Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Proper Relay Module with Proper Isolation

Status
Not open for further replies.

xmen_xwk

Full Member level 3
Joined
Sep 12, 2014
Messages
172
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Activity points
1,373
I need to control around 2A to 3A AC solenoid/coil with arduino. For that I got a 5V relay module. But after reading this article. I realized I would need 2 different power supply, one for arduino and one for relay. But doing that also doesn't guarantee of proper isolation. I was wondering how would I do proper isolation ?(Not 100% obviously but better)

Now second question
OptoRelayChannelData-800.jpg

The above schematics shows, using NPN transistor we are controlling the relay. But with software it will work opposite, when Signal Pin will be LOW, the relay will be ON. And relay will be OFF when signal is LOW. I want to do it correctly if its not a problem ? So to do that, I want to replace VCC with signal pin and signal pin to GND. Will that be a problem with isolation ?


Thank you
 

Hi,

It seems both sides of the optocoupler use the same GND, then you don't need a optocoupler. A bjt is sufficient.

The relay should be rated for an isolating voltage (coil to contacts) more than your AC voltage.
Mind to use a snubber at the contacts of the relay to avoid EMI/EMC problems.

Klaus
 

The GND is for relay only. Not connected to arduino. And about snubber, will just putting on AC side will be enough ?
 

Hi,


And about snubber, will just putting on AC side will be enough
usually yes.

But in detail it depens on many parameters. Like load, PCB layout, sensitivity of the circuit...

Klaus
 

Hi,



usually yes.

But in detail it depens on many parameters. Like load, PCB layout, sensitivity of the circuit...

Klaus
Could you please explain little more ? like how to calculate or know how load and other things matters.

Thank you :)
 

Hi,

wether a snubber is sufficient depends on some parameters.

PCB Layout. If you have a good layout, then a snubber should work. If you have a bad PCB layout then even with a snubber you will see problems.

EMI/EMC include magnetic waves. All lines with high voltage/current pulses transmit magnetic waves.
All other lines within this magnetic wave will receive the magnetic wave and produce voltage and/or current pulses.

Klaus
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top