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1  Using Arduino / General Electronics / Re: Driving 12V signal from 5V pin on: July 29, 2011, 01:13:59 pm
Wow. It seems like to do what I really want to, which I think is read and write, I'm gonna need a lot more than I initially thought. Since the eeprom data pins are input and output, I will need a SIPO shift register to write data, and a PISO shifter to read it back into the arduino. I will also need a gate of some kind so that the shift registers in opposite directions don't screw each other up.

Since both A9 and OE pins require 5V or 0V or 12V in different circumstances, I suspect that I will want a more complicated chip to manage that independently. Guess I'll start over on my schematic and see where it goes.
2  Using Arduino / General Electronics / Re: capacitor codes on: July 29, 2011, 12:00:40 am
Sorry, I've never seen such a chart, and I have a whole pile of completely unmarked capacitors so it wouldn't do me any good if I had one. I would definitely recommend a good capacitance meter if you plan on identifying many mystery capacitors.

Sparkfun has a nice kit for a pretty good one:
3  Using Arduino / General Electronics / Re: Driving 12V signal from 5V pin on: July 28, 2011, 11:57:28 pm
It requires 5V to read the data, but for this application I really just want to program it, it is going to be used in an entirely different system. That being the case, I only need to switch between 12V and ground.

pwillard, I mainly didn't like the chip idea because I am working on a shield sized board, and it already has 4 rather large ICs on it, and the routing it pretty hairy already. I don't have much room to spare, and I doubt I can get two more DIP-8 components and all of the routing on without extending the board, which would not be the end of the world I suppose. After looking at the chip, its quite nice. I would not need to use a diode to protect my 595 because the chip would be in between.
4  Using Arduino / General Electronics / Re: Driving 12V signal from 5V pin on: July 28, 2011, 04:38:23 pm
That feels like overkill. I already have a 12V signal from Vin. I just need a way to switch it to the eeprom based on a 5v pin. Yes, that should work, but isn't there a simpler way?
5  Using Arduino / General Electronics / Driving 12V signal from 5V pin on: July 28, 2011, 04:03:19 pm
I am attempting to make a shield to program my 64KB eeprom module (27SF512- datasheet at I am using three 74HC595 chips to shift out the 16 bit address and the 8 data bits. All of the logic is fine at 5V, except part of the programming protocol requires me to set several pins on the eeprom to 12V.

I need to somehow convert the 5V signal from the arduino to a 12V signal to give the eeprom. I am pretty sure I can do this with a single transistor, but my circuit skills are a bit weak and I'm afraid I'm not sure how to connect it, which model I should use, or what kinds of resistors I will need.

Additionally, one of the address pins needs to be given 12V to initialize an erase operation. That pin is also connected to an output from one of my 595s. Do I need a diode or something to protect that pin from getting fried? Will that be enough, or do I need a more complicated circuit to ensure its not getting 5V and 12V at the same time? Not sure what will happen in that case.

I've attached my circuit as it stands now in eagle. The OE pin is not attatched to anything, and the A9 pin is only connected to the 595, not to the other 12V line that needs to be put in there. We can assume Vin will be a 12V supply, so that is easily accessible. Any tips would be greatly appreciated.
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