Relay stops working properly after connecting battery to relay

Other Hardware General Electronics
1

Hey, I'm building an automated gardening system as a small project and I ran into a problem with connecting a mini pump(Voltage: 2.5-6V) to Arduino. I have DHT11, water level sensor, soil humidity sensor, and mini pump (connected to relay). Without a connected battery, the relay works as I intended to (2 seconds on, 5 seconds off if humidity < 30% (video1)). As soon as I connect the 9V battery relay starts getting false signals and starts turning off/on randomly (video2). Do you have any idea what causes this?

Relay working as it should(video1): Imgur: The magic of the Internet
Relay not working properly(video2): Imgur: The magic of the Internet

Thanks

2

what type of 9V battery?

these are no go for anything requiring more than a trickle of current

image
image1176×760 70.1 KB

3

It's 9V alkaline 6F22

4

probably not enough current

voltage drops quickly when you draw 250mA... and I assume your pump draws more...

image
image852×592 42.6 KB

5

Thanks for the help, I will try with a different battery. Any suggestions on which one should I pick?

6

LiPos would be able to provide more current

if you don't read French, I suggest you google translate this article by @hbachetti RitonDuino: Alimenter un ARDUINO sur Pile ou Batterie

➜ Google translate in english

7

If you have no Lipo experience, you need to research proper Lipo handling and use
protocols. One mistake and it could burst into flames.

8

fair point, always be careful with LiPo