could some one point me in the direction of a good voltage multi meter with arduino project i want to use my uno as multi battery charger almost like a charger switch for solar panels but only for smaller then 3 amp battery's i want the uno to take a read from say 3 or 4 batterys and decide witch one has a lower voltage then the next and switch my relay board to charge that battery and i think i can do this with a switch case code and modified arduino multi meter project ? maybe im open to all suggestions or thoughts on this thanks !
Hi, Can you provide more detail on the batteries and solar panel specs?
well i can on the battreys i have not got sola stuff yet was going to start on this side of the project i was going to use 2 battry back up supplys as inverters for my bench in the shop not much power is needed out there the two back up inverters are rated at 600 watts each and they have 2 12v 6amp hour batterys in each for a total of 24 v going to the inverter and the panles i plan on getting are 12v out put with only like 800 mill amp max and 80 to 150 milly amp constant .. so with this lower rateing i want it to charge each battery sepret witch would be fine if the were seprit so i want to use some relay blocks to uese a float battery on each so that battery wil be placed in the system when it is charged and the other remvoed and put on charge.. now i only use the shop every 3 days or so so they have plenty of time to charge up on the low solar out put but i wont be there to switch the chargeing batterys around and the more expensive simpler way to do this is buy enought panles to charge them all at once but i kinda want to do it the other way with the arduino for fun and lowr cost ...
thanks for looking in to it !
I'm not sure doing this with an Arduino is going to lower your cost as there are lots of simpler circuits that will do the job cheaper, but it should be a fun project that's true 
I'd think you'd want to setup some voltage dividers from 13V down to 5V so you can monitor when your batteries hit the fully charged (is that 12.6V?) state without load and sure, you can use the Arduino to select the next battery via a set of relays when the one that's presently on charge is full...and maybe drive some status LEDs to show which is where (or an LCD display for bar graphs or whatever). All very possible.
Unless your solar panels output >13V you'll need some kind of external circuitry to step the voltage up so you do get some charge in the batteries too.
And if you really want to get cute the Arduino could drive servos to track the sun for your panels too. Nothing beats the scope creep that's possible with these things
Good luck !
yeas this is all part of my plan mabe not the lcd .. i have a lil truble codeing that kinda stuff but it sounds like you have a good idea of what i want to acoplish my problem lies with with the voltage divieding part to get the arduino to do a read of the battery i have heard of it being done to use a lcd as a multi meter .. but i have not found out how to do the voltage reading with the arduino and get a number back and what kinda ic or curcit could i use or are they all made and could buy them ?
Hi,
You'll find lots of really good explanations for 'voltage divider' thru google.
I really rate Jeremy Blum's youtube tutorial on electrical engineering basics, and I keep going back to that one to make sure I've got my maths right:
There are also lots of Ohms Law calculators online which will sort out what values to use on your resistors, just be sure you cater for the maximum power your panels will be able to output, which as you say is a bit of an unknown for you right now.
Actually finding the voltage value in your Arduino sketch is pretty straightforward. Using AnalogRead() (analogRead() - Arduino Reference for details) you'll get a value on the pin with a range of 0 (corresponding to 0V in this case) to 1023 (corresponding to the maximum voltage your voltage divider circuit will provide, again the choice of resistors and the input voltage maximum will define what voltage that corresponds to. All values in between have a linear relationship to the input voltage, so to get the voltage, simply multiply by the maximum (say it's 4.6V as a result of your divider, just multiply the AnalogRead() value by 4.6) and you have your voltage that you can make decisions on in your sketch, fire off the relevant relay, light up LEDs, display on screen or whatever.
Hope this helps - sounds like a really fun project you're embarking on,
Geoff
awesome thank you varey much !!! thats some 5 star help yeah i did see a jermmy blum video or 2 i dident know he coverd this he is the best thank you again i know know what i need to get started... yay geek out time hahaha...