ESP8266 Community Forum

I built a plant sensor that should simply pump water when soil moisture (measured with a capactivie sensor) is too low.

I am using a relay to turn on/off the 5V water pump. The pump turns on and works perfectly when I connect the pump to the 5V pin of the Wemos D1 mini.

However, when the electrical wires go through the relay wemos shield, the pump just emits a light sound like there is not enough current and so it does not work when the relay is on. If I start to play with the wires like moving them or taking out and then in from the breadboard, I can observe that sometimes the pump starts to work slowly.




I am very noob in electricty and circuits but to me looks like there is not enough current arriving to the pump when connected through the relay.

Would you know a way to solve this issue?

I am using the same power source to power the wemos and the pump because I saw a youtube video of a guy who built exactly the same project with the same components. In the picture I use a 2A power bank but I also used a 3A power adapter that I usually use to power a raspberry pi.

Everything looks good with your setup, all I can think of is that the relay is not fully closing causing a high resistance or something?

Can you test directly jumpering across the relay C and NO terminals and see if the pump runs? If yes then the relay / drive circuit likely has some problem.

If no then possibly you have excessive voltage drop somewhere due to a poor joint etc. measure the DC voltage at the relay N/O terminal, activate the pump and see how much the voltage drops.

For this type of pump a transistor or MOSFET switch can be easier to use than a relay. Smaller and more power efficient.

See also https://www.instructables.com/id/Batter ... -Watering/ for similar project

I would say that your setup looks ok, but..

Your pump draws min. 350-500mA (by looking from internet of similar pumps), and all other gadgets pull the same amount at least. lets say you have it close to 1-1.5A+ current draw.

The breadboard wires are very thin, so you have multiple points of possible failure.

Test the setup with 2A supply, I suppose your power bank has 2A output?

Also try out each component separately, so that you know for sure they work as intended.

I would double the power wires and see if it fixes the issue or use thicker ones..

Hope you solve it out.