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Sound Impact Sensor Buyer's Remorse — Parallax Forums

Sound Impact Sensor Buyer's Remorse

sunblocksunblock Posts: 55
edited 2012-10-31 09:49 in Propeller 1
I purchased a handful of the sound impact sensors as a proximity alert, and was working with the SpinStampa dn Basic Stamp 2px.
Then I decided that since the end game was really to use the propeller and it's multi-processing/threads, I started to shift gears.
I mean grind gears. The Sound Impact Sensor is a 5VDC device! Pays to read the fine print I guess.

However, I hooked it up anyway and I actually started to work! At least the lights blink when it "hears" something and there is a measurable pukse on the signal line.
an someone explain what I am seeing? If it's a 5V device, souldn't it take 5V to operate it. Or is that an overly simplicitic view?

Sunblock

Comments

  • JonnyMacJonnyMac Posts: 9,108
    edited 2012-10-31 08:49
    While it might work it could be on the ragged edge of electrical spec. I would suggest you operate the device at 5V and protect the Propeller's input with a $0.05 resistor (3.3K or higher).
  • sunblocksunblock Posts: 55
    edited 2012-10-31 09:10
    Should i protect sll propeller inputs, from all sensors, with a 3.3 or 4.7k resistor? Even if its a 3.3v sensor? Like the 4d tilt or pir sensor?
  • JonnyMacJonnyMac Posts: 9,108
    edited 2012-10-31 09:37
    No need if the device is 3.3v. It doesn't hurt, though, especially if you're a new programmer. A resistor can prevent a collision of IOs due to a programming error (i.e., you turn what's supposed to be an input to an output).
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-10-31 09:49
    Hi sunblock;
    sunblock wrote: »
    Should i protect sll propeller inputs, from all sensors,
    with a 3.3 or 4.7k resistor? Even if its a 3.3v sensor? Like the 4d tilt or pir sensor?

    The Sound Impact Sensor, while designed to be powered from 5V,
    is designed to be directly connected to the Prop's 3.3V pins.
    It has a 1K protection resistor built in right on the board. No extra resistor needed.

    Yes, 1K is lower than the usual 3.3K or 5K often recommended.
    The reason this is OK is the sensor uses a bipolar NE555D.
    Since this is the bipolar version it's output is no higher than 4V when powered from 5V.
    The 1K is able to keep the pin input current less than 0.5mA.

    If you broke the Prop pin it has to be from some other cause.

    One should always check the schematic, spec sheet, and components to
    be sure what happens and take appropriate pin protection.
    No, you needn't always add protection resistors.
    I depends on what your doing.

    Duane J
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