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Need help with propeller based project resetting itself. — Parallax Forums

Need help with propeller based project resetting itself.

radialrandyradialrandy Posts: 78
edited 2012-10-14 07:09 in Propeller 1
Ok I got a problem with one of my projects. Its used in an automotive racing application. the problem is that its picking up some EMI and powering down and powering back up. The thing thats causing the interference is a 12volt push button on dash that powers a small solenoid in the rear of car. None of this is wired to the propeller based controller. When ever I push the button to trigger the solenoid the propeller based controller with shut down as soon as I release the button and restart. Now I know that the kick back voltage from the coil is causing this. What I need to figure out is how to prevent my propeller based controller from being sensitive to this. I have many other alot higher power devices on this car that make a lot of noise too but this little solenoid seems to be the only thing thats causing me problems. Any ideas on how I can make this propeller immune to these emi's?
thanks
Randy Westmoreland
www.leashelectronics.com

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2012-10-13 08:48
    None of this is wired to the propeller based controller.

    Proximity?
    Space. Shielding.
  • LeonLeon Posts: 7,620
    edited 2012-10-13 08:48
    Has the solenoid got a diode across it, and a snubber circuit?
  • train nuttrain nut Posts: 70
    edited 2012-10-13 08:59
    Are you running the prop with the serial interface disconnected. My on going project was resetting each time I pressed a button to put the project into a different mode. I found this only happened when the serial interface was disconnected. Since then when the serial line is disconnected I short the reset and rx lines to ground and no more resets.

    Ben
  • radialrandyradialrandy Posts: 78
    edited 2012-10-13 09:00
    The button and wire for solenoids is less than 12" from controller. Solenoid does not have diode. I know how to fix the problem with the solenoid. But I sell these to customers that may have crappy wiring and I need my controller to be bullet proof like other factory automotive controllers.
  • StefanL38StefanL38 Posts: 2,292
    edited 2012-10-13 09:10
    please post a schematic how the propeller-chip gets its 3.3V
    best regards
    Stefan
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-10-13 10:35
    The reality of a 12Volt automotive set up is that it is a small world with a lot of devices that cause spikes to be generated on the mains. Honking the horn or switching to high beams might cause as much trouble as the solenoid you mention. And the starter solenoid is another.

    So you might try all of these to see if the Propeller is only resetting on one or many items.

    Are use using a voltage regulator that is specific for automotive applications? That may be the fastest fix. The LM2940 is one that is. It may work better than a 7805 or 7803.3 as it claims it is for automotive environs. You might add another regulator that steps the 12-13.8v down to 9v before the Propeller to see if that will clean up the problem. In this way, you might insert an 'automotive rated' device without a whole rebuild.

    If those items don't fix the problem, it might be time to consider using some MOVs and added low-pass line filtering to get rid of transients. Because MOVs can only trap so much power, these days they are being used in series with a fuse. The reason is that the fuse dies and the MOV will live to serve again. So don't just use MOVs that are unfused. You will never know when your protection has failed.

    All the above is on the mains as you mentioned resetting is your problem. If the i/o is having trouble, other fixes are also needed.

    Customers with 'crappy wiring'. It is hard to say how you are going to please them. The worse thing they can do is to provide power to the Propeller with very small wires or very high resistance connections. And if corrosion is a problem, you have another way to seek trouble. In other words, all power to the Propeller should be on wire of ample size and on a circuit that is not ganged with too much load.

    At this point, just because it occurs when you release the solenoid button, it seems to be flyback directly related to that solenoid and a snubber diode on the solenoid should work. I suspect that you are going to just have to educate your customers to 'good wiring practises'. Snubbers at the source are better than a huge protection scheme on the Propeller board, but both are worthwhile.

    BTW, the Propeller actually has two different modes of reset depending on how you connect the Brown Out pin (BOE). You might look at enhancing the configuration of that particular pin and the RESET pin. You may not need a reset at all if this is not to be reprogrammed. But you certainly need to avoid Brown outs that may be caused by spikes to the voltage regulator before you bother with these items.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2012-10-14 07:09
    Been doing a bit of further research.
    While the LM2940, which outputs 1 amp is designated an automotive regulator, the data sheet does not explain why.

    The LM2937, which outputs only 500ma is also designated an automotive regulator, and the data sheet explains that it was designed to handle transients of +60 down to -50 volts.

    Maybe both work the same, but the LM2937 PDF gives you a clearer idea of what to expect. While transients can go higher or lower in voltage, the extreme have less actual power. So this range would likely block most if not all brown out resets.
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