5 ms·

This isn't that crazy -- you can get something as available and low cost as an ESP8266 ($1.72 in singles) down to ~.01mA to ~.005mA if you implement the hardwar

by Hasz 9y ago

This isn't that crazy -- you can get something as available and low cost as an ESP8266 ($1.72 in singles) down to ~.01mA to ~.005mA if you implement the hardware watchdog timer, use sleep mode, remove extra LEDs, etc and keep the external libraries to a minimum. There's a couple of other tricks, but it's a good place to start. By using a low leakage FET on the SDA SCL lines and sacrificing a bit of speed, you can have up 127 i2c sensors that only use power when they measure. A good low quintescent current buck boost regulator can squeze every last bit of power for your chip even when the battery is basically at 0 capacity (2.7V for Lion, .8V for Alkaline) and use very little power on it's own. Dropping the system frequency can also improve performance.

YZF 9y ago
I built a system once based on a Microchip PIC running with a 32.768KHz crystal main clock. The CPU draws about 11uA when running in this mode. Imagine you can do something useful with only 32768 instructions/s vs the 1 billion you get a modern CPU ;)
- DamonHD 9y ago
  Our AVR based setup uses the 32768Hz clock to wake up every two seconds to then do as much as it needs to at 1MIPS - "race to idle". Almost exactly the performance (other than the better I/O and the multiply op) that I used to get out of a Z80A or a 6502 (eg BBC Micro).
dragontamer 9y ago
> A good low quintescent current buck boost regulator can squeze every last bit of power for your chip even when the battery is basically at 0 capacity (2.7V for Lion, .8V for Alkaline) and use very little power on it's own. While that's fundamentally true, buck/boost converters also have a level of inefficiency. Old crappy ones are 80% efficient... good ones are 90% efficient, the best may be 95% or even 98% efficient. "Squeezing out" the last few volts of a Lithium Ion or NiMH doesn't make much sense. There's probably less than 2% of power below 3V on a Lithium Ion, and less than 2% of power below 1.0V for a NiMH. So the 98% efficient Buck Converter ends up lowering your life, because there's so little power between 0.7V and 1.0V or so. If you can run a circuit without a converter, that would generally be superior. For example, an Arduino can run down to 1.8V. So a 2xAA battery or a 1x Lithium Ion can be run without a boost/buck converter, and really capture that last 2% or so of power (as opposed to losing 2% in the conversion process)
- exmadscientist 9y ago
  >If you can run a circuit without a converter, that would generally be superior. No, this will waste a lot of power in the high-supply-voltage region of the battery's discharge curve. There are three regimes to consider, for (say) the case of running 3.3V nominal parts off a 1S 3.7V Li-Ion cell. Other nominal supply and battery voltages are very similar, they just shift the locations of the regimes around a bit or introduce boost converters. Regime 1: Battery voltage above system voltage. Here you want a high-efficiency buck converter. This minimizes the current you draw from the battery: instead of drawing (say) 10mA at 3.7V, you draw 10mA × 3.3/3.7 × 0.98 ~ 8.7mA at 3.7V. A buck converter is generally superior to a buck-boost as the peak efficiency is higher, and for this scenario boost functionality will never be necessary. Regime 2: Battery voltage slightly above system voltage. In this regime the appropriate solution is a low-quiescent-current low-dropout linear regulator (aka LDO). This regime exists because of the finite efficiency of a switching regulator. With an imaginary 100% efficient switcher, you never need an LDO. The lower the draw on the system rail, the wider this regime gets. For micropower circuits (average draw in the single-digit microamps) one might always be here. For higher power draws (tens of milliamps), this regime might be too small to justify the added complexity of including an LDO and you just skip right over it. Regime 3: Battery voltage at or below nominal system rail voltage but above minimum. The best thing to do here is absolutely nothing: just run the system directly off the battery. This is possible with a regulator with a bypass FET. Once the regulator goes into dropout, it just turns on the bypass transistor and connects things directly (with a small R_ds(on) drop of course). A few regulators have these built in. Other regulators are efficient enough in dropout that they don't actually benefit much from the bypass transistor. This also assumes you're near the end of the battery discharge curve. If you aren't, then you're potentially heading into boost or buck-boost territory, which I'm not going to cover here. Deciding which of these three regimes are important enough to warrant the design time for optimizing is a key part of low-power circuit design.
  - dragontamer 9y ago
    You make some solid points, it all depends on the battery I guess. As you've noted, a 3.7V Lithium Ion battery (which is 4.2V when fully charged) would waste a lot of both voltage and current (excess current typically runs with higher voltage) if feeding a battery directly. But for a 3.3V part, you really want to be running a LiFePO4 Cell, with nominal voltage of 3.2V. The chemistry itself provides you the maximum efficiency, as opposed to building devices to convert a 3.7V part to 3.3V. ---------- Compensating for the flaws of a slightly mismatched cell or battery is one approach. But I have my bets that selecting the proper battery to begin with is the optimal approach. In any case, I think I can agree with you that using a standard 3.7V (4.2V when fully charged) battery on a 3.3V circuit... it probably would be most efficient to use a pure Buck Converter. 3.3/4.2V == 78% converters would gain you energy early in the charge, while near the end of the charge... 3.3/3.6V == 92%+ converters are still a net benefit.
sbierwagen 9y ago
"This turnkey off the shelf product isn't all that hard to do yourself-- just buy the components, make your own PCBs, do some surface mount soldering, then write all your own software, including the wireless mesh network stack."
- derefr 9y ago
