Ground problem

[Pady]

Hi everyone,

I m doing relay operation using micro controller.
I have one problem is that, I have +24 Vdc & gnd for power supply.
Two types of power supply i used. i.e. one for microcontroler i.e. +5 V using 7805. & other
one is for Relay supply.
So, problem is that i want to seperate these two grounds but i have only one ground.

So plz suggest me any idea.

 

[rushi53]

Need more clarification on question.

Is your relay operated on 24 volts OR your output device is operated on 24?

I have used on 5 v and 12 volt relays. I have never heard of 24 volt relay.

 

[ericgibbs]

Hi everyone,

I m doing relay operation using micro controller.
I have one problem is that, I have +24 Vdc & gnd for power supply.
Two types of power supply i used. i.e. one for microcontroler i.e. +5 V using 7805. & other
one is for Relay supply.
So, problem is that i want to seperate these two grounds but i have only one ground.
So plz suggest me any idea.

hi,
Use a opto-isolator on the output pin of the PIC to isolate the relay driver transistor base

 

[ericgibbs]

Need more clarification on question.

Is your relay operated on 24 volts OR your output device is operated on 24?

I have used on 5 v and 12 volt relays. I have never heard of 24 volt relay.

hi rushi,
The 24V relay option is a common voltage.

 

[Pady]

Need more clarification on question.

Is your relay operated on 24 volts OR your output device is operated on 24?

I have used on 5 v and 12 volt relays. I have never heard of 24 volt relay.

No no. My relay operates on 12v. My problem is that, i want to seperate "relay ground" & "controller ground" but I have only one ground with 24V dc.

 

[Vizier87]

Grounds can be 'commoned' and is supposed to be commoned. It is the better way if your wiring is going to be long.

 

[Arkham00]

No no. My relay operates on 12v. My problem is that, i want to seperate "relay ground" & "controller ground" but I have only one ground with 24V dc.

So use two regulator IC, a 7812 to get the 12Vdc and a 7805 to get the 5Vdc.

Just use separate wires (or traces) from 24Vdc/gnd to the two power regulators.
In this way, you'll minimize the effects of the relay spikes.

 

[Hero999]

Using two regulators would mean you have to connect the grounds together.

Here's how to use an opto-isolator.

If you want to power a 12V relay from 24V just connect a resistor in series with a similar value as the relay coil's resistance.

For example, if your relay is 250R, connect a 220R to 270R resistor in series with it.

If you don't know what the the relay coil resistance, look at the datsheet or measure it with a multimeter.