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Powering a QuickStart wih a Human Interface Board externally — Parallax Forums

Powering a QuickStart wih a Human Interface Board externally

blittledblittled Posts: 681
edited 2014-06-26 18:06 in Propeller 1
I was wondering if I could use an external 5V power supply connected to VDD and VSS on the female header on the Human Interface Board? I want to connect an Arduino Due and Propeller together and have the QuickStart use the 5V from the Due. Thanks.

Comments

  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2014-06-26 09:51
    Yes, I've powered Quickstarts using that method many times. I'm not sure if it's a good practice, but it works. ;)
  • David CarrierDavid Carrier Posts: 294
    edited 2014-06-26 10:46
    VDD on the Human Interface Board connects directly to VDD on the Propeller QuickStart. Both boards are designed to draw power from external supplies on VDD, and they have protection diodes to prevent their supplies from drawing current from the VDD. We recommend putting a Schottky diode in series with your supply, if you intend to use the barrel jack on the Human Interface Board or the USB port on the Propeller QuickStart, to prevent those supplies from forcing current into your supply.

    — David Carrier
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-06-26 11:08
    Why is Vin called Vdd on the Human Interface Board?

    It seems like the name differences between the HIB and QuickStart could be a source of confusion (it was for me). The pins labelled VDD on the QuickStart are 3.3V while VDD on the HIB is Vin. (Correction VDD on HIB is 5V as David explains in post #6.)

    I'd think VDD on the HIB should be labelled Vin (or VIN).

    I had to look at the schematics of the HIB to figure out why you guys were suggesting butting 5V on VDD which I had always thought referred to the 3.3V line.

    Edit: I made a correction based on information David provided in post #6.
  • kwinnkwinn Posts: 8,697
    edited 2014-06-26 17:51
    Duane Degn wrote: »
    Why is Vin called Vdd on the Human Interface Board?

    It seems like the name differences between the HIB and QuickStart could be a source of confusion (it was for me). The pins labelled VDD on the QuickStart are 3.3V while VDD on the HIB is Vin.

    I'd think VDD on the HIB should be labelled Vin (or VIN).

    I had to look at the schematics of the HIB to figure out why you guys were suggesting butting 5V on VDD which I had always thought referred to the 3.3V line.

    It pays to ALWAYS check the schematics. Helps keep the smoke in the chips. I have seen 2.7V, 3.3V, and 5V all referred to as Vdd at times. I think the input voltages to a chip or board should be referred to as V2.7, V3.3, V5.0 for pre-regulated inputs or V5-12 for inputs that go to a regulator or a device that has a wide voltage range.
  • David CarrierDavid Carrier Posts: 294
    edited 2014-06-26 18:06
    Duane,
    On any board we manufacture, we try to label the unregulated input voltage as VIN ans the regulated voltage that most of the circuitry powers from as VDD. On the Human Interface Board, the VIN net it not exposed, so it isn't labeled. VDD on both boards requires a regulated voltage, and it should not be treated as a VIN. Since the Human Interface Board's supply is 5 VDC, 1.7 volts higher than the Propeller QuickStart's supply, then it can power VIN on the QuickStart, and that is why they are connected when the boards are coupled.

    — David Carrier
    Parallax Inc.
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