A new board in the Teensy series, the Teensy 3.2, has just been released. It is almost identical to the Teensy 3.1, but has a better 3.3V regulator, so that more 3.3V power can be used by peripherals. We’ll have to make some tiny changes to the PteroDAQ data acquisition system so that it will recognize the Teensy 3.2, but nothing major, as it will use exactly the same code as the Teensy 3.1. I’ll have to reinstall the Teensyduino development system and find out how (or whether) it distinguishes between the boards.
(Update 2015-Sept-19:00: The Teensyduino software treats the Teensy 3.1 and Teensy 3.2 identically, so there is nothing that needs to be done to PteroDAQ but to change some info items to be “3.1/3.2” instead of “3.1”.)
The addition of the voltage regulator is a substantial improvement to the board, allowing about 500mA of current on the 3.3V line, rather than the 100mA limit of the Teensy 3.1.
I still think I’ll recommend the Teensy LC for the electronics class, as a somewhat better price/performance ratio for the needs of the class, but the Teensy 3.2 is a good choice if you need a little more processing speed or the more complex DMA capabilities.
Gas station without pumps 
Teensy 3.2’s power output are spec. for 250 mA and the maximum voltage input at 6 volts, due to PCB thermal dissipation limits. However, the actual regulator chip is capable of up to 10 volts input, and up to 500 mA output. These higher limits are intended to allow Teensy 3.2 to be more rugged when used with non-USB power sources which aren’t well regulated 5 volt sources.
Comment by Chris O. — 2015 September 27 @ 07:22 |
I didn’t see the Teensy 3.2 power specs on the Teensy 3.1/3.2 web page (possibly buried somewhere on one of the forum posts—it seems to take a while for the information to get to the official web pages, or possibly I just overlooked it). I was just looking at the specs for the regulator on the schematics.
I didn’t do a thermal calculation, but you are probably right that thermal limits are the main problem, which means that it is neither the input voltage nor the current alone that matters, but the power dissipated in the regulator, P=(V-3.3)I. If they’ve decided that 6V and 250mA are ok, that puts the limit at 675mW, which would allow about 400mA for a 5V input, or 67.5mA for a 10V input. With input voltages of 3.7V to 4.65V, one could use the full 500mA. (The regulator they used has a very small dropout voltage, so you should be able to run with as low as 3.7V, which could be handy for battery-powered applications.)
Also, if the problem is thermal, then 500mA current could be taken intermittently even at a 6V input, as long as each use is short enough that the regulator does not heat up too much, and the duty cycle is small enough that the average power dissipation stays below the 675mW limit.
Comment by gasstationwithoutpumps — 2015 September 27 @ 08:33 |