First Project - Low Flow Solenoid and Arduino on Battery Power

Afternoon Everyone,

This is my first post here, I’m absolutely new to all of this and looking for some guidance on a little project I’d like to work through.

I’ve got a couple of plants on my balcony and through trial and error I have determined that plants appreciate water… on a fairly regular basis. Now I have no idea why, probably a question for another forum but regardless i’m here to solve a problem and not learn plant biology.

My plan is to set up a tank, hanging or elevated on the balcony. (Think 8" diameter PVC pipe, capped, mounted vertically).

It will have a single outlet at the bottom going in to a low flow, low pressure, low voltage solenoid.

Past the solenoid, I will have a small resevoir which will have several small fish tank sized tubes running from the bottom. The small tubes will come out of the bottom and in to each plant.

Essentially, it’s gravity fed watering system with a solenoid to stop the flow.

I would like to run the solenoid through arduino, a 24 hour timer and possibly a wifi module so that I can remotely monitor the watering.

I’ve used to grab some components but I have some concerns.

  1. The 9V battery is not the correct choice. I don’t have mains power and lithium would be better. Is there a recommended battery pack that would last a very long time… 6-12 months? Or is that a pipe dream? Happy to charge it once a month potentially but this solution is designed for extended periods away from the home. What would you recommend?

  2. Is the timer I’ve included necessary? The function would be to open the solenoid for a few 30 seconds or so, only once per day.

  3. Is there a better solution in general that you can think of? There’s plenty of irrigation options for mains connecter, tap connected systems but very little for battery powered, gravity fed systems. There are some solar powered fountain pumps that could do the job… 12V fish tank pumps that could also, but I feel a solenoid would be the least stressful, least prone to failure option… allowing gravity to do the heavy lifting.

  4. Monitoring the system via wifi may not be necessary, howwever phase 2 would allow for a water level indicator on the attached tank. If it got below a certain level, it would send an email alert or i’ll build a server and front end portal to monitor a collection of them for my home.

Really apprecaite your feedback. This is first project and i’m sure i’ll mess it up. Thank you in advance


Make a search for irrigation projects. There are plenty of them. That will give You answers to quite some questions. Check how those guys found their solutions.
Doing that Your list of questions is a lot shorter.

How long a battery lasts depends on just on the battery itself, also on the amount of current drawn. Especially the solenoid may draw a lot.

I've got a couple of plants on my balcony and through trial and error I have determined that plants appreciate water.. on a fairly regular basis. Now I have no idea why,

This is very common with plants, certainly no great biological surprise.

  1. The 9V battery is not the correct choice.

You can be sure that is correct. One or two 18650s would be a far better bet. They have lots of grunt and excellent shelf life. You probably need to examine sleep modes etc., as there is virtually no action in this project - lots of sleeping. If you are prepared to use solar power, I think it would be better employed to charge the battery rather than run mechanical stuff.

  1. Is the timer I've included necessary?

Probably not. While plants like a drink, they aren't very fussy about the delivery time and the internal counter should be adequate.

Lots of ambition here. I've developed my own platform (mobile app, hardware, software) which uses LoRaWAN to monitor and control irrigation to plants. I have several raised beds with each bed having its own valve (controls flow), meter (measures flow), soil temperature and moisture sensor, and mCU with BLE (registration) and LoRaWAN (remote control and monitoring). I developed a mobile app and backend to tie it all together.

Having said that, it took me a few years to do in spare time, and I'm a software engineer. There are a LOT of things to consider for outdoor projects. For your gravity fed system, you'll want to post your solenoid valve. It's probably a 9V-12V DC latching valve, which means you'll either need to step up the voltage to the solenoid or step down to Arduino. Check out for some regulators. You'll also want to "kick" the solenoids open using a CDU (Capacitor Discharge Unit) circuit if stepping up. If it's an AC valve, then forget batteries.

Getting a year of battery life will be tough without replenishment especially if using WiFi + controlling valves. My guess is you'll have better battery life stepping up the voltage when you need to open the valves instead of constantly stepping down for the mCU, but it also complicates your circuit.

Adding solar can be dangerous with LiPo batteries, but it may not be a big deal on your balcony. LiPo is a volatile chemistry, so get a temperature monitoring charge module (Adafruit has one). I would personally suggest a different battery chemistry.

I think that's enough to get you going.

My project for reference

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