Makerverse Nano Power Timer HAT for Raspberry Pi Pico

Setting an Interval

 Set one of the six DIP switches to set one of the following intervals. More granular intervals are available by setting more than one DIP switch at a time - the resulting interval will always be shorter than the shortest interval selected.

Battery Charging

The battery charger on-board can only be used with single-cell Lithium Polymer cells. By default, the Makerverse Nano Power Timer HAT ships with charging disabled to allow safe use with other batteries (Alkaline, NiMH). To enable charging for single-cell LiPo, close the CHG EN jumper by adding solder. For charging to commence, the battery must be connected before connecting the Pico to another power source or USB. Connecting a battery to an already-powered Power Timer HAT will not initiate charging. By default, the charge current is set to 100mA. Enable 330mA fast-charging by soldering the CHG FAST jumper.

Charger States and LED Behaviour

The charge indicator LED (CHG) indicates the status of a connected rechargeable battery (if any). The following table summarises its behaviour (while the Pico is plugged into USB power).

By design, the power LED will be on by default when the device has power, if you want to disable it to stretch as much power out as possible, cut the link between the pads marked PWR LED. You can always resolder the bridge later if you decide you want it back on.

PiicoDev Compatibility

A PiicoDev connector is provided, connected to GP8:SDA and GP9:SCL - that makes this HAT compatible with existing PiicoDev tutorials for Pico with no changes to example code.

Specifications

• DONE Pin: Connected to GP22. Send GP22 HIGH to send the DONE signal.
• Timer standby current: 35 nA
• Dimensions: 20.8 x 61.7 mm
• Battery Connector compatibility:
  
  • 3x Alkaline or NiMH cells in series (Charger must be disabled, open the CHG EN jumper)
  • Lithium Polymer (single cell)
• Charge current: Selectable 100 mA or 330 mA

The following example works like a simple datalogger. The Pico powers-up, records a single data point (read from the ADC) and then signals to the Power Timer that it is DONE. The process will repeat after the user-set time interval. To read the log file the Pico can be plugged into a PC and Thonny used to open or copy the file. If you haven't used Thonny to program a Pico before, see the getting started guide.

The MicroPython code example below assumes that the Raspberry Pi Pico is disconnected from USB and powered by a battery connected to the Nano Power Timer HAT. This code should be saved as main.py onto the Pico to ensure the program runs on power-up. 

from machine import Pin, ADC

DONE = Pin(22, Pin.OUT) # setting this pin High will remove power, and wait for the next interval
adc = ADC(0) # Pin 26

x = adc.read_u16()

# Opening with "a" for appending
with open("log.txt", "a") as logFile:
    logFile.write(str(x))
    logFile.write('\n') # New line
    logFile.flush() # Ensure data is written
    logFile.close() # Really ensure data is written
    
DONE.on() # Assert DONE signal; powers down Pico

For help getting started with Pico and Thonny, see our guide.

• Hardware Repository (PCB Project)
• Schematic
• Makerverse Nano Power Timer Tutorial - this is the tutorial for the original Nano Power Timer that this design is based off.