Solving Amp Hour Meter Problems: Wiring Series vs Parallel

[mrjeffy321]

faust9, might I trouble you for the 2nd installment of the circuit diagram?
Also, upson further inspection of the first circuit fiagram I see a couple parts (resistors) that I didnt originally get, a 4.7k orm resistor (R8), and I am not too sure what the W's stand for or the 'PB's, or the part labeled 'SW' that has a symbol like an 'I'

 

[faust9]

faust9, might I trouble you for the 2nd installment of the circuit diagram?
Also, upson further inspection of the first circuit fiagram I see a couple parts (resistors) that I didnt originally get, a 4.7k orm resistor (R8), and I am not too sure what the W's stand for or the 'PB's, or the part labeled 'SW' that has a symbol like an 'I'

I'm sorry. I'll upload those tomorrow morning(I don't have the figs on my computer). the the 4.7k can be replaced by anything greater than 1k. I used 4.7K because it is a common value found in digital electronics. The SW is a PBNO(Push button normally open) switch. The W's are connectors(like bannana plugs--though those are a little big). The W's are for in-circuit programming. You'll have to get some 0.1 pin headers for those. Read the Atmel docs for the chip pinout. PB stands for I/O port.

 

[faust9]

Go to figure 5 of this document:
http://www.ee.washington.edu/stores/DataSheets/voltreg/7805.pdf

That is your power supply. Use a wall-wart. The outer part of the plug is + and goes to pin 1 and the center part of the plug is - and goes to pin 2 usually. Most wall-warts us a center negative scheme but not all. You can use any PS from 6 to 12 v and I'd estimate a minimum current rating of 200mA

Here's a VERY good demonstration fo switch bounce:
http://www.ece.utep.edu/courses/web3376/concepts/debounce.html

Here's a simple debounce circuit:
http://www.all-electric.com/schematic/debounce.htm

You don't 'need' the schmitt, avr's are designed to operate in some pretty extreme situations. A simple capacitor between the switch an ground will work fine(use a moderetly low pull -up resistor R8 though 4.7K minimizes current draw from the source and allows the cap to charge moderetly quickly).

If you were using a higher end processor then I'd say use the Hex-Schmitt to debounce--here it's not required.

 

[mrjeffy321]

OK, thanks.

Thats leaved me with some more questions.
whis wall wart you speak of, what is that? is it the MC78XX/LM78XX thing that is in the PS diagram or is that the voltage regulator? (is is that a stupic question because they are the same thing).
In the DC parameters circuit (figure 5), it show a .33 uF capacitor, should that one de tantalum too? how important is it for it to be .33 uF, how about 1 uF, or something close. this would ger inserted into the original diagram right between the button and pin 1 right (with another of the leads going to pin 2)?
Are you saying I need a separate power supple for this "amp hour meter" circuit, other than the power that I would be putting through my normal circuit?, I have to plug it in so to speak, for it to work?

I understand the purpose for the debounce circuit, but I don't see how I need one. you said earlier about that SW piece, the PBNO, is a switch, but I never understood who I need it, I don't see how I need a button for this to work.

 

[faust9]

1uF will work--it can be a cheap ceramic BTW. Also, it's always good to have a reset. And, P/S can mean the source from the wall to the reg or the portion of your ckt which eventually powers up all of your components.

The decoupling needs to placed a physically close to the processor as you can get it(I usually use DIP sockets and solder the cap under the chip on the socket between the power and ground pins. You can actually buy these pre-decoupled sockets--just make sure the cap is connected between the correct pins.

 

[mrjeffy321]

Since my parts just recently arrived, and now I am trying to put the stuff together, I have started a new thread that targets in more on that since I still need lots of help,
https://www.physicsforums.com/showthread.php?t=72777