Didier Stevens

Thursday 22 September 2022

Quickpost: Tuning The Electric Energy Consumption Of My TV

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

TLDR: reducing the sound volume level of our TV has no (significant) impact on its electric energy consumption, but reducing the back-lighting does.

Here in Belgium, mainstream media is full of news with tips to reduce energy consumption.

Some good tips, some bad tips … That’s mainstream media for you 🙂

Recently, there was an article with the following tip: “reduce the sound volume level of your TV to save energy” … (I’m not linking to this article).

It is true that a speaker (and the audio amplifier) requires power. And that there is a positive correlation between electric energy consumption and sound volume level. Large speakers can draw quite some amps…

But I was a little doubtful that lowering the sound volume level of our TV with a view clicks, would have a significant/measurable impact. Because some time ago, I already made measurements, and our TV drew 120 Watt maximum. So I did not expect a big impact.

Anyways, one has to make measurements to know if there is a (significant) impact or not.

We have a 55 inch QLED Samsung TV from 2018. The test protocol I worked out is the following: start to play a long movie (LoTR) and measure the electric energy consumption during one hour exactly (with a GW Instek GPM-8310 digital power meter). Don’t touch the TV or remote while testing is going on, and make sure that no dynamic settings are enabled that can influence the electric energy consumption (like ambient light based brightness control).

I measured at 3 sound volume levels: 20, 19 and muted. And I did this twice.

Here are the results:

Sound levelElectric energy consumption (Wh)
20117,74
19117,74
0 (muted)117,66

For our TV, there’s no difference between a sound volume level of 20 and 19.

And by completely muting the TV, we save 0,08 Watts. That’s a very small amount. To put that in perspective, we would have to watch 125 hours of muted TV to power a 10 Watt LED light-bulb for 1 hour.

Of course, that’s for our TV. If you have a TV with a powerful soundbar and extra speakers, your measurements will be totally different.

While going through all the settings of our TV, there is one thing I noticed: the back-lighting setting was set to its maximum (20).

I reduced the back-lighting to 10 and measured again. That made a significant change: 77,666 Wh in stead of 117,74 Wh (both at sound volume level 20, our usual setting). That’s a 34% reduction in electric energy consumption. That’s a significant reduction, but …, don’t forget that the back-lighting setting happened to be at its maximum.

We will keep it like that for the moment, and see if we still enjoy watching TV.


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Wednesday 14 September 2022

Quickpost: An Inefficient Powerbank

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

I tested a small powerbank that I have, and it’s very inefficient.

It takes 10.07 Wh to charge:

And it delivers 5.95 Wh when I discharge it (5V at 0.250 mA).

So I only got 59% back of the energy I put in.

This powerbank is quite old, it might have become so inefficient over the years. Google searches tell me that you should get at least 85% efficiency.

Although this powerbank still works fine, and his very handy to me because of its small form factor, I’ll see if I can get a more efficient one with a similar form factor.


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Tuesday 13 September 2022

Quickpost: “Exploding Multimeter”

Filed under: Hardware,Quickpost — Didier Stevens @ 12:22

I made a mistake and destroyed my old multimeter.

It’s a 30+ year old multimeter, and it had become very dirty because of all the dust it collected while I used it in a home renovation project, years ago. It was still functional, so I used it for years like that.

But recently, after discovering YouTube “restoration videos”, I got the idea to open it up and clean it.

The result was very good. Until I used it the first time to measure a 230V cable. Then there was a big flash inside the casing, and all the lights went out.

This is how it looks now (notice the black soot marks on the orange plastic):

And the burned diodes:

What went wrong? The meter also has aluminum foil to shield the electronics:

And I was not careful enough when I put it back, and it shorted the 2 connectors:


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Friday 2 September 2022

Quickpost: Standby Power Consumption Of My Bosch 18V Chargers

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

I have 2 Bosch 18V “power for all” chargers. A normal charger (AL 1830 CV) and a fast charger (AL 1880 CV).

