Newbie project-Solar monitoring system

I live offgrid in N. Ireland and I have a small solar array I wish to monitor using a display & log using an sd card, or wifi to a screen on my computer. I want to monitor input of amps as well as battery voltage.

So, an LED display like this one (?), and I'm looking at the current controller buying a Uno R3 package just to play with arduino in other ways as well)

I see this tutorial:, but am not clear if this is the right direction... newbie and all. It seems good, but just looking for a bump in the right direction as this is my first project.

Many thanks! RMD


Sounds like a good and workable project.

You might want to use an LCD display that uses up only 2 pins. These have a small interface board on the back, and there are some details here:

A Starter Kit with many input and output devices would be like this: (This has a modified version of Arduino Duemilanove with 3-pin connectors and higher-current 3.3V supply).

DISCLAIMER: Mentioned stuff from my own shop…

Firstly, welcome to the land of Arduino.

Secondly, can I suggest you re-name the title of this topic, 'Newbie Project' is pretty bland and does not convey anything about the topic. To suggest a better heading, try 'Solar System Monitoring'

Did you read 'How to use this forum - please read' sticky first, it really might be worth your while as a 'newbie'?

Radmacdaddy wrote: I live offgrid in N. Ireland and I have a small solar array I wish to monitor

When you say 'small', can you quantify that for us, how small?

For measuring the input current form your solar panel you really should look at using uni-directional current sensing devices. The link you gave for the Allegro current sensors are nice units but as you can see, they only have bi-directional units available. I have been watching for some months the same units, and it seems the uni-directional sensors are not so readily available. If you were to use a bi-directional sensor, you end up wasting half your available resolution, as you only measure current going from the solar panel towards your battery, and never the other way around.

Depending on the size of your maximum solar input current in Amps plus a little extra, you again need to match that to an appropriate sensor range. If your max solar input current is say 50 Amps, then I believe the 50 Amp uni-directional sensor would be a good choice. If your max solar input is only 10 Amps, then it would be wise not to use such a device as you will again loose much of your available span range and need to use some extra circuitry such as an op-amp to provide the necessary gain to match the input span of the analogue input on your Arduino which is 0 to 5 Vdc, otherwise you will only record large steps of input current change instead of more accurate finer points of change.

I will hope to make my code available soon for the system I am working on, the link is in my signature. I am at close to the stage of installing the current sensing section, though I will be using the smaller ASC712 units.


The current draw is the big item. The higher you go, the harder it is to deal with physically. I measure up to 200A and wanted to avoid devices that were put in series with the current, so I used a current sensor (google it). The device you show is fine up to 50A or so, although the wires get pretty darn big there as well. For real accuracy, you will want to measure the voltage also so think about how you're going to sample that. There's a web site that discusses this is huge detail take a look there for ideas.

They're in Wales so you should be able to drop them a note if you want to.

All great advice, I appreciate it folks, thanks.

I can see I am in dire need of a language course in electrical engineering. I am lost with much of what is likely even simple language you are using. I'll review the links and go from there.

My small grid presently consists of an 60w solar array of three panels, with a new 240w bosch panel I will add or replace the other unit with today or tomorrow. All feed to a simple "Solar Panel Charger Controller Regulator 10A 12V/24V-- with Overload, Short Circuit, Under-voltage and Over-charging Protection" feeding to a 80ah leisure battery.

Updates to follow! Thanks.

LOL, many people have exactly the same problem with the language. Even after you get proficient enough with the words, you'll have problems with the jargon. Each sub-field has a specific language they speak. Get volts, amps, resistance, and reluctance under control first then you'll have a much easier time understanding.

With your particular project, you'll be facing wires that are bigger than you expected and hard to bend, hook together, or even purchase due to the content of metal in them. But, it's a really cool and useful thing to do and well worth the effort.

But people love to help with projects like this, so you won't have too much trouble getting advice and suggestions.

you'll be facing wires that are bigger than you expected and hard to bend,

The wiring for most of these type of projects is as much a mechanical exercise as it is electronics.

Your system is very small so the wires won't be too large, that said it often makes sense to use wire much larger than you currently need because one day you'll add panels and/or batteries and that will save you from a re-wire job.

60w solar array of three panels, with a new 240w bosch panel I will add or replace the other unit with

How the heck do you live on such a small system? No fridge, TV, computer...


Radmacdaddy, you might be interested to know that I installed one of those Allegro ACS712 current sensor chips today to measure the solar charge current on my HydroSolar system.
On this other thread “Standalone DataCollecting Webserver”,144976.0.html there is a person instrested in the code behind my system.
If you are as well, then I think I will to start a separate topic to explain the deatils and code for people that could be interested.


Hi Paul, really sorry for the delay in responding to your kind request. I'd love the opportunity to work with your code. I am also hoping to have a good shopping list for the parts I'd need. Could you put that out too? This is a first project, so step by step will set me up, I'm sure for learning to be more independent.

