Select the Right Varistors for Overvoltage Circuit Protection | 25 Amp Circuit Breaker

Yes you are correct, I was remembering from just people recommending power USB power supplies, but looking at the latest data, it seems that current is always less than 215mA. That chip looks good.

Operating temperatures are another consideration. Assume the ambient operating temperature for this application ranged from 0 to +70°C. This would be within the MOV’s -40 to +85°C rating, and there would be no requirement for derating of surge current or energy across this temperature range.Taking high-line tolerance into account, a 275-V ac-rated MOV may be chosen for this example. Using a 2-hp, single-phase, medium-sized motor, the MOV’s required surge-current rating would be determined by the peak current induced at the motor supply. Assuming a service location for the motor and a line impedance of 2 Ω, it was determined that a 3-kA lightning surge was possible. In this case, one datasheet indicates a maximum clamping voltage of 3 kA at 900 V, which is below the 918-V suggested stator-winding withstand capability. If the motor’s operational life were estimated to be 20 years and specified as being able to withstand 80 lightning transients during term of service, the datasheet pulse-rating curves would verify a rating of 100+ surges.

In San Diego (where I live) residential electricty rates start at 15 cents per kWh. Lower electric rates are available if you charge the car at night, but you have to agree to pay a crazy-high rate of 53 cents per kWh at other times. That wouldn’t work for me, but YMMV.

I do not disagree that this is not the best way to do it. I have only used it for temporary installation, and only when I can frequently inspect everything involved for signs of elevated temperature. At home, I had a licensed electrician install a NEMA 6-50 and a 40A circuit (which we de-rate to 32A for EVSE service) in our garage for our car charging needs.

Adjusting settings via the Fn menu is generally a good experience. A very nice touch is that you can use the up/down/left/right directions of the 4-way controller to move the cursor between Fn menu items, and then use the front control dial to adjust the settings. This is nice because