Can this relay found here:


Be used with an Arduino Mega? The description given seems to specify that you should hook it up to their dedicated 'Featherwing Board' but it's the only relay available on their site. Looking at the pins it has it seems it should hook up to an Arduino with no problems. Has anyone here had the chance to use this relay with an Arduino microcontroller? I asked them about this on their forum but I haven't received a reply yet.

PS: I want to use it to connect a 'Strobe Siren 12VDC' and the relay I was looking to get is out of stock at my local shop.

https://store.nerokas.co.ke/index.php?route=product/product&product_id=1398 https://store.nerokas.co.ke/index.php?route=product/product&product_id=1679



There's not a lot more to be said really.

It's a relay, and they provide a MOSFET and associated circuitry to drive it cleanly.

Just connect power and ground to the Arduino, along with the "Signal" pin to the GPIO pin of your choice, and away you go.

Note that the relay is a 3.3V relay, so you must power it by the 3.3V pin, not the 5V pin.

  • That relay draws way, WAAAY more power than the 3.3V line on and Arduino puts out. The data sheet says it draws 100-200mW. That's just the relay. The logic circuitry and LED will probably draw 20-50mW more than that. As I recall the 3.3V line on most Arduinos only provides ≈50mA of 3.3V, which is completely inadequate. – Duncan C Mar 25 '19 at 22:45
  • @DuncanC That was the case 10 years ago. Back then the 3.3V pin was powered by the internal 3.3V regulator in the FT232R chip. That is no longer the case, and hasn't been for many years (since the Uno R2). Now it has a dedicated 3.3V regulator that can provide a few hundred mA (LP2985 - 150mA). – Majenko Mar 25 '19 at 22:47
  • At 3.3V, 200mW is 60mA. The LED has a 1k resistor, so would be around 3mA. That's 63mA - less than half what the regulator can provide. – Majenko Mar 25 '19 at 22:50
  • Ok, that relay quotes 200 mW, not 200mA. That isn't quite as bad as I thought. However, the Arduino store says the current limit of the 3.3V line is 50mA, and that's still over the limit: store.arduino.cc/usa/arduino-uno-rev3 – Duncan C Mar 25 '19 at 22:59
  • To quote the specs tab on that page: "DC Current for 3.3V Pin 50 mA". And that's from the page for the current Rev3 board. – Duncan C Mar 25 '19 at 23:00

That is a 3.3V device. you'll need to give it a separate 3.3V power input, and it needs much higher current at 3.3V than the Arduino can supply.

I don't know if you can feed it a 5V logic signal or not. (If it needs 3.3 V control signals as well, and it's current needs are modest you could step down the voltage from an Arduino 5V digital output to 3.3 with a simple voltage divider circuit.)

You'd be better off getting a 5V relay. If you do a Google search on "Arduino Relay" you'll find tons of them. You can get 1 relay, 2 relay, 4 relay, and more on a board. Many have optical isolation to make sure the relay coils don't add noise to the logic lines.

In general it's a good idea to use a separate power supply for the relay, or at least use a power supply with plenty of current to spare, and add filtering capacitors between the 5V rail and ground right next to both the relay and the Arduino. These capacitors serve to filter out variations in voltage as the relay coils are powered on and off.

(Even "digital" relays draw a large amount of current from their power source when they first turn on, and abruptly stop drawing current when they turn off, which introduces a lot of noise on the power line. "Naked" relays need "flyback diodes" to avoid reverse currents that will destroy transistors, but the "digital ready" relays I'm talking about have those built in.)

Here is one such relay I found from Googling "Arduino relay".


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