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Reading schematics, im doing it wrong.

Discussion in 'General Electronics Discussion' started by honken, Oct 22, 2012.

  1. honken

    honken

    8
    0
    Oct 9, 2012
    Hey.

    Well, been trying to follow a schematic, but now i think i got the wrong parts.
    Not sure how this happen, maybe to big of an ego "a mr knows it all".

    Anyway here is the schematic:

    [​IMG]

    Questions:
    1. Top arrow, getting confused by this one, i thought it might should be a 78L05, but then i looked more at it, and it has 3 legs, and at the point i did not know how to use it, but now i think its the wrong part and i misunderstood that part.

    2. Set, not sure about this button, should be a "select program"-button, so i got my self some buttons, that have 4 legs, but i tried them with a led, only connecting the 2 legs on one side, then i could turn on the led by pressing down, but not sure if it is such a button needed here.

    The PIC, well got the pic programmed, but not sure if the shop did it right, but so i dont need to back there again (or get me a programmer my self), i need to be sure about question 1 and 2 first.

    going to be powering this device with three 3v pin-button batteries.

    Original creator post from this is found here: http://www.josepino.com/circuits/led_chaser2


    One more question i can ask, is if the 78L05 is correct, then how to read the schematic?
    (L = Leg)
    In Gnd Out
    L1 L2 L3

    Im guessing its not turned backwards or anything like that, then it should be:
    1k ohm -> L1.
    L2 gnd -> Negativ (-)
    But what about L3? the out? space? :)



    Thanks in advance.

    Honken
     

    Attached Files:

    Last edited by a moderator: Oct 22, 2012
  2. shrtrnd

    shrtrnd

    3,665
    453
    Jan 15, 2010
    When I click on your schematic, I only get dots.
    Try again, so we can see it.
     
  3. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    It's a zener diode/resistor configured as a crude voltage regulator...

    Should be a momentary, just like you describe...

    What kind of button cell? You might not have enough current to get it fired up at all... Also using button cells you might find it better to just use 6V (aka 2 button cells in series) and a rectifying diode to drop you down to 5.3ish Volts that the PIC will be happy with and you can skip any other regulation like the zener/resistor or a 7805... But, again the button cells might not provide enough current for this application and it won't run that long even if it does work...
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
  5. honken

    honken

    8
    0
    Oct 9, 2012
    yes, i placed 3 in a series, because i thought i needed to use 9v in total, but if i can skip that transistor/regulator it would be awesome.
    I'm not comfortable with thinking outside the box just yet with these electronic things.
     
  6. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Since the source code was not provided I'm going to assume there is no attempt to limit current to the LEDs with PWM in said circuit, and I advise you to add resistors where I have indicated with read dots... The value of these resistors should be 1/2 the calculated value for your LEDs based on a 5.3 Volt supply... Note the addition of a 1N4001 diode in the circuit and the change to a 6 Volt supply, this avoids any other regulation and gets you to about 5.3 Volts that the PIC will be perfectly happy with...

    *** EDIT Alternatively you can add a single resistor at pin 7 if and only if one LED is on at a single time, if there is any trailing or shadowing of the lights this is not a good alternative... OR alternatively you could add full value resistors to pins 2,3,5,6 and skip the resistor on pin 7...


    [​IMG]
     

    Attached Files:

    Last edited: Oct 22, 2012
  7. honken

    honken

    8
    0
    Oct 9, 2012
    Thanks.

    Now it feels like this schematic will change a lot. The source (that i dont have either), has fading effect on the lights. And this circuit uses 8 lights, i think i will only be needing 6 lights, but since i yet to learn assembly i cant write code just yet, i know that a text editor will work for writing the code, but to be able to program a PIC im not sure, have yet to find a PIC programmer (pickit etc) that works in Mac OS X (else i would need to install Windows on a virtual mashine). I think when i get into the coding bit it wont take long to be "ok" at, since i´v been doing some other languages, like Shellscript, PHP, Java and so on (not that im a master, but i get around).

    Most important for this project i want to copy (also to learn more), is to make it as small as possible, since this will me mounted in to a RC car for fun and show :)

    And i have had this feeling for the past 2 weeks, like its x-mas. Just want it to be done, but i need to learn more on how things work and why they work at the same time.

    To be clear: Regarding the software, i have yet to find a bundle (programmer and application), at the resellers here in thailand, so im not saying there aint no application for mac, just that i have yet to find a bundle :)

    /Honken
     
    Last edited: Oct 22, 2012
  8. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    When it comes to electronics, the available and compatibility of Windows applications still reigns pretty superior to *nix offerings... You will really limit your options if you force yourself to stick to *nix in this field... Not saying you can't find alternatives, but it will be just that, you will be seeking out alternatives in many cases, not all of course...

    My advice get yourself a cheap Windows laptop (or desktop) and do your development on there, it will save you a bunch of aggravation in the long run... Having access to old school serial and parallel ports is also a plus in this hobby if you want to easily interface to computers at some point...

    Well thus far, the changes are only minimal just a few simple ones... If you want less LEDs just leave off the first and last LED in the schematic, this will keep the pattern mostly the same since you can't modify the firmware... But, it will not be as smooth obviously as you chopped it up...

    As for programming assembly is the 'hardest' of all languages to learn... In the end if you get a firm grasp of assembly you can be a superior programmer and optimize code very well, but it's not going to be necessary 99% of the time... Learn C if you want to have the most flexibility...
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,174
    2,690
    Jan 21, 2010
    In the circuit with the zener regulating the voltage, the series resistance neatly limits the current through the LEDs.

    Of course it does so at the expense of the input voltage, but if you're using white LEDs, their Vf will be sufficient to keep the PIC operating.
     
  10. honken

    honken

    8
    0
    Oct 9, 2012
    Im not sure about one thing more now, when i think about it. It might be that the LED is white, but the casing is coloured instead. Since the plastic on the LED is red/yellow and green (of the ones i got). Maybe this is some helpful information?

    /H
     
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