New Google Classroom update makes it harder to cheat on quizzes | Lrd12 Overload Relay

Let’s see, you’ve pooh-poohed my 12kV hit and [Scott_Tx]’s 90V one, so I guess 440V three-phase (was it the high leg, or one of the low legs?) is the sweet spot for you. Lucky for our edification that the boots did indeed save you. I knew someone who was quite thoroughly taken out by 220V in a basement while wearing (presumably damp) leather sandals.

I’m wondering why nobody is simply rectifying a 120vac input for dc wiring the secondary coil? It means you don’t have to swap the coil location or use a dc power supply. I have a trans with a secondary resistance of 82ohms. Putting 120vdc through it would be about 175watts (assuming I do a good job of determining wire size and 1.46amps is ok)

The one negative that most stands out in my mind for the Sony A33 actually has the least to do with its abilities as a camera. The first thing that comes to mind when thinking about shooting with it isn’t whether I’ll be able to bring back the shots I want with it, but rather whether the battery will last long enough to do so. We have no doubt that the Sony A33 will meet the fairly generous shot-life numbers quoted under the CIPA specs (340 shots with the LCD, 270 with the EVF), but in actual practice, with the camera rattling off hundreds of shots in amazingly short order, what most struck me was just how fast I seemed to run out of battery life. It’s quite easy to run through a full battery in just a couple of hours of active shooting, and two batteries should be considered a minimum for a day of serious shooting.

The melted solder was probably a secondary failure. When SSRs fail they often turn into heaters as his did and the heat from the base plate itself melted the solder before incinerating the plastic housing.

It’s a little unusual to see an effective pixel resolution for an electronic viewfinder, but we believe the reason effective resolution is some 20% lower than the EVF’s actual pixel count is that Sony has selected an LCD with approximately a 4:3 aspect ratio, but are only using the central 16:9 aspect ratio swathe of the display. This is likely done both to match the rear-panel LCD display aspect, and also because even with this crop, the EVF already has a generous 1.1x magnification — much higher than that of most APS-C DSLRs — and a somewhat tight eyepoint of 19mm from the viewfinder eyepiece (18mm from the eyepiece frame). Were the whole display used, the eyepoint would fall uncomfortably low — it’s already just a little tight for eyeglass wearers. Thankfully, it includes an unusually wide -4 to +4 diopter adjustment range, better mitigating the tight eyepoint for those with eyeglass prescriptions inside this range. It also has a 100% field of view, and three step automatic / manual brightness control.

Besides the overexposure bias, I also found the A33′s metering system was prone to more variation than I’m accustomed to seeing in an SLR. The few times I had it locked down on a tripod, shot to shot exposure seemed pretty consistent, but on several occasions shooting handheld, I found significant variation between successive shots, apparently resulting from fairly minor changes in framing. I’d of course expect exposure to vary to follow changes in the scene, but the amount of variation I saw between very similar shots taken with the A33 was unusual.

While we didn’t encounter any exposure accuracy issues in our lab tests, I had a little trouble with the Sony A33 and A55′s exposure system in the field. Under bright sunlight, I was generally shooting with -0.3 EV of exposure compensation dialed in. Looking at my photos on the computer later, it seemed that many of them really could have used -0.7 EV. The overexposure bias seemed fairly universal under bright lighting, regardless of whether the subject itself was low- or high-key. Shots under lower lighting didn’t seem to have the same issue, though.

• A 24-V dc circuit • Current waveform for surge is 8 × 20 μs; voltage waveform is 1.2 × 50 μs (these are typical industry-standard waveforms) • Peak current during the surge = 1000 A • The MOV must be able to survive 40 surges • Other circuit components (control IC, etc.) must be rated to withstand 300 V maximum

not exactly mains but when i was a kid i enjoyed playing with photoflash caps and at one point had one fully charged to about 330V and discovered the negative post to the AA battery was also connected to the cap and put the entire shot up one arm, across my damn heart and out the other arm, my whole body locked up for only about a second (maybe 2) and i think i fell over (like people in taser videos but i was sitting). it sure shook me up and im glad it was only a small cap

Last year, Sonos announced plans to add support for Apple’s AirPlay 2 to its speakers. AirPlay 2 is a significant feature in that it will allow iPhone and iPad users to send audio from basically any app to Sonos’ great-sounding speakers. And you’ll be able to tell Siri to play tracks from Apple Music on Sonos systems; the Sonos One smart speaker doesn’t currently let you launch music from Apple’s service with voice commands, but AirPlay 2 is a roundabout way of introducing that convenience. The difference is that you’ll be doing the talking to your phone instead of the Sonos.

I did find the small body and grip a little problematic when shooting with a long or heavy lens, though: I spent quite a bit of time with the excellent Sony 70-200mm f/2.8 mounted on the camera, and did experience some wrist fatigue by the end of the day. Since the camera is capable of very fast live autofocus during video recording, I often found myself wanting to zoom during the recording, something that would be anathema on a conventional video-capable SLR. Doing so required that I carry more of the weight of the lens/camera assembly on my right hand, so my left could operate the zoom ring more smoothly. The result was a lot of weight for my right wrist to carry, and the small grip made it more difficult than otherwise. When shooting normally with smaller lenses, though, I never found the grip uncomfortable.

This dead-screen issue was so pronounced that I found myself dropping back to 6 fps rather than 10 on the A55, and shooting in short bursts at what I thought (hoped?) were the decisive moments. More than with many cameras with lesser speed or buffer capacity, I found myself shooting to manage the camera’s buffer, more than simply focusing on the subject and the action taking place. It would have been a lot less aggravating if I could have at least seen thumbnails of just-captured shots immediately after taking them.