5 ms·

This is an interesting page for several reasons: First, I think it would be a great idea for any future Single Board Computer or Router designer -- to design t

This is an interesting page for several reasons: First, I think it would be a great idea for any future Single Board Computer or Router designer -- to design their product such that it will work with any power supply from 5V to 12V (assuming that the power supply can provide enough amperes at that voltage). Even better might be to design a SBC or Router such that it works with say, a minimum 500 milliamps at 5V -- which should make it compatible with just about any consumer power supply out there... Yes, I know this is wishful thinking for several reasons. But let's look at the WRT54G & WRT54GS -- apparently these will work a power supply providing any voltage from 5V to 15V -- so long as it provides enough amperage at that voltage... To be able to accomplish this is a great design practice for Routers, SBC's, and other small computing devices. Also interesting: Look at the table of input voltages, supply current and watts. Note that Watts, in general, goes down (not by a lot, and not at every voltage, but generally, linearly) as Voltage goes up... That's an interesting effect... If the article is correct, then this seems to be the work of the "integrated 150kHz step-down switching regulator". I think it would be highly interesting (at least, if you are a SBC and/or Router manufacturer) to test all available step-down switching regulators -- and craft similar tables of input volts, amps and watts -- over the regulators' range of voltages. (Octopart anyone? https://octopart.com/ https://octopart.com/) Which regulator produces the best response over the range of voltages it handles, and then, go an extra step -- research and discover WHY that is, what are the reasons in Physics -- for the phenomenon? I think that that would be a highly interesting endeavor! (And of course, I'm also open to any suggestions for webpages for people who have already done this, or something like this!)

mozman 3y ago
You would appreciate this video about constant voltage transformers used in vintage computers: https://youtu.be/X3y7OUERyJg?si=ewtEzh_gGBCAZrRQ https://youtu.be/X3y7OUERyJg?si=ewtEzh_gGBCAZrRQ Usagi Electric has a lot of great videos.
osamagirl69 3y ago
It sounds like you would enjoy a career in electrical engineering. Most undergraduate EE curriculum will offer a class (usually both an undergraduate level and a graduate level version that covers more advanced typologies) specifically dedicated to answering the questions you are asking. Lucky for you the course notes are available for many of them. For example 6.334 from MIT https://ocw.mit.edu/courses/6-334-power-electronics-spring-2007/ https://ocw.mit.edu/courses/6-334-power-electronics-spring-2...
Goz3rr 3y ago
> Note that Watts, in general, goes down (not by a lot, and not at every voltage, but generally, linearly) as Voltage goes up... I would say it flattens out pretty quickly and doesn't keep going linearly. This probably has to do with the fact that the device was designed to be powered from 12V so the supporting components of the power supply would have been chosen to maximize efficiency around that input voltage. EDIT: I was curious and had a WRT54G v2.2 laying around (unlike the 1.0 used by OP), which results in this graph: https://i.imgur.com/CBNTtRI.png https://i.imgur.com/CBNTtRI.png The lower power usage can probably be explained by my later revision having less LEDs and more integrated chips instead of several discrete ones.
Scoundreller 3y ago
This “higher input voltage is more efficient” can also happen with bridge/protection diodes. (E.g. devices that accept AC or DC, or any polarity of DC, or at least safely refuse to function if you plug in a barrel connector with the wrong polarity) They’ll cause a fixed voltage drop, so the higher the voltage you put in, the lower the proportion of your power you lose. 240V computer power supplies are a bit more efficient than 120V ones because of this.
quietpain 3y ago
First, I think it would be a great idea for any future Single Board Computer or Router designer -- to design their product such that it will work with any power supply from 5V to 12V (assuming that the power supply can provide enough amperes at that voltage). Devices that do that have been available for 10+ years, e.g. the OKI series: https://www.mouser.com/datasheet/2/281/oki-78sr-56393.pdf https://www.mouser.com/datasheet/2/281/oki-78sr-56393.pdf It's about the size of your thumbnail, costs around $5 and takes input voltage up to 36V These are my go to devices when I'm installing something in an old device, e.g. adding bluetooth to an old amplifier. edit: handling more power would require some more space but isn't exactly rocket science.
Rediscover 3y ago
> ...Router designer ... to design their product such that it will work with any power supply from 5V to 12V... I am one of those who often makes purchase decisions around the internal power circuitry. I'm not at my lab desk at the moment (so I cannot report on that stuff), but I'm dragging around an old laptop, a small SBC (used as a general-purpose computer) and a monitor that I was employing earlier in cramped quarters for 40 minutes or so. The laptop is happy with 11.5V but doesn't have problems with 11-18V (9V 600mA will still charge the battery, slowly, during very mild use). The SBC has an NB679 buck converter so it's good for 5.5-28V. The monitor (2200 nits baby!) will accept 7-24V. These are older kit I use for crawling around with, but most of my "normal" equipment likewise has large input tolerances. Non-normal equipment (used for areas at home where tool loss/damage may occur) mentioned: OLPC XO-1 (great screen, kinda tough, freakin' old), FriendlyElec NanoPC-T4 SBC, FeelGood P7 field monitor (compact with a thick aluminum chassis).
- Scoundreller 3y ago
  USB-C Mac laptops will happily take power at seemingly any voltage in the spec. Can plug in a USB-A -> USB-C cable and it will charge overnight at 5V1A, or at least increase endurance during operation. 9V, 12V, 15V, 20V, all good too. I wonder if it will accept anything in-between as well... it should? And where it tops out. Solar panel rigged to a USB-C cable anyone? With ooooolder laptops, I found, as you did, that it's happy to take 12V and buck down everything, but can't boost and wouldn't charge at all. I sometimes use "incompatible" power bricks with a modern Dell laptop and they sometimes top-out of where they'll charge. Probably expecting 20V but getting 16V and not enough to get the cells topped up. Made the mistake of thinking that same modern Dell laptop would take in 5V over USB-C to charge overnight like the MacBook... it did not.
mikewarot 3y ago
The chip in question is likely the 3.3 volt variant of the regulator chip. Looking at the data sheet[1], it can be made variable with a voltage divider. (Provided you disconnect the rest of the circuit, of course) The physics of step down converters are well known, they've been around for a very long time. [1] https://web.archive.org/web/20051001031947/http://www.anachip.com/downloads/datasheets/power/sw_reg/AP1501.pdf https://web.archive.org/web/20051001031947/http://www.anachi...

