Powering a Teensy 3.1 on a breadboard

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BoMadsen

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Hi,

I am a very happy new owner of a Teensy 3.1, and all is working perfectly. Currently I am building a project on a breadboard, and the teensy is powered through USB. But soon I will need to move my little project board away from a computer, and use an external power source.

I have bought one of these to power the board: https://www.sparkfun.com/products/10804

My question is, how to wire that up to the teensy? Currently my breadboard is setup with 3.3v from the teensy on both power rails, and GND on one side and AGND on the other. Is it as simple as just soldering both the left and right headers to the powerstick and putting it on the board?

ps. I can see that if I want to run the teensy on external power while the USB is connected I need to make some modifications, but that is not the plan. It will be either external power or USB, not both.
 
BoMadsen said:
Is it as simple as just soldering both the left and right headers to the powerstick and putting it on the board?
Click to expand...

Yes.

However, be careful. If you ever accidentally switch the power stick to 5V, your Teensy 3.1 will be instantly destroyed. That little switch, which looks just like the on-off switch is effectively a safe-kill switch. If you ever, even once for a brief moment, use the wrong switch, your Teensy 3.1 will be dead.

There's also no protection against reverse polarity power, but that's probably less likely.
 
One possibility if you don't want to cut the VIN/VUSB trace and you have regulated 5v, is to use a DIY USB cable and feed it back through the USB port. http://www.adafruit.com/products/1390

I keep wanting to wire up a connection with multiple power inputs (2 USB inputs plus others, all power supplies will be grounded together) and power outputs (1 USB output, plus extra power plugs). The output USB would get the D+/D- from the first USB input, but the power would come from either the first USB input, the second USB input, or other regulated 5v inputs. This would allow for more amps than a typical USB cable from a computer provides.
 
PaulStoffregen said:
Just be careful to design it so that current can't flow back into your PC's USB port if the other sources have slightly higher voltage.
Click to expand...
Yep, I was thinking of an on-off-on type switch, so power only comes from one source. Or just put diodes on all of the inputs, and use step up/step down type voltage regulator, and not depend on the inputs giving us 5v regulated.
 
Hi Michael,

Thank you for the input. However, I have no problem running either USB or external power. So I believe there is no need for me to cut anything on the Teensy?
 
Only if you don't plan on having both USB and external power plugged in at the same time.

The thing I want to build would allow me to program the Teensy and test it with the external power source(s) I plan to use, without replugging, etc. I've been starting to program neopixels and they can be power hungry (with 32 or so neopixels, you are getting to the point that it might get up to 1-2amps, which is more power than most computers put out on a USB port, but within the power you can get from batteries).
 
Sorry that I've come to this thread late, but I just stumbled upon it. Could someone please explain why running the Teensy 3.1 on 5V would fry it? The "Using External Power and USB" page (https://www.pjrc.com/teensy/external_power.html) indicates that it can operate stand-alone at 5V.

Is this the situation being described above? If so, it makes sense to me.

"USB can operate with 3.0 volts if UCAP is connected directly to power, by shorting the "3V" pads. Please refer to the schematic. However, UCAP must not be driven above 3.6 volts! Never short the 3V pads if the power supply can go over 3.6 volts"

If not, then what am I missing?

Thanks.
 
The teensy is a 3.3v chip, running the chip from 5v will destroy it. So, really you've got three main options for powering it:

-> 5v Via USB
-> 3.7-5.5v via Vin pin (electrically, this is connected to the 5v USB line)
-> 3.3v via the 3.3v pin.
 
But in the link I gave the very first sentence is:

"Teensy can operate from power applied to it's Vcc (or +5V) pin and Ground."

also it says:

"Recommended Operating Parameters

Voltage Range Maximum Clock USB Operation
4.5V to 5.5V 16 MHz Yes"

Thanks.
 
Oh I see the confusion;
The link you're looking at is true for the Teensy 2.0. Not the Teensy 3.1.
 
Thanks for the clarification.
So given that it can be powered from 3.7 - 5.5V on Vin, is the real issue the danger of inadvertently applying 5V to the 3.3v pin?
 
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