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power rating on breadboard

Discussion in 'Electronic Design' started by Andrew Tweddle, Jan 21, 2004.

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  1. Tried this once when I was a student. The design was coming along nicely
    for 2 days then one mistake with a CRO probe and the whole thing blew up
    in front of me. Lucky to have retained my eyesight. In general
    prototyping with mains voltage is best done with a real circuit board
    and a more experienced engineer to check your work, unless you wish to
    become a victim of electrocution or an exploding cap etc.

    regards Andrew
  2. lsiu

    lsiu Guest


    What is the average power rating of a breadboard? Can I use it to
    prototype circuits with ~170 Vdc and ~100mA (> 20 W)?


  3. You bet, those currents and voltages are well within the ability of a
    typical breadboard. IIRC on the packaging that comes with the standard
    Radio Shack breadboards indicates the contact resistance is normally less
    than one milliohm (I forget the exact number though) for recommended wire
    sizes such as 22 AWG. It also indicated the contact resistance decreases
    somewhat with use.

    Some people rather conservatively (IMO) limit themselves to relatively low
    currents such as one amp. I personally use them regularly with 22 AWG wires
    with continuous per pin currents in excess of three amps (sometimes as high
    as seven amps), without any trouble or melting/deformation.

    Admittedly I do have a couple breadboards with some melted holes, but those
    were caused by other abuses. In one case I tried cranking something like
    ten amps through a single old loose breadboard hole filled with a 26 AWG
    wire (much too small) and a little bit of damage occurred in a few seconds.
    In another case an NTC inrush limiter was in much too close proximity to the
    breadboard and the heat did severe damage to quite a few holes even though
    the current was quite small (a couple amps or less).

    With the Radio Shack brand breadboards I try to keep the adjacent pin
    voltages below 200V but have never had any problems with arcing even with
    voltages on adjacent pins of over 400V. I've played with voltages as high
    as around 2kV with breadboards, although I've never tried placing 2kV
    between immediately adjacent pins.
  4. The current is no problem, but I would be worried about the voltage.
    Many designs just have a piece of thin tape between the backs of the
    contact strips and a metal back plate. I would worry less if you were
    using one without the back plate, or added an extra layer of
    insulation under it. That is getting to be enough voltage to be
    dangerous if it shows up in an unexpected place.
  5. henryf

    henryf Guest

    There's no such thing as an average power rating of a
    breadboard, but you ought to keep paper-phenolic boards below
    250 F (121 C).
    ~100mA (> 20 W)?

    I don't know, can you? :)
  6. Bob Stephens

    Bob Stephens Guest

    They can deteriorate a *LOT*. My office is by the ocean, and the salt air
    corrodes the contacts significantly in a matter of a few months. Also the
    spring contacts get fatigued with use causing unreliable and annoying
    intermittent contact. I've quit using them all together.

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