Relay connection

How do I connect a C7-A20X Relay 24 DC V (datasheet: to arduino?
I don't know how to connect it because it is not similar to other relays that I've seen in other topics, as they have a IN pin which connects to any digital PIN on ARDUINO. I reefer to this type of relay:

On my relay I don't know which pin is the IN pin. To make the connections with the relay I have a socket (datasheet: This is what I got:


You can't directly drive a relay coil with the Arduino because you can't get enough current, and relays also often require more voltage.

You need a driver circuit. "Relay boards" often have a built-in driver, but a socket does not. The socket is just a different (easier?) way of wiring the relay.

A relay with a 24V coil also needs a 24V power supply in addition to the driver.

Driver circuit for a motor or relay. (It shows 12V and a motor but it can also be used with 24V and a relay.)

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Do not connect a relays directly to your arduino. Even if it has a 5V coil (which your relais does not have), don't do it. It might not kill your Arduino instantly but it will eventually damage it.

  1. Arduinos have 5V outputs (only Realys with a 5V coil voltage will work)
  2. Arduino can drive up to 40mA on a single pin (but that's really the maximum. If your relay needs more than 40mA it will damage your arduino)
  3. Relay are an inductive load, if you connect that without the right protection circuit to your arduino it will generate a high voltage on swithcing off (the protection curtcuitry in your arduino will probably protect it from immediately being destroyed but it's not made to withstand that kind of abuse for prolonged periods of time)

You might want to use a product like the TPL7407A or anything similar to drive your relay. This is a 7 channel triver with most of the protection circuitry already included (I'm still using a freewheeling diode tough, but I'm paranoid). See it's datasheet here: TPL7407LA data sheet, product information and support |

Don't be discouraged by this response please. You'll be getting there, I'm sure!

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Hi, thanks for your answer, very useful, but the think is that I'm not really using an arduino board, I'm using CONTROLLINO MEGA, which works at 24 VDC (datasheet: (I said ARDUINO 'cause sometimes it's easy for people to give answers when the read ARDUINO instead of CONTROLLINO). Both CONTROLLINO and my relay work at 24V, so I guess this is OK (isn't it?). Do you think I still have to use a transistor like the one you suggested me?

What kind of relay driver? Transistor?

Thank you?

Not necessarily; after all, the internals do not work on 24V.

Did you check the user manual that you linked? There are some specs in there.

The board has onboard drivers so you should be OK.

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Okay, I read the manual. CONTROLLINO has got relay outputs, so I guess I can use them, instead of using my external relay, right?
The manual says:
" The maximum permissible switching current per relay is 6A (at a maximum of 30V / DC). The relay outputs are potential free!"
What does that last sentence mean? If I use the relay outputs (I want the relay to control an electrovalve), How should I do the connection??

ps.: I have a 24VDC power supply for CONTROLLINO and the electrovalve which also works at 24 VDC

Looks like a quite cool and capable little device.

Sadly, neither the manual nor the datasheet mentions if the Digital Outputs are made to drive relais directly. I'd use at least a freewheeling diode parallel to the relais (look it up on how to install it) to protect the outputs.

It says that you can use two halfe bridge outputs to drive a motor in both directions. This could imply that there is some kind of protection against back EMF already built in. Maybe contact support and ask.

"The relay output are potential free" means, that they are galvanically isolated from the rest of the device. So to use them you have to connect both sides of the contact (like a light switch). The upside is, that this gives you a lot of freedom on what you want to drive with that output.

You should be able to easily control the valve from either the halfe bridge or the relais outputs (for the halfe bridge output check with the supplier first and post your findings here)

@juanfer_jf, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project.

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