Tiny Tim improves and gets Smaller

I finally switched Tiny Tim over to a lipo battery. Almost everything worked when I tested the new battery, the only thing that failed in a major way were the two 2812 LEDs which, either didn't come on or came on for a very quick moment and went dark. So Tim is now smaller again without the "huge" AA battery pack at it's tail.

The 2812 story was interesting. It wasn't going to be happy jumping to the 7.6v of the 2S lipo. So I tried various voltage divider setups which didn't work either. I ended up using a common 5v regulator and the lights work fine again. I think I was maybe using too high resistor values in the divider and the 2812s didn't like it. At any rate, they apparently want a good regulated power source, and I wasn't giving it one before I switched over to using the regulator.

On the whole, going from 5-6v of the AA pack to 7.6v has made it a snappier mover. I tried it initially with the battery on the bench and found it would lift the back off the desk under hard break.

Next up is probably attaching a claw or drop mechanism and ultrasound sensor and then take on the Sparkfun autonomous ping-pong ball into cup challenge. I'll probably control it via wireless from a second on board micro-controller. The drop, ultrasound, and autonomous navigation micro (and additional battery) can all be put into a single "module" that I can then bolt to Tim. All the navigation micro needs to do is control the differential drive like a remote control would. This way, the existing micro etc on Tim doesn't change at all in order for the challenge to be accepted.

Ending up Small

It's easy to get swept up in trying to build a robot that has autonomy and the proximity, environment detection and inference, and feedback mechanisms that go along with that. There's something to be said about the fun of a direct drive robot with just power control and no feedback. So Tiny Tim was born! For reference, his wheels are 4 inches in diameter.

A Uno is used with an analog joystick shield to drive Tim. He is not intended and probably never will be able to move autonomously. Direct command only. Packets are sent over a wireless link from the controller (5v) to Tim (3v3). Onboard Tim is an 8Mhz/3v3 Pro Micro which I got back on Arduino day :) The motors are driven by a 1A Dual TB6612FNG Motor Driver which is operated very much like an L298 dual hbridge (2 direction pins and a PWM). Tim's Pro Micro also talks to an OLED screen and his wireless board is put out behind the battery to try to isolate it a little from the metal. The OLED screen needed 3v3 signals, so Tim became a 3v3 logic robot.

He is missing a hub mount, so the wheel on the left is just sitting on the mini gearmotor's shaft. At the other end of the channel is a Tamiya Omni Wheel which tilts the body slightly forward. I've put the battery at the back to try to make sure he doesn't flip over during hard break.

A custom PCB would remove most of the wires on Tim and be more robust. But most of Tim is currently put together from random bits that were available. The channel and beams should have a warning letting you know what can happen once you bolt a few of them together ;)