Powering pump (with timer) from solar

Using Arduino Project Guidance
#1

I have ordered the following components for my project:

The aim of the project is to use these items as well as some mosfets, capacitors, light sensor, leds and maybe a small display (to show voltage out of solar and out of battery) to turn the pump on and off on a timer (that may change depending on temp once I add a temperature probe) during daylight hours.

I would like to keep the solar system and the pump system separate (on different nanos).

For charging the battery I need to make sure I do not overcharge. To do this I am looking at using 2 voltage dividers, one between the panel and the mosfet and another between the mosfet and the battery. This way I can tell when the battery is charged and turn the charge off using the mosfet. Both nanos and the pump will be powered off the battery.

I am guessing that when the solar panel is charging, it will spike the power that is coming out of the battery (as the solar will be connected to the same terminals as the nanos and pump). The nanos say they should operate between 7-12v, and I know they can go a bit outside of this, but I am worried the onboard regulators will overheat or the power will go well above what they can handle and kill them instantly. I would also like to keep the pump to a max voltage (its only a small pump so I don't want to fry it).

So how and where should I be regulating the voltage? I'm guessing the battery won't want to have too much voltage input, but may want more than 12v? Should I regulate the voltage from the panel down to 15v and then the voltage out of the battery (to the nanos and pump) down to 13v or something? How would I go about this?

Thanks

#2

The pump needs 12V AC to run , so you cant run it off a battery.

#3

Good point, thanks for that, I will sort out a 12v dc to 12v ac inverter, that shouldn't be too hard.

#4

MicWit:
Good point, thanks for that, I will sort out a 12v dc to 12v ac inverter, that shouldn't be too hard.

Does that pump really run on AC?
The blurb says "all models come with 12V AC adaptor".

It is a bit ambiguous but I took that to mean it came with an AC mains adapter that output 12V DC.

#5

It's going to be much easier to find a 12V DC pump for sure.

Do check the pump carefully - almost all such small pumps I've seen so far run on 12VDC (or 240VAC). It's probably written on the pump.

#6

Yeh, thats how I read it as well! So I opened the box and on the converter it is 240v ac > 12v ac! Not sure why a pump would run of ac! Its a low wattage pump, I think I will look into options for a straight ac - dc conversion. I was told it shouldn’t be too hard.

#7

AC motors are quite simple and possibly cheaper than BLDC motors. A 12VAC adapter only needs a transformer, a DC adapter needs more components (rectifier, stabiliser). That are two possible reasons.

One thing for you to consider: your 10W solar panel will be able to provide power for about 2W continuous or average draw. So you can run your 12V 3W pump about half the time, and have just enough power left for your Arduino to run continuously. Though if you're up north you won't even get that much power in winter - this factor of 5 is my rule of thumb living a hair south of the tropic of Cancer.

By the way, I found a pdf from the manufacturer which rates this pump at 5W, and also mentions 12V AC. Also I hope you're not planning to pump water to any significant height, as it maxes out at 60 cm (and for any reasonable flow you have to stay below 30 cm).

Your best bet is to find another pump - a 12V DC model. That will work much better with your batteries.

MicWit:
So how and where should I be regulating the voltage? I'm guessing the battery won't want to have too much voltage input, but may want more than 12v? Should I regulate the voltage from the panel down to 15v and then the voltage out of the battery (to the nanos and pump) down to 13v or something? How would I go about this?

You don't regulate the voltage as a solar panel is a current source rather than voltage source. You do need at least a basic charge controller (an MPPT version gives best results). For these low power panels you can buy sets that have controller and battery in a single case, that's the easiest.

#8

The panel is going to power the pump. Why are you using two nanos to control them is it because they are far apart?
If you are not in a sunny climate you might want to do some calculations on how much power you will get and how much will be lost in things like inverters or long cables.

#9

It shouldn't be an issue. That is correct, it is a 5w 12v ac pump (so I found in the manual). It is just for a lettuce small hydroponic system, so just need to lift water out of the sump into a 50mm pvc, so 20-25cm head height.

As far as power requirements go, I will have a light sensor so it will only run during the day, and it will run for half an hr and then be off for about 3hrs. Only needs to water them 3 or 4 times a day, so thats a run time of 1.5 to 2hrs a day which is 20w total (plus running arduinos).