Measuring the power consumption of these 2 chargers in standby mode (plugged into a 230V outlet, but no battery connected) with a GPM-8310 powermeter, I obtained the following results:

AL 1830 CV: 476,33 mW

AL 1880 CV: 344,39 mW


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Sunday 31 July 2022

Quickpost: iPad Pro Charging – Power Consumption

Filed under: Hardware,Quickpost — Didier Stevens @ 9:01

I charged an iPad Pro (12.9 Inch) and measured the power consumption (at 120V and 230V). According to the specs, this iPad has a battery with a capacity of 40.88 Wh.

Procedure: when the iPad Pro turns itself of because of a low battery, I started to charge the iPad with an Apple A2347 USB C charger and measured the AC power consumption of this charger. It consumes around 21 Watt, this value starts to diminish when the battery approaches full charge. When at 100%, the charger will still deliver power, slowly decreasing to 3 Watts, and then it stops delivering power for charging. At that point, I stop the power consumption measurement.

I did not use the iPad while charging.

This measurement was done twice: at 120V 60Hz and 230V 50Hz (using an AC power supply).

ACWhDuration
120V 60Hz57.17103:07:48
230V 50Hz57.55903:09:16

There’s not much difference between the two measurements, but what I’ll certainly take away from this test, is that it takes around 57 Wh of AC power to charge a 40.88 Wh battery!

Update: when I did these tests, my iPad Pro had around 84 charging cycles.


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Monday 25 July 2022

Quickpost: Standby Power Consumption Of My USB Chargers (120V vs 230V)

Filed under: Hardware,Quickpost — Didier Stevens @ 16:11

I did not explicitly specify in my post “Quickpost: Standby Power Consumption Of My USB Chargers” that I did my tests here in Flanders, Belgium and thus that the mains electricity is 230V 50Hz.

I wondered what the results would be in other parts of the world, like the USA. To answer this question, I redid my tests with the USB chargers powered by an AC power supply that delivers electricity at 120V and 60Hz.

The devices I tested are:

  1. Apple A1357
  2. Apple A2347
  3. Anker A2053

The no-brand USB charger was not tested, as the input specs specify 220V – 240V.

I connected each one to the AC power supply (120V 60Hz) and used a powermeter (GPM 8310, resolution 0,1 µW) to measure the standby power consumption over 24 hours.

This is the result:

Model24 hours (Wh)1 hour (Wh)1 year (Wh)
Apple A13572,04250,0851745,5125
Apple A23470,54730,0228199,7718
Anker A20533,75270,15641369,7360

24 hours is the measured data, the “1 hour” and “1 year” columns are calculated based on the 24 hours data.

And here is the summary for 120V and 230V:

Model1 hour (Wh, 120V 60Hz)1 hour (Wh, 230V 50Hz)
Apple A13570,08510,1202
Apple A23470,02280,0530
Anker A20530,15640,2114

It’s clear that my USB chargers consume less standby power at 120V 60Hz than at 230V 50Hz.


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Tuesday 12 July 2022

Quickpost: Standby Power Consumption Of My USB Chargers

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

I did some tests with my USB chargers: how much power do they consume when plugged into a power socket without charging any device (standby)?

The devices I tested are:

  1. Apple A1357
  2. Apple A2347
  3. Anker A2053
  4. No-brand: Chacon EMP604USB

I connected each one to a powermeter and let it measure the standby power consumption for 24 hours.

This is the result:

Model24 hours (Wh)1 hour (Wh)1 year (Wh)
Apple A13572,88470,12021052,9155
Apple A23471,27230,0530464,3895
Anker A20535,07340,21141851,7910
No-brand: Chacon EMP604USB5,64730,23532061,2645

24 hours is the measured data, the “1 hour” and “1 year” columns are calculated based on the 24 hours data.

The no-brand USB charger consumes the most: around 2 kWh per year, which is still less than a switched off Philips Hue lamp.

Using the same cost as for the Philips Hue lamp, that no-brand charger costs me around €1 if I would leave it plugged in for a whole year without letting it charge anything.


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Sunday 3 April 2022

Power Consumption Of A Philips Hue lamp In Off State

Filed under: Hardware,technology — Didier Stevens @ 17:25

A Philips Hue lamp is a LED lamp that can be controlled wirelessly. It always draws power for its control circuitry, also when the LED is turned off.

