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Thread: Neon/Fans/Anything controlled from your PC

  1. #21
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    Already found them . Was waiting for the go ahead on this. Going to pop out and buy one now. Makes this entire project a hell of a lot simpler for me.

    Thanks, I'll update when it's built.

  2. #22
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    Quote Originally Posted by Blues View Post
    Whit or without any load connected?
    Silly me, that was with.

    I get 4.85 without.

  3. #23
    Constant Bitrate
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    Quote Originally Posted by Andrew_C View Post
    I have looked at the data-sheet and read a few forums but I can't figure out the logic to how it works (ULN2803). I get what the diodes are for, but I can't figure out how to put it on a PCB??
    Connect the ULN2803 inputs directly to the parallel port outputs.
    Connect the ULN2803 outputs to one side of each relay coil (or directly to your load, if it's small and you don't want to use a relay).
    Connect the other side of the relay coil (or load) to 12V.
    Connect the common free wheeling diode output to 12V.
    Connect the GND pin to ground.

    That's it, besides ULN2803 you only need the relays.


    If you are not familiar with the term "darlington transistor" you can read about it here: http://en.wikipedia.org/wiki/Darlington_transistor

  4. #24
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    Quote Originally Posted by Andrew_C View Post
    Silly me, that was with.

    I get 4.85 without.
    Then it should have no problem driving a MOSFET with a 4V threshold(max), since MOSFETs draws virtually zero current from the Gate pin.

  5. #25
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    Quote Originally Posted by Andrew_C View Post
    I have to say you definitely know your stuff in this area and thanks a lot for your input. I am interested in the Photo Voltaic relay but I can't fin'd a good source of them in the UK.
    Here's one UK source: http://uk.farnell.com/solid-state-relays
    Here's one that can handle 1A DC continuous load current (Connection C): Omron G3VM-61B1 http://uk.farnell.com/omron-electron...pno/dp/9918965
    And here's one that can handle 3.6A DC continuous load current (Connection C): NEC PS710A-1A-A http://uk.farnell.com/nec/ps710a-1a-...p-6/dp/1682874

    And another UK source: http://uk.rs-online.com
    Same Omron G3VM-61B1 as above http://uk.rs-online.com/web/search/s...duct&R=4801166

  6. #26
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    Thanks for the replies.

    I have just designed this. Looks good to me but could do with approval?


  7. #27
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    Hard to tell anything from that drawing. The only thing in there is a ULN2803 darlington array and a diode. YOu can't tell what all the connections are going to in your drawing.
    What's the diode in the drawing for? You can just connect pin 10 directly to 12V.
    It would be easier if you made a schematic.
    If you don't have a program for drawing schematics and PCBs, you can use CadSoft Eagle which is available in very popular freeware version: http://www.cadsoft.de

    But the circuit is pretty straightforward.
    If you want to connect relays to the ULN2803, the schematich should look like this, just add 7 more realys to the other outputs if you want.
    And instead of AC mains you could of course connect the load to 12V and GND.
    http://jaspreetscodezone.blogspot.co...llel-port.html

  8. #28
    Fusion Brain Creator 2k1Toaster's Avatar
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    Also beware that your circuit will behave extremely unpredictably upon booting. The ports send out random junk on initialization. You may want a simple SIPO register ANDed with your outputs to make a very very simple "key" almost.
    Fusion Brain Version 6 Released!
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    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
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  9. #29
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    Found this parallel port kit with ULN2803.
    This is pretty much how a relay interface should look like unless you want to add the functionality 2k1 Toaster mentioned.

    Look for kit 74 http://www.kitsrus.com/kits2.html

  10. #30
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    Quote Originally Posted by 2k1Toaster View Post
    Also beware that your circuit will behave extremely unpredictably upon booting. The ports send out random junk on initialization. You may want a simple SIPO register ANDed with your outputs to make a very very simple "key" almost.
    You can use an MIC5801 / UCN5801 instead of ULN2803 and then keep the "clear" input high until your PC has booted up.
    http://uk.rs-online.com/web/search/s...ic5801&x=0&y=0
    http://uk.farnell.com/micrel/mic5801...801/dp/1213485
    Datasheet: http://www.micrel.com/page.do?page=/.../mic5800.shtml


    Instead you can also use a serial input latch to connect to your parallel port. This way you can get more than 8 outptus.
    Read here: http://www.phanderson.com/printer/serial/serial1.html
    Or this application note: http://www.micrel.com/_PDF/App-Notes/an-2.pdf

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