Maker School: Ping-Pong Ball Stomp Cannon

Maker School: Ping-Pong Ball Stomp Cannon: …you saw it here first!

Chancre Crab Eats Gooseneck Barnacle

Our Chancre Crab (aka. Brown Crab, Edible Crab, Pastie Crab) enjoyed a feast recently.  We had found a washed up fish-box that was covered in Gooseneck Barnacles.  I scraped a few off the plastic box and strung them up our little marine aquarium.  They were fascinating to watch — sieving the water for food then retracting into their shells to eat.  That was until Chancre got wise to them and decided to get piece of the action for himself — even moving rocks so he could reach them!

We had a campfire-cooked lunch on the beach

 

Lack of activity

Apologies for the lack of activity here.  I've been focussed on building up my new venture:  Maker School — putting real tools in the hands of kids and working on real projects.

You can see more at : www.makerschool.net

Exploring Flight

Experimenting today with different wing shapes using a compressor blowing down a tube to create a sort of wind tunnel.  Kinda.

Bernoulli's Principle:  the faster the flow, the lower the pressure.

 

 

Our Marine Aquarium

A few pics from our marine aquarium.  Will be posting more on this as time goes by.  It's very exciting to have a window into the lives of creatures that you usually wouldn't see.

Can you cook popcorn with a magnifying glass?

Well, amazingly, the short answer is YES — but, it's all about the method.

A regular magnifying glass is able to set fire to a popcorn kernel quite easily.  This however is not what we want.  We need the moisture inside to boil, cook the starch and then burst the shell explosively.

We used a larger magnifying lens — a flat 'fresnel' book magnifier — and sat the kernels in some cooking oil in a teaspoon.  I think the cooking oil is there just to spread the heat around the kernel rather any cunning cooking chemistry.  After a while it will start bubbling (some of it's moisture boiling off) then after a while longer, if you're lucky, it'll explode.  We managed to get a good few of them to pop but only one made a lovely big popcorn — the others were kinda half-hearted attempts at popping.

Focussing the sunlight too tightly on the kernel lead to burning.  A loose focus on the teaspoon head spread the energy out to a more controllable level.

After all this discovery we went inside and hit the stove with a saucepan.  They all popped in no time.  It just goes to show how much energy your stove kicks out!

NEW: Photo School

3 day course for kids aged 12+ with an interest in art or photography…

6-8 June 2012
http://guernseyphotoschool.com/ 

Motor Timer Circuit

I've built a simple little circuit for controlling the run time of a motor.  It's based on a 555 timer chip in monostable mode — which means when you press the button, it runs the motor for as long as you set with the knob.

It's can currently range from ≈ 1sec to ≈ 12secs.  Modifying this range is as simple as changing a capacitor or resistor.  For example, doubling the size of the capacitor would result in a range of ≈ 2-24secs.

The idea is to use this on a model aircraft instead of rubber band power - which can be a bit of a faff.

I'm not sure about the motor yet - it's just been scored from a CD-ROM drive and the power supply here is a 9V battery - which is quite heavy.  Happily, the circuit will accept voltages from 2-18V so there's plenty of scope for experimentation without having to alter the circuit.

I translated the circuit from a breadboard test to a stripboard layout and used Pages on the Mac to draw a template.  I then printed and stuck the template onto the stripboard which gives a really nice reference as you're adding components.  This diagram is version 2 which ironed out a few layout issues.

If it actually gets strapped to a model plane… you'll see it here.   :)

GRZR Robotic Lawnmower is Mobile

For the first time, our robotic lawnmower project has mobility and a modicum of intelligence. Two bump sensors dictate which way the robot should turn on impact with an obstacle. It's still early days.



The robot is powered by 4 AA cells via a boost regulator that gives us a constant 5V.  An Arduino does the thinking and drives 2 continuous rotation servos.

We also did a test today on the blades and motor.  Bottom line - it works well when there's not much grass to cut but the tiny motor soon gets bogged down and the blades lose speed.  We're going to need a MUCH more powerful motor and that will mean we need to re-think the power source for the whole robot.