Hacker needs help

Projects General Guidance
1

For a LONG time, I wanted to build a variable AC voltage project. Yes AC!!!
The opportunity arrive at my door steps. I had a 1.5 KW voltage stabilizer, that need fixing
It has ALL ( almost all) the components; namely:

  1. Variac
  2. Mechanical system to "adjust" the voltage using a printed circuit with a POT. By mechanical I mean a STRONG DC motor and system of gears to MOVE the Carbon Brush to the desired voltage level.
  3. Most importantly TWO micro switches to control the movement of the arm (Carbon Brush) to mark the clock and anti clock max movement of the ARM.

Since I have no documentation for the printed circuit, I decided to replace it with an Arduino.

The project status:

I teared the device apart. and checked that if I bypass the board that I do not understand and keep the wiring. By that I mean I have the following:

The input to the board is 110 AC to a transformer with a bridge rectifier.
The DC wiring is using the following:

2 wires to the DC motor the turns the ARM
2 @ 2 for the two micro switches.

The missing link is How the stabilizer recognize the deviation in the input voltage and move the arm to compensate for the difference to achieve the correct adjusted voltage.

I presume the logic is IN THE CIRCUIT BOARD that has the POT.

In my view this is a very challenging project that will benefit the arduino community.

As I said before the most detailed (and difficult) part of the project is ALREADY done.Namely The motor system and the control of the arm. All we need is to replace the board with arduino and make use of the wiring.

I am sure you have zillion questions.....please shoot them

P.S. Just in case you wondering what the arduino will do Here is my objective:

  1. Input a value for the voltage,

  2. Read current voltage and adjust the motor movement to achieve the desired new value OR

  3. provide TWO switches to move the ARM clock or anti clock and display the voltage value as the arm move ; until I reach the desired voltage ( semi automatic)

2

To read the AC voltage safely use a transformer, as described here How to build an Arduino energy monitor - measuring mains voltage and current — OpenEnergyMonitor 0.0.1 documentation

3

I assume there are existing relays for the DC motor (on/off & direction)? You'll need to know the relay coil voltage and make a driver circuit. (The Arduino can only put-out 5V at 40mA or less and that's not enough to drive a relay coil.)

Or, you can get a relay board with the drivers built-in, or you can use a solid state relays that can be driven from 5V low-current, or you can get solid state motor driver board (but you'd have to find a driver that can handle the motor current).

For the voltage measurement, you can measure rectified & filtered (and transformer isolated) DC. You will probably need a voltage divider (2 resistors) to bring th voltage to less than 5V so the Arduino can read it. Then, just scale/calibrate the DC/ADC readings to the AC voltage. (The energy monitor is a little more "critical" because it has to measure the phase difference between the voltage & current.)

  1. Input a value for the voltage,
  2. Read current voltage and adjust the motor movement to achieve the desired new value

There are 3 states.... Turn on the DC motor to raise the voltage, reverse the motor to reduce the voltage, or do nothing.

You'll probably want some [u]hysteresis[/u] so the motor isn't constantly moving back-and-forth trying to set the "perfect" voltage. (That's the 2nd time today I've written 'hysteresis'.) ...Furnaces & air conditioners have hysteresis (or "swing") so they so don't switch on & off several times per second.

  1. provide TWO switches to move the ARM clock or anti clock and display the voltage value as the arm move ; until I reach the desired voltage ( semi automatic)

I don't quite understand "semi-automatic" but you could have "up" and "down" switches/buttons to set a new target-voltage (like the up/down switches on a thermostat).

  1. Variac
  2. Mechanical system to "adjust" the voltage using a printed circuit with a POT. By mechanical I mean a STRONG DC motor and system of gears to MOVE the Carbon Brush to the desired voltage level.

I haven't seen anything like that in a million years... They still make 'em but you don't see 'em everyday. The ones I saw weren't voltage stabilizers, they were remote-control theatrical light dimmers.

P.S.
You don't really need a programmable microcontroller... This could be done with a [u]analog comparator[/u] and an optional pot to adjust the reference voltage for tweaking/adjusting the AC output voltage.

It would take some more electronics to make use of the limit switches, but it wouldn't have to be anything that requires software.

