suggestion for blog topic -- low power design - Page 1
Forum section: electronics / general

author: cksa
author_rank: Regular Contributor
timestamp: September 11, 2010, 02:14:09 pm
content: I remember dave breifly talking about low power electronics design on the amp hour. It might be a good blog topic to expand upon this. What are some of the common techniques? How can I avoid pissing away current in using a 10k pull-up resistor?I'm sure many of us will find such an episode interesting

author: Simon
author_rank: Unknown
timestamp: September 11, 2010, 03:08:31 pm
content: it is probably a very broad subject that starts with choosing low power parts and knowing the details specs of your parts and how far you can push them

author: Zero999
author_rank: Super Contributor
timestamp: September 12, 2010, 08:47:29 am
content: It depends on the input impedance and the logic levels.Here's a PIC tutorial I'm following which discusses the issue of pull-up resistors, read the first couple of pages.http://www.gooligum.com.au/tutorials/baseline/PIC_Base_A_4.pdf

author: Simon
author_rank: Unknown
timestamp: September 12, 2010, 09:01:29 am
content: you using assembly ?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 12, 2010, 09:48:22 am
content: QuoteThat's not always the case - the knack is understanding how to get the result you need with the lowest power, and in some cases, the lowest power part is not the best choice.In many cases the critical parameter turns out to be the length of time tnings are turned on, not the current draw whilst on.A good example is sensing analogue values, e.g. temperature or pressure, on a low duty cycle.In this sort of application you need to turn on the sensor and often an amplifier, wait for it to settle, read the value and then turn off.In practice, the settling & measurement time is often the most critical value, as everything is powered, and often the CPU running as well.Where there is an amplifier, a fast opamp is generally more desirable than an ultra low power one, as the latter will be trading speed for power draw.For a microcontroller, things like the number of different selectable clock rates and watchdog rates, provision of different levels of sleep, available wakeup methods and oscillator start-up time can make a bigger difference to overall power draw than the actual current draw in each mode.

author: djsb
author_rank: Super Contributor
timestamp: September 12, 2010, 12:41:35 pm
content: I wonder how NASA manage it on their Mars rovers. That's got to be the ultimate design challenge. Pity they don't have any design info available. They probably use FPGA's anyway. It'd be great to learn some of their tricks.David.

author: Simon
author_rank: Unknown
timestamp: September 12, 2010, 01:06:27 pm
content: yes well the mars rover panels did not need to generate enough power to lift their weight into the sky, moving something along the ground is feasible, but lifting it under it's own generated power is a bit more tricky

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 12, 2010, 01:14:11 pm
content: Quote from: djsb on September 12, 2010, 12:41:35 pmI'm sure that given their budget, they probably have their own ASIC design team and perhaps some chip fabs.

author: migsantiago
author_rank: Frequent Contributor
timestamp: September 12, 2010, 01:35:29 pm
content: http://voyager.jpl.nasa.gov/faq.htmlQuotehttp://wapedia.mobi/en/Intel_8086?t=3.QuoteNasa may not always use the state of the art microprocessors. I've read they're still using old Intel processors, since their reliability has grown during all these years. They are mature processors.

author: Zero999
author_rank: Super Contributor
timestamp: September 12, 2010, 01:36:22 pm
content: Quote from: Simon on September 12, 2010, 09:01:29 amWhat me?Yes, I'm getting there.Give it a go, it's more efficient, meaning you can use cheaper MCUs for the same tasks.

author: Simon
author_rank: Unknown
timestamp: September 12, 2010, 01:42:16 pm
content: Quote from: Hero999 on September 12, 2010, 01:36:22 pmI've not had something yet that maxs out the resources of the pic, as it is my dynamo controller needed a delay putting in the program to keep the software in sync with the rest of the world