Dave Mueller

Member Since: April 23, 2011

Country: United States

  • Since you’re just measuring relative light, don’t worry about attenuation. Anything that is “transparent” will work, and since the attenuation should be constant over time, you readings will be consistent. If you were trying to measure absolute light levels, then you would need to worry about it. Choose a window based on workability, durability (any chance someone could break glass?) and environment (I think UV damages polycarbonate). I’d go with acrylic.

    You should be able to find attenuation characteristics online if you Google hard enough. Since you’re only concerned with visible light, I don’t think you’ll find anything significant. Check Edmund’s Scientific for ideas and maybe data.


  • Prosessor?

  • Or adding a tiny heat sink to a surface mount transistor when the manufacturer didn’t provide enough ground plane for proper heat dissipation.

  • This isn’t what I expected based on the web site.

  • “In optical terms, the region that is in focus is known as the “depth-of-field.” Not exactly, but that’s how people learn it. Depth of field should be more accurately referred to as depth of acceptably out of focus. Only one plane is ever in focus, the subject plane. Everything else is out of focus. There is a parameter called the circle of confusion, it is how large a circle a point is rendered. Somebody picks a COC based on what most people would consider “sharp”. The COC for 35mm is smaller than for 4x5" film, since 35mm is usually enlarged a greater amount. But all this is splitting hairs.

    For a given aperture, depth of field varies only with magnification. If you fill the frame with a flower using a wide angle lens, or use a telephoto lens and still fill the frame, the depth of field will be the same. What changes is the distance to the subject, and the angle of view (how much background you get). Again, just splitting some hairs.

  • Yeah, how about an option to opt OUT of free shipping?

  • Actually, not. Although they use the same voltages and impedance, true RS-485 devices are 2 wire, half duplex. There’s no way to connect an RS-422 device, which would have a pair each for TXD and RXD, to the 485 device. You’d have to connect the TXD and RXD pairs together, but you can’t tri-state a 422 driver. The only thing RS-232 and 422 have in common is the functional descriptions of the pins, such as TXD, RTS etc. Electrically they’re completely different, and only share one physical connector - the 9 pin D sub miniature. RS-422 is most commonly used with a 37 pin connector following the RS-449 pinout. RS-232 specs call for 25 pin D sub. RS-232 on the 9 pin and 8 pin modular connectors is technically different spec numbers.

  • The 9 pin connector on the RS232 shield should be a male since the Pi should be configured as a DTE (data output on pin 3, input on pin 2).

    Edit: Nevermind, I checked the schematic on Linksprite’s website, the 9 pin is configured as a DCE (data output on pin 2, input on pin 3), so the female connector is appropriate. But unusual IMO.

  • Pssst… April 8th has past. Or perhaps your estimate should be 2015? :-)

  • CAT5 is 8 wires each 24 AWG. What you use it for is up to you, the copper doesn’t know what’s printed on the jacket :-) For this project, it’s convenient because it is 4 color coded pairs in a tight bundle, and he doesn’t need a lot of current for each LED.

No public wish lists :(