[SpiROSE] Reducing the costs

As SpiROSE had slightly shifted towards a rotating plate design, we had to list of the upcoming purchases that will be needed for the project. Yet, it quickly turned out that the costs were consequent after the first dimensions of the project were discussed.

Since we wanted – and still strongly desire ! – to have an excellent resolution for our screen, and given the maximum physical dimensions of the rotating plate stated by the mechanic, we ended up with a staggering number of almost 9000 LEDs, which represented a third of the total costs ! Other configurations were simulated, where the LED amount was decreased, significantly decreasing the costs. Having fewer LEDs implies that, if the size of the plate remains the same, we lose some resolution (but it also means that we have fewer traces to route and fewer components to solder). As regards the LED drivers, as Adrien explained, the multiplexing capability of the drivers allows to significantly shrink their numbers, allowing huge savings.

We then have to optimize each component with regard to its cost.

  • For some electronic components, we can benefit from the free sample policy from many electronic distributors, the LED drivers are planned to be bought this way.
  • The cost of SpiROSE structure can be alleviated by diminishing the thickness of the metal plates and bars needed to build it. The least stressed parts of the structure can be thinner, and since we buy a certain volume of metal, we can again reduce the costs, without endangering the integrity of the SpiROSE.
  • PCBs are a consequent part in the final costs of the project, so the smaller the cheaper. If we manage to shrink its sizes, with regard to the rotary base and the fixed base ones, we again shrink the costs. Another way for the LED PCB would be to buy small PCBs and assemble them together, since it is often cheaper to buy many small ones than a large ones, if they have the same total area. But finding an easy and solid way to perform it is not easy task. In our cheapest simulation, we still have to solder more than 2000 LEDs, which can be performed by the PCB manufacturer, but it has a price. We are discussing whether or not it might be feasible and reliable.
  • Being also expensive, the motor will be chosen carefully. It requires sufficient torque to have the rotation initiated and to counterbalance the air friction , as well as to withstand the speeds we are aiming to reach for the rotary panel.
  • Finally, we can change the model of the SBC and/or the FPGA to choose the one that fits exactly our needs. But it is risky to do it now, if ever we underestimated our needs , then this optimization would be pointless.

The exact dimensions of SpiROSE will be fixed early this week. The upcoming week, we will be working on the LCD screen, the tests with the LEDs and hopefully begin designing the electrical components 🙂



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