I'd have to think abut this, but I think there's a way to use diodes with the limit switches so the motor can only run one direction after hitting the limit switch... If you can figure-out how to do that it would be somewhat fail-safe because the limit-switch operation would be independent of any active electronics or software. (But if you make it independent, the software won't "know" you hit a limit.)

4

I will use numbered list to encourage us to interact.

  • Yes the Variac is a single coil so the device is not isolated for safely. but opto coupler can be used
  • There are NO relays used by the device.The circuit board is smart enough to move the arm clock or anti clock
  • By "semi-automatic" I mean I am pushing Up or Down buttons to reach the desired voltage. As against giving the desired voltage and Arduino will do Up and down.
  • I will go for the semi automatic... Much easier to implement.
  • I will use L298 bridge IC as the motor driver
  • To move forward I will do the project in phases. I will build the motor driver make sure that I can use arduino to move the arm and using my Multi meter to go UP or Down using Two switches

Waiting eagerly to get your green light

P.S. I will look into your analog approach solution, but I prefer using Arduino.

5

I'd think that the easiest way to get the motor run is a ready-made H-bridge module, coming with Arduino example code. At least you can have a look at such boards, for getting up your own circuit quickly.

Then look at the Arduino examples for reading and debouncing buttons, and make the motor turn left or right accordingly. In the simplest case you give the direction to the motor driver, then turn the motor on as long as the button is pressed. If the motor turns too fast, you can use PWM to reduce the motor speed.

6

Perfect....I actually meant a module rather than IC when I mentioned L289
They call the module with the same name as the IC used.

My "second" phase is to let Arduino monitor the Current voltage setting so I can press the up or down.
Here I will need some help from you .

7

The safe (isolated) translation of the AC voltage to Arduino-compatible DC of 0-5V has already been mentioned. You can use analogRead() to get that voltage, and (here optional) convert it into true AC effective voltage, for later display on a LCD or TFT display. You can use a cheap shield with a LCD display and buttons, if you like. Then make the motor turn as long as a button is pressed. If the button is released, stop the motor.

8

Hi,
Can you post a picture of the old board so we can see what they were using to control the DC motor?

Did you do a basic mud map of the various connections to the PCB, pot and power supply and motor?

Thanks.. Tom... :slight_smile:

9

Tom....if you can solve the puzzle...I do not know how I can repay you !!!
I had a week on this board but I failed.

Once you relieve the picture I can explain ALL the wiring

Please let me know once you receive it

10

Hi,
You need to attach the image.
Use REPLY rather than QUICK REPLY, it has an attachment facility.

Tom... :slight_smile:

11

Here it is

12

My third attempt

13

You have exceeded the number of posts you can make in a 5 minutes period. Please try again later.

14

if you have an email...I can sent to ???

15

I reduce it to one third....I am trying again

VariacSmall.jpg
VariacSmall.jpg1296×968 434 KB

16

Here is the wiring:

  1. Two wires to the far RIGHT are the ac 110 volt input to the board
  2. The Red and Blue Top Right are the motor
  3. The two wires Green and Red are for the TWO micro switches that inform the board you have reached the physical boundaries of the Variac.
  4. The POT to middle left side is to set up your voltage that you need to stabilize.

THAT IS IT NO OTHER WIRING !!!!!!!!!!

17

The two transistors are very odd

D667

B647

18

Before I took it apart , I made sure all the parts are in good working condition.
What drive me crazy is the fact that ONLY ONE place the the board get info from is the 110 v ac
ALL THE OTHER WIRING are self explanatory The Motor wires turn the motor clock and anti clock AUTOMATICALLY.

The micro switches warn the motor of the mechanical boundries

AND the POT tells the motor WHERE TO STOP.

VERY VERY smart board.

19

Hi,

2SB647 and 2SD667.

Where did the power wires to the transformer come from, the input or output of the Autotransformer?

Tom.... :slight_smile:

20

That IS the question. I do not know .
This is the key to this board.

It cannot be the INPUT , because I am using 220 volt as the MAINS. I did a little test on the board as a stand alone , I gave it 110 volt because that was measured input when it was wired before taking it apart. I also attached a small Dc motor to see if I CHANGE the 110 down to say 95 volt will the motor spin ?. IT DID NOT.

P.S WITH THE DEVICE ATTACHED AND CONFIGURED AS 220 volt mains, the device is offering a 110 volt outlet.

These are all the clues that I can think of.