I’m hoping to use this category in my site to keep a project diary, so you can look forward to reading my random thoughts and musings.

Seriously though this project is, for me, the most daunting of the two to be completed this semester. I have little to no experience of systems and control so even coming up with initial ideas has been a huge struggle. My main stumbling bock has been the PIC chip circuit we created in the last week (details here), what is it? what can it do? how do I use it?!?

This will have to be my first area of investigation…

• To produce a product that can be part of a batch production
• The product must include some mechanical or electronic or a combination of systems
• As the product is to be mass produced I need to work to a specific target market
• To explore areas of concern in my subject audit
• To produce an e-portfolio documenting my design process
• To utilise CAD/CAM to produce a quality product
• To develop strategies to work effectively and efficiently with new materials and processes
• To work with due regard for the workshop safety of myself and others

They fall under two (somewhat disparate!) titles, Lights and Money Boxes. The first thing that came to mind when thinking about this project was to make something that lights up, seemed to me the most obvious thing to do when you’re not sure about the range and scope of electronics. After doing a little research on components I came up with the ideas below:

LIGHTS (research images here and here)

• Childs customisable night light – different cases (colours, designs), plug in/battery operated, cases could be milled out of acrylic and would clip on to the base unit, can be turned on/off or put on to the light detection mode (light sensor to tell bulb to switch on)
• Childs customisable bedside lamp – different cylindrical cut outs/colours (slot on to the base unit), plug in/battery operated, cylinders could be laser cut and shaped around a form, motor inside to rotate the piece work cylinder. Can be on/off/light detection/rotating.
• Solar powered, customisable garden light – unit would sit on a spike to be positioned in the ground or on a clamp to fit on branches or garden furniture, cases could be milled from acrylic and clip onto the base unit, would be designed to switch on in low light.
• Adults bedside light – would be made out of semi-transparent/frosted plastic (thin veneered wood?), interesting shape, on or off would look sculptural, would have a dimmer function on turning it off to help you get to sleep, would leave a light facing the ceiling that would dim gradually over the course of 5 – 10 minutes to prevent the sudden switch from light to dark 

 After becoming a little more comfortable with the idea of making an electronic product things started getting a little more interesting. I loved toys with movement and sound when I was little, there was something a little bit magical about an object that could move or talk with little input (although I still think Furbys are a bit strange, even for me) a real sense of childish glee overtook me when I realised that I now have the opportunity to make something like that myself! My product though, was to be something useful; I didn’t want it to become the fad toy that would be abandoned once the next big thing was out. One object I always cherished as a child was my money box (hmmm… never really thought about it but I was quite a materialistic child…). It would have to be interesting though, like the Halloween themed coffin box, putting the coin in the designated area caused the skeleton in the coffin to reach out and drag the coin in to the grave (mwah ha ha ha! oh, sorry got distracted). I wanted to make mine just as interesting:

MONEY BOXES (research images here and here)

• Safe Money Box – To look very high tech with a keypad locking mechanism, poss. movement and sound effects when unlocked (clunk, hiss of releasing pressure seal for inputting the correct code, siren for hazardous waste and rotating hazard lights for incorrect code).
• Dragon Money box – Dragon would open mouth and stick out tongue to accept coin, pressure switch on the tongue would tell the mechanism to reverse pulling it back in and shutting the mouth, the head would then tilt back to deposit the coin into the dragons stomach, could also include light and sound, more scope for movement.

So here are my starting points, next step research and development…

While the dragon’s face is beautiful it would need simplification or I will spen the bulk of my time making the form.

Both ideas were well received however one will be much more achievable in the time scale I have to complete this project. While the dragon money box would be a cool project, working out the mechanisms for the moving parts and sculpting the case whether for the final piece or to vac form over will take more time than I have.

The keypad safe has more scope for using the CNC machinery we have in the workshop such as the laser cutter. I have researched a keypad kit from Tech Supplies that has the scope for the alterations I would like to make. The kit has a buzzer that sounds when the keys are pressed, a bi-colour LED that glows green or red to indicate the locked/unlocked status and a terminal block to connect up a solenoid bolt.

