Sunday, August 23, 2009

Pimp my Telescope Part 2

After describing the general design ideas in part 1 and how the Laser was fitted into the system, the remaining parts are less fency.
On switch controls the environmental lamp, the one the Laser flashes prior to engaging as safety warning. And two other switches turn on the LEDs for the polefinder and the finder scope. But there as well I had a problem before. Your goal is to get the selected object exactly into the center of the crosshair illuminated via the LEDS. When is it in the center? When you can't see it anymore. Didn't like that, so the microcontroller does not simply switch on the LEDs, it keeps them flashing. Simple implementation but one of the once you have seen it you do want to miss that again.
The power line is connected to one of the analog-digital converters of the microcontroller to measure the voltage of the battery and if it droppes below a threshold, the control LED on the PCB starts flashing. Oh, did I mention I use LiPo batteries with 11.1V known from RC helicopters as power source? They are compact, cheap, do not discharge when not used - very important! - but have one downside, they should never get discharged entirely. That's the reason for that warning light.

The dew shield and the temp sensor I will connect to the board later the year. And the next major improvement is to listen to the Autostar internal bus to understand its two-wire interface protocol. Then I want to respond to the autostar computer in the beginning when it is in the scanning phase and tell it is a Meade focuser. This should enable the focuser screens on the Autostar and the connected laptop. I could use these buttons then for various things like turning on the laser via the computer. Or I connect a motor to the focuser that understands the standard I²C protocol the microcontroller outputs to the RJ-11 connector. I am not that thrilled about the autostar protocol of the focuser, all you can do is selecting the speed of the focuser motor and not its absolute position but okay, we have to live with that.
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