a AC voltage to the input of AVR ports and if i give a 15Vac supply to the port what will be the output on LCD screen or in general.
Just before trying it out,I thought better consult the experts... I dont want my parents to throw me out of the house so can u all help me plz...

THanks...TC

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

NO NO NO!!!!

Read the datasheet for the AVR you are using! You cannot exceed you VCC level on any pin, typically 5 volts or 3.3! 15VAC would certainly damage your AVR.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

At some point you will actually READ the excellent datasheet from atmel that tells you to not apply any voltage greater than a few tenths of a volt higher than the absolute maximum to any pin. Thats about 5.5V. Above that the smelly magic smoke starts leaking out onto your Mom's curtains.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

It might not just leak smelly smoke, but small pieces may fly out of chip!

This warning ALSO applies to input voltages below ground. So, AC is a definite no-no!

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

... or maybe read the Atmel application note where they connect 240V AC to a PICAXE input.

Not directly of course, but it can be done...

Here you go - I've even found it for you :)
http://www.atmel.com/dyn/resourc...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
... or maybe read the Atmel application note where they connect 240V AC to a PICAXE input.
Heresy...sure it wasn't a AVR chip!

Whilst it works fine, I don't suggest newbies to try it. I spotted this ripper in the AN

Quote:
Simply connect an oscilloscope probe to the mains and another to PB0.
Oh yeah, I'd like to see that!

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Ok...guys thanx for the help,But my actual doubt was wheteher i can connect AC supply to AVR ports. As we hav transformers of different ranges i can drop the voltage to appropiate level but can we give AC supply...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

No - DC only, and then as stated before you must not exceed the voltage range quoted in the data sheets...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

...or use suitably large resistors and a design as the Application Note suggests.

We seem to be starting to go round in circles here?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

nikhillife11 wrote:
Ok...guys thanx for the help,But my actual doubt was wheteher i can connect AC supply to AVR ports. As we hav transformers of different ranges i can drop the voltage to appropiate level but can we give AC supply...

I suggest you to take basic lessons before start programming AVR. Otherwise it will be a costly, and huge disapointment.

Basically you need a STABLE 3.3V-5V DC (DIRECT CURRENT) supply to get to work your AVR properly.
Otherwise you will kill your AVR, blow up your capacitors, kill your programmer, and burn your computer.

Take for exapmle a 9V battery and build this circuit:
http://www.chibots.org/?q=node/485

Or build something like this:
http://shaunak.ws/journal/buildi...
But with the experience of yours, maybe it won't be a good idea.

Or buy one like this:
http://www.cubeternet.com/servle...
Buy only "regulated" type.
And before connecting it to the AVR measure the voltage it provides, because if you bought "unregulated" type, it will provide a voltage over 5V and you kill your AVR again.

It is also a good practice to connect a diode series with the Vcc input like this:
http://highfields-arc.6te.net/co...

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

OP does not seem to be asking about powering an AVR from AC - just whether it is possible to connect AC to input pins.

Well that's the question I'm assuming anyway....

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You can connect anything with proper signal conditioning. What part of the AC signal are you looking at? The peak to peak amplitude? The zero crossing timings? We can show how to scale this info down into a 0-5V signal suitable for connection to an AVR input.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

thanks to all...and special thanx to Marti,Bob and mill for encouraging me....Actually I am trying to make a 3 phase monitoring system using AVR..

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Do NOT connect 230V to the avr through a resistor. Millwood, you should now better than to encourage such a stupid thing to a beginner!! And if the professor did it, I`m sure it was in a attempt to get rid of bad students.

15V trough a resistor divider is more ok, the dev-board might blow up if somethings goes wrong, but at least there will be some brain activity left if you touch it.

Just remember that you will need to offset it so that the voltage never goes far below GND.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Three little transformers... one on each phase.. would step the volts down and give isolation.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Chill down Kherseth...I was going to use the idea which has been mentioned above by Mr. Bob....I have a circuit in mind...just wanted to know whether AVR ports take AC voltages in range 5Vac to 15Vac.. Bob your cool mate..

Also does anyone has a link to working AVR32 or AVR 128 programmer. I always need to get it programmed from shops around here...lol

Thanks

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Most of us just buy a stk500 or a avr dragon.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Quote:
Also does anyone has a link to working AVR32 or AVR 128 programmer.

Start here: https://www.avrfreaks.net/index.p...

As of January 15, 2018, Site fix-up work has begun! Now do your part and report any bugs or deficiencies here

No guarantees, but if we don't report problems they won't get much of  a chance to be fixed! Details/discussions at link given just above.

 

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

millwood wrote:
kherseth wrote:
Do NOT connect 230V to the avr through a resistor. Millwood, you should now better than to encourage such a stupid thing to a beginner!! And if the professor did it, I`m sure it was in a attempt to get rid of bad students.

it was an attempt at showing the students (and apparently quasi-professionals too) that it takes more than reading the datasheet to understand it.

I have been working for 6 years with soldering iron, and I still burn myself sometimes. The same applies for making any kind of mistake. You just do mistakes, it just happens. Playing with 230V is DANGEROUS, and this needs a lot of experience, precautions and full attention.
It's definitely not for beginners. Maybe you do know what you want, maybe your idea is right. You're just not got to used to that not to touch the wire, beceause there's not 5V but 230V. And you're dead.

So most important thing: make your circuit so, that you shouldn't be able to touch the 230V parts under ANY CONDITON.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Just to be a devils advocate, I have demonstrated to students that it was quite safe touch 240V, but only when I was sure that no part of me was touching anything else!

An isolation transformer is a must when prototyping or servicing equipment where circuits are directly line powered/interfaced. Not for newbies!

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I feel I brought this thread a bit OT with my earlier comment, so sorry about that.

Yes, you may connect just about anything to the ports, as long as the signals is properly attenuated. So, don`t drive the pin voltage much below GND or above VCC.

I believe some suggestions have already been made regarding the original questions.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

From what I have learned it is not very smart to rely on the safety features of a circuit to get the system working. It is kind of like driving into a wall and relying on the airbags instead of just braking.

And why rely on the internal diodes, when you could scale the signal by adding one more resistor?