Many thanks! Randy

Solar monitoring system :, older system (2007) with an Atmega8535, and (in french) with an Arduino

Program sources of both :

Hi Randy,

If I could get from you more specific details on your system as you have it now and how you use would be great. Also, think about what things you may need or want your system to do in the future.

What are your input charging sources, so, total solar capacity, other sources you may wish to monitor, wind, hydro, nuclear? Your battery setup, cell voltage, number of cells, Amp/hr capacity of each cell, battery configuration (parallel or series)? Will the monitoring system be powered from the battery direct or via inverter? Does inverter go into pulsed standby mode or is it always online?

We need to determine that you have available capacity in your existing system to operate such a monitoring system, even though the little Arduino doesn't consume a lot of power, we need to be certain you have the battery capacity to run this 24/7.

Are you thinking of web based display or just a local display or both?

Having all this information beforehand can help you understand better how to design a suitable monitoring system. There is probably little point banging something in either thinking or hoping it will work.

If you can put together such a list Randy we will be better able to assist you in your endeavour. Just ask if you find something you don't fully understand, there are plenty here who are willing to help.

What parts do you have so far, or are we starting with a blank sheet?

For my project, I recently bought and have made ready to install one of those 50 Amp Allegro hall effect sensors. I bought the 50 Amp uni-directional. On that link you provide in your first post, there is at this point in time one available, might be worth grabbing if you don't already have one. The one I bought was not on a PCB, just the chip, so I mounted it in a good sized DIN rail terminal fuse, a pretty good fit actually. I have photos I'll try to get off my smartypants phone if I can. This sensor will go inline with my inverter in the coming days so I will then be able to see and monitor the current from the battery to inverter.

lndk, bon projet, though I have to say providing links as you have is most likely not going to help Randy.


Ok… thanks Paul… good requests.

BTW, I just reviewed your hydro webpage… cool looking space, though it was not operational, or registering. Looks cool!

  • I have two 110 ahr leisure batteries in parallel, 12v output (that’s parallel, yes?)
  • I have 1 240 watt Bosch panel
  • I have 3 small panels equaling 80 watt
  • I have them running through a Solar Panel Charger Controller Regulator 10A 12V/24V-- with Overload, Short Circuit, Under-voltage and Over-charging Protection
  • I presently only use all of this to power: iPhone, iPad, Macbook Pro, a dvd player/led projector, led strip lighting (used as long as it takes to light my lanterns &/or candles), a small audio amp which links to the projector, AA & AAA usb powered battery charger, and various other USB powered items - not all at once, but often more than one at once

In future, I will be adding solar panels & batteries as needed as I relocate to a larger yurt. In this space I will also be adding:

  • a 6KW diesel generator (with it’s own battery)-I hope to setup a starter & kill switch from about 20’ away within my new yurt to the shed it will be living(I’d like to monitor this as well)
  • a propane fridge which may need some minor current
  • an instant propane hotwater heater which may require some minor current
  • more LED lighting
  • 12v water pump to move water around my woodstove heated hot tub
  • likely a larger battery bank
  • several more panels
  • possibly-bicycle powered washing machine

I’d like to have both an LED monitor and be able to access via my iPhone or mac. I like the look of COSM, but more the look of high charts. Highcharts history view is very cool.

I am starting with a clean slate all around… my cup is definitely not overflowing as far as this stuff goes. :wink:

I like the sound of what you mentioned, the 50 amp rigged up. I’d love step by step… but maybe I won’t be so lucky?

Looks like spam to me carolfische, first post I notice, that link has nothing to do with what this topic is about.

Monitoring systems can have a great role to play in our lives, though I would suggest we not become too dependant upon them.
I can tell you carolfische, it does not make me feel safe at all, and am curious to hear why you would think that.
For the most, they help pass the time and give some joy as well as frustration, not a feeling of safety.

For others reading, the original poster and I have been in private email contact to discuss further his project.


EDIT: suspected spam post deleted, please disregard my post here in relation to spammer ‘carolfische’.

carolfische's post deleted by moderator I think.


I want a solar monitor too! I started to play with the arduinos for 2-3 months ago. Right now I'm keen in this project: from Adam Humphreys. Its a KWh logger for attiny84. I have modified the sketch to serve me - and it works good and does not need much parts. You can do it his way with a OPamp, or easy with ASC712 they have 5-20-30A and more(other sensor).

The advantage it can loog the totals of the last 84 days! As I only have a smal PV (Solar:75W - Battery 12V/115AH) I modified to logg -Maximum Voltage/Amper per day -Minumum Voltage -AH inn/out 56AH max ... (with one ASC712 - supposing negativ current count as OUT, and all positiv as solar current) -Wh - up to 1000Wh/day