  I think the GP comment was intended in the sense that it's trivial for someone who does this for a living as an employee of a hardware product company to get this sort of power-draw out of bog-standard components; they weren't suggesting that it's an easy DIY project.
  - sbierwagen 9y ago
    Well sure, a hardware company isn't going to buy this. Check their pricing page. http://www.thingsquare.com/start/ http://www.thingsquare.com/start/ This is the Arduino business model-- easy introductory hardware for beginners. An actual hardware company wouldn't buy these for the same reason a router company wouldn't buy Cisco hardware and tape over the logos: there wouldn't be any margin. I would characterize GGP's argument as more that this isn't unprecedented, and again, sure. Lithium cell-powered electronics have been around for decades, adding wireless isn't new. The point is that thingsquare is supposed to be easy. You buy their kit and press a button. You don't need to buy individual parts, or do assembly, or write glue code, or know what I2C is. This is a common disease of the engineer's mind. "Why does anybody buy a car new? Just buy one used, and replace parts yourself when they break! Heck, why buy parts, when they're just metal and electronics? It should be easy enough to do your own aluminum casting, and wind your own electric motors." "You fool, you buy aluminum? Bauxite is everywhere! Just smelt it yourself, it's not hard." Etc etc.
    - Hasz 9y ago
      I wasn't trying to suggest breaking out the sputtering chamber, but anyone with a decent background in physics and basic algebra could learn and build something similar. My only argument for doing so is that everything is now extendable, whereas a "thingsquare' locks you into some particular engineer's design decisions that made sense then, but won't make sense for every use case now. Arduino sits right in the sweet spot of "easy to get off the ground" and extendable enough to use for all kinds of things", and that's largely why it is successful as a platform. This product sits so far off into "easy to get off the ground" territory that it misses too many use cases. A board like this could be spun up for $25, shipping, parts, software, all in. I would be amazed (and very interested) if you could get an aluminum smelter up and running for $20.
cushychicken 9y ago
>you can get something as available and low cost as an ESP8266 ($1.72 in singles) down to ~.01mA to ~.005mA Source? I have never seen anyone get an ESP8266 down to 5 uA sleep current on its own. You'd need to get a really low-leakage external FET for power sequencing.
zitterbewegung 9y ago
They have passive WiFi systems that have no need for a battery: https://www.youtube.com/watch?v=AZ-tISX-7Cw https://www.youtube.com/watch?v=AZ-tISX-7Cw
- sbierwagen 9y ago
  Research prototypes exist, yes, but Jeeva Wireless has yet to ship any parts. Once they do, they're going to be very limited on range, power and # of devices on the same band.
DamonHD 9y ago
Our OpenTRV hardware (AVR ATMega328p) can easily do a year on a pair of AAs, sending one secure stats frame every 4 minutes, eg our REV2 design: https://github.com/opentrv/OpenTRV-Arduino-V0p2/tree/master/Arduino/hardware/REV2/20140224-r2643-V0p2-Arduino-REV2-4th-cut/V0p2_Main_PCB2 https://github.com/opentrv/OpenTRV-Arduino-V0p2/tree/master/... The processor is down to typically a couple of uA waking every couple of seconds to see what needs doing. See the log at the end of this as I was originally driving the power down: https://github.com/opentrv/OTRadioLink/blob/master/content/OTRadioLink/utility/OTV0P2BASE_PowerManagement.cpp https://github.com/opentrv/OTRadioLink/blob/master/content/O... Our target is in fact 2 years life, including driving the valve, off a pair of AA NiMH hybrids. Slightly longer term our aim is to get off batteries entirely: https://github.com/opentrv/OTWiki/wiki/Energy-Harvesting-Feasibility https://github.com/opentrv/OTWiki/wiki/Energy-Harvesting-Fea... which is why I spent Tuesday at this meeting: http://www.earth.org.uk/note-on-Energy-Harvesting-Dissemination-Event.html http://www.earth.org.uk/note-on-Energy-Harvesting-Disseminat...
solidr53 9y ago
Here is a really old blog about using NRF24 with 18 months on coin cell. https://maniacbug.wordpress.com/2011/10/19/sensor-node/ https://maniacbug.wordpress.com/2011/10/19/sensor-node/ I had a idea that i didnt follow through, but worked well (the code sucks, i know). https://github.com/birkir/sensornodes https://github.com/birkir/sensornodes
trelliscoded 9y ago
TI actually makes a specialized power regulator for their OMAP product line to do exactly that. It's this weird little part that includes the power regulating circuitry and some of the analog audio codec stuff for some reason.
cylinder 9y ago
May I hijack to ask if someone can hack together a cheap solution for this? My beloved dog will be flying in the cargo hold of an A380. I will be seated above in the passenger section. 15 hour flight to Australia. I have to drop him off in his kennel four hours before departure at the freight office at the airport. They will take him to the plane. After the flight, he will be picked up and driven about 10 miles away to a quarantine facility. I would like to build something to put inside the kennel which will allow me to track its location at the freight office and then confirm he's been brought on board. Then at landing, I want to track the kennel from plane to quarantine. Note this is in a different country as departure. I'm thinking of getting a used Nexus phone and a Project Fi SIM (so I can have data overseas too). However this will be rather clunky and I'd rather not put a bunch of batteries in his kennel for a flight. Any ideas??
- brokenmachine 9y ago
  Any airline experts here that can comment on if you're allowed to put DIY electronics with batteries in the cargo hold of a plane these days? Especially DIY stuff with radio transmitters (and probably lithium batteries)?
  - cylinder 9y ago
    from what I gather, can't put an external battery pack into cargo hold unless it's NiMH, NiCad. A cell phone would be fine, but issue would be that the phone battery would most likely die during the 15hr flight.