The reason there is 2 arduinos is I want to run one that will act as a charge controller for the solar, and another that will turn the pump on and off, that way I can work on the pump one and the battery will still charge abd vice versa. It also means down the track I can duplicate the solar one for other systems that will use solar charging a battery.

#10

There exist 5V (DC - they come with USB plug) 2W pumps which can provide more than enough water for hydroponics, and even pump it up a bit higher. Those will make your life a lot easier.

#11

wvmarle:
There exist 5V (DC - they come with USB plug) 2W pumps which can provide more than enough water for hydroponics, and even pump it up a bit higher. Those will make your life a lot easier.

That sounds great, I haven't seen them. Most of the low power pumps I have seen didn't have any head height. Do you have a link to one u would suggest? I could return this one.

#12

This is the 5V SL180. 2W, 1m head. There’s also a 1.2W model available.

The SL280, 12V 4.5W is rated 3 meters, in practice a bit less but no problem to get good flow 1.5m up.

#13

wvmarle:
The SL280, 12V 4.5W is rated 3 meters, in practice a bit less but no problem to get good flow 1.5m up.

It's not in English so I cant read it, but from what I can see we are talking 280L/hr flow for 4.5W which is rated way better than my pump (if it actually does this) which is awesome!

I decided to order one like this.
NOTE: ignore the title, from the photos it is actually a 4.2W 12V DC 280L/hr pump with a 2m head height. So pumping at 25cm, this should move a lot of water, and will run directly off the battery. Because it is only 4.2w, this also means that 2hrs of good sunlight, or a few hours of poor sunlight will run this pump for the up to 2hrs per day I will need. One day of good sunlight will charge the battery enough to run it for a few days.

We are in Northern NSW, Australia. This means a cold winters day for us may get down below 15C (60F) so sun shouldn't be too much of a problem.

#14

Hi MicWit,
I am in Victoria and have played around with solar panels for a while, my dads shed is all 12v lights run from two 80ah batterues and charged by 120watts of panels on his roof.

Beware the solar panel. Take note of the maximum voltage and amperage (never the two shall meet) its one or the other and they usualy go to 21volts which is what it will do on your battery.

Pulse Width Modulation controllers have been around for a long time and are real cheap on ebay. A controller will regulate your panel charge to your battery and also control the load and cut off the battery when it drops to 10.5 volts.
Well worth the price unless you are doing this for the sake of DOING IT.

The solar panel is a weird supply, it will give you different voltages depending on the current you draw. From 21 volts at no current to maximum amps a no voltage. This is not linear so theirs no easy mathmatical solution.

Rule of thumb i use is expect to get 60% of the panel wattage and only for up to 6 hours a day. This gives you a ballpark wattage for the day to work with eg. 6 watts by 6 hours, 36 watts a day.

Your battery will allow you to draw 60% before it drops below 12 volts and reaches 100% discharge at 10.5 volts so,
12v x 7amps = 84 watts gives you around 50 watts usable without damaging the battery.

If you are going to monitor the panel and the battery you can use the voltage monitoring on the panel to detect when the volts drop below a predetermined point (say 5 volts) as your day/night monitor without adding more hardware like light monitors.
Thats what a solar panel is.

With the pump make sure your pump does not supply to much water or your plants will all wash away.

Sounds like fun.

#15

Hi,
What is wrong with a car window washer motor?

Check the caravan and outdoor goods stores for 12V DC pumps.

Tom… :slight_smile:

#16

Daz1712:
Beware the solar panel. Take note of the maximum voltage and amperage (never the two shall meet) its one or the other and they usualy go to 21volts which is what it will do on your battery.

I realise now that the solar panel I got has a pmax of 12v (so its not really a 12v I guess) and an open circuit of 16v. So I am guessing that when charging it will never reach the 14.4-14.8v the battery needs to charge? I am looking at this one at supercheap with details here (KT70715) as it has a pmax of 17v.

Daz1712:
Pulse Width Modulation controllers have been around for a long time and are real cheap on ebay. A controller will regulate your panel charge to your battery and also control the load and cut off the battery when it drops to 10.5 volts.
Well worth the price unless you are doing this for the sake of DOING IT.

