Wednesday, 8 October 2014

Putting the Electronics together – Planning

The main reason that I’ve been tinkering with electronics is my longer term goal of embedding some interesting lighting effects into a Steam Punk prop. That was where all of this started.

Now I have some decisions to make about which lighting effect circuits I want to include.

I want:

  • A pulsing/fading light acting as a power indicator and with a cool translucent – through hole cover (i.e. the Mac power indicator);
  • Chasing lights to come on when the trigger is pulled; and
  • A torch-light at the front of the prop

I’ve done a couple of pulse fade circuits, all with varying degrees of success (well … appearance). My two favourites are the 9V PUT transistor pulse fade that I found in the Make! book and the ATTiny85 pulsing LED that I modified from the Arduino as ISP sketch. The PUT version is neat and quite cheap, it doesn’t require any expensive parts (relatively), the most costly part is the PUT transistor (2N6027), but, at around $0.27AUD per transistor, I can live with that, this pushes the PUT version to around $0.73 per board. The ATTiny85 version has far fewer parts, but the ATTiny85 is much more expensive than a PUT transistor so it ends up costing around $2.48AUD.

The Chasing Lights is a bit of a no brainer, I’m going to go with the ATTiny85 + LED Sub-board option. The total cost of the board and sub-board comes to $4.37AUD.

Finally, I’m going to rebuild the 2x2 SMD LED Matrix project and change the layout a little. This was a great learning circuit for a couple of reasons and at a cost of around $0.49 it’s nice a cheap too!

There are a couple of additional costs, such as switches. For the chasing lights, I’ll either use a momentary switch or a lever switch, which way I go is going to depend on the way that I design the trigger for the prop. Apart from that, there’s about $1.00 worth of wire.

So, the embedded electronics come in at (PUT) $6.59 or (ATTiny84) $8.34 … plus the switches.

Electronics Block Diagram

The above block diagram shows the overall design using the ATTiny85 Pulse/Fade component while the one below shows the overall design using the PUT Pulse/Fade component.

Electronics Block Diagram - Alternative Pulse

With the PUT Pulse/Fade, I’ve dropped a switch and put the SMD LED onto the 9V power source, rather than the 5V regulated power source.

My next step from here is to put these circuit boards together on a prototype “board” to test the overall concept.

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