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Propeller Protoboard Question — Parallax Forums

Propeller Protoboard Question

Mike GreenMike Green Posts: 23,101
edited 2007-08-29 00:02 in Propeller 1
What's the current rating of the 1uH inductor in the servo power circuit of the Protoboard?

Comments

  • RaymanRayman Posts: 14,789
    edited 2007-08-28 16:25
    I know you're waiting for someone from Parallax, but...

    My guess is that it's a Bourns PM1210-1R0J rated at 400mA...
  • Franz AchatzFranz Achatz Posts: 140
    edited 2007-08-28 16:32
    thats correct.
    1uH/0.7 Ohm/400mA

    http://www.mouser.com/search/refine.aspx?Ntt=810-NLV32T-1R0J

    Franz
  • Mike GreenMike Green Posts: 23,101
    edited 2007-08-28 21:43
    Thanks everyone. It's not really the answer I wanted to hear though. I'm running the Protoboard at 6V and feeding Vin to the servo circuitry. I'm actually powering two monaural amplifiers from this using a TBA2002 (or something like that) rated at 8W peak (at 12V or so). I think they're rated at 2-3W peak at 6V which is probably enough for my needs. With two amps and a realistic efficiency, I'm well over the inductor rating at high volume levels. I think the average sound levels are low enough to manage.

    For Parallax: It doesn't make sense to use an inductor rated at 400ma in a circuit that, even with only one servo, can easily see peak currents in excess of 1A. With 4 servo headers, it's easy to go way beyond that and yet be within a reasonable current demand for Vin. How about beefing up the inductor or providing an easier way to add a higher power inductor in its place?
  • Paul BakerPaul Baker Posts: 6,351
    edited 2007-08-28 22:29
    No we specified Murata LQH32CN1R0M53 which is a 1 ampere part, however now that I am looking at the board and datasheet I can see a substitution was made. I will test the component and see if it will handle the specified current, if not those who need the extra ampacity can substitute the component on thier board since the Murata part is pad compatible.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.

    Post Edited (Paul Baker (Parallax)) : 8/28/2007 10:35:40 PM GMT
  • Paul BakerPaul Baker Posts: 6,351
    edited 2007-08-29 00:02
    I've just tested the part at 1 A, the case temperature steady states at 48 C (120 F) in 33 C ambient (yes my lab is presently 92 F) and seems perfectly capable of sustaining that current. When it was cranked up to 2 amps, the case temp reached 127 C (260 F) and failed after approximately 30-45 seconds.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.
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