12V relays or 5V relays?

Hi all,

I am working on a project which involve the use of 8 channel 12V relays to control 12V actuators. The actuators, relays and Arduino all share the same 12V power supply. But then it got me thinking, what difference would it make if I used 5V relays instead?

I know these voltages are the required voltage to power and activate the electromagnet in the relay, but are there any advantages or disadvantages when using 12V relays over 5V relays, and vice versa? What are the considerations one should make when choosing the relays?

As you are going to need to drive the relays with a transistor or similar (the Arduino can not drive relays directly) I would use 12 volt relays as the 12 -5vdc voltage regulator probably won't be rated for the relay coils.

Not much difference.

If you already have a 12v power supply, it makes sense to use 12 relays.

Sometimes it may be necessary to have the load powered by an ‘isolated’ power supply.

All the relay coils will need some kind of buffer for the Arduino to drive them, unless it is built into relay board/module already.
The biggest risk to running the Arduino off the same supply as the actuator is the actuators causing current hiccups and resetting the Arduino. It’s better in that case to give the actuator a separate supply from the Arduino supply - so one supply on the Arduino to control the relay coils, and a 2nd supply to power the Actuators on the contact closure side of the relays, with no connections between them.

"I am working on a project which involve the use of 8 channel 12V relays to control 12V actuators"

You might go with the 12v relays as you can operate them from the actuator power supply. Use something like an NPN transistor to control the relays from an arduino 5v pin.

Actuators? Bi-directional control?
12 actuators could mean 24 relays.
Or, 12 H-bridges.
How big are those actuators (stall current).
Post a link.
Leo..

CrossRoads:
All the relay coils will need some kind of buffer for the Arduino to drive them, unless it is built into relay board/module already.

Yes the relays are already built into a relay module: 2PH63091A.

CrossRoads:
The biggest risk to running the Arduino off the same supply as the actuator is the actuators causing current hiccups and resetting the Arduino.

It would be best for my project if the system uses only one power source. I was planning to use a buck converter to step down voltage to 5V and then feeding it to the Vin of the Arduino. The 5V pin is then wired to the VCC of the relay board. With the jumper removed, JD-VCC of the relay board and the actuators are directly wired to the 12V battery. They all share a common ground. Will this setup work?

Wawa:
Actuators? Bi-directional control?
12 actuators could mean 24 relays.
Or, 12 H-bridges.
How big are those actuators (stall current).
Post a link.
Leo..

The actuators are bi-directional, positional feedback actuators with an inbuilt potentiometer inside. There are 4 actuators, so I am using a 8 channel relay board. 3 of the actuators have stall current of 650mA rated at 12V. (https://s3.amazonaws.com/actuonix/Actuonix+L16+Datasheet.pdf) The 4th actuator is a heavy duty one, with a stall current of 20A rated at 12V. (https://cdn.shopify.com/s/files/1/0061/7735/7891/files/Heavy_Duty_Linear_Actuators_PA-17.pdf?13226) The potentiometer wires (+, wiper and -) will be wired to the analog pins of the Arduino.

I am somewhat following the schematics of this tutorial: https://www.hackster.io/robotgeek-projects-team/control-a-large-linear-actuator-with-arduino-8a3953
except that mine uses a single 12V battery with a buck converter to step down voltage to 5V for the arduino, and the JD-VCC and VCC jumper removed (as mentioned above)

Nanren123:
I was planning to use a buck converter to step down voltage to 5V and then feeding it to the Vin of the Arduino.

Which Arduino.
An Uno/Mega needs a minimum of 6.6volt (7-12) on the V-in pin for the onboard regulator to make a stable 5volt.
If you have a stable/reliable 5volt supply, then connect it to the 5volt pin.
Leo..

I am using an Arduino MEGA 2560.

Wawa:
Which Arduino.
An Uno/Mega needs a minimum of 6.6volt (7-12) on the V-in pin for the onboard regulator to make a stable 5volt.

In that case, perhaps I should step down to 7V with the buck converter instead? Would this setup solve the current hiccup issue raised by CrossRoads?

CrossRoads:
It's better in that case to give the actuator a separate supply from the Arduino supply...

The best option.

A small cellphone charger, connected to the USB socket, is an easy way to power the Arduino.
Leo..

Wawa:
The best option.

A small cellphone charger, connected to the USB socket, is an easy way to power the Arduino.
Leo..

So the best case would be a 5V power supply for the arduino and 12V for the relay coils and the actuators?
Is there really no alternative for using a single power source?

"Is there really no alternative for using a single power source?"

There are plenty of single source alternatives, but they need to have sufficient power to power the arduino and motors you are using. 120vac wall power is a single power source, as is a 12vdc battery. It is usually best to split the single power source between the arduino and the motors in various ways.

"I was planning to use a buck converter to step down voltage to 5V and then feeding it to the Vin of the Arduino. "

That would work, but connect it to the 5V pin on the power header.

Connecting to Vin will run it thru the 5V regulator, and will not result in 5V to the board.

zoomkat:
split the single power source between the arduino and the motors in various ways.

Would using a buck converter to step down voltage before feeding it to the Arduino while directly feeding power to the relay coils and motors be considered 'splitting' the single power source?

CrossRoads:
Connecting to Vin will run it thru the 5V regulator, and will not result in 5V to the board.

Sorry, I am alittle confused. I thought the 5V pin is usually used to output power to other electrical components in the system, which in this example would be to the VCC of the relay module. I actually also need it to supply voltage to the inbuilt potentiometers of the actuators as well as other components I have in my system (16x2 LCD, etc). But I realised that an insufficient supply voltage would result in a lower than expected output voltage after passing through the 5V regulator in the arduino after reading what you said. Would stepping down the voltage with the buck converter to perhaps 7V instead of 5V solve the problem?

Thanks for bearing with me. I am still quite new to this.

I thought the 5V pin is usually used to output power

If you are powering the Arduino from the power jack or by the USB connector, the 5V pin on the Arduino is a power output pin.

However, you can power most Aruinos by attaching an external 5V power supply to the Arduino 5V pin.

I suggest you never use an external power supply on the Arduino 5V pin WHEN you also have the USB cable plugged in.

Feeding 7V from the Buck Converter to Vin is a good option.

larryd:
Feeding 7V from the Buck Converter to Vin is a good option.

I will do that. Thanks!