Shop OBEX P1 Docs P2 Docs Learn Events
Newbie needs Help....... — Parallax Forums

Newbie needs Help.......

jeighteejeightee Posts: 3
edited 2006-08-27 17:56 in Learn with BlocklyProp
Is it possible to use relays with the homework board, or am·I barking up the wrong tree?· I have the ULN2003 and a 5vdc coil 120vac 1A·relay but just can't seem to get it to work.· I'm trying to switch·a pneumatic·solenoid on/off and just don't know enough about anything, any words of wisdom·our slaps in the·face are welcome!· I do have to say·I wish·I would have·discovered the wonderful world of micrcontrollers sooner!! I'm having·such a good time!! I think·I've been at it for about a month·now and cannot believe the awesome power! I·digress...· THANKS!

jeightee·

Comments

  • Martin HebelMartin Hebel Posts: 1,239
    edited 2006-08-25 04:34
    The only source of current on that board is the small 5V regulator for the BS2. It may not supply sufficient current. Use Vin if possible instead to your relay.


    To verify you have it connected correctly:

    
                            +V
                              |
                              |
                            Coil
                              |
ULN2003 output  ___|



    If you are powering 120V, a better choice may be a Solid State Relay, which is controlled essentially as an LED is.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Martin Hebel
    Southern Illinois University Carbondale - Electronic Systems Technologies

    Personal Links with plenty of BASIC Stamp info
    StampPlot - Graphical Data Acquisition and Control
  • jeighteejeightee Posts: 3
    edited 2006-08-27 06:39
    Thanks for the reply!!· alas I still have not been able to get it to work.· Here is a "schematic" of how I have it hooked up right now, I hope it's clear enough to get the gist.··Please tell me what i'm doing wrong!· I'm wondering if I·need to·use·just the·BS2 module.......Help!!·
    bmp
    bmp
    uln2003schematic.bmp
    1M
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-08-27 14:23
    If your schematic is accurate, then your circuit is wrong.· I have attached a critique and solution.

    Post Edit --
    The output of a 2003 isn't like a logic gate, that's a frequent misunderstanding.· It is an open-collector transistor, the load connects to the output and the other side goes to +V.

    Post Edited (PJ Allen) : 8/27/2006 2:27:15 PM GMT
    jeightee.JPG
    770 x 388 - 30K
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2006-08-27 15:40
    PJ -

    I looked at that schematic for 20 minutes last night, and I KNEW what was wrong. The problem was that every time my eyes traced back the relay leads, it was connected to the "right" (and electrically left) terminal of the power supply.

    General convention usually dictates that the positive will be on the LEFT and the negative will be on the RIGHT, and sure enough when I traced it back it said "5 V" leading me down the garden path again! Further down it INDEED says + and - but that didn't enter my visualization <sigh>.

    GOOD EYES!

    Regards,

    Bruce Bates

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    <!--StartFragment -->
  • jeighteejeightee Posts: 3
    edited 2006-08-27 17:56
    IT WORKS!!!! I'm so HAPPY!!!! Thank you so much!! That was exactly the problem! I wish i could send you some cookies or some kind of tasty treat. Excuse my giddiness, this was the first real snag in my path to enlightenment and it feels good to have it solved. Thanks again ever so much!!!

    onwards!!!

    jeightee
Sign In or Register to comment.