Power

Power Rails

VIN

The voltage at the battery terminal (if switch is connected). Equal to V_BATT_IN.

V_BATT

The measured voltage of the battery?

V+

The regulated output power (VBATT - 4.4V) of the BQ24074 battery charger.

VBUS

4.35 V - 10.5 V From solar panel. OPTIONALLY Connected to V_USB_IN via the switch

3.3V

The main, regulated 3.3V supply, coming from U8 (the main regulator)

3.3V_SW

The 3.3V supply on the sensor board

3V_CODEC

The 3.3V supply to the codec chip (from U11)

3V_QWIIC

The 3.3V supply to the first QWIIC connector

3V_QWIIC2

The 3.3V supply to the second QWIIC connector

3V_SD

The 3.3V supply to the SD card

3V3_ICS

The 3.3V supply to the ICS mic

3v3_SPH

The 3.3V supply to the SPH mic

RTC_3V

Coin cell

USB_VIN

Voltage source supplying the Teensy USB_VIN pin. 3.3V from the regulator by default. Can be switched to V+ or V_USB via jumpers.

V_BATT_IN

Positive battery terminal

V_USB_IN

USB supply voltage after fuse and diode

USB_VIN

MicroMod input

Configuration

Teensy	OLED	mA	mW
F0	y	134	546

F0 : Full Power, minimal processing

Power Testing

Device	Current (mA)	Power (mW)	Method
SD	20	80	Regulator off
WIO-E5	9	36	Low Power Mode

Total	29	116

SD Card

The SD Card power consumption was tested by turning the SD Card regulator on and off and measuring the difference in current and power using the built-in fuel gauge.

In SDIO mode using the SDFat library, the SD Card was initialise using sd.begin(SdioConfig(FIFO_SDIO)) and the power was measured for 20 seconds. Then the power was measured for 20 seconds with the power to the SD Card's 3.3v regulator turned off.

Mode	Current (mA)	Power (mW)
Dis	-126	-505
En	-146	-585
Dis	-126	-505
En	-146	-584
Dis	-126	-505
En	-146	-584

It seems like there's a 20 mA (80 mW) difference in draw with the SD card enabled over a measured span of 20 s. So it might be worth keeping the independent regulator.

WIO-E5

The WIO-E5 power consumption was tested by switching the chip to low power mode using the AT+LOWPOWER command. The command and mode was verified by echoing the command and response via Serial to a laptop before disconnecting the laptop to log power consumption.

Mode	Current (mA)	Power (mW)
Dis	-115	-462
En	-124	-498
Dis	-115	-461
En	-124	-497
Dis	-115	-461
En	-124	-497

A difference of 9 mA (36 mW) was measured over a span of 20 s. It's unclear if an additional regulator would further reduce this.

I have not tested auto low power mode or the impact of turning the serial connection off (which is recommended). There seems to be a Serial.end() function, which should do the trick.

Teensy Sleep Modes

NB: Snooze v6.3.9 does not work on Teensy MM. It will not program properly. It requires modifications listed in https://github.com/duff2013/Snooze/issues/114. I have forked the library and applied these and overridden the Teensy library version and it seems to work (at least partially).

Teensy sleep modes are tested with 5V USB power though the USB Power monitor (battery not attached).

Mode	Voltage (V)	Current (mA)	Power (mW)
On	5.07	112	570
Sleep.	5.10	27	140
Deep Sleep	5.10	17	86
Hibernate	5.10	16	83

In theory, this seems like the Teensy could run for 11 days on low power.

LTC2956 Timing and resistors

The main feature we want is for the timer to be able to turn off for about 5 minutes at a time.

$r_{period} = 400 \times t_{period}/N_{range} [k\ohm/s]$ for $r_{common} = 100k$

R		State
Long*	1.02MΩ	Power Up
Range	61.9kΩ	Delay
Period	117kΩ	Period	102s to 14min
Common	100kΩ	Sleep
NRange	1024

• Can also be left open...

Setting $R_period$

RECOMMENDED tPERIOD	NRANGE	RRANGE* [kΩ]
0.25s to 0.8s	1	9.76
0.4s to 3.2s	4	17.4
1.6s to 12.8s	16	26.1
6.4s to 51.2s	64	35.7
25.6s to 3.4min	256	47.5
102s to 14min	1,024	61.9
6.8min to 55min	4,096	78.7
27min to 3.6hr	16,384	100
1.82hr to 15hr	65,536	127
7.28hr to 58hr	262,144	162
29hr to 233hr	1,048,576	210
233hr to 932hr	4,194,304	280