Can you send me a link to a Pulse Width Modulation controller (I looked it up on ebay and didn't come up with anything I thought would work)? The battery chargers started at about $20 and probably wouldn't be the best quality anyhow, I could probably make something similar for about $5 or so and have more control over it.

Daz1712:
If you are going to monitor the panel and the battery you can use the voltage monitoring on the panel to detect when the volts drop below a predetermined point (say 5 volts) as your day/night monitor without adding more hardware like light monitors.
Thats what a solar panel is.

The issue with this is what charge would I get on a cloudy day? If it dropped below this and the plants didn't get water for a day that would pretty much kill them.

Thanks for your advice, this is very helpful.

#17

Hi,
Can I suggest you avoid non electronic suppliers for you solar panels.

Here in Australia try Jaycar and Altronics they have a very good online service and have some panels at better prices than you are quoting at the moment.

Also check them out for solar powered water pumps.

Tom.... :slight_smile:
PS I do not work for these companies, but find there is a big difference between auto and diy sellers and electronic sellers when it comes to these sort of products. They will be able to tell you about the product you want to purchase, a mechanic or gardener would be limited in their knowledge to the instruction manual.

#18

MicWit:
I realise now that the solar panel I got has a pmax of 12v (so its not really a 12v I guess) and an open circuit of 16v. So I am guessing that when charging it will never reach the 14.4-14.8v the battery needs to charge? I am looking at this one at supercheap with details here (KT70715) as it has a pmax of 17v.
Can you send me a link to a Pulse Width Modulation controller (I looked it up on ebay and didn't come up with anything I thought would work)? The battery chargers started at about $20 and probably wouldn't be the best quality anyhow, I could probably make something similar for about $5 or so and have more control over it.
The issue with this is what charge would I get on a cloudy day? If it dropped below this and the plants didn't get water for a day that would pretty much kill them.

Thanks for your advice, this is very helpful.

Hi again,
Dont throw that panel yet, Try it first as some of the cheaper panels are terrible with the so called written specks.
As i said just allow for about 6 to 8 actual watts of charging from your 10 watt panel.

The controller i have used is like these two on ebay and i find it a good little work horse although not adjustable.
Its a Controller because you have connections for your panel, battery and load so it regulates the panel charge by connecting the panel across the battery until the battery reaches a preset voltage then disconnects it until the voltage drops to a preset voltage then repeats. This continues with the on/off becoming shorter and shorter as the battery reaches full charge hence PWM.
It also monitors the load and cuts power if the voltage drops below 10.5 volts or the current exceeds the allowed amperage of the controller. Not bad for the price.

https://www.ebay.com.au/itm/LCD-5-10-15-20A-Solar-Panel-Battery-Regulator-Charge-Controller-12V-24V-Auto-GC/262913509929?hash=item3d36ddca29:m:mwbA12vOGplqrz5j2CCdVnQ

First one has an actual volt meter and both are reported as in Ausrtalia so wait time should be short but now you see what they are have a look.

The ones marked MPPT are not good unless they cost heaps and the one i bought off ebay was a fake.

Re the cloudy day and using the panel to detect day/night is the same when using a light sensor, you must set it for the level you need. I mean solar panels do not produce any voltage without a light source so set the ref voltage low to indicate the end of day.

As for cloudy days it pays to allow for a battery that will run your pump over 3 days without any real charging from the panel to be on the safe side.

Think the project through step by step first and then run some tests so you have figures to play with.

  • How much water do i need to pump over what period of time for the plants.
  • How long will the pump run for each day.
  • How many watt hours does this come to and how long will it run on battery alone.
  • How many watt hours does my panel charge into my battery each day.

You have not mentioned alot about the system you are trying to set up.
Like is this a soil based system where you are irrigating the earth and will stop at a ceriain moisture level then recheck it at a certain time or are we talking full hydroponics where the water must be kept at a certain level and cycled every so often?

More info please.

#19

Daz1712:
…
As for cloudy days it pays to allow for a battery that will run your pump over 3 days without any real charging from the panel to be on the safe side.
…

  • How much water do i need to pump over what period of time for the plants.
    …
    You have not mentioned alot about the system you are trying to set up.
    Like is this a soil based system where you are irrigating the earth and will stop at a ceriain moisture level then recheck it at a certain time or are we talking full hydroponics where the water must be kept at a certain level and cycled every so often?