by Hasz 9y ago

YZF 9y ago

I built a system once based on a Microchip PIC running with a 32.768KHz crystal main clock. The CPU draws about 11uA when running in this mode. Imagine you can do something useful with only 32768 instructions/s vs the 1 billion you get a modern CPU ;)

DamonHD 9y ago
Our AVR based setup uses the 32768Hz clock to wake up every two seconds to then do as much as it needs to at 1MIPS - "race to idle". Almost exactly the performance (other than the better I/O and the multiply op) that I used to get out of a Z80A or a 6502 (eg BBC Micro).

dragontamer 9y ago

> A good low quintescent current buck boost regulator can squeze every last bit of power for your chip even when the battery is basically at 0 capacity (2.7V for Lion, .8V for Alkaline) and use very little power on it's own. While that's fundamentally true, buck/boost converters also have a level of inefficiency. Old crappy ones are 80% efficient... good ones are 90% efficient, the best may be 95% or even 98% efficient. "Squeezing out" the last few volts of a Lithium Ion or NiMH doesn't make much sense. There's probably less than 2% of power below 3V on a Lithium Ion, and less than 2% of power below 1.0V for a NiMH. So the 98% efficient Buck Converter ends up lowering your life, because there's so little power between 0.7V and 1.0V or so. If you can run a circuit without a converter, that would generally be superior. For example, an Arduino can run down to 1.8V. So a 2xAA battery or a 1x Lithium Ion can be run without a boost/buck converter, and really capture that last 2% or so of power (as opposed to losing 2% in the conversion process)

