Grove relay stuttering

Other Hardware Motors, Mechanics, Power and CNC
1

I have bought this Grove relay: Grove - Relais | Kiwi Electronics.
I use it to drive a low-power water pump with a 9v battery. So the pump circuit is isolated from the Arduino circuit.
When the Arduino sends 'high' to the relay, this relay begins to stutter. Contract-release at high frequency. This only happens if the pump is attached. I have bought multiple relays and they all behave in the same way.
When I use a non-grove relay, such as Twee-kanaals 5V relais module | Kiwi Electronics I do not have this issue.
I made a small film of both relays: https://photos.app.goo.gl/szHHE5EGqjHzJy3f7 (shared google photo's album).
Why does this happen? What can I do to correct this issue with the Grove-relais?
I want to use these Grove-relays because they need to be used by students that are used to work with Grove components.
Please help!

Schema:

image
image1215×911 38.1 KB

Implementation:

image
image1215×911 165 KB

2

9 volt battery... Is it a fire alarm battery? If it is, put it away and use 4AA batteries.

1 Like
3

It's a normal 9v Block battery. What would be the difference with 4AA batteries? The relay should not "be aware" af what is attached on it's 230vAC-30vDC pins, right?

Edit: I tried with 4 AAA batteries (have no holder for AA). Exact same effect.

4

Which Arduino are you using?
How are you powering the Arduino?

1 Like
5

It will never work properly until you get a stable power source. 9V batteries do not cut it.

6

That is correct
How are you powering the arduino?

7

I use an Arduino Uno, powered over USB. I use a digital output port (7) which is set to high. This pin 7 is connected to the SIG pin of the grove relay. If I use the exact same Arduino, power supply and code, but just switch the Grove relay with a 'normal relay', though using the same SIG pin, then that relay works properly.

8

It does work properly with the 9v battery with the other relay, just not with the Grove battery. And the 9v battery is for the pump, it is not powering the Arduino or the low-power end of the relay.

9

What powers the low power side of the relay?
Time for schematics.

1 Like
10

@mvermand
There is no reason why it should not work, however, the grove relay is a very very poor design.
You may find some that work and some that don't.
There is nothing you can do.
Maybe send it back and ask for a refund.

11

Arduino uno with Grove shield, connection to grove-relay. high-power side of the relay basically just switches 9v battery power to the pump.

I added the schema and picture of the circuit to my original post.

12

@mvermand
Even if it did work, it draws so much currwnt you could only use one with an UNO

13

You are right. For the small project we do not need more than that, but indeed, it draws a lot of current.

14

So what will you do since you can't use these relays?

15

May be a kickback diode in parallel with pump motor would help, diode cathode (end with band) toward + would help.

16

The link posted shows a 3 volt relay, are you powering a 3V relay with 5V?

17

@mvermand
Problem solved.
Turn any relay into a grove relay with these adaptors

The grove relay is a very very poor design.
You may find some that work and some that don't.
There is nothing you can do.
Maybe send it back and ask for a refund.

18

Is this the Grove relay that you have?

Screenshot 2024-02-22 at 10.13.38 AM
Screenshot 2024-02-22 at 10.13.38 AM1552×1068 62 KB

19

Looking at the schematic for the Grove relay:
The relay operates at >120mA drive current at 3V
The circuit provides about 1mA drive current to the NPN transistor driving the relay coil
The NPN transistor has a minimum guaranteed Hfe of 85 at 100 mA collector current
Therefore there is no guarantee that the relay will operate under those conditions

If you absolutely have to use the Grove relays you could try lowering the 4k7 base resistor to the NPN transistor to say 2k2 if my bar napkin arithmetic is correct.

20

See post #17