For my inaugural post to this blog, I thought I’d share last weekend’s project:
(The beer wasn’t central to the project; it’s there for scale.)
It’s not just a minimalist piece of art.
The object of this project was to make something that would look good on my desk and be able to display my “business metric of the week.” It needed to be easily addressable from a script interface.
Right now this is sitting on my desk updating with some of our key business stats every five minutes. (My desk is messier and more institutional than our dining room table shown in the photos.)
My desktop PC (Win Server 2008) is running a scheduled task every 5 minutes. The scheduled task is a Powershell script making SQL calls and writing to a serial port.
So the whole data flow might be shown as
Datastore -> SQL -> Powershell -> virtual serial port -> USB -> Arduino -> MAX7221 -> LEDs
The project wasn’t very complicated, but without a PCB, I spent several hours trimming wires and soldering:
The best surprise of this project was the IKEA photo frame that I used as a case. To give a shadowbox effect when used as a photo frame, it includes a interior box that is removable. I may stock up on these to use as project boxes. $5 each, the interior is 5″x5″x ~1.25″.
So I backed the front glass with a piece of white paper. The face of this is made to be dry-erase marker friendly, so that I can label my numbers. Frosted glass might have been nicer but with this, I can also print out a custom piece of paper if needed with “hard coded” labels.
I think I might put together a PCB sized for the frame. I could make it half height and then have an option to have four rows of digits (2 MAX 7221 controlled by one Arduino.) Bummer that the free version of Eagle can’t deal with this size.
I wanted to have the top row in green and the second row in red. But since I wanted to drive these with one MAX 7221 ($10/each) I could only use one current setting resistor. This made brightness matching a problem. So both rows are red.
I also was exploring using alphanumeric displays, but those won’t work so well with a 7221 since they have only one common cathode for all 14 segments.
If there’s interest in code or more info, let me know, and I’ll post it.
[So this blog writing thing isn’t too bad… I should type something up this thing’s big steampunk inspired brother, the gauge machine…]