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.

Lego Keyboard for Electronic Organ

This morning I got a first draft of real organ software running on the 16f684 / programmable sound generator circuit I've been building. Once I got the software up and running I tested it with just a probe, then very quickly wanted a keyboard. I have plans to make a permanent one from wood and brass, but I wanted something NOW. So I spent about 20 minutes in my son's room and came up with this lego creation. The only parts not stock legos are the reed switchs and magnets for the circuits. I got really lucky and the magnets I had were a perfect press fit into the bottom of the lego keys.








I hot glued the reed switches to some poster board which I then glued to a stack of legos. A rubber band provides spring back for the keys that pivot on a lego shaft. I soldered wires from the reed switch out to a header I could plug into my bread board. When you push a key the magnet attached to it closes the reed switch beneath the key. The micro reads the state change and commands the sound generator to produce the note. Right now it only has one voice.








Here's a shot of the breadboard. The big 40 pin bug is the sound generator and the little one to the right is the 14 pin 16f684 pic micro. The board to the right is my pic programmer, and to the left is my arduino. The big battery and small board in the top right corner is my portable 5 volt power supply. With this package and my laptop I develop hardware and software while I ride the bus to work in the morning.

Electric Organ Prototyped

A couple weeks back I bought an old programmable sound generator chip from BG Micro. I got a breadboarded circuit working this morning, using a 16f684 as a controller. My plan is to build a simple digital synthesizer, but right now it's just running a simple hard coded loop that sounds like a car alarm.