Project Update

Well after Tom-Tom and Diana visited last weekend I now have the remainder of my tools and such so I'll be working on the Parallel Port LCD project this weekend. It seems like I'll probably need to power the display and backlight from the 9V battery anyway because the parallel port could be damaged if my math is wrong, and I don't wanna risk ending this project early cause I cooked the port!

More to come later I hope....

Just for kicks...

Here is a sketch I made up on the back of some weird letter from a college about something... I dunno. It's the basics of the idea cooking in my head for how to make the Ohmmeter for this project! Enjoy!

Meter...thingy

After my multimeter broke last May I've been wanting to build my own.... I ended up replacing mine with a retail one of the same type because I needed it, but I still played with the idea with of designing my own. Here is what I have so far! It only has provisions for measuring voltage and current at the moment, next is the ohmmeter. It has ranging controlled by the chip for the voltage where as the current only has two ranges, a fused 10A range, and an unfused 500mA range (I wonder about the wisdom in my fuse placement a lot here...), whereas the voltage has the following ranges:

• 5V
• 10V
• 50V
• 100V
• 200V
• 500V

I'm doing this as best I can with the knowledge I have, I am not looking at any kits or guides on the internet as I want to see if I can do it myself and then compare it to the "right way" to see how close I got. My biggest concerns right now is that the transistors I picked for the Voltmeter ranging can't handle the power correctly, that the fuses need better placement and that I am pretty sure (almost 100%) my differential amplifier sub-circuit is incorrect, close to right but not quite there.

Comments are of course welcomed!

Here it is: