aemlic delivers power at too-low a voltage

A project log for The AEMLIC Solar Harvesting board - My Journey

I setup, learn about, and experiment with Jasper Sikken's AEMLIC Solar Harvesting board available at Tindie.

kenken 09/23/2022 at 13:120 Comments

When the LIC voltage is very low, just enough for the aemlic board to activate the LOAD (3.3V) pin, the Pico is only turned on for a few seconds, often less than 20 seconds. This is not enough time to do anything useful. My C program in the Pico fires an interrupt when the aemlic STATUS pin goes low, giving the Pico just enough time to write its data to the built-in Pico flash memory. As long as the solar cell attached to the aemlic board is harvesting energy from the sun or an artifical light, this cycle can go on indefinitely. The LIC becomes charged just enough to activate LOAD, the Pico turns on for a few seconds, the LIC voltage goes below a threshold, and the Pico stops functioning.

The Pico requires at least 60 seconds of power to do something at all useful, and perhaps as much as ten minutes to perform its ultimate mission. It will also need to draw more current to support a tiny joystick and tiny display.

My question now is, how can I control the aemlic to wait until the LIC is suffiently charged? Currently, I manually disconnect the Pico power line, wait until the aemlic has re-powered the LIC, and manually re-connect the Pico power line.

I have read the e-peas documentation "e-peas DATASHEET AEM10941". The aemlic board is based on this chip.
and see also:

Page 11 (section 8 System Configuration) describes the threshold level Vchrdy, the "Minimum voltage required on the storage element after a cold start before enabling the LDOs". LDO is an acronym for Low Drop-Out.

Table 7 summarizes the eight operating modes offered by the AEM10941. According to the aemlic documentation, using internal resistors, the aemlic sets Vchrdy to 2.6V.

I believe that I need a value of 2.7V to power the Pico for one minute, and about 3.0V to power it for about ten minutes.

How can I make this happen?

I have some MCP112 Micropower Voltage Detectors (a type of transistor?). Should/could I use one of these between the aemlic LOAD pin and the Pico power pin? Or something similar?

What other technology options are there?