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Finishing up project, need advice... — Parallax Forums

Finishing up project, need advice...

The Lazy DestroyerThe Lazy Destroyer Posts: 21
edited 2006-02-05 00:08 in General Discussion
So I just finished up one of the projects of mine I did over winter. It's a graphical G-meter w/ temp, compass, time. It also stores highest G's reached in each direction (forward and backward). This is for my motorcycle so I have some questions.

First is the power supply. I saw this link on two power supplies (one 400MA, one 1A). Would it be any different to use the single larger one, or use a couple of the 400mA versions to keep them separated (one for microcontroller, one for sensors and other chips, one for backlit LCD)?

Filtering: some of my electronics (EEPROM) documentation shows basic wiring but doesn't mention caps at their power supplies. This project does not have a A/D converter but I still would like everything done right. I have a few 1mA tantalum caps laying around, would these work okay? They are all basic, accelerometer chip, temp/humid chip, one small EEPROM chip all from Parallax. Any ideas on cap values for the LCD? It is a I've also heard of doing something like using a large resistor between + and GND near the particular electronics for filtering. Does this sound right or have I misheard? If so, what values to use? 47K/470K?

Thanks for any help! I can pick up code pretty quick but I'm still a bit slow with some aspects of electronics.

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-02-03 12:53
    Bypass capacitors, 0.1 - 0.01uF, across the +V and GND pins of ICs is a Good Practice, especially in a "real world" situation.·

    Filtering requirements are relative to what it is that needs to be filtered out -- there isn't a one-size-fits-all solution.
  • Jim RicheyJim Richey Posts: 82
    edited 2006-02-05 00:08
    Looks like a really cool project! To answer your questions about the power supply and filter requirements could take days of gathering opinions from those who have been there,but it's mostly common sense.
    For the power supply,you can't go too big.so stay on the safe side with the larger one.What I don't understand is why a power supply is used, at all ,when the device is to run off the motorcycle battery.
    As for the filter caps,it's my opinion that you cant' use enough of them. It's not absolutely necessary to place exact sizes,but use several sizes both large and small wherever they fit in.Maybe 220uF in front then a few .1uF near the important chips that generate noise.
    I'm sure others can offer their more scientific views,but without a little more experience on your part,things might get frustrating and expensive.
    Good luck,please keep us filled in!
    Jim

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    Thanks, Parallax!
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