Hello all,
I want to use two relays for this project. I already have a grove relay setup and running but I’m confused with how to add the second relay as it isn’t grove. Do I just connect jumper wires between the pins of the GrovePi board outlet and the relay? Thanks
1 Like
It’s really hard to help you with the small amount of information you’ve provided.
In general, the way the Grove device works is that it either sends a digital signal, or an i2c data request to the associated Grove actuator, and the actuator does what it is commanded to do.
I strongly suspect that you cannot simply “attach a relay” to the Grove board, these are low-power digital signals and cannot drive something as heavy as a relay without destroying the electronics on the Grove board.
If you want to drive relays with a Grove board, you need to:
- Get more than one Grove relay module.
- Get the schematic of the Grove relay module you have, and build another one from scratch.
I would strongly suggest #1, (getting another Grove relay module), unless you happen to be very good at electronic construction, have the schematic, and can get the correct parts.
If you can tell us more about what you want to do, and give us relevant details, we might be able to help more.
Hey, sorry. So it’d be hard/close to impossible to attach a non grove relay to the GrovePi? I’ll try to be as detailed as possible. I have a relay like the one in this picture : https://www.amazon.com/SunFounder-Channel-Optocoupler-Expansion-Raspberry/dp/B00E0NTPP4 I was thinking that maybe I could just connect the 4 pins from the relay to the 4 pins of a digital output of the GrovePi board with 4 male to female jumper wires. However, I’m assuming that isn’t possible. Do I really have to buy a Grove relay? That’s the only possibility?
2 Likes
Here’s what the Grove relay board looks like. (I don’t have one, I grabbed this off the Internet)
It is designed to interface with the Grove controller board in a very specific way.
The relay you mentioned is an optically-isolated relay board, not a Grove relay board and without seeing schematics and/or datasheets, I cannot say if they are interchangeable or not.
How much experience do you have with digital electronics?
1 Like
It’s fine, I ordered one. Luckily with free shipping so I only had to pay like 3 bucks. I have experience in programming but amateur experience in electrical engineering. I don’t think I’d be successful at toying with a relay. Thanks for your help!
2 Likes
You did the right thing! 
I’ve been messing with this stuff for - oh - maybe 45 or so years - and given my choice I’d rather “get the right part” rather than mess with stuff and maybe ruin everything.
Good job!
Let us know how it works out.
2 Likes
The one big caution is to make sure you have enough power for your Raspberry Pi, AND the Grove board, relays, (they can draw a lot of power!), and everything else you want to do.
If you don’t have enough power, (5v at enough amps), things will appear to work, but won’t. . . . (i.e. the relay may not actually close)
So make sure the 5v supply you are using has enough power for everything you’re doing. 
1 Like
Given that you are asking the question - yes. Going with a second Grove relay for your project is the best approach.
No, it is not the only possibility, just the best. Using the relay you linked would require you to build some custom cables from two Grove Pi digital ports to the dual relay. The GrovePi can source up to 40mA through a digital output port so it probably could drive the relay you linked but there are no guarantees when you are “off the beaten path” designing your own system.
1 Like