Auto regulated voltage using electro mechanical mechanism

Top goal: keep ac source at 220 volt all the time.
The "pseudo code"!!! goes like this:

Part A (The monitoring )

  1. sample input ac voltage, reducing it to safe level (arduino level)
  2. rectified dc fed to A0
  3. using arduino to detect UP or DOWN from a value that represents 220V

Part B ( The feedback )

  1. Activate dc motor RIGHT or LEFT to control the arm of a Variac.

In this early stage I wand to get green light on the concept and really do Part A. I want to build part A and see if the motor does it's thing while I vary the source around the 220 V. As a matter of fact I may develop it further to provide me with ANY ac value I feed to it.

I am ready now for the firing squad.....

By that I mean there may be an electronic solution to it . and save my self the agony of a mechanical one.

Hi,
Yes it is possible.
single-phase-flush-type-motorised-auto-transformers-500x500.jpg
I have had a few through the workshop, they are not super fast to adjust output, but they do work well if the hysteresis is set up correctly.

Tom.... :slight_smile:

single-phase-flush-type-motorised-auto-transformers-500x500.jpg

Wow My dream came true ( within the hour!!!!) wow.

What is your advice ? Shall I reinvent the wheel ?? I hope not

Hi,

The units that I have looked at were analog controlled with a simple window comparator and a couple of relays.

Arduino could add a voltage display and any alarm systems, such as too low or high mains input.

Contact noise from the auto-transfomer brush could be a problem when adjusting high currents, so averaging sample voltage may be needed.

Tom... :slight_smile:

What do you mean by

And you are absolutely right about the Variac hysteresis A serious obstacle

They make motorized Variacs but they are expensive and I assume they have AC motors (probably controlled by a relay).

  1. sample input ac voltage, reducing it to safe level (arduino level)
  2. rectified dc fed to A0

And, transformer isolated and filtered, of course. :wink:

By that I mean there may be an electronic solution to it . and save my self the agony of a mechanical one.

That depends... It's not easy to adjust "clean AC" electronically and it's even trickier if you need to boost the voltage. A "chopped AC" [u]phase-controlled dimmer/motor controller[/u] is cheaper & more compact than a Variac. You just have to make sure that the phase detection and TRIAC control are electrically isolated from the line voltage.

And you are absolutely right about the Variac hysteresis A serious obstacle

It's not that "serious". Just add some hysteresis to your code... If you're going-up and shooting for 220V, keep going 'till you hit 221V (or whatever) and when you're going down, keep going down 'till you hit 219V (or whatever). Give yourself a range/zone (or "window") where nothing happens so the thing doesn't constantly "hunt".

...You could also add some delay or averaging/smoothing so it doesn't react to every little glitch in the power.

Why the need for this.
Many modern appliances don't care if AC varies between 80 and 260volt.
Leo..

The device you suggest has been around since at least the 1950's. Radar ground stations used them.

Those and saturable reactor regulators.

No electronics were used.

There are better ways these days.

Allan

Mains voltage stabilizers are used in third-world countries, where power is flaky.
Google “mains voltage stabilizer”, and go to images for factory units and diagrams.
Most of them are made with a small transformer with many taps, that add or subtracts a small voltage from the mains voltage. Taps are selected with relays.
Leo…

Hi,

"Simple Window comparator" is a dual comparator circuit configured to give a hysteresis property rather than a single change over point.

Depending on the load, there are UPS. Uninterruptible Power Supplies, available that have output voltage stabilization.

Laboratories and remote sensing stations use them, where the mains supply is unstable.

Tom... :slight_smile:

Except for size, I wonder why you haven't used a "constant voltage transformer"? Maybe they are hard to find now days.

Paul

Thanks for your comments and here is my conclusions( based partially on your posts ):

  1. This is an "old fashioned way" to get stabilized ac source.
  2. There are many ways to achieve it with present day technology.
  3. I better steer away from circuits that deal with more that 50 v

I have variable dc bench power supply in my small lab, and I wanted a similar ac one. Why you may ask.
Just for experimental reasons and NOT FOR NORMAL USE

The key here, is programmable ac power supply.( Variac is viable solution but not programmable)