External power help
- Thread starter Balam
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- Cut VIN-VUSB pad (Once you do that, Teensy only works with external power connected)
- Connect the pots to 3.3V
- Use AGND instead of GND for the pots
- Use INPUT_PULLUP in pinMode() for the buttons
Try this:
https://www.pololu.com/product/2594
FPF1320 Power Multiplexer Carrier with USB Micro-B Connector.
This breakout board for Fairchild’s FPF1320 acts as a power multiplexer, allowing you to select which of two power sources is connected to a load while blocking reverse current into either of the sources. It handles up to 1.5 A of current at 1.5 V to 5.5 V and also breaks out a USB Micro-B connector that can be used to supply one of the input power rails.
https://www.pololu.com/product/2594
FPF1320 Power Multiplexer Carrier with USB Micro-B Connector.
This breakout board for Fairchild’s FPF1320 acts as a power multiplexer, allowing you to select which of two power sources is connected to a load while blocking reverse current into either of the sources. It handles up to 1.5 A of current at 1.5 V to 5.5 V and also breaks out a USB Micro-B connector that can be used to supply one of the input power rails.
If you ever use the USB port at the same time as another power source you need to cut that trace. Other wise the USB 5V rail is connected to the output of your PSU and thats always bad. It's pretty easy to resolder the connection so slice away.
I'm sorry if it's insulting - do you ever need the teensy on without the computer? you can just run the teensy from the usb without any other supply.
I'm sorry if it's insulting - do you ever need the teensy on without the computer? you can just run the teensy from the usb without any other supply.
thanks
I am an artist and love to learn!
after doing some reading about usb and external power
I want to be sure that I will not make a mistake to power my project.
I rather ask than be sorry.
thanks all of you for your great help.
the greatness of a discipline is to encourage others to explore it.
I am an artist and love to learn!
after doing some reading about usb and external power
I want to be sure that I will not make a mistake to power my project.
I rather ask than be sorry.
thanks all of you for your great help.
the greatness of a discipline is to encourage others to explore it.
Oh well that grand then
You are right to always double check that you've enough power to run a project over usb however if you're only using push buttons and pots you're going to be fine to run over USB. Push bottons - using input pullup as mentioned earlier - draw about 0.1mA when pushed, so If you attached a push button to every pin on the teensy and pressed them all at once you'd still be using a TINY ammount of power!
The pots could be a problem if their parrallel resistance becomes very low. 10 X 330Ohm pots in parallel have a combined parrallel resistance of 33ohm, which draws 100mA; I'd probably still run that from the USB but if they were any lower it would start to get risky. You go right ahead and use 10k pots to be sure - then run the whole thing of the USB port
You are right to always double check that you've enough power to run a project over usb however if you're only using push buttons and pots you're going to be fine to run over USB. Push bottons - using input pullup as mentioned earlier - draw about 0.1mA when pushed, so If you attached a push button to every pin on the teensy and pressed them all at once you'd still be using a TINY ammount of power!
The pots could be a problem if their parrallel resistance becomes very low. 10 X 330Ohm pots in parallel have a combined parrallel resistance of 33ohm, which draws 100mA; I'd probably still run that from the USB but if they were any lower it would start to get risky. You go right ahead and use 10k pots to be sure - then run the whole thing of the USB port
here is the final implementacion
12 touch sensor from sparkfun
https://www.sparkfun.com/products/12041
( http://cdn.sparkfun.com/datasheets/Sensors/Capacitive/AT42QT1010_Datasheet.pdf) = At 3 V current drain averages less than 500 µA in Fast
mode.
3 10k potentiometers
would this still run fine under usb power ( I still need to add external power for a separate attiny85 controlling leds )
12 touch sensor from sparkfun
https://www.sparkfun.com/products/12041
( http://cdn.sparkfun.com/datasheets/Sensors/Capacitive/AT42QT1010_Datasheet.pdf) = At 3 V current drain averages less than 500 µA in Fast
mode.
3 10k potentiometers
would this still run fine under usb power ( I still need to add external power for a separate attiny85 controlling leds )
I'll show you all the numbers step by step
So running from USB at 100mA - teensy has a linear regulator which essentially just chops off the excess voltage but keeps the current the same which means we've got 3V3 100mA to play with. (yeah that was a really simplified explanation, but it'll be fine for this case!)
12 touch sensors @ 500uA = 6mA
3 10k pots = 3 X 0.33mA = ~1mA
Total current draw of your inputs is 7mA. I've looked around and the highest number if found for the teensy current draw was here needing 51.4mA. So the total you're drawing from that 3V3 rail is 58.4mA out of 100mA.
NB: that 100mA is the minimum from any USB port other than one on a non-powered USB hub. Most will actually be higher, but I don't know how to be sure of how much and individual port can source.
Edit:
I've just googled that atiny chip, and depending on how many LEDs you want to drive you might be able to run that of the 3V3 rail as well!
The attiny itself needs 2.5mA at 3V3, 4MHz clock - leaving you just shy of 40mA to drive LEDs with. So it'll depend on how much current your LEDs need.
So running from USB at 100mA - teensy has a linear regulator which essentially just chops off the excess voltage but keeps the current the same which means we've got 3V3 100mA to play with. (yeah that was a really simplified explanation, but it'll be fine for this case!)
12 touch sensors @ 500uA = 6mA
3 10k pots = 3 X 0.33mA = ~1mA
Total current draw of your inputs is 7mA. I've looked around and the highest number if found for the teensy current draw was here needing 51.4mA. So the total you're drawing from that 3V3 rail is 58.4mA out of 100mA.
NB: that 100mA is the minimum from any USB port other than one on a non-powered USB hub. Most will actually be higher, but I don't know how to be sure of how much and individual port can source.
Edit:
I've just googled that atiny chip, and depending on how many LEDs you want to drive you might be able to run that of the 3V3 rail as well!
The attiny itself needs 2.5mA at 3V3, 4MHz clock - leaving you just shy of 40mA to drive LEDs with. So it'll depend on how much current your LEDs need.
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