@MicWit Although the panel may not deliver all the power you were expecting don’t forget that on cloudy days the plants will require a lot less water so things may balance out. When and how you water will also be important. Watering the surface in full sun will lead to a lot of evaporation. Power will be much more critical if you are going for full hydroponics.

#20

Daz1712:
Dont throw that panel yet, Try it first as some of the cheaper panels are terrible with the so called written specks.
As i said just allow for about 6 to 8 actual watts of charging from your 10 watt panel.

Yeh, I will be testing the panel to see what it actually produces, will hook it up to the battery and throw a multimeter on it and see what voltages are being produced. I think you are correct, as it seems a lot like other solar panels that have different pmax etc values.

Daz1712:
The controller i have used is like these two on ebay and i find it a good little work horse although not adjustable.
Its a Controller because you have connections for your panel, battery and load so it regulates the panel charge by connecting the panel across the battery until the battery reaches a preset voltage then disconnects it until the voltage drops to a preset voltage then repeats. This continues with the on/off becoming shorter and shorter as the battery reaches full charge hence PWM.
It also monitors the load and cuts power if the voltage drops below 10.5 volts or the current exceeds the allowed amperage of the controller. Not bad for the price.

https://www.ebay.com.au/itm/LCD-5-10-15-20A-Solar-Panel-Battery-Regulator-Charge-Controller-12V-24V-Auto-GC/262913509929?hash=item3d36ddca29:m:mwbA12vOGplqrz5j2CCdVnQ

Solar Panel Charger Controller Regulator 10a 12v/24v Auto Switch CE TSR Safe /t for sale online | eBay

First one has an actual volt meter and both are reported as in Ausrtalia so wait time should be short but now you see what they are have a look.

Awesome, I think I was searching for the wrong term. That first one with the voltage on it seems well worth paying the extra few $s, and I found this one with a USB 5v 1A that could run the arduino. Do you think that one will do the job?

Daz1712:
Re the cloudy day and using the panel to detect day/night is the same when using a light sensor, you must set it for the level you need. I mean solar panels do not produce any voltage without a light source so set the ref voltage low to indicate the end of day.

As for cloudy days it pays to allow for a battery that will run your pump over 3 days without any real charging from the panel to be on the safe side.

Think the project through step by step first and then run some tests so you have figures to play with.

  • How much water do i need to pump over what period of time for the plants. - 16L for about 30mins
  • How long will the pump run for each day. - 3-4 times so 1.5hrs-2hrs
  • How many watt hours does this come to and how long will it run on battery alone. 4.2*5 = 8.4 watt hours per day, allow a bit more if the pump uses more that it says, and to take into account the arduino and controller, so 10 watt hours per day. As you said, battery has about 50 usable watt hours, so 5 days on battery should be fine.
  • How many watt hours does my panel charge into my battery each day. - On a sunny day lets say its only 6w of the 10w panel and charges (over the winter) 6 hours at full charge. That would be at least 36w on a sunny day. So using 10 or so will be easy done.

Daz1712:
You have not mentioned alot about the system you are trying to set up.
Like is this a soil based system where you are irrigating the earth and will stop at a ceriain moisture level then recheck it at a certain time or are we talking full hydroponics where the water must be kept at a certain level and cycled every so often?

More info please.

So it is for lettuce in 50mm pipe. There will be an overflow as well as a slow drain that will drain at half the rate the pump can pump in (excess will go through overflow). I want it empty of water most of the time, from experimenting with a manual one at the moment (that I rock backwards and forwards to fill or empty) I optimally want about 3hrs with no water, 30-40mins with water. On a hot day the roots would dry out faster so I may use a temperature probe to down the empty time to 2hrs (to stop root rot and get oxygen to the roots they need to be out most of the time).

I know I could turn the pump on for less time and put the drain on a solenoid, but by just turning the pump on a bit longer keeps some water flow when it is full and makes less places to break (or at least easier fixes).

There will be 6 rows of about 1m of pipe, plus the (just over 1m) of pipe up ceach side (one the water will go in, the other will drain), so that's a total of about 16L when full. The sump is a 100L storage container, which is what I will fill with water and the nutrients.

So would you suggest that controller? If so, I will order it now, if not, I will get the other one you suggested.