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moving from a development board to a bread board

Discussion in 'General Electronics Discussion' started by dniym, Jul 24, 2012.

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  1. dniym

    dniym

    3
    0
    Jul 24, 2012
    First of I am quite new to the world of micro controllers, transistors and such.
    That being said please forgive any stupid questions or lack of information that I am sure to fail to provide.

    I have a development board which I used to program a 20 pin micro controller, the software side of it is working as desired and I would now like to move this project to a breadboard.

    My supply voltage is 12 volts DC,
    This 12 volts will be running through a 5 volt voltage regulator to feed the micro controller.
    The outputs of the pic will trigger several NPN style transistors which will turn on LEDs connected to said outputs. (the LEDs are pre-wired for 12 volt operation)

    Thus they will have a common annode connected to +12v and their cathodes will be switched to ground via the transistors. (low side switching)

    My hurdle at the moment is the oscilliator clock frequency, on my board it's a simple 2 pin quartz style 8mhz oscillator.

    This appears to run through a pair of resistors which appear to be ~3 megaohm
    My pins that the OSC connects to are RA1 and RA5, is this as simple as connecting the osc between these two pins with a 3 megaohm resistance between them? The end unit will be subject to vibration, is there something I should be using other than the crystal?

    Here is a sketch of what the end design is so far, if something looks way off or isn't clear please let me know!

    [​IMG]
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Read the datasheet for your mico and the datasheet for your oscillator the chips are capacitors, values will be specified usually in the datasheet for your mico...

    Personally if I need an external OSC (I generally stick to internal OSC micros nowadays) I use 3 pin resonators as it's a single component and $ for $ cost effective (make sure to enable this setting in the micro fuses) they might not be a accurate as crystals but they work fine for 99% of all applications...

    For a simple circuit like that you might very well consider porting the code over to a 16F628A (or similar, I just picked the 16F628A as it a popular choice) if you need the 8 MHz speed find a chip with an internal 8 MHz, it just simplifies the build process and one less thing to worry about... If you have no more expantion planned you can tailor the I/O pin count to better suit your design as well...
     
    Last edited: Jul 24, 2012
  3. dniym

    dniym

    3
    0
    Jul 24, 2012
    Thank you for your reply:

    I am actually using a PIC16F785, I just set it to the INTOSC - RA4 as CLKOUT, RA5 as I/O and tuned it to 8mhz. I removed the jumpers on my test board and it works as desired. Now do I need to jumper between RA4 and RA5 on my breadboard to ensure the clock works or is this done internally?
     
  4. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    If you set 'INTOSC - RA4 as CLKOUT, RA5 as I/O' then RA5 is now a normal I/O line and RA4 will be pulsing (sharing) the clock signal out for use on another device...

    For your application it's probably best to set INTOSCIO and both pins will be usable I/O pins, or can just be ignored...

    BTW No jumpers needed for the OSC you are not self contained, using either setting...
     
  5. dniym

    dniym

    3
    0
    Jul 24, 2012
    Sweet, thanks you've been a huge help. It's now functioning on the breadboard, one more question:

    Now I just need to wire in my switches and pull up resistors and I should be off the dev board!
     
  6. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    The way you have the switches wired, those are not pull up resistors, more so acting as buffered pull down resistors for the switch...

    If they are supposed to be pull up resistors they will be in the same location but instead of wired in series, one end should be attached to +5V, and bump up to 10K so you don't waste as much...

    [​IMG]

    The PIC16F785 has built in weak pull ups, on PORT A so it might be beneficial to move your switch over to PORT A and use the build in pull ups, so you can eliminate the two external ones...
     
    Last edited: Jul 24, 2012
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