Alterations I want to make:

• A siren to sound if a wrong code is entered
• A pressure seal like sound effect when the door opens (clunk, hsssssss)
• A seperate LED for the locked/open status, one green, one red.
• Use of clear acrylic to show the inner workings (fit in with the high tech look and feel)
• Experimenting with other lights to make the best of  the effects of LEDs end on to clear acrylic.

• To produce a toy safe using the Tech Supplies keypad kit as a starting point.
• As stated in my Project Brief the safe needs to be able to be part of a batch production, to this end I need to utilise 2D/3D modeling programmes to create the case as the data can then be easily sent to CAM/CNC machinery for production.
• To add additional LEDs and buzzers to the original kit to make the safe more interesting.
• To aim the safe at a young, tech savvy audience by making the safe look high tech (possibly exposing the electronics so you can see how it works), making the case look futuristic and including some interesting sound effects.
• The safe must be sturdily built and unable to open unless the proper key sequence it entered.
• To combine metal and plastic to give a futuristic feel.
• To alter the keypad kit programming to suit my new components/requirements.

The kit comes from a company called Tech Supplies (http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Products/CHI008) and contains the basics I need for making my safe.

Before I received my kit I had assumed that the keypad would work by assigning an input to each number on the pad so the microcontroller would know which buttons had been pressed, this would take up the majority of pins on my 18 pin chip leaving very few to use for outputs such as lights and sounds. On arrival I found that the microcontoller used a surprisingly simple method of scanning that reduced the number of pins needed to 7. It manages this by breaking the pad up into 3 columns and 4 rows, assigning the columns to inputs and the rows to outputs. If all the outputs (rows) are switched off the signal to the microcontroller along the inputs is 0-0-0. if a button is pressed while the rows are switched off the signal remains 0-0-0, however if you switch one of the rows high and press a button in that row for example 1 the signal to the microcoltroller will be 1-0-0 telling it that button 1 has been pressed. if the signal had been 0-1-0 it would tell the microcoltroller that button 2 had been pressed. The PIC scans the keypad by continuously switching each of the output rows high in turn, waiting for an input signal back corresponding to the button pressed. The full description of the workings of the kit can be found here chi008.

In putting it together I knew that I would need to reposition elements such as the LED and the keypad itself so I soldered it together using flying leads:

This means that I can easily fit the components into my case design and shorten/neaten the wires as required. 

Time to test… (connects up battery pack with eyes squinched shut in anticipation of failure) It Works!! The bi-colour LED glows red to show that the circuit is in it’s locked position, as the code is entered the buzzer sounds for each button press and once the correct code is used the bi-colour LED changes to green and the output for the solenoid (just a connector block at the moment) registers a 4.5v signal when measured with a multi meter then resets after 5 seconds. So I have a working circuit, now all I need is to create my case, connect up a solenoid for my locking mechanism, add in any additional lights and sounds, re-programe my chip and test it all over again (not much to do then…).

A solenoid in it’s simplest form is a device that converts electrical energy into mechanical movement. It is a coil of wire that becomes a magnet when a current passes through it, the magnetic force then moves the metal core. They are used in many objects such as door bells, car door locks, actuators for model railways etc and there are may different types. Solenoids can have linear or rotary motion, can move the metal core by pushing, pulling or both so which do I need?

I found this animation while looking to see what a solenoid actually looks like and have stumbled across exactly what I need. To act as a bolt the solenoid will need to sit in the safe door and remain pushed out when the safe is locked or off (no point of having it in there if all you have to do to unlock it is to take out the batteries), when the safe is in its unlocked position the power being sent to the solenoid needs to pull it in so therefore I need a ‘pull’ solenoid. To ensure that the bolt returns to it’s original position once the power is cut off a spring is needed to force it back.

Off I go to trawl the world of solenoid suppliers…