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protecting the propeller against emi — Parallax Forums

protecting the propeller against emi

supportsupport Posts: 15
edited 2011-01-15 16:40 in Propeller 1
i have this project where there is huge strobe light that is being fired off by the propeller chip and it is causing the chip to reset midway in the program. I've tried putting the chip in a tin enclosure but it is still resetting, any suggestions as to what else i can do.

thanks in advance, --Henry--

Comments

  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-01-14 14:56
    Could you please provide more details of your set-up?
    Is your Propeller on a PCB or breadboard? If it's on a PCB, does it have a ground plane?
    Is your tin enclosure grounded?
    Are your power and logic grounds well separated?

    A photo of the set-up might help, too.
  • SapiehaSapieha Posts: 2,964
    edited 2011-01-14 14:58
    Hi support.

    Correct dimensioned coils/Ferrite-beds on Power and signal wires to it and separate Power supply To strobe light ---> Need help little
  • supportsupport Posts: 15
    edited 2011-01-14 15:16
    ElectricAye wrote: »
    Could you please provide more details of your set-up?
    Is your Propeller on a PCB or breadboard? If it's on a PCB, does it have a ground plane?
    Is your tin enclosure grounded?
    Are your power and logic grounds well separated?

    A photo of the set-up might help, too.

    i am using the prop proto board with usb, i don't think it has a grounding plane i think it is just double sided. the tin enclosure is grounded. power and logic are separated, although the logic side input is just a pulse of vdd to get the program running, and all the program does is send 30 pulses to a transistor to turn on a circuit on and off.
  • supportsupport Posts: 15
    edited 2011-01-14 15:19
    Sapieha wrote: »
    Hi support.

    Correct dimensioned coils/Ferrite-beds on Power and signal wires to it and separate Power supply To strobe light ---> Need help little

    the strobe is a 500 watt strobe so it has its own power supply and dedicated cable. it is a professional photography strobe pack.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-01-14 15:23
    Support, Do you have debug statements in your program. Many of the Prop boards with USB or even if you leave the Prop Plug connected are reset when not attached to a computer if you debug statements that are driving pin 30 on the Prop.

    This problem has bit me more than once.

    Duane
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-01-14 15:26
    Add a stiff (~1K) pullup to /RST. The Prop's internal current source may not be adequate to keep small induced glitches on /RST from resetting the chip.

    -Phil
  • supportsupport Posts: 15
    edited 2011-01-14 16:12
    Duane Degn wrote: »
    Support, Do you have debug statements in your program. Many of the Prop boards with USB or even if you leave the Prop Plug connected are reset when not attached to a computer if you debug statements that are driving pin 30 on the Prop.

    This problem has bit me more than once.

    Duane

    once the program is loaded, the the prop board is disconnected from computer and runs by itself. here is the code.30 flash with led ring small and big final.spin30 flash with led ring small and big final.spin
    spin
    spin
    30 flash with led ring small and big final.spin
    314B
  • supportsupport Posts: 15
    edited 2011-01-14 16:14
    Phil Pilgrim (PhiPi) wrote: »
    Add a stiff (~1K) pullup to /RST. The Prop's internal current source may not be adequate to keep small induced glitches on /RST from resetting the chip.

    -Phil

    can you elaborate, that might just solve the problem. i'm looking at the prop board and don't know where the reset pin is.
  • Bobb FwedBobb Fwed Posts: 1,119
    edited 2011-01-14 16:35
    I had the same problem for a while from EMI around our propellers. I put a 2.2K pull-up resistor on the RES line, but that didn't fix it completely, if there was enough interference, it would still reset the chip. I then added a 0.1µF ceramic capacitor on the line as well, and never had a problem again (well, never another problem with random resetting).

    Place both the resistor and (more so) the capacitor as close to the reset pin on the propeller as possible.
  • Andrey DemenevAndrey Demenev Posts: 377
    edited 2011-01-14 18:26
    I also recommend to isolate the circuit by means of an optocoupler
  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-01-14 20:36
    support wrote: »
    can you elaborate, that might just solve the problem. i'm looking at the prop board and don't know where the reset pin is.

    I think Phil means the RESn pin.

    Look at the pin diagram on page 4 of the data sheet for the QFN chip:
    http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/PropellerDatasheet-v1.2.pdf

    With some luck and a magnifying glass, you might be able to follow the trace on your proto board. There's a tact switch connected to that pin.
  • HumanoidoHumanoido Posts: 5,770
    edited 2011-01-15 13:21
    Use of an isolated grounding net may help.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-01-15 16:40
    ElectricAye wrote:
    With some luck and a magnifying glass, you might be able to follow the trace on your proto board. There's a tact switch connected to that pin.

    Ken posted the traces of the Prop Proto Board on this thread. See post #10.

    Duane
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