Intro to the AVI-TAR User interface, Mk 1

In the last post I showed a profile shot of the AVI-TAR. I'll fill in some of the details in this post.

Visual Interface:

I tinkered with a few different display types before settling on a PCD8544 type screen. It's an 84x48 pixel LCD with LED backlighting. For now, I have it in a basic angled housing that sits on a replacement rail. Here's an operator's view:

(Don't mind the rough edges...prototype 3D printed plastics FTW!)

When powered up with no magazine inserted, you'll see this home screen:

The parts are:

• Upper left corner: battery voltage/status
• Middle left (purple outline): burst setting - right now in "safe" mode
• Lower left (green outline): round counter
• Center (red outline): magazine bar graph (empty right now - no mag inserted)
• Upper right (no outline): status messages
• Middle right (blue outline): rounds remaining in magazine
• Lower right (inverted text): selected magazine capacity

With a new magazine inserted:

I'm in 3-round burst mode with a full 100 round mag, ready to engage.

In addition to the home screen there are menus, some simple, some more complex, for setting modes, magazine sizes, viewing counters, etc. etc. More on that later. The settings are all controlled through a navigation rocker on the bottom of the hand grip:

If you've ever seen an S&T TAR-21, you'll wonder why that bottom cap is removable. I did, anyway. You really can't store anything in the hand grip since it's hollow all the way up into the main body cavity and you need a screwdriver to remove it in any case so it's not very practical in the field. I printed up this part as a replacement. Note the spherical depression that the switch sits in...keeps it from getting manipulated or damaged when the bottom of the grip drags or drops. 

The switch is a 3-position rocker (up, down and push-to-click) so you can have both hands on the gun and tucked in while you change burst settings, for example. My original idea was to put membrane switches on the side of the top rail. That's a no-go because you have to take your hand off the grip to push buttons AND which ever side you pick you're going to piss off opposite-handers. 

That was a fun bit of CAD work that took 5 versions to get right. I'm brand new to 3D printing, BTW, and if you've got any mechanical talent it's pretty simple to pick up. There's plenty of good free 3D CAD programs out there to play with. Dive in and make a mess the first few times...nobody will care and you'll learn quickly what works.

Next post I'll dive into the electronics. They're pretty simple and modern half-bridge motor driver ICs make the power side almost child's play.