Author Topic: EEVblog 1384 - Halve Your Processor Power Consumption!  (Read 2793 times)

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Offline EEVblog

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EEVblog 1384 - Halve Your Processor Power Consumption!
« on: March 31, 2021, 10:02:19 am »
Halve Your Processor Power Consumption using Diffusion Capacitance!
Dave demonstrates a neat but tricky technique to PWM a processor's power pin to reduce power consumption.
https://en.wikipedia.org/wiki/Diffusion_capacitance
MIT: http://web.mit.edu/6.012/www/SP07-L16.pdf
Colorado University: http://ecee.colorado.edu/~bart/ecen3320/f99/pdf/ch4_4_5.pdf



Power a micro with no power pins!
 
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Offline TrickyNekro

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #1 on: March 31, 2021, 10:23:02 am »
I seriously do not buy it until I try it. Chips usually have some bulk capacitance inside on the power rails but that´s just ridiculous... And the switching frequency is quite low.
And you are driving a whole LCD bus let alone the processor itself. Edit: Which as stated below could be powering the processor.
And it´s April first coming fast to Aussieland so... no... Something is up... It can´t be that nobody ever tried that before, I have been on the internets for a while...

No no no no no... I saw quite well how good your acting was on the Keysight video... no no no no...

Edit: Actually reading a character from the LCD and then going to sleep plus the PWM BS, could also explain the low PWM frequency... really good call from the guy below!
« Last Edit: March 31, 2021, 11:27:03 am by TrickyNekro »
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Offline graybeard

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #2 on: March 31, 2021, 10:25:29 am »
It is not diffusion capacitance.  Diffusion capacitance is due to minority carrier storage of forward biased junctions.  You are using the the reverse biased substrate junction capacitors.  They are never forward biased.

You are lowering the current since the PWM is lowering the average voltage the microcontroller sees.  The internal voltage will have a sawtooth edge.
« Last Edit: March 31, 2021, 11:04:49 am by graybeard »
 

Offline chekhov

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #3 on: March 31, 2021, 11:13:08 am »
So in this example processor is actually takes it's power from SPI/whatever lines from display board if I understand the joke right? :)
 

Offline TrickyNekro

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #4 on: March 31, 2021, 11:23:13 am »
So in this example processor is actually takes it's power from SPI/whatever lines from display board if I understand the joke right? :)
Good call! But that really depends on the LCD driver, you got to get the LCD in write mode for that to happen! Which of course it´s pretty reasonable!
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Offline nctnico

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #5 on: March 31, 2021, 12:06:32 pm »
I seriously do not buy it until I try it.
Look what timezone Dave is in and what date it is in Australia..  >:D
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 
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Offline golden_labels

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #6 on: March 31, 2021, 12:27:59 pm »
Assuming that the internal capacitance would really allow that and ignoring all the problems associated: how would that differ from simply lowering supply voltage? ATmega328P has pretty linear dependency of current consumed and supply voltage. My bullshit sense is tingling.
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Offline TrickyNekro

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #7 on: March 31, 2021, 12:52:41 pm »
I seriously do not buy it until I try it.
Look what timezone Dave is in and what date it is in Australia..  >:D
I´ve seen many strange things in my life ok... enough to doubt what I know... and I know brown-out can be disabled in AVRs... But sure the Aussie is trying to pull a Roo on us...  :-DD :-DD
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Offline Cnoob

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #8 on: March 31, 2021, 12:53:55 pm »
Fascinating until I looked at the date.
Dave I think you do the best ones on you tube :-+
 
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Offline drussell

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #9 on: March 31, 2021, 01:01:30 pm »
He was like 3 hours early...  :)
 

Online Anthocyanina

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #10 on: March 31, 2021, 02:20:45 pm »
This sounds just like capacitive deractance at work
 
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Offline woofy

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #11 on: March 31, 2021, 04:06:20 pm »
Its not just microcontrollers it works on.
I've been using this technique on my core i7 desktop, PWM'ing the power at 11.574 uHz
 
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Offline tocsa120ls

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #12 on: March 31, 2021, 04:07:12 pm »
To be honest, I liked MickMake's video better.
« Last Edit: March 31, 2021, 04:14:34 pm by tocsa120ls »
-------
Short circuit - long fire
 

Offline woofy

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #13 on: March 31, 2021, 04:30:25 pm »
I used to subscribe, but Mick hasn't posted since a year ago, anyone know if he's ok?
 

Offline tocsa120ls

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #14 on: March 31, 2021, 05:01:04 pm »
I used to subscribe, but Mick hasn't posted since a year ago, anyone know if he's ok?

He's tweeting all right.
-------
Short circuit - long fire
 
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Online SiliconWizard

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #15 on: March 31, 2021, 05:51:59 pm »
That was a fun one.
 

Offline MK14

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #16 on: March 31, 2021, 06:45:48 pm »
It can be done. Using the following device, you really can cut your electricity bills in half.

 
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Offline os40la

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #17 on: April 01, 2021, 04:02:01 am »
I smelled something fishy as soon as I noticed his DaveCad of the CMOS Inverter looked a little bass ackwards.
Looked more like a buffer, eah?

Plus.. My calender was close by..
« Last Edit: April 01, 2021, 04:05:37 am by os40la »
"No, but I did stay at a Holiday Inn Express"
 

Offline EEVblog

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #18 on: April 01, 2021, 05:45:15 am »
He was like 3 hours early...  :)

No, I'm alway on time.
 
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Offline garethw

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #19 on: April 01, 2021, 05:54:08 am »
Oh Dave, you get me every year. Although I worked this one out before the end of the video. Good work!
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Offline garethw

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #20 on: April 01, 2021, 05:57:44 am »
Its not just microcontrollers it works on.
I've been using this technique on my core i7 desktop, PWM'ing the power at 11.574 uHz
What duty cycle?
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Offline Ranayna

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #21 on: April 01, 2021, 07:50:35 am »
I have to admit: The Troll in the thumbnail was a dead giveaway. ;) But that might also be because i know those hideous things from when i was a child, they were all the rage back then.

But again i have to congratulate: You can get stuff like this across so professionally, that I can really believe them, being the layman that i am.
 

Offline woofy

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #22 on: April 01, 2021, 08:17:24 am »
Its not just microcontrollers it works on.
I've been using this technique on my core i7 desktop, PWM'ing the power at 11.574 uHz
What duty cycle?
30-40% on time.
 

Offline golden_labels

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #23 on: April 01, 2021, 01:10:21 pm »
<insert the sound of slow clapping here>

I smelled something is wrong, but haven’t realized it’s April’s Fools. Dave got me. Good job. :D
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Offline srb1954

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Re: EEVblog 1384 - Halve Your Processor Power Consumption!
« Reply #24 on: April 01, 2021, 01:51:39 pm »
He was like 3 hours early...  :)
When I first saw the video I thought it was a joke as my calendar had already ticked over to April 1st. But I am in NZ and and we are 2 hours ahead of Australia so it would have still been 31st March in Australia when Dave released the video.
 


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