Hello, I need some help

[terramir]

hello guys I need some help designing several things, mostly they will be based on cheap pic processors because they are versitile. I need to learn several things. first of all I have a few questions that maybe some of you can answer.
About D/A converters on the pic. I saw the circuit was simply a resistor and a capacitor, but what can I use if I want to measure voltages outside of the operating range of the pic?
Like 0V to 17.5V with a pic with an 8-bit converter. the chips have like an operating range of 4.0 to 5 volts how could I fix it up to measure something like that, also I have an other question is it possible to measure current with a pic actually the same pic on a different pin?
Also is it possible to use every pin of port B seperately? like to use pins in high and low / on off status in order to start different functions?
because I want to build the following things
#1 a li-ion charger with my custom specs because I want to protect the cells this is possible if I configure the pics to do certain things.
#2 A charging computer that will determine depending on the voltages of several different banks what to charge, and then start the appropriate charging chip. I would have several chargers for my li-ion bank one charger that could be switched between my gel-cells and another one for my NIMH bank.
but for this I need to
A. learn how to design
Voltage meters, ampmeters and switches, based on pic computers.
these just need to take measurements in order to determine what needs a charge and turn on the appropriate circuit.
then I need to learn how to build a circuit that can control the current and voltage accurately based on a pic design in order to build the li-ion charger circuits
Hope some of you guys can help,
Any suggestions I would be greatful for
terramir

 

[Nigel Goodwin]

hello guys I need some help designing several things, mostly they will be based on cheap pic processors because they are versitile. I need to learn several things. first of all I have a few questions that maybe some of you can answer.
About D/A converters on the pic. I saw the circuit was simply a resistor and a capacitor, but what can I use if I want to measure voltages outside of the operating range of the pic?

You just need a simple resistive attenuator to feed the input, have a look at my PIC tutorials, where I use opamps and resistive attenuators as part of my analogue to digital tutorial.

Like 0V to 17.5V with a pic with an 8-bit converter. the chips have like an operating range of 4.0 to 5 volts how could I fix it up to measure something like that, also I have an other question is it possible to measure current with a pic actually the same pic on a different pin?
Also is it possible to use every pin of port B seperately? like to use pins in high and low / on off status in order to start different functions?
because I want to build the following things

Yes you can use every pin seperately. As for measuring current - you simply measure the voltage drop across a resistor in the circuit. The main problem is getting this referenced to 0V, as the 0V input is common to all the inputs on the PIC you need to generate a voltage from the current, which is referenced to ground. Using an opamp is probably the easiest way.