Hi All,
I just want to run this by other users. I need to power a 12V DC, 5-8A water pump.

Ideally, I would create my own PCB with a relay and protection circuit, but time is short, so I'm looking to use the following two devices: a relay and a snubber. Would this be adequate, or do I need to add any additional protection? Maybe a flyback diode — but is that necessary if a snubber is already included?

Hailege 2pcs 12V 30A One Channel Optocoupler Isolation Relay Module Support High and Low Trigger 12V : Amazon.co.uk: Business, Industry & Science
and
Hailege 5pcs RC Absorption Circuit Module Circuit Anti Interference Protection Module Electromagnetic Surge Protection for Relay Switch Thyristor : Amazon.co.uk: Business, Industry & Science

DJ

 

That looks to me like an AC opto relay .
...is it rated to turn off with DC
Looks like the 12 v DC is the switch control voltage

 

That looks to me like an AC opto relay .
...is it rated to turn off with DC
Looks like the 12 v DC is the switch control voltage

It can handle up to 30V DC

 

The snubber should be adequate for the relay module driving that pump motor.

 

Purchase one of those ready made modules from any of the E-commerce sites. Those will already have everything in a nice Pwb at a lower cost than individual components themselves.

 

Maybe a flyback diode — but is that necessary if a snubber is already included?

That relay module has a flyback diode across the coil.

 

Purchase one of those ready made modules from any of the E-commerce sites. Those will already have everything in a nice Pwb at a lower cost than individual components themselves.

Can you send me an link please

 

That relay module has a flyback diode across the coil.

Where is this, i dont see it

 

That relay module has a flyback diode across the coil.

I believe the TS is concerned about transient voltage across the relay contacts causing arcing and contact pitting.

 

Where is this, i dont see it

 

View attachment 369131

Should there be a diode on output terminals as well? Or is the snubber

 

Not on that module. The diode mainly protects the transistor that activates the relay coil.
Add the snubber across the contacts COM and NO.

 

But should I also add a diode between NO and GND?

I will add the snubber but the diode would that be beneficial?

 

Probably not needed but install the diode directly across the pump motor.

 

Why not use a similar available board that uses a power mosfet??

 

Probably not needed but install the diode directly across the pump motor.

The issue is thr pump is complete unit , with a long wire not do not have access to the motor with exception of at the end of wires where I could place a diode on the connector/ wire

 

Why not use a similar available board that uses a power mosfet??

Maybe in the future, I believe there would be heat impact with that option?

 

The issue with any mosfet device is that a transient event that will arc across relay contacts for a few milliseconds may completely destroy a power semiconductor device. An electromechanical relay may suffer a bit of contact damage but continue to function for most of it's normal lifetime .
Based on the lack of details in the description by that source, I would not deal with that supplier.
I do not assume that product specifications not stated are what I would accept.

 

Maybe in the future, I believe there would be heat impact with that option?

Or a opto relay designed for DC and with built in protection
Relays are good, but contacts can be a problem.

 

Maybe in the future, I believe there would be heat impact with that option?

Should be possible using a low Rds-on Mosfet.
If insisting on a relay to switch that kind of DC load, you definately require a diode across the contacts, otherwise expect to see a sustained arc across them.
Been there- done that.