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Thread: Powering Teensy and other stuff together

  1. #1

    Powering Teensy and other stuff together

    Looking for some help with solving a rather odd power issue I'm having with a somewhat multi-layered project.

    The main components are:

    1. Teensy 3.2
    2. Teensy Audio Board
    3. Adafruit TS2012 Amp (physically separate circuit)
    4. SparkFun RGB and Gesture Sensor - APDS-9960
    https://www.sparkfun.com/products/12787
    5. Also some touch sensors: 1.8 V – 5.5 V; 17 ľA at 1.8 V typical

    Prototype using battery powered speakers in place of the TS2012, and using USB 5V power adapter for Teensy/Audio combo works great. All sensors work as they should. But I don't want to use battery powered speakers - want everything to run from a single power supply. When I tried to move this project over to a self-contained unit with its own power supply for both Teensy and the TS2012 amp, I ran into issues.

    My dad helped me with a power supply which is a basic 9V 650 mAh wall adapter to a 7805 regulator, split out to two 5v rails (let's call them A and B) that have been separated using 1N4005 diodes. We started with 10 Ohm resistors, but we went with diodes for more isolation/protection. Everything checks out on a meter for both 5v rails (A & B), and no shorts.

    When I power the Teensy/Audio Board with rail A, and power the TS2012 Amp with rail B, things work... sort of. The amp works great. I get sounds off the Teensy setup, but the APDS-9960 doesn't appear to fire up and stops working. The gesture sensor is max 3.8v, and I have verified it is getting 3.3v.

    As soon as I move back to the USB power, everything runs fine, including the gesture sensor. This leads me to believe that the circuit is not getting enough power, but I don't know what to try next. I've been through the project eliminating several potential wiring issues, rechecking. I have blown one Teensy 3.2 board in the process because of an exposed voltage wire that I tracked down too late. Even with a fresh Teensy, this power issue persists.

    I read elsewhere on the forum that Teensy 3.2 + Teensy Audio Board are about 91mA.

    I can't be the first person to try something like this, so what are people's experiences and recommendations for powering Teensy projects + other stuff along with it?

    (Attachment upload isn't working, so I was unable to send schematic of power supply)
    Last edited by Shivasongster; 05-13-2018 at 12:18 AM. Reason: typo

  2. #2
    Here's a link to the power supply schematic -

    https://www.jeremydeprisco.com/wp-co...DadSketch2.jpg

    NOTE: We started with 10 Ohm resistors, but we went with 1N4005 diodes for more isolation/protection.

  3. #3
    Junior Member
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    With either the 1N4005 or the 10 ohm resistors in the circuit, you do not have +5V whereas in the USB case, you do.

  4. #4
    So do you think I should power this project with +12V, regulated differently to make sure I get a solid +5V?

  5. #5
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    Why not get those 12V epoxy sealed 5V 30A palm sized PSUs off ebay, I'm running one on a T3.5 with dual LCDs and a crapload of electronics and its been working even in -20 temps
    Search for "5V 30A voltage stabilizer", its even running a servo!

  6. #6
    OK, thanks for the suggestion. I looked and I see there are a variety of choices. 30A seems like overkill for my project, but the 3A or 5A might be just fine.

  7. #7
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    Heres a picture of what it looks like:
    It is a pic listed off Google search engine

    They take 8 to 40 voltage input (even though the label says 12/24)
    The documents online show this and i've tested the models i've received as well with a bench powersupply
    The cutoff voltage is about 7.8 volts.

    I have 3.3, 5v and 12v versions for testing needs

    http://www.droking.com/image/cache/p...-1500x1500.jpg

  8. #8
    Got it... will probably give it a shot.

  9. #9
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    Hello,

    I am using 3.7 V Li Po battery to power teensy 3.6 which is connected to audio board.
    I am able to get the same voltage at Vin Pin but the voltage reading at 3.3 V pin on teensy 3.6 is 0V.
    The board was working properly before, now I am facing this problem.
    Can you help me with this?

  10. #10
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    you didnt connect the lipo to a 3.3v pin did you? the absolute max on any 3.3v pin is 3.6 volts, the lipo could have destroyed the mcu, is the teensy chips getting hot?

  11. #11
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    No I did not connect Li Po to 3.3V pin.I connected it to Vin( 3.6-5V).
    Yes, the teensy is getting hot.

  12. #12
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    If it's getting really hot, I would disconnect everything from it and just try it on USB to see if you could load a simple blinking led sketch to it
    If it continues to get hot and not detect on the PC, chances are there was a short somewhere and it probably fried the chip

  13. #13
    I've been away troubleshooting since my initial post. I've made some progress, but also some significant setbacks remain and I am stumped.

    When I last left my thread, I was having issues with erratic behavior when powering my Teensy Audio project (see list of parts above). I stepped away to find several errors in both hardware and software configuration. In one case, a 5V wire on one of my proto boards was partially melted and most likely cause one of my Teensy 3.2 boards to die. Proto board replaced and I replaced the Teensy.

    I've built a variable power supply like the one mentioned above from a LM317. That was powering the circuit OK, but then I still saw erratic behavior on the gesture sensor. On further inspection, I've had to clean up how I was treating the mixer gain values. I had lots of occurrences where vol would go over 1.0, inducing distortion and sometimes retriggering touch sensors. I understand the distortion piece, but I still do not fully understand the sensor issue there.

    Now at least I have everything working fairly well via USB power again, either from the laptop, or from a USB wall adapter.

    I've returned to weaning myself off the USB so I can power with my power supply. The project will NOT run from a 5V PS at all! Meter says I've got at least 5V on the Teensy side and on the Stereo Amp (TS2012) side, but doesn't run. Switching back to USB, everything is fine.

    Many expletives later, I seem to be right where I was a week ago. Time to step away for sure. Suggestions welcome. I'm going to Dunkin' !

  14. #14
    Post Dunkin' update...

    Here's some picts of the meter readings...

    https://www.jeremydeprisco.com/teensy-test/

  15. #15
    After a weekend away from things, came back with a few ideas. Still not getting anywhere.

    The power supply that always works is a PowerXcel USB Wall Charger like this one:

    https://www.cvs.com/shop/powerxcel-u...2?skuId=973634

    Otherwise, all 5V power supplies (LM7805, LM317) that I have tried have failed to power this project. Jut to recap what I am running:

    1. Teensy 3.2
    2. Teensy Audio Board
    3. Adafruit TS2012 Amp (physically separate circuit)
    4. SparkFun RGB and Gesture Sensor - APDS-9960
    https://www.sparkfun.com/products/12787
    5. Three (3) AT42QT1010 and AT42QT1011 touch sensors: 1.8 V – 5.5 V; 17 ľA at 1.8 V typical

  16. #16
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    The failed powersupplies, are they supplying enough current? the voltage won't show the current passing, you'd need to put it in series with the connection in current mode, which can read most of the time up to 10Amps max

    also make sure you have common ground between your chips

  17. #17
    Looping back to this... the power supply was providing enough current, but there were some other factors. In the end, only a non-switching power supply with a transformer worked for this project.

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