Design Project

1 Circuit Design

sboard2.jpg

Learn It

  • The LEDs you're going to use are very bright, 1W models.
  • They'll work with a good-quality 9V battery, but because LEDs have very low internal resistance, if connected directly to the battery they'll draw too much current, quickly overheat and burn out.
  • To reduce the current flow and divide the voltage, we'll use a 56 Ohm, high power(2W) resistor connected in series with the LEDs, this will stop this from happening.
  • You're going to need to design a compact Stripboard circuit to take all the component parts. We use DIYlc for stripboard design in School.
  • Resource: You can load DIYlc from the open drive in School, in the G:\Design Engineering\Student Home software\DIYlc\ folder. Double-click the 'diylc.exe' file to start.
  • Resource: At home, DIYlc is available for download here.

Try It

  • Download this DIYlc file into your H: drive, and use File -> Open in DIYlc to open and view it. You can't just double-click on it.

sboard_task1.png

  • This is an example of a stripboard circuit. A few important points have been picked out, which you might want to consider in your design.
    • Strain relief holes only take a few seconds to drill, but will prevent your power wires from breaking off again and again.
    • 3mm holes in the PCB will allow you to poke M3 machine screws through them to secure the lights at the bottom of your housing.
    • The spot-face cut is to prevent the steel nuts we use from creating a short-circuit and burning out your LEDs.
  • You are seeing the finished circuit from the component side (the side with no copper tracks on it).
  • To make life a little easier, the tracks are also shown (as if you had X-ray vision).

sboard_flow1.png

  • Here you can see the path that electrons take through the circuit. Remember that the electrons are unable to jump over the thin gaps between the copper rows of stripboard.
  • Electrons travel in from the red wire, arriving at the middle row of the stripboard and attacted towards the negative end of the battery (black wire).
  • As the only route they are presented with is to travel through the + leg of the LED, they pass through here and emerge at the bottom.
  • From here, the only route the elctrons can take now is to travel through the 2W resistor, to the top row of the piece of stripboard.
  • Once at the top row, the electrons are able to travel up the black wire to the negative terminal of the battery, completing the circuit.

Badge It

circuit1.png

  • Using the example circuit provided to you above, use DIYLc to create the circuit shown above on a stripboard.
  • Tip: When inserted in stripboard, the LEDs occupy 3 columns and 3 rows.
  • Tip: You'll need to keep two 3mm holes to mount your PCB to the housing. Remember that creating a hole in a row of this size prevents current from travelling past that point in the row.
  • You will be awarded a badge for your work :
    • Silver: All components added to stripboard design.
    • Gold: Workable final design is 16x7 or under.
    • Platinum: Design is 12x6 or under.