5 ms·

Does anyone know how much power this would use while waiting for commands, considering it really needs to be running 24/7?

by dan1234 13y ago

simcop2387 13y ago
Looking at the hardware he's got there, 10-15 mW max.
notimetorelax 13y ago
Not much I'd think. It is based on a microcontroller [1] that runs on 50MHz frequency. If my calculations are right then maximum consumption for it is 0.0486 Watt. [1] http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K10_50&webpageId=132639102321170846DD8B&nodeId=01624698C9DE2DDD8B&fromPage=tax http://www.freescale.com/webapp/sps/site/prod_summary.jsp?co...
drostie 13y ago
Assuming that the FFTs handle independent slices of data (as I can't see why you'd go back to the time domain), the data throughput they're handling is 2048 * 15 bits * 80 Hz = 2.5 Mbps. That may sound like a lot, but it's not unprecedented and it does not require huge power consumption; think of a USB connection hub or perhaps an ethernet hub. Actually the thermodynamic requirements of that sort of computation are much much less than the practical requirements; at room temperature the minimum power to handle that bandwidth is only 3 × 10^-15 watts; the FFT doesn't need to add to that because the FFT is a reversible computation. We're a long way away from perfection in this sense.
Retric 13y ago
Not much, I have seen similar projects powered by leaching energy from radio waves.
swamp40 13y ago
It has a plug for a wallbrick, and I don't think the author optimized his hardware or code for ultra-low power - ie small batteries. (Running 80 FFT's every second isn't going to be great on batteries.) The Kinetis K10 he used WOULD BE an excellent processor choice for an ultra-low power design, though. You could have a low-power comparator monitor for noises and only wake the processor up when it heard something interesting. With some simple tricks like that, you could probably run for months on a couple AA batteries.
- stephencanon 13y ago
  > Running 80 FFT's every second isn't going to be great on batteries. Assume for the moment that floating-point were used instead of fixed-point: A 2048-element real-to-real FFT requires a bit less than 40Kflop, or 3.2Mflop/sec to get 80FFT/sec. Modern hardware is capable of > 1Gflop/joule, so the raw compute of 3.2Mflop/sec actually takes something on the order of 3.2mw. Of course, the computation is being done in q15 instead of float, which (in theory) should require something on the order of 1/2 the energy. On the other hand, the processor can’t just do FFTs. It’s spending energy going in and out of lower-power states, running other code, etc, etc, and I don’t have any data for the energy usage of the M4 specifically, to say nothing of the other components on the board. In principle though, the energy actually consumed by performing the FFTs should be pretty minimal; most of it will be going to everything else unless the hardware and software are both very carefully designed for efficiency.

Does anyone know how much power this would use while waiting for commands, considering it really needs to be running 24/7?

by dan1234 13y ago

Does anyone know how much power this would use while waiting for commands, considering it really needs to be running 24/7?

simcop2387 13y ago

Looking at the hardware he's got there, 10-15 mW max.

notimetorelax 13y ago

Not much I'd think. It is based on a microcontroller [1] that runs on 50MHz frequency. If my calculations are right then maximum consumption for it is 0.0486 Watt. [1] http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=K10_50&webpageId=132639102321170846DD8B&nodeId=01624698C9DE2DDD8B&fromPage=tax http://www.freescale.com/webapp/sps/site/prod_summary.jsp?co...

drostie 13y ago

Assuming that the FFTs handle independent slices of data (as I can't see why you'd go back to the time domain), the data throughput they're handling is 2048 * 15 bits * 80 Hz = 2.5 Mbps. That may sound like a lot, but it's not unprecedented and it does not require huge power consumption; think of a USB connection hub or perhaps an ethernet hub. Actually the thermodynamic requirements of that sort of computation are much much less than the practical requirements; at room temperature the minimum power to handle that bandwidth is only 3 × 10^-15 watts; the FFT doesn't need to add to that because the FFT is a reversible computation. We're a long way away from perfection in this sense.

Retric 13y ago

Not much, I have seen similar projects powered by leaching energy from radio waves.

swamp40 13y ago

It has a plug for a wallbrick, and I don't think the author optimized his hardware or code for ultra-low power - ie small batteries. (Running 80 FFT's every second isn't going to be great on batteries.) The Kinetis K10 he used WOULD BE an excellent processor choice for an ultra-low power design, though. You could have a low-power comparator monitor for noises and only wake the processor up when it heard something interesting. With some simple tricks like that, you could probably run for months on a couple AA batteries.

stephencanon 13y ago
> Running 80 FFT's every second isn't going to be great on batteries. Assume for the moment that floating-point were used instead of fixed-point: A 2048-element real-to-real FFT requires a bit less than 40Kflop, or 3.2Mflop/sec to get 80FFT/sec. Modern hardware is capable of > 1Gflop/joule, so the raw compute of 3.2Mflop/sec actually takes something on the order of 3.2mw. Of course, the computation is being done in q15 instead of float, which (in theory) should require something on the order of 1/2 the energy. On the other hand, the processor can’t just do FFTs. It’s spending energy going in and out of lower-power states, running other code, etc, etc, and I don’t have any data for the energy usage of the M4 specifically, to say nothing of the other components on the board. In principle though, the energy actually consumed by performing the FFTs should be pretty minimal; most of it will be going to everything else unless the hardware and software are both very carefully designed for efficiency.