Update on the Drawbot

While writing finer control software for the Drawbot I discovered an previously undetected issue with the driver board. It took me a couple of days to isolate and fix the issue, but once I nailed that down the bot really started behaving well. This video shows it with its intended control scheme implemented. There's a Python application running on my pc which communicates drawing commands over the Arduino's USB-serial interface. The Python app calculates an 8 deep Hilbert curve, and translates it into the appropriate drawing commands. The legs of the curve are about 1/4 of an inch long, and have 32 steps each, making the overall resolution of the bot about 128 dpi. Not too shabby for about $65.00 in parts - including the cost of the Arduino.

Drawbot makes its mark

This evening I got my drawbot up and running for the first time. The mechanics are still pretty shakey, but the electronics have been burned in for several hours now and I'm pretty confident they're solid. The 'bot is based on an Arduino with a dual axis opto-isolated unipolar stepper motor driver shield that I designed and built myself. As soon as I can figure out a place to put them, I'll post the Eagle files for the shield.




I'm writing a PC application in Python to do some image manipulation and drive the 'bot. When I get it further along I'll post again.

Archimedes would be proud

For a school project, my 11 year old is taking on, for the night, the persona of Archimedes. Part of the project was coming up with three artifacts related to his character, so last weekend we built this catapult.

It's modeled after a picture we found on the internet. Built from 1/2 inch square pine, with a white oak bow and bamboo axels.

Of course, it being Easter last Sunday we tested the beast on the most available item, and discovered it will shoot a jelly bean 30 feet.

Surprises from the Arduino

As an expansion to the organ project I've been working on I bought a rotary encoder. Of course I got it surplus, and it came without any data. So yesterday I hooked it up to my Arduino to see if I could make some sense of what it did. After about 10 minutes of bread boarding, and 10 writing a sketch (well modifying one of the examples) I had a thing. On reset it would play a constant tone - if I twised the encoder one direction the tone would get lower, the other way it would get higher - cool.


















The surprise came because I didn't put any limit checking into the code prior to the call to tone() - hence, when twisting the encoder brought the pitch down to zero - or into the negative numbers - I got some really interesting results. Give a listen.

Razor E100 Scooter Repair

I bought a Razor E100 electric scooter at a garage sale for $10.00 a while back. Right off I discovered it needed new batteries (no surprize there), so for another $32.00 and an hour's work it had new batteries. Unfortunately it still didn't work. This past weekend I spent some time tracking down the problem with the little control board. Turns out there was a little surface mount transistor that had gone bad. I don't have any surface mount transistors, so I cobbled up installing this through-hole 2N2222. Everything works great now! We'll see how long the spit and baling twine fix lasts once the weather turns nice and my boys start abusing it. Sorry for the blurry picture - I didn't feel like walking up the stairs for my real camera and I used my flip cam.

ONE DAY BUILD - Auto Waterer

Last Saturday I put this together for my wife. She has a bunch of potted plants living out the winter in our basement. Unfortunately watering them gets to be a real pain, as we have to go upstairs for water, and dole it out to each plant individually.




















I upcycled the guts of a battery powered shower cleaning sprayer, keeping just the pump. I added about $12.00 of plumming parts from the big box, and a #5 (non-recycleable) bucket. When I explained to the plumming guy at the big box what I was doing he even went out of the way to give a piece from the scrap bin - saving me about $6.00.




















It's pretty simple right now, the float switch is wired inline with the motor and a wall wart. When you pour water into the bucket the float switch closes and the pump comes on. There's about 25 feet of 1/4 inch tubing coming off the output of the pump. Over every plant I drilled a small hole in the tubing. With the pump on, all the plants get a health squirt of water. When the pump empties the bucket the float switch turns it off. It will pump 3 gallons of water in about 5 minutes. So now, every couple days I carry a couple gallons of water down the stairs, dump them in the bucket, and forget about it. [Image] One of these day's I build a moisture sensor and an alarm so it will tell me when it's time to water - or even do it with an Arduino and an ethernet shield so it will send me a tweet - or have it's own web page with a web cam - or - or - or -

Long Time no Post

I can't believe it's been so long since I posted here. Over the past months I've spent a lot of time putzing in my wood shop. I've got a project that's almost ready to put up here. Also after many months of work my wife and I finally got the basement put back together, so I have a real office/electronics workspace now. Using this new space I've recently put the finishing touches on a new version of the B.bro robot. This version has the same mechanics, but a cheaper power supply and motor driver, and is implemented with all custom circuit boards instead of protoboard.

Around the perimeter of the top board are six three pin connectors. They accept sensor modules. The photo shows two digital light sensors and an infra-red proximity sensor. I also have built analog light sensors, and I'm working on a sound sensor now. I just put the finishing touches on the hardware a couple days ago. Now it's time to write some cool software for him.