BTW, one more thing, If using the Amazon relay board, or one that uses a similar relay, It may pay to open the optional vent hole, in the top centre.
Otherwise ionization of the interior can occur.

 

Great I will be adding a diode and Snubber.

Vent hole ... Is there any examples?

 

Great I will be adding a diode and Snubber.

Vent hole ... Is there any examples?

Of What?
The centre dimple hole can be seen in the previous pictures.
It just has to be drilled out.

 

Of What?
The centre dimple hole can be seen in the previous pictures.
It just has to be drilled out.

Is that normal practice?

 

Is that normal practice?

Ozone in an enclosed space like a relay is quite corrosive so you need to vent that off or it could destroy the relay and or it's coils. So I guess if you like your relay yes if not kill it.

 

In most cases these sealed relays are fitted to prevent ingress of flux material in the manufacturing, So you have the option of venting them before use.

 

CERTAINLY there is a requirement to select a relay with contacts rated for the aapplication. UNFORTUNATELY not only is that not covered adequately in many school classes, it is not always covered in product literature, either. It would be the contact application voltage-breaking rating.
That is why some DC application power ratings include the inductive load circuit rating.

 

Yes, this relay shows the max DC voltage the relay can handle is 30V 30A

 

If insisting on a relay to switch that kind of DC load, you definately require a diode across the contacts,

For inductive spike suppression, the diode needs to be across the load not the contacts.

 

For inductive spike suppression, the diode needs to be across the load not the contacts.

Yes, I confirmed with the manufacturer, they already include the diode on the motor part of their device. So I now just have a snubber.

 

INDEED!! The SNUBBER connects across the contacts, the diode connects across some types of inductive load. BUT understand that when I diode across a load conducts, the current flowing in the inductor is producing a magnetic flux! That will alter the performance of a relay, solenoid, or motor. THAT is why some relays and switches have larger contact opening gaps than the intended voltage would require just to avoid breakdown. It does require a longer gap to extinguish an established arc.

 

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

For a 12V DC pump drawing 5 to 8A, a relay module rated at 30A should be more than adequate, but check that the rating is for DC loads, not just AC.

The snubber module can help reduce electrical noise and arcing, but for a DC motor load I would still add a flyback diode across the pump terminals (for example a 1N5408 or similar). The pump motor is an inductive load, so when it switches off it can create a voltage spike. The diode is a simple and effective way to protect the relay contacts and electronics.

A good setup would be:
12V supply → relay contacts → pump → 0V, with the diode fitted across the pump (reverse biased during normal operation). A fuse close to the power source would also be a good idea for safety.

 

One important bit of information that is missing is the actual application for this control package. Is it for a cartpet cleaner machine? or possibly for the water system in an RV?? Or maybe in the "head" of a medium sized "boat?" The typical "RV" application simply uses an adequately rated pressure switch monitoring the system water pressure, and when any use is started, the pressure drop immediately switches on the pump.

AND, I AM GUESSING that the 12 volt supply would be from a battery under most conditions, with a voltage increased during times that the engine system engine is operating.

 

One important bit of information that is missing is the actual application for this control package. Is it for a cartpet cleaner machine? or possibly for the water system in an RV?? Or maybe in the "head" of a medium sized "boat?" The typical "RV" application simply uses an adequately rated pressure switch monitoring the system water pressure, and when any use is started, the pressure drop immediately switches on the pump.

AND, I AM GUESSING that the 12 volt supply would be from a battery under most conditions, with a voltage increased during times that the engine system engine is operating.

The missing detail is the actual application. Knowing whether this is for an RV, boat, carpet cleaner, or another system would make a big difference.

Many 12V water systems simply use a properly rated pressure switch that turns the pump on when pressure drops. If this is a battery-powered setup, the supply voltage may also vary depending on whether the engine/charging system is running, so that should be considered in the design.

 

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

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

For a 12 V DC pump, usually a flyback diode alone is enough. If the relay module already includes an RC snubber across the relay contacts, the relay will have some protection against arcing, but that is not equivalent to a flyback diode across the pump.

 

If an adequately rated pressure switch is used, there is no need for a relay. That means less power consumption /less battery drain.