mozman 3y ago

You would appreciate this video about constant voltage transformers used in vintage computers: https://youtu.be/X3y7OUERyJg?si=ewtEzh_gGBCAZrRQ https://youtu.be/X3y7OUERyJg?si=ewtEzh_gGBCAZrRQ Usagi Electric has a lot of great videos.

osamagirl69 3y ago

It sounds like you would enjoy a career in electrical engineering. Most undergraduate EE curriculum will offer a class (usually both an undergraduate level and a graduate level version that covers more advanced typologies) specifically dedicated to answering the questions you are asking. Lucky for you the course notes are available for many of them. For example 6.334 from MIT https://ocw.mit.edu/courses/6-334-power-electronics-spring-2007/ https://ocw.mit.edu/courses/6-334-power-electronics-spring-2...

Goz3rr 3y ago

> Note that Watts, in general, goes down (not by a lot, and not at every voltage, but generally, linearly) as Voltage goes up... I would say it flattens out pretty quickly and doesn't keep going linearly. This probably has to do with the fact that the device was designed to be powered from 12V so the supporting components of the power supply would have been chosen to maximize efficiency around that input voltage. EDIT: I was curious and had a WRT54G v2.2 laying around (unlike the 1.0 used by OP), which results in this graph: https://i.imgur.com/CBNTtRI.png https://i.imgur.com/CBNTtRI.png The lower power usage can probably be explained by my later revision having less LEDs and more integrated chips instead of several discrete ones.

Scoundreller 3y ago

This “higher input voltage is more efficient” can also happen with bridge/protection diodes. (E.g. devices that accept AC or DC, or any polarity of DC, or at least safely refuse to function if you plug in a barrel connector with the wrong polarity) They’ll cause a fixed voltage drop, so the higher the voltage you put in, the lower the proportion of your power you lose. 240V computer power supplies are a bit more efficient than 120V ones because of this.

quietpain 3y ago

First, I think it would be a great idea for any future Single Board Computer or Router designer -- to design their product such that it will work with any power supply from 5V to 12V (assuming that the power supply can provide enough amperes at that voltage). Devices that do that have been available for 10+ years, e.g. the OKI series: https://www.mouser.com/datasheet/2/281/oki-78sr-56393.pdf https://www.mouser.com/datasheet/2/281/oki-78sr-56393.pdf It's about the size of your thumbnail, costs around $5 and takes input voltage up to 36V These are my go to devices when I'm installing something in an old device, e.g. adding bluetooth to an old amplifier. edit: handling more power would require some more space but isn't exactly rocket science.

Rediscover 3y ago

> ...Router designer ... to design their product such that it will work with any power supply from 5V to 12V... I am one of those who often makes purchase decisions around the internal power circuitry. I'm not at my lab desk at the moment (so I cannot report on that stuff), but I'm dragging around an old laptop, a small SBC (used as a general-purpose computer) and a monitor that I was employing earlier in cramped quarters for 40 minutes or so. The laptop is happy with 11.5V but doesn't have problems with 11-18V (9V 600mA will still charge the battery, slowly, during very mild use). The SBC has an NB679 buck converter so it's good for 5.5-28V. The monitor (2200 nits baby!) will accept 7-24V. These are older kit I use for crawling around with, but most of my "normal" equipment likewise has large input tolerances. Non-normal equipment (used for areas at home where tool loss/damage may occur) mentioned: OLPC XO-1 (great screen, kinda tough, freakin' old), FriendlyElec NanoPC-T4 SBC, FeelGood P7 field monitor (compact with a thick aluminum chassis).

Scoundreller 3y ago
USB-C Mac laptops will happily take power at seemingly any voltage in the spec. Can plug in a USB-A -> USB-C cable and it will charge overnight at 5V1A, or at least increase endurance during operation. 9V, 12V, 15V, 20V, all good too. I wonder if it will accept anything in-between as well... it should? And where it tops out. Solar panel rigged to a USB-C cable anyone? With ooooolder laptops, I found, as you did, that it's happy to take 12V and buck down everything, but can't boost and wouldn't charge at all. I sometimes use "incompatible" power bricks with a modern Dell laptop and they sometimes top-out of where they'll charge. Probably expecting 20V but getting 16V and not enough to get the cells topped up. Made the mistake of thinking that same modern Dell laptop would take in 5V over USB-C to charge overnight like the MacBook... it did not.

mikewarot 3y ago

The chip in question is likely the 3.3 volt variant of the regulator chip. Looking at the data sheet[1], it can be made variable with a voltage divider. (Provided you disconnect the rest of the circuit, of course) The physics of step down converters are well known, they've been around for a very long time. [1] https://web.archive.org/web/20051001031947/http://www.anachip.com/downloads/datasheets/power/sw_reg/AP1501.pdf https://web.archive.org/web/20051001031947/http://www.anachi...