Member Since: January 21, 2010

Country: United States

  • I'm also using a stepper with an Arduino 2560, and a ramps board with a TMC2130 stepper driver. The ramps board plugs into the mega like a shield, so everything connects together solidly. However, I'm running it on my telescope, with an EQ-2 mount. All that I need to provide is a steady pulse stream.

    I was looking at your code to see how the encoder was going to be used. I noticed in the comments that you were using 86,400 seconds as the length of a day. While true, this number doesn't account for the Earth revolving around the sun as well. This means that the earth turns an additional 360 degrees in ~365 days, nearly one degree per day. Therefore, sidereal time needs to be used to correlate the speed of the stars relative to the earth. A sidereal day equals 86164.0905 seconds per day, not 86,400. Here's a link that explains it way better than I can.

  • I've started experimenting with using photo polymer film to create masks for etching. After being cut to size, you peel a transparent, protective layer off the film, and stick it to the cleaned copper board. The film is adhered to the copper using a laminator on low heat, or an iron on very low heat. Too much heat will turn the film dark blue, and the film will be ruined.

    After generating the layout using Eagle cad, it is printed with a laser printer on a clear sheet. I make the clear sheet by running a blank laminator pouch through my laminator. The result is a clear plastic sheet that will withstand a pass through the laser printer. The laser printer needs to be set to print dark, just like with toner transfer.

    I double stack identical printed patterns, since the printouts aren't totally opaque. Everything gets lined up, and taped in place. Then, the whole thing is placed inside a Handy Vac bag, and the air gets sucked out. That presses everything together nice and flat.

    The board is then exposed to UV light for a few minutes. A UV lamp, or the sun can be used. After exposure, the printed mask is removed, as well as a second protective layer from the photo film. The board can be developed using a simple sodium carbonate solution, about 1% by weight in hot tap water. Sodium carbonate is also known as washing soda, available just about anywhere that laundry detergent is sold.

    The exposure to UV causes the film to become insoluble in the carbonate solution, but where the film was covered by the mask, the film will dissolve, so the mask needs to be a negative image. Keep agitating the board in the solution until the clear film has dissolved, leaving the now purple traces stuck to the board.

    After development in the carbonate solution, the board can be etched like any other board. The purple traces can be removed by putting the board in a dilute solution of sodium hydroxide, or just plain drain cleaner. After a few minutes, the mask will begin to just peel up and fall off the board, leaving shiny copper traces.

    I purchased a 5 meters by 30 cm roll of the film from China for less than 10 dollars, and that should last me for good long time. I'm still not sure that this method is better than toner transfer, but my results are getting better with practice.

    There are several YouTube videos that show how this process works , and a Google search for dry film polymer will provide more information.

  • I just bought one of these, and the comments were quite useful to get the unit to work.
    A word of warning - After soldering the right angle header to the GPS board, be very careful when removing GPS plugged into breadboard. The breadboard tends to grip the pins tightly, and I actually tore the traces off of the GPS board, leaving the pins stuck in the breadboard. I was able to repair the board, and then I added a 2 x 2 perfboard under the GPS, so I can pull the unit out by the perfboard.

No public wish lists :(