exmadscientist 9y ago
>If you can run a circuit without a converter, that would generally be superior. No, this will waste a lot of power in the high-supply-voltage region of the battery's discharge curve. There are three regimes to consider, for (say) the case of running 3.3V nominal parts off a 1S 3.7V Li-Ion cell. Other nominal supply and battery voltages are very similar, they just shift the locations of the regimes around a bit or introduce boost converters. Regime 1: Battery voltage above system voltage. Here you want a high-efficiency buck converter. This minimizes the current you draw from the battery: instead of drawing (say) 10mA at 3.7V, you draw 10mA × 3.3/3.7 × 0.98 ~ 8.7mA at 3.7V. A buck converter is generally superior to a buck-boost as the peak efficiency is higher, and for this scenario boost functionality will never be necessary. Regime 2: Battery voltage slightly above system voltage. In this regime the appropriate solution is a low-quiescent-current low-dropout linear regulator (aka LDO). This regime exists because of the finite efficiency of a switching regulator. With an imaginary 100% efficient switcher, you never need an LDO. The lower the draw on the system rail, the wider this regime gets. For micropower circuits (average draw in the single-digit microamps) one might always be here. For higher power draws (tens of milliamps), this regime might be too small to justify the added complexity of including an LDO and you just skip right over it. Regime 3: Battery voltage at or below nominal system rail voltage but above minimum. The best thing to do here is absolutely nothing: just run the system directly off the battery. This is possible with a regulator with a bypass FET. Once the regulator goes into dropout, it just turns on the bypass transistor and connects things directly (with a small R_ds(on) drop of course). A few regulators have these built in. Other regulators are efficient enough in dropout that they don't actually benefit much from the bypass transistor. This also assumes you're near the end of the battery discharge curve. If you aren't, then you're potentially heading into boost or buck-boost territory, which I'm not going to cover here. Deciding which of these three regimes are important enough to warrant the design time for optimizing is a key part of low-power circuit design.
- dragontamer 9y ago
  You make some solid points, it all depends on the battery I guess. As you've noted, a 3.7V Lithium Ion battery (which is 4.2V when fully charged) would waste a lot of both voltage and current (excess current typically runs with higher voltage) if feeding a battery directly. But for a 3.3V part, you really want to be running a LiFePO4 Cell, with nominal voltage of 3.2V. The chemistry itself provides you the maximum efficiency, as opposed to building devices to convert a 3.7V part to 3.3V. ---------- Compensating for the flaws of a slightly mismatched cell or battery is one approach. But I have my bets that selecting the proper battery to begin with is the optimal approach. In any case, I think I can agree with you that using a standard 3.7V (4.2V when fully charged) battery on a 3.3V circuit... it probably would be most efficient to use a pure Buck Converter. 3.3/4.2V == 78% converters would gain you energy early in the charge, while near the end of the charge... 3.3/3.6V == 92%+ converters are still a net benefit.

sbierwagen 9y ago

"This turnkey off the shelf product isn't all that hard to do yourself-- just buy the components, make your own PCBs, do some surface mount soldering, then write all your own software, including the wireless mesh network stack."

derefr 9y ago
I think the GP comment was intended in the sense that it's trivial for someone who does this for a living as an employee of a hardware product company to get this sort of power-draw out of bog-standard components; they weren't suggesting that it's an easy DIY project.
- sbierwagen 9y ago
  Well sure, a hardware company isn't going to buy this. Check their pricing page. http://www.thingsquare.com/start/ http://www.thingsquare.com/start/ This is the Arduino business model-- easy introductory hardware for beginners. An actual hardware company wouldn't buy these for the same reason a router company wouldn't buy Cisco hardware and tape over the logos: there wouldn't be any margin. I would characterize GGP's argument as more that this isn't unprecedented, and again, sure. Lithium cell-powered electronics have been around for decades, adding wireless isn't new. The point is that thingsquare is supposed to be easy. You buy their kit and press a button. You don't need to buy individual parts, or do assembly, or write glue code, or know what I2C is. This is a common disease of the engineer's mind. "Why does anybody buy a car new? Just buy one used, and replace parts yourself when they break! Heck, why buy parts, when they're just metal and electronics? It should be easy enough to do your own aluminum casting, and wind your own electric motors." "You fool, you buy aluminum? Bauxite is everywhere! Just smelt it yourself, it's not hard." Etc etc.
  - Hasz 9y ago
    I wasn't trying to suggest breaking out the sputtering chamber, but anyone with a decent background in physics and basic algebra could learn and build something similar. My only argument for doing so is that everything is now extendable, whereas a "thingsquare' locks you into some particular engineer's design decisions that made sense then, but won't make sense for every use case now. Arduino sits right in the sweet spot of "easy to get off the ground" and extendable enough to use for all kinds of things", and that's largely why it is successful as a platform. This product sits so far off into "easy to get off the ground" territory that it misses too many use cases. A board like this could be spun up for $25, shipping, parts, software, all in. I would be amazed (and very interested) if you could get an aluminum smelter up and running for $20.

