something that might save you some headaches.

ok, i've been working on a precision ohm meter for about a month. After i finished routing the traces it came to me, since the display, the keys, power, and logic are all on one side of the board i could use it as the base for a wide range of projects.

All the parts are available on digikey (even the nice handheld case)

here's a quick preview of the board if you guys want more just ask.

PCB Diagram

I certainly appreciate your willingness to share and I'm definately interested in what you are trying to share.

However, the web site you chose for sharing generates difficult to close pop-ups. Please use someplace else.

there, fixed the links

This is pretty cool, and is something I have been thinking about for a while. In my case, I was actually thinking a graphical LCD (one of those single color 128x64 LCDs out there), and coupled to its own ATMega processor, as well as a third ATMega for sound. Basically the same idea, but something that could be used for anything from a simple all-in-one microcontroller experimenter's board to a piece of test equipment, to a hand-held game system...

Great job!


like i said it's part of a precision ohmmeter

like i said it's part of a precision ohmmeter

I understand that; for such a purpose a simple LCD display is all that is needed.

BigBoy - do you have a write up on how it works? Maybe a sketch to share? I would be very interested in a precision ohm meter. What values does it read?

Was there a special reason to use the I2C port expander to drive the LCD?

in a precision ohm meter - what function do the UP, DOWN, RIGHT, LEFT pushbuttons serve?

Sorry for some many simple (dumb?) questions, I'm very much a noobie on programming stuff -

Keep the good info coming on this project.

Ken H>

I don't have much of a write up, i'm still working on it as part of my ohm meter, and i've only started to work on the code.

the way it works is wverything goes over the I2C bus to save space, the lcd is a 8x2 alpha-numeric that has an onboard driver, It has 5 buttons(up down left right and select) which all have latches, the buttos are there so you can navigate an on scree menu, both the buttons and lcd are connected by 12c bus extenders so as soon as i get the code running it should be a simple function call to deal them, the whole thing is run off a 9 volt battery that has a 700ma 5 volt regulator.

sorry if this is breif but most of the work i've done is on the analog part, which i'm still tinkering with.

part numbers lcd - NHD-0208BZ-FL-GBW regulator - lt1129-5 bus extender - PCA8574 case - hammond manufacturing 1553D-BAT

This sounds like an interesting project - please do keep us updated on status. As it gets to completion with some code, I'd sure like to see it. as I mentioned before, I'm very interested in a precision ohm meter - do you have any feel yet for accuracy goals?

Ken H>

the oohm meter (not show) should have an accuracy of <.05% from 1 ohm to 1 megaohm

The files have been downloaded 10 times so nobody else can see them now

Hi there! Could someone repost the files? They were removed. Thank you! Take care! :)

repost these up PLEASE :slight_smile: