Shop OBEX P1 Docs P2 Docs Learn Events
DC 12V <15 amp Current Monitoring — Parallax Forums

DC 12V <15 amp Current Monitoring

BobBob Posts: 9
edited 2005-03-02 16:53 in BASIC Stamp
I'd like to build a circuit to monitor the current coming out of a battery charger and would like to use a basic stamp to monitor the current draw and then fire off an electronic rely to turn the 12 volt line off after the battery reaches a peak charge.

Can anyone point me in the right direction regarding monitoring this type of current using a basic stamp.· Do I need to pass one of the 12 V DC wires through some sort of coil and then monitor the coil output with the stamp?·

Any hints would be greatly appreciated!

Thanks,

Bob

Jacksonville, FL

Comments

  • SPENCESPENCE Posts: 204
    edited 2005-02-28 03:01
    Hello bob,

    build or buy a current shunt ie. .1 ohm, 1 ohm etc pass current through it and read the voltage across it with a a/d converter.

    If you use a .1 ohm , 12 amps will cause a voltage drop of 1.2v.

    If you use a 1 ohm shunt the 12 amp flow will cause a 12 v drop across the shunt.

    I have found small shunts like that at hosfelt.com in the past.

    73
    spence
    k4kep
  • KenMKenM Posts: 657
    edited 2005-02-28 07:28
    Bob,

    What kind of battery are you charging, NiMH, NiCad, Li Ion, lead acid?
  • BobBob Posts: 9
    edited 2005-02-28 12:49
    KenM
    ·
    I'm actually building an Aluminum anodizing setup - so the current draw will probably most closely resemble a lead-acid battery.· Apparently when anodizing, the setup draws current while the parts are anodizing, and once the surface is anodized, the current draw drops off rather suddenly.

    Because the timing is dependent on the surface area of what is being anodized, I can't time the parts.
  • HulkHulk Posts: 68
    edited 2005-02-28 13:55
    Try this link:

    Click here: Allegro | Product | ACS754

    Are you going to use the stamp to determine di/dt?· Great idea!· Please post your progress.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    8184265-56bd-00410041-.jpg

    Basic stamp Newbie
  • BobBob Posts: 9
    edited 2005-03-02 13:25
    Thanks for all the thoughful responses!· I have ordered the AllegroMicro 50 amp current monitor and will interface it to my Basic Stamp via an ADC0831.· I'm also going to experiment with a home built current shunt - a 10' or possibly a 100' length of #10 AWG wire and measure the voltage drop over the length of the wire.· Again, thanks to everyone for getting me started.· I'm just collecting parts, and have a lot of learning / designing to do, but I'll keep you posted as things progress.· Bob
  • nick bernardnick bernard Posts: 329
    edited 2005-03-02 14:05
    where can you buy them?

    *edit*
    i found the online store via froogle, but $20 seems high.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    League Bowling.... it's not a sport, it's a way of life
  • SPENCESPENCE Posts: 204
    edited 2005-03-02 15:11
    Bob.

    You might try the local appliance repair shop for some nichrome wire which is used in heating elements. It comes in various resistances and should be available in short lengths. Much higher resistance than 10 ga wire. In fact the repair shop should be able to give you some out of burned out elements.

    73
    spence
    k4kep
  • Jim McCorisonJim McCorison Posts: 359
    edited 2005-03-02 16:53
    That makes at least two orders that Allegro got from this thread. I also have some samples coming.

    Nick, The $20 is for a eval platform. The chips themselves are only $5.50 each in single unit quantities.

    Jim
Sign In or Register to comment.