Shop OBEX P1 Docs P2 Docs Learn Events
Opto Isolation — Parallax Forums

Opto Isolation

blacksheep45blacksheep45 Posts: 41
edited 2009-06-30 10:29 in BASIC Stamp
Hello,

I am looking to Optically isolate my BS2 from a limit switch and I was wondering if anyone could advise me on an Opto Isolator to use?

Kind Regards

Shaun

Comments

  • steve_bsteve_b Posts: 1,563
    edited 2009-06-23 17:44
    You could use a 4N35 easily enough.

    Just don't forget to limit the current to the LED portion of the opto-isolator.

    Cheers

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    <FONT>Steve



    What's the best thing to do in a lightning storm? "take a one iron out the bag and hold it straight up above your head, even God cant hit a one iron!"
    Lee Travino after the second time being hit by lightning!
    LED Phototrans to stamp.JPG
    600 x 600 - 11K
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-06-25 09:45
    Will a 4N35 be able to handle an input current of 3A?



    Kind Regards



    Shaun
  • stamptrolstamptrol Posts: 1,731
    edited 2009-06-25 10:37
    No way. Why would an input to the Stamp draw 3A?

    Give us a bit of a schematic of what you're trying to do.

    Cheers,

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tom Sisk

    http://www.siskconsult.com
    ·
  • RoboticsProfessorRoboticsProfessor Posts: 54
    edited 2009-06-25 15:14
    You are not very clear, but it seems you are saying you need to use a Basic Stamp to drive/control a 3 amp load through an opto-isolator.

    If so, the one suggested by others will work fine, but you need additional circuitry.

    The "output" side of the isolator is usually tied to the base of a MOSFET, FET or transistor that will handle the desired current. That way, low current, 5 volts, is used to control a solid state device that has the current capacity you need. Is this what you are asking?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Richard Vannoy

    Programming and Electronics Instructor
    www.RichardVannoy.info
    ·
  • LeonLeon Posts: 7,620
    edited 2009-06-25 15:52
    Your limit switch shouldn't take 3A! Does whatever you are switching when it actuates take 3A?

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • blacksheep45blacksheep45 Posts: 41
    edited 2009-06-29 09:00
    Hello,



    I am connecting the basic stamp 2 to a modem. The modems maximum output current is 3A.

    I am not 100% sure how an opto isolator works but i was looking for a way to isolate the stamp from the modem just incase it runs its max output current and blows the stamp. Anyone got any advice on how to use the opto isolator?



    Cheers



    Shaun
  • LeonLeon Posts: 7,620
    edited 2009-06-29 10:46
    You seem to be more than somewhat confused! The modem probably takes a maximum of 3A from the power supply, which is nothing whatsoever to do with the load presented to the Stamp.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • $WMc%$WMc% Posts: 1,884
    edited 2009-06-30 01:22
    I think what Shaun is looking for is an opto-iso that can be driving directly from the stamp with out any inter face drivers. I too have been looking for such and OPTO-ISO. but haven't found any.

    If anyone has an OPTO-ISO that draws less than 15mA at 5vDC on the control side, and can swicth 120vAC at 2 to 3 amps on the working side. Please post it.

    Thanks in advance!


    ______$WMc%__________

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The Truth is out there············································ BoogerWoods, FL. USA
  • Mike GreenMike Green Posts: 23,101
    edited 2009-06-30 04:00
    You really need a Solid State Switch. These contain an opto-isolator feeding a triac that does the actual AC switching. They have control circuitry to minimize the switching noise by switching at AC zero-crossings. They can be driven directly from a Stamp I/O pin and some of the cheaper ones can handle 2 to 3 Amps. Here's one common used series that uses only 3mA to turn on up to 3A: www.crydom.com/en/Products/Catalog/d_2w.pdf.
  • PrettybirdPrettybird Posts: 269
    edited 2009-06-30 10:29
    Solid state relays can do alot. Easy to use and all self contained. Easy plug and play. Not expensive on ebay. Just search solid state relays. They are use in industry alot for machine I/O
Sign In or Register to comment.