[SOLVED] Voltage reference problem. Power converter Vs Microcontroller

[Hatimoooo]

Hello everyone.

I'm having a trouble figuring out where the problem is, in my configuration.

I have a AC/DC power converter supplying a load. I wanted to get the voltage across that load using a voltage divider and sending the information to a PIC microcontroller.

The problem is: whenever I connect the negative pin of the output to Vss of the microcontroller, it stops working (without connecting the voltage I'm getting from the divider).

Here is a small schematic for the problem



Thanks a lot.

 

[amayilsamy]

Check your AC/DC converter output. Post the values of the resistor and power supply output..

 

[Hatimoooo]

The output is good. 48Vdc with a small ripple ~200mV
The resistor values are 140kOhm (up) and 9.4kOhm

 

[amayilsamy]

Connect a resistor between Vss of Controller and Negative of Power supply.

And check If there is any voltage across both terminals of the resistor with reference to GND.

 

[Hatimoooo]

I did it with a 150 Ohm resistor. I got 1.0V
I'm sorry to say this, but what was the point behind this test?
Thanks

 

[amayilsamy]

Post your power supply circuit. I think your power supply not having proper ground

 

[Hatimoooo]

Well, it's a three phase Dd0 transformer, SCR half controlled rectifier, LCLC filter then the load.
The power supply I'm using for the PIC is a Metrix AX503.

PS: I did the test again and I'm getting weird signals now :shock:
Do you have an Ebook for tips in electronics in practice?

Thanks

 

[amayilsamy]

Post your SCR based rectifier . I think some AC signals in your power supply . i.e power supply output is not pure dc.

 

[Hatimoooo]

Do you mean that there is a problem with the Metrix AX503 ?
How can I filter my signal/ supply Vdd ? Are there any recommended values for capacitors ? Are there some other practical solution?
Please let me know
Thanks

 

[amayilsamy]

There was problem in AC/DC power supply. Kindly check with the voltage divider circuit using Vcc of controller . Use Bridge rectifier for AC/DC conversion. I think Its works well.

 

[Hatimoooo]

Hello.
I found the solution to the problem.
I was using the Power supply Metrix AX503 for something else simultanuously (other than powering the PIC).
When I disconnected it that "something else", the PIC seems to be working well with the (-) and Vss connected together.
But I still can't understand why. Are the (-) of the Metrix related in someway? Normally, I should be able to put them in different potentiel without any problem.

Thanks a lot Mr amayilsamy for you time.

 

[amayilsamy]

Post your total schematic. Then only We find a what is the problem ..