Good on ya' mate! That'll keep you busy for a while.
Yes, you will need to program the PIC. Fortunately there are a number of simple PIC programming circuits you can build. One that I have had luck with (note the caveats on the main page) is the
NoPPP (No Parts Pic Programmer) There are also other designs available. Googling "DIY PIC Programmer" or something similar should get you good results. Some of the newer PICs (the 16f627a, for instance) offer Low Voltage Programming, but that still requires that you program them with a "high voltage" (12v) programmer at least once to set them into LVP mode. Some of the newer PICs also have internal timing circuits, removing the need for a ceramic or crystal resonator unless you require highly precise timing. The catch in using a newer PIC, however, is that if the code is written for a 16f84, then you don't want to have to re-write it. You've got enough to do on this project, already!
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Another small question, the diagram shows one pin from the microchip connecting to each PWM output, well it's my understanding that PWN cables have three wires (black, white and red). If the microchip only outputs to one wire then I'm guessing that it's the white one and that black and red are battery and ground?
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Yes.
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Also, what is a 4MHz Ceramic Resonator? I've looked one up, a little $1 part that I've seen before but what does it do?
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This controls the timing for the base level of operations on the PIC. If you put a 10MHz resonator on the PIC, you would essentially be "overclocking" it. As the resonator "vibrates" the voltage changes, providing a stable timing circuit to the PIC. The PIC then uses this to control all communications and data movement within the chip. You can actually use the frequency of the resonator to determing how long it will take the PIC to execute any specific machine language command quite accurately.
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- I need a way to recharge the battery without a car, I'd like to build a battery charger that could charge it using a household 120V AC plug. How simple would that be? I assume I can't just plug one end of the plug to the + and - ends of the battery.
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Well, no... but it is almost that simple. All you need is a DC voltage source of about +13.6 volts or so. A variable power supply, a "wall wart" transformer of the kind that takes up all the space on your power bars when you plug in the scanner, speakers, etc., or the battery charger used by your FRC team will all work well. You can also find trickle chargers, and fairly cheap car battery chargers at a hardware/automotive store like Canadian Tire (not that you have a Canadian Tire in Palm Bay, but you definitely have something similar. UAP-NAPA dealers might be a good start point.) Just be cautious that if you are using a "dumb" charger (ie a constant voltage source, or anything that does not specifically advertise itself as either a trickle charger - where the current is so low that it doesn't much matter - or a smart charger) then you have to be careful to not overcharge the battery. The scientific way to determine a car battery's charge is by measuring the density of the electrolyte (acid). Your school's auto shop probably has a small turkey-baster like device for doing this.
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- I'd like to be able to make something, perhaps a small LCD screen that could tell me the amount of charge left in the battery. So that I never drain it all the way and so that when it's charging we know when it's done. I believe the drop in voltage is how you can tell the amount of charge left? Like when the Vex controllers show voltage on the little LCD.
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This would be nice, and once you've finished all the rest of this project I suspect you will have no problem building one of these. But do the meat and potatos first, and save this for dessert.
Good luck,
Jason