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Forum Index : Microcontroller and PC projects : ok so here`s what i want to do

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sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 01:59am 08 Jul 2011
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i have a 36 volt dc power supply ok ..6 times 6 225 a/hr batterys i run my inverter of this system ...i have a three phase 40 volt wind geneator i also have 6 times 60 watt solar panels ...ok ...
now i want to see on my screen the added voltage of the batterys that is a volt
meter for twelve volts "say "pin1" input" a voltage for 24 volts say "pin two " and a total voltage of around 36 volts"'"" and i also would like the maxi to put out a square wave at 3 volts or i will use the expander to boost this voltage... and i have a freq counter as well "program" ..so if any body can tell me how to do this i would be in your debt and much appreacition ..thanks to any who r up to the chaniglige... ..sparkey
and yes my sppelling is well to be sent after sorry...
technicians do it with least resistance
 
Keith @

Senior Member

Joined: 19/06/2011
Location: Australia
Posts: 167
Posted: 03:44am 08 Jul 2011
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Sparkey

Your message does not provide enough information about what you are trying to do in any detail.

If you could for example give some indication of whether the the 12v and the 24v are to be combined in hardware to 36v or are combined in software.

What do you need a 3v square wave for? and what frequency?

Grammar aside spelling mistakes will be underlined in red as you type so you can right click using the mouse to choose from a recommended correction.
The more we know, the more we know we don't know !
 
sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 10:16am 08 Jul 2011
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oh ok sorry i`m not the best grammer ...i want to display on the screen 3 voltage readings given that at "12"24"36" i can run network cable to the batterys...given also a common ground ..or negative so that each has a higher reading than the other/...the reason being for this is that if a particular battery is falling down i will be able to tell which is failing...at any rate a display on the screen would have three lines of text in basic mode as" batt1=12,456...batt2= 24.654. and batt three /or total voltage is 38.453 ..etccc... and as well i would like to be able to measure the input current from the solar cells there is three sets in paralell so giving a total of aprox 41 volts but i do realise that using a shunt cable and taking a voltage drop would be approprite to read with a nother pin on the "i/o" as well i know it can be done i just dont know how ...poor me the one left standing there saying "well somebody tell me how "...also i would like to read the output of the freqency that the inverter is running i have a simple program to measure the totasl voltage and the freq at the output of my inverter ....does this help any ...regards sparkey please let me know of further questions i am not the best at explaining things but "well we will get there eventully...::

:typically once i have the program set too three voltages i ..then casn go for six voltage readings of each battery...thanks to all who have ansewerd or read my storyn ..it is real.....fact...Edited by sparkey 2011-07-09
technicians do it with least resistance
 
Dave Everett
Regular Member

Joined: 24/06/2011
Location: Australia
Posts: 43
Posted: 11:30am 08 Jul 2011
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Sparkey, you need a voltage divider on each circuit to bring the voltage down to within the safe range for the PIC32. This consists of 2 resistors.

2 resistors, R1 and R2. R1 and R2 join together and that join point goes to the Maximite AD input. The free end of R1 goes to the positive terminal of the battery you are reading and the free end of R2 goes to ground. The grounds of the batteries and the maximite must also be joined.

The formula for choosing the resistors is:
Vout = Vin x (r2 / ( R1 + R2))

Where:
Vout = 3.3v
Vin = 12v or 24v or 36v depending on which voltage you are reading
The resistances are in ohms. Plug this into an excel spreadsheet and you can adjust the values until you get the right voltage.

Example: for Vin of 12v, R1 = 10k, R2 = 3.3k, I get a Vout of 2.97v

Generally I assume voltages will go a little higher than expected. For example, a 12v battery gets charged at about 13.8v, so I would use 13.8 as the Vin value for a 12v battery.

I'd also place a resistor in series between the battery and the voltage divider to limit current into the circuit, maybe 60 ohms. You might want to protect the inputs with 3.3 zener diodes to ground.

Dave
 
sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 11:59am 08 Jul 2011
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thank you and yes i am using a 1meg pot as a divider in series with a 4.7 k to gnd
and the problem is not so much the hard whare its the programme i need to do the outputs on the screen ..i have a single program but i think that i just need some help with it ...regards sparkey
technicians do it with least resistance
 
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