Powerbank usage; running Teensy 4.1 + sensors on 5v vs. powering sensors from Teensy 3v

A

ajreijn

Active member
Hi there,

I had a hardware question. I aim to build a small data collector to take with me on a biking trip. I want to use a powerbank as the power source. Simplest would be to just power the Teensy 4.1 using a powerbank (5v) and then powering the sensors in the circuit using the 3v output on the Teensy. I was wondering if this method has any drawbacks perhaps due to the 5v > 3v conversion. Alternatively I could create a separate 5v power input and power both sensors and Teensy directly from the 5v powerbank. With the downside of having two micro-usb inputs instead of one.

Would love some insight into the smartest way to go.

Sincerely,
Anne-Jan
 
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You don't say which Teensy you propose to use, but if T4.x I believe that 150mA should be available for your sensors.
If the sensors can be powered from 3.3v then that should be fine. It also overcomes the potential need to step voltage up/down to talk to the sensors.
 
Thanks! I'm running 4 I2C sensors (gyro, 2 magnetometers and a clock), so 150mA should be plenty. So then 3.3 is the preferred way to go, right?

(sorry I failed to mention Teensy (4.1) version - I've corrected it above)
 
The one issue that I can think of is many power banks will turn off if the power used is below some threshold. In the Teensy 3.1/3.2 era, I recall Paul had published a circuit that would draw just enough extra power to keep the power bank happy. Of course the Teensy 4.x draws a bit more power than the 3.2, so I don't know if it has the same issue.

I bought the following from Crowd Supply that claims to allow low wattage devices to be powered with power banks, but I haven't used it:
 
Ah I hadn't thought of that. Will do some testing in that regard. If I do any interesting/substantial finds I will surely post them here.
 
ajreijn said:
Ah I hadn't thought of that. Will do some testing in that regard. If I do any interesting/substantial finds I will surely post them here.
Click to expand...
My experience is, that it can work if consumption is not too low. Writing to microSD is usually sufficient to keep powerbank on.
I trick I also did is to run Teenys4.2 from LiPo and attach it via adafruit backpack (id 2124) to powerbank (outdoor type with solarpanel).
Powerpank will either load LiPo or run Teensy while loading LiPo. This allowed me to keep Teensy running while replacing powerbank or interfacing with PC. Important is that powerbank is not a switch-on type, so it will deliver energy to run teensy and load LiPo.
Wiring:
VIN-VUSB: cut
Pwerbank goes to USB
5 V from VUSB goes to backpack.
3.7 V from backpack goes to VIN
GND goes to GND
 
WMXZ said:
My experience is, that it can work if consumption is not too low. Writing to microSD is usually sufficient to keep powerbank on.
I trick I also did is to run Teenys4.2 from LiPo and attach it via adafruit backpack (id 2124) to powerbank (outdoor type with solarpanel).
Powerpank will either load LiPo or run Teensy while loading LiPo. This allowed me to keep Teensy running while replacing powerbank or interfacing with PC. Important is that powerbank is not a switch-on type, so it will deliver energy to run teensy and load LiPo.
Wiring:
VIN-VUSB: cut
Pwerbank goes to USB
5 V from VUSB goes to backpack.
3.7 V from backpack goes to VIN
GND goes to GND
Click to expand...
Was thinking in the same line. But perhaps my circuit running 4 I2C sensors and writing to SD card every 100ms is already enough consumption.
 
Probably best to keep it simple and use just 1 power bank having ordinary 5V USB power output with 1 USB cable.

Every power bank is different. None come with reliable tech specs. Even the claimed battery capacity is usually just a made up number. The only way to really know is by testing with your actual circuitry.
 
PaulStoffregen said:
Probably best to keep it simple and use just 1 power bank having ordinary 5V USB power output with 1 USB cable.

Every power bank is different. None come with reliable tech specs. Even the claimed battery capacity is usually just a made up number. The only way to really know is by testing with your actual circuitry.
Click to expand...
I would agree to keep it simple. But if I wanted to have an data acquisition system that I setup, start, check the functionality, and replace PC with Powerbank without restarting Teensy, then this requires a little bit more than a USB cable.
 
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