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Thread: what voltage for a teensy 2.0

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    what voltage for a teensy 2.0

    Because of serious space constraints, I would like to use a Teensy 2.0 to control two motors and an IR receiver. The motors (and motor controller) need 6 volts. The Teensy 2.0 needs 5. How much damage would I do to the Teensy if I gave it 6 volts? Is there an on-board voltage regulator?

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    Senior Member+ Theremingenieur's Avatar
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    As you can see on the PJRC website containing the Teensy schematics, there is no voltage regulator. Thus, 6V might put your Teensy 2.0 to danger.

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    Quote Originally Posted by Theremingenieur View Post
    As you can see on the PJRC website containing the Teensy schematics, there is no voltage regulator. Thus, 6V might put your Teensy 2.0 to danger.
    Any suggestions for voltage reduction? As I said, space is at a serious premium. I recall reading about placing an LED between the + and - from the rail and chip to reduce the voltage. Do you thik this will work?

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    Senior Member PaulStoffregen's Avatar
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    Best option would be something like a LP2950 and a 10 uF capacitor.

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    Senior Member+ Theremingenieur's Avatar
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    Reducing voltages with LEDs or diodes is a common and cheap practice with some serious risks: since they subtract a fixed voltage, all dirt and spikes (you wrote you are driving motors, thus on 6V, you risk to have spikes up to 12V) will come through, also only lowered by that 1.x V which are eaten by the diode(s). That’s why I’d rather consider a low drop voltage regulator in a SOT23 housing which does not eat more space than a LED. Intelligent routing provided, you might operate that LDO regulator even without additional capacitors since the Teensy has already oneon the 5V side and your 6V are decoupled, too, I guess. If you can manage to keep PCB traces below 2 or 3cm from existing cap to ldo and ldo to existing cap, you should be fine.

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    Thanks. Do you have any SOT23 voltage regulators in the store?

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    Just saw a problem. The sot 23 is surface mount. I will be using a protoboard. Hmmm...

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    Senior Member+ Frank B's Avatar
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    Senior Member+ Theremingenieur's Avatar
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    Quote Originally Posted by bps View Post
    Just saw a problem. The sot 23 is surface mount. I will be using a protoboard. Hmmm...
    You said above that space was a concern which is highly contradictory when using a protoboard. IIRC, the 2950 voltage regulators exist(ed) in TO-92 housings, too. In case the renowned distributors do not longer carry them, you might try your luck on eBay or Aliexpress.

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    Senior Member+ Frank B's Avatar
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    mouser has 56.286 in stock.

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    Senior Member+ Theremingenieur's Avatar
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    In TO-92? Am surprised!

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    Senior Member+ Frank B's Avatar
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    sure, see link in #8

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    Perhaps I am using the incorrect term for the board that I'm using. Let me explain what I am doing and you'll see why my remarks are not contradictory. I am building a robot (small, barely a robot, more as a proof of concept, if I can use that term) inside an Altoid can. Hence the space limitation. Adafruit has a protoboard (or whatever you wish to call it) which is sized for such a can. BTW, it seems to fit better in the lid although it will fit in the case). I've decided to use a lipo with a power boost circuit to power the teensy and another 6v lipo for the motors. I think I can just cram everything in. Might have to use my foot or sit on the top (ala luggage) to do so.

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    Senior Member+ Theremingenieur's Avatar
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    So, it was perhaps a misinterpretation on my side. When people talk about projects, my first associated thoughts are commercial and mass production which in my eyes implies (among others) a custom PCB where you would naturally use SMD components to save space and production costs.
    On the other side, when I hear protoboard, my associated thoughts are, at least when it goes beyond prototyping, rather not writable in public...

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    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by bps View Post
    I've decided to use a lipo with a power boost circuit to power the teensy and another 6v lipo for the motors.
    Maybe run the Teensy 2.0 directly on 3.7 volts?

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    3.7 volts

    Quote Originally Posted by PaulStoffregen View Post
    Maybe run the Teensy 2.0 directly on 3.7 volts?
    If a teensy 2.0 will run well on 3.7 volts, that'll solve many problems.

  17. #17
    Senior Member PaulStoffregen's Avatar
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    Yup, problem solved. Teensy 2.0 can run just fine on 3.7V.

    All we needed was a little more understanding of your project. Before msg #13, nobody could have known what your power source really was. We all tried to answer the question you originally asked.

  18. #18
    Senior Member PaulStoffregen's Avatar
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    However, be very careful never to plug the USB cable in while the battery is connected. The last thing you want is 5V power from your computer running directly into the 3.7V battery, or your 3.7V battery trying to power your computer when you shut it off.

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    I m going to attach the 3.7 volt lipo via an Adfafruit module that adds lipo capability and provides a switch. I'm also trying to determine whether I can socket the Teensy. If I can, I'll remove it for reprogramming rather than leave it in circuit.If I must solder the Teensy to the board because of space considerations, would it be enough to switch off the 3.7 v or remove it entirely for reprogramming? When you suggested that the Teensy can run off 3.7 volts, it solved an earlier problem of isolating the Teensy from the motors. I can power the Teensy from the 3.7 v and the motors off a separate 6 v lipo. Does that make sense? I have room (barely) for both batteries.

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