I wondered how much power it consumes in the off state. Doing some research, I found a couple of forums where people asked the same question, and getting answers that is was very little, varying from 0,01 A to 0,02 A.

I got similar results for the current when I measured this:

Figure 1: Switched off Philips Hue drawing 0,0175 A (varying easily with 25%)

But I wanted a more precise answer, and not only the current. I am more interested in the power (Watt) consumption. As our domestic electricity meters measure real power over a period of time.

Thus I measured the power consumption of a 1100 Lumen color Philips Hue lamp that I had switched of via the smartphone app over a period of 10 days.

Figure 2: Test setup

And these are the numbers I got after 10 days:

Figure 3: After 10 days of operation in the off state

0,07756 kWh over a period of 10 days, that’s 0,32316 W. Notice that the display indicates KWh, but that should be kWh (lowercase k for kilo).

Extrapolating to a whole year, that’s 2,831 kWh. Which in my case, correspond to a cost of €1,50 (roughly speaking) per lamp per year.

With online numbers claiming the current to be between 0,01 A and 0,02 A, at first I expected the power consumption to be higher. But the power factor is quite low (around 0,10), explaining a lower power consumption.

Update 2022/09/01: I redid the test for one day (24 hours) using a more precise powermeter (GPM 8310) and measured 8,9188 Wh for 24 hours, or 0,3713 W.

Monday 2 November 2020

Quickpost: Portable Power

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

I did some tests to generate electricity (230V AC) with a portable 12V battery (well, it’s 10 Kg).

I have a 12V VRLA battery with a capacity of 35,000 mAh. That’s 12V times 35 Ah = 420 Wh. Or equivalent to a 116,667 mAh (420,000 mWh / 3.6 V) USB powerbank.

Charging this 12V battery with a 12V battery charger connected to a 230V power outlet takes almost 7 hours (6:57) and requires 0.49 kWh. That is measured with a plug-in electricity meter with a .00 kWh precision. And I’m working under the assumption that the power requirement of the electricity meter is so small that it can be neglected.

Then I use this fully charged battery to power a 230V 150W halogen lamp via a 12V DC to 230V AC power inverter (modified sine wave).

It runs for 2 hours (2 tests: 2:01 and 2:03) and consumes 0.30 kWh.

Of the 0.49 kWh energy I put into my system, I get 0.30 kWh out of the system. That’s 61%, or a bit better than half of the energy I put into the system.

The main phases where I expect the energy losses are occurring, is in 230V AC to 12V DC conversion and electrical to chemical energy conversion (charging); and chemical to electrical conversion and 12V DC to 230V AC conversion (discharging). I believe the highest energy loss to occur in the power inverter.

And with energy loss, I mean energy that is converted into forms that are not directly useful to me, like heat.

Remark that the halogen lamp test stopped after 2 hours, because the power inverter stopped converting. The battery voltage was 11.5 V then, and I could still draw 1 A at 11.5 V for an hour (I stopped that test after 1 hour).

Next I’m going to try out a 12V to 5V adapter and power some USB devices.

Monday 28 September 2020

Quickpost: USB Passive Load

Filed under: Hardware,Quickpost — Didier Stevens @ 0:00

I just received a USB passive load. It’s basically 2 resistors connected to the USB power wires in parallel, each with a switch in series:

It can draw approximately 1, 2 or 3 amps (depending on switch positions) from a 5 volt USB source.

The resistors can dissipate 10 Watts, and will become very hot.

The resistor for 1 amp (4,7 ohms, tolerance 5%) maxed-out my FLIR One thermal camera (> 150 °C), but I could measure around 220°C (that’s close to 451°F) with another thermal imaging camera.

The second resistor (2 amps: 2,2 ohms, tolerance 5%) maxed-out that other thermal camera too: this one got hotter than 280°C.

I’m referring to 451°F, because presumably, that’s the temperature to ignite paper. Something I’ll have to test out in safe conditions.

I also measured the resistors, and they are well within tolerance:

Here is a short thermal imaging video of the first resistor heating up:


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