Blink LED so it can be seen when data is sent / received?

Discussion in 'General Electronics Chat' started by spinnaker, Dec 23, 2011.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,014
    I designed the attached RS232 interface for use in debugging PIC projects.

    After I got it all built I realized I have a couple of design flaws.

    1. I built in a 5v voltage regulator to provide 5V supply. After reading the data sheet again I see that the MAX232 works fine over a range of operating voltages. It would probably be easy to interface input to the mcu (which I will rarely use anyway) if the supplies were the same.


    2. I designed the PCB backward on the RS232 and TTL connections. Just a minor annoyance but connector TTL-1 is physically under RS232-2 and visa versa. It would be nice to have them switched.

    I added some LEDs (hey I have a whole bunch of LEDs and would like to use them, besides blinking LEDs are cool :)) to know when data transfer occurs but they pretty much look like they are just on. What I would like to be able to do is to get them to blink much like the lights on a router when transfer occurs.

    Is there any easy way to do this?

    Also if I did remove the regulator and just used the same supply from my project mcu, how would I deal with the different voltages? I guess on some MCU supplies there would never be enough voltage to light the LED anyway. Would it be easier just to have a supply just for the LEDs?
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Add a small surface mount counter/divider (or PIC), so they only blink on every 16th or 32nd pulse so it looks cooler.

    A SOIC 12F683 would fit nicely, then you could simply blink 4 times/second or so when RX or TX is high, and it wouldn't be as much of a load as a TTL counter.
     
  3. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,014
    Yeah I was thinking of using a PIC. I have a bunch of 18f14k22s but they are DIP and kind of large.

    I'm just wondering if it is all worth it, unless I can think of something else useful for the PIC other than to just blink the LEDs.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Blinking LEDs to inidcate Tx or Rx is much better than blinking LEDs for no reason!

    Maybe get a bi-color SMD LED that is Red/Green for TX/RX, that'd be neat.
     
  5. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,014
    :D:D:D

    Just like the movies! :)
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Reminds of the "Magic Three Switches" that get flipped when anything important needs to happen. It's always the same 3, even though there's tons of switches around them.
     
  7. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    4,887
    1,014
    I used to run a TI 960B that ran a huge automated test system. It had tons of test equipment all mounted in a rack.

    The 960 B had tons of blinking lights. It had a bunch of toggle switches. To boot the system, you would key in a cold boot sequence, it was maybe a half dozen or less instructions which would boot the card reader, which booted the hard drive. It got down to where I had that sequence down so well I could key it in a second or so.
     
  8. sheldons

    Active Member

    Oct 26, 2011
    616
    101
    have a look here this may be useful......you can add the extra parts to drive the led(s),transistors etc
     
Loading...