Problem measuring multiple voltages using arduino for stabilizer

I have a 10 KVA servo voltage stabilizer that I am trying to control with Arduino Uno R3.

I have removed all prior circuitry and just transformers and motor is left (because the original circuitry was damaged and it is out of warranty)

I have attached the circuit I am using now.

Voltages (input and output) to be measured are rectified and passe through a voltage divider and read from A0 and A1 pins.
Pin 6 and 7 are used to activate appropriate relay to drive the AC synchronous motor in appropriate direction to stabilize the output.

Expected behavior:

  1. Arduino measures both input and output voltages using A0 and A1 pins and activate appropriate relay to drive motor than in turn stabilizes the voltage.

Here are my observarions:

  1. As soon as the circuit is powered on the motor does not rotate properly instead it vibrates at same position. Also All relays are activated at same time.
  2. When I remove the GND pin and then recheck, the arduino rotates motor in either direction (I guess due to incorrect/ noise values at the A0 and A1 pins)
  3. When I connect Arduino GND pin to “12 VDC regulated” power supply’s -ve terminal then also above vehavior (#2) is observed.

I have checked for short circuits and everything and did not found anything wrong. I have replaced Arduino Uno board, relay board and wiring to make sure no component is defective.

Usually the tutorials on internet use relays that are activated by LOW signal. The relays that I am using are activated by HIGH signal and turned OFF using LOW signal (yes I have checked this several times).

Is my circuit correct, to measure 2 different voltages? What should I do to fix this weird behavior?

Hi,

Can you please post a copy of your complete circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Not Fritzy please.
829243240b6e76b76af16294bda4786b0785f0cf.png
Can you please post a copy of your sketch, using code tags?
They are made with the </> icon in the reply Menu.
See section 7 http://forum.arduino.cc/index.php/topic,148850.0.html

Also your choice of motor control relay, you should have a pair of relays with extra contacts to use to make sure that only one can be activated at a time.

What is your electronics, programming, arduino, hardware experience?

Thanks… Tom… :slight_smile:

Hi Tom,

I got this working.
Actually the issue was with step down transformer that I was sharing between 12 VDC regulated power supply and to measure Output voltage at A1 pin.
I was using 2 transformers previously. Now I use 3 transformers (12 VDC regulated power supply, Input step down and output stepdown; one for each)

I had to use a separate transformer to step down output voltage (of 10 KVA stabilizer) and measure it using A1 pin.

TomGeorge:
Also your choice of motor control relay, you should have a pair of relays with extra contacts to use to make sure that only one can be activated at a time.

What is your electronics, programming, arduino, hardware experience?

Thanks… Tom… :slight_smile:

I am using 3 relays to control forward and reverse direction of motor and one for output relay (that is used to cut off output in case of very high or very low voltages that are out of range of this stabilizer)

I am an electronics engineer by education and software developer by profession :slight_smile:
Just getting started to make home automation system using Arduino and RasPi 3.

Hi, Good to see its functioning to your requirements.

Its unfortunate when something like this, that has perfectly working hardware and is worth a fortune and the controller dies. Its good when it can be resurrected it with modern controller.

Tom.... :)