cushychicken 9y ago

>you can get something as available and low cost as an ESP8266 ($1.72 in singles) down to ~.01mA to ~.005mA Source? I have never seen anyone get an ESP8266 down to 5 uA sleep current on its own. You'd need to get a really low-leakage external FET for power sequencing.

zitterbewegung 9y ago

They have passive WiFi systems that have no need for a battery: https://www.youtube.com/watch?v=AZ-tISX-7Cw https://www.youtube.com/watch?v=AZ-tISX-7Cw

sbierwagen 9y ago
Research prototypes exist, yes, but Jeeva Wireless has yet to ship any parts. Once they do, they're going to be very limited on range, power and # of devices on the same band.

DamonHD 9y ago

Our OpenTRV hardware (AVR ATMega328p) can easily do a year on a pair of AAs, sending one secure stats frame every 4 minutes, eg our REV2 design: https://github.com/opentrv/OpenTRV-Arduino-V0p2/tree/master/Arduino/hardware/REV2/20140224-r2643-V0p2-Arduino-REV2-4th-cut/V0p2_Main_PCB2 https://github.com/opentrv/OpenTRV-Arduino-V0p2/tree/master/... The processor is down to typically a couple of uA waking every couple of seconds to see what needs doing. See the log at the end of this as I was originally driving the power down: https://github.com/opentrv/OTRadioLink/blob/master/content/OTRadioLink/utility/OTV0P2BASE_PowerManagement.cpp https://github.com/opentrv/OTRadioLink/blob/master/content/O... Our target is in fact 2 years life, including driving the valve, off a pair of AA NiMH hybrids. Slightly longer term our aim is to get off batteries entirely: https://github.com/opentrv/OTWiki/wiki/Energy-Harvesting-Feasibility https://github.com/opentrv/OTWiki/wiki/Energy-Harvesting-Fea... which is why I spent Tuesday at this meeting: http://www.earth.org.uk/note-on-Energy-Harvesting-Dissemination-Event.html http://www.earth.org.uk/note-on-Energy-Harvesting-Disseminat...

solidr53 9y ago

Here is a really old blog about using NRF24 with 18 months on coin cell. https://maniacbug.wordpress.com/2011/10/19/sensor-node/ https://maniacbug.wordpress.com/2011/10/19/sensor-node/ I had a idea that i didnt follow through, but worked well (the code sucks, i know). https://github.com/birkir/sensornodes https://github.com/birkir/sensornodes

trelliscoded 9y ago

TI actually makes a specialized power regulator for their OMAP product line to do exactly that. It's this weird little part that includes the power regulating circuitry and some of the analog audio codec stuff for some reason.

cylinder 9y ago

May I hijack to ask if someone can hack together a cheap solution for this? My beloved dog will be flying in the cargo hold of an A380. I will be seated above in the passenger section. 15 hour flight to Australia. I have to drop him off in his kennel four hours before departure at the freight office at the airport. They will take him to the plane. After the flight, he will be picked up and driven about 10 miles away to a quarantine facility. I would like to build something to put inside the kennel which will allow me to track its location at the freight office and then confirm he's been brought on board. Then at landing, I want to track the kennel from plane to quarantine. Note this is in a different country as departure. I'm thinking of getting a used Nexus phone and a Project Fi SIM (so I can have data overseas too). However this will be rather clunky and I'd rather not put a bunch of batteries in his kennel for a flight. Any ideas??

brokenmachine 9y ago
Any airline experts here that can comment on if you're allowed to put DIY electronics with batteries in the cargo hold of a plane these days? Especially DIY stuff with radio transmitters (and probably lithium batteries)?
- cylinder 9y ago
  from what I gather, can't put an external battery pack into cargo hold unless it's NiMH, NiCad. A cell phone would be fine, but issue would be that the phone battery would most likely die during the 15hr flight.