GrovePI board in combination with relay board and NC relay

grovepi
relay
iot

#1

Hi Everyone,

I am doing my first steps in the IoT world and bought a Raspberry Pi 3 and a GrovePI starter kit. I intend to use Windows IoT, mainly because I use a limited amount of Visual Studio in my daily work and like to be in a familiar environment for now.

In my project I would like to measure temperature, humidity, but I would also need to reset anther device once every 24h. There is no other way then to basically remove the power to that device for a while. I thought to use a normally closed relay that I would open once every day for about 10 seconds. However, there does not seem to be a NC Grove relay that I can connect to the Grove board.

Hence my question: is it possible to stack a relayboard on top of the GrovePI board? If so, what would be the best option?

Thanks for your kind help!

Wim


#2

Hi @wim.borgers,

So if I’m right, you want to have a way of cutting the power to a device with the GrovePi, but you’re saying you can’t-do this.

So, if I understood correctly, you’d just need to use a Grove Relay (which you already got one in your starter kit), then connect it to your GrovePi with a Grove cable and then actuate it with a python script. But in order to do this, you have to adapt a Grove cable so that the VCC signal of it goes through the relay.

This to me looks doable, so probably I’m missing something from your message.

Thank you!


#3

@RobertLucian Thanks for your reply.

Well, sort of. :slight_smile: I would like to cut off power to an external device using a relay for about 1 minute every 24 hours. The Grove Relay is open when it is not powered. In order to disconnect power using the Grove Relay I would need to activate the relay for 23h59 minutes every day, and then deactivate it for one minute.

It seems to me that a situation like that should be avoided. I can imagine that the relay is not designed to be powered that long, and might even ‘stick’ when it is deactivated. Hence I am looking for a relay that is closes the circuit when NOT powered, and needs power to interrupt the circuit.

Hence my idea to use relays on a RelayBoard that can be set to ‘normally closed’ or ‘normally open’ and connect the circuit in such a way that I only need to activate the relay for one minute per day. And that leads to the question of stacking of boards. :slight_smile:

I do not know if tampering with the Grove cable and VCC signal could solve this. To be honest, that is outside of my current knowledge.

Thanks for your input!
Best regards,

Wim


#4

Hi @wim.borgers,

Alright, I understand where you’re pointing at.

If I were you, I’d use one of the following relays and adapt a Grove cable so I can pair it with a GrovePi. With this relay you have the advantage of using both modes: NO or NC modes, which is great.

As you can see on this relay’s page, you’ll have to cut the end of a Grove cable and adapt it so it can be plugged in the grey socket. So, here’s how you should pair the Grove cable’s wires:

  1. The Black wire of the Grove cable should go to the GND port of the Sparkfun’s relay.

  2. The Red wire of the Grove cable should go to the 5V port of the Sparkfun’s relay.

  3. The Yellow wire of the Grove cable should go to the CTRLport of the Sparkfun’s relay.

As an example, here’s what I did with my Grove cable so I can use it on a project where header pins had been used.

If you feel like there’s anything else to talk about, please tell us.

Thank you!


#5

Hi @RobertLucian,

Now I understand. That is a great suggestion. I will check it out! Thanks!

Best Regards,

Wim


#6

Hi @wim.borgers,

That’s great to hear.
It would be nice to keep us updated with what you’re doing.

Thank you!