Additionally, like member ci139 above, I feel the TS is withholding crucial information from us. What type of motor only consumes 40 microwatts? And driving what type of load? Is this some sort of electric wristwatch movement?

Me too. I have the feelng this has nothing to do wuth a marathon run, but is some sort of competition to operate for the longest time. In which case mAh count! But I'd like to know if the NiMH is a given requirement... and what are the rules..

 

? what size / TYPE the NiMH (also the motor specs won't hurt)
note: the NiCad is more to that 1.2V while NiMH is more to 1.4V
_______________

other
https://www.eetimes.com/designing-with-ultra-low-voltage-mosfet-arrays/ (never done any sub-threshold circuits, donno if 40µA efficient switching regulator can be achieved)
? https://en.wikipedia.org/wiki/Tunnel_field-effect_transistor (my UV mechanics teacher studied at ? Denmark where they had a iC prototyping machine . . . if you have an access to one)

more https://www.electronicdesign.com/te...7652/whats-all-this-subthreshold-stuff-anyhow
https://www.semanticscholar.org/pap...46c601bb7b1df29a1f36c911c2a98b8409cc/figure/0
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.123.9037&rep=rep1&type=pdf + https://www.aldinc.com/pdf/SubthresholdDesign.pdf , https://uwspace.uwaterloo.ca/bitstr...d=D04856FEC35C6A67FFA28F97D04C77F1?sequence=1 , http://www.onmyphd.com/?p=mosfet.subthreshold.model , https://hal.archives-ouvertes.fr/hal-02294338/document , http://www.eng.auburn.edu/~vagrawal/THESIS/KIM_S/S.Kim_HonorsThesis_FINAL.pdf
http://www.iannaccone.org/data/140.pdf

 

Wow, thanks gentlemen. That is a lot of information and gives me quite a few options to experiment with. To answer some of your questions, yes, I am using a garden variety AAA NiMH battery. The motor is a small, lightweight pulse motor so that is why the amperage is so low. This motor is just for fun, it can't handle any load and performs no work. So, I need to order some components and make some smoke - thanks again!

 

So..... there's no higher purpose behind this?

 

correct. its for hobby not industry.

 

higher purpose

now that you mentioned i actually start recalling the options (but screw that) . . . ok i recalled one example - the human is somewhat spelled to use plastics because there is plastics/fiber spirit around/above the human spirit . . . similar is wearing clothes and colors -- where among other "higher reasoons" wearing dead sheep or cotton around you camouflages you from (higher) spirits as those subjects .e.g. you appear to them as walking tree or a "smart"(read. evil)-sheep
. . . wearing colors is wearing spirits (yellow=young spirit of mom Fe+(iron) II-gen. stars , young-/mid-aged spirit of (also) dad, (fire) , power ...) . . . (violet(lavender) old spirit of sis and/or spirit of grandma . . . life wisdom , experience , calmness) . . . (green young spirit of sis , mid age spirit of mom, nature , life . . .) ((the spirits age is set by it's experience - the spirit excists all over it's experience level . . . you only be focusing (if so) to it's particular experience level . . . so in ideal you would *address the entire "beast" . . . requires you to be very experienced to do that very thing* )

i posted a lot of fuzzy links but they won't solve the essential problem-set

• linear regulation needs to be not low Ohmic until the \(V_{IN}\rightarrow V_{OUT}\)
  ... then the MOSFET would be a better choice but requires higher voltage to be driven
• going swithing is likely going pulsed/interleaved switching - which defines a conflict
  • the control needs to run at low power to keep the overall efficiency up
  • but the switching is only efficient if it's fast (requires concentrated energy)
• the 40µA TARGET is low enough to make the whole design challenging

it's a whole head-ache from the start to the end to pick/spot the right options (the combination of)

• more trivia
• the battery has the greatest mAh capacity at low drain
• the battery has the least mAh capacity at high drain
• the battery recovers relatively . . . slow from instant pulse drain
  so everything hi-energy density events need to get their energy slowly "pre-buffered"
• . . .