Ground problem

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Pady

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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.
 
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,
Use a opto-isolator on the output pin of the PIC to isolate the relay driver transistor base
 
rushi53 said:
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.
Click to expand...

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

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rushi53 said:
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.
Click to expand...



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.
 
Grounds can be 'commoned' and is supposed to be commoned. It is the better way if your wiring is going to be long.
 
Pady said:
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.
Click to expand...

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.
 
Last edited:
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.
 

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