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Thread: Teensy programing mode

  1. #1
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    Teensy programing mode

    Hello!

    I power my teensy 3.6 and a gprs module with battery. I have recognised that when the battery is getting empty the system restarts (it is probably because the GPRS module can consume up to 2A for a few ms), then the voltage goes up because the system restarted, and then when gprs takes a lot of current again restarts.. And does it for a few times. I charge the battery but the teensy is not running.


    I think after a while teensy goes into programming mode or something like that. And works again only when I connect it to the computer and reprogram it.
    How can I prevent this? There is an MCP100-315DI/TO on reset and 3.3V Pin with a bypass capacitor for such a case.
    So I do not understand what is wrong.


    Thanks,
    Ted

  2. #2
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    Which battery are you using? What are its specs?

    Pete

  3. #3
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    Long wp7-6

    Ted

  4. #4
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    Erm, its a 6V battery, it should be fully charged at 6.5V and dead at 5-5.25V, at which point you should probably disable the GPRS. Really draining a lead acid will shorten its life considerably.
    Its hard to say, if the Teensy 3.3V rail is falling into the 1-2V range its anyone's guess as to what happens.

    2 things you can probably do is. Set up the Teensy to disable the GPRS once the battery voltage goes below 5.5V. Add a Diode(cathode toward Teensy) and a large capacitor between the diode and the Teensy. Run power to the GPRS separately. The capacitor will act as a reservoir and the diode will prevent the extra power from being drawn back toward the GPRS or battery when its loaded at high current.

    An example would be a 1N5817 diode, a 1000uF capacitor and a 70mA load from the Teensy. If your at 5.5V and the voltage of the battery drops to say 2V you will have about 23mS before the voltage on the cap reaches 3.6V after that the Teensy 3.3V rail will start to fall. You can connect a voltage divider to the battery and poll the voltage several times a minute and average them. Keep in mind at 5.5V the battery is effectively dead. There are several datasheets for the battery with graphs indicating load and at what voltage they are empty.

  5. #5
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    Thanks!
    But my problem is that the input voltage is can very from 5-48 V.. And some of our clients use 6 other 12 the another 24V input voltage...
    We use many other chips on this projects, and happened only with teensy..


    Quote Originally Posted by Donziboy2 View Post
    Erm, its a 6V battery, it should be fully charged at 6.5V and dead at 5-5.25V, at which point you should probably disable the GPRS. Really draining a lead acid will shorten its life considerably.
    Its hard to say, if the Teensy 3.3V rail is falling into the 1-2V range its anyone's guess as to what happens.

    2 things you can probably do is. Set up the Teensy to disable the GPRS once the battery voltage goes below 5.5V. Add a Diode(cathode toward Teensy) and a large capacitor between the diode and the Teensy. Run power to the GPRS separately. The capacitor will act as a reservoir and the diode will prevent the extra power from being drawn back toward the GPRS or battery when its loaded at high current.

    An example would be a 1N5817 diode, a 1000uF capacitor and a 70mA load from the Teensy. If your at 5.5V and the voltage of the battery drops to say 2V you will have about 23mS before the voltage on the cap reaches 3.6V after that the Teensy 3.3V rail will start to fall. You can connect a voltage divider to the battery and poll the voltage several times a minute and average them. Keep in mind at 5.5V the battery is effectively dead. There are several datasheets for the battery with graphs indicating load and at what voltage they are empty.

  6. #6
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    Well, you have given us no pictures, no schematics, no code. So its tough to have any idea whats going on.

  7. #7
    Senior Member PaulStoffregen's Avatar
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    Some DC-DC converters have terrible behavior if you don't add extra capacitors. These parts in particular caused a lot of pain & suffering.

    Quote Originally Posted by ted View Post
    We use many other chips on this projects, and happened only with teensy..
    Teensy does have some important differences when compared with other chips, like AVR. If you read that old thread, one of the issues is the incredibly low power consumption when Teensy 3.x gets less than about 1.5 volts. Most other chips continue to draw current, because they start up their oscillator by default or have other stuff that's active while the chip is held in a reset state. This pretty dramatic change, from almost no current to the normal current draw as the voltage rises can play havoc when using a miniature DC-DC converter, especially one that has a very wide range input and lacks enough capacitance at its input and output.

    It's easy to get stuck in a mode of thinking that Teensy must be the defective part here. But the reality is likely that Teensy only has more demanding power requirements, especially the much wider range from no load to full load current, than those other parts you've tested.

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