DM42: The internal view (hardware components)

[jebem]

Estimate for battery current consumption - Take 2:

According to a video presentation of the DM42P prototype by Günter Schink at the HHC2016 published on youtube on Sept 21, 2016, the power consumption values were measured for a "few test runs" in these conditions (please check the video at 25:43):

DM42P Hardware

Power consumption:

- At 27MHz, continuous ops: 50h

- Screen ON but idle: 2000h (~80 days)

- While OFF ??


I don't know what battery capacity was used for the above test runs.
So, assuming a standard nominal 210mAh CR2032 battery cell, the current consumption for the above hours of operation would be:

- At 27MHz, continuous ops: 50h Translates to 4.2mA average (my estimate in a previous post above was 5.25mA avg in worst case scenario)

- Screen ON but idle: 2000h (~80 days) (This means Power ON, idling) Translates to 0.1mA average

- While OFF ?? Current consumption while in power OFF state remains unknown until a good soul can take some readings and share the results


One note on heavy loads on the CR2032 battery cells:

The DM42 figure of 4.2mA current consumption when running a looping program for long periods of time is above the recommended standard continuous current supply for any CR2032 battery cell if we want to be able to consume all the cell nominal capacity.

This applies also to other machines like the HP-35S, HP-20B, and HP-30B (however HP have designed two CR2032 cells in parallel in the power supply to reduce the heavy current loads imposed per battery cell).

The standard continuous current discharge for a CR2032 is 0.2mA (this corresponds to a 15Kohm load, and that is the value used by the manufacturers to test its CR2032 products in order to evaluate the actual available capacity).

Of course the CR2032 can supply above the 0.2mA, typically up to 10mA on extreme heavy loads (or even more, depending on brand/model), but the battery will be stressed and its life (meaning, its capacity) will be shortened accordingly.

Those extreme 10mA heavy loads may typically result in 1 Volt dropped in the battery internal impedance, meaning that for many processors the cut-off voltage is very close to happen in these conditions.

So, I would expect to see a single, good quality (lower internal impedance over time among other factors), above average 220mAh ~ 240mAh capacity, CR2032 battery cell powering the DM42 for a good amount of time (up to a maximum of 2000 Hours), as long as continuous looping programs are not run all the time (and the amount of write operations to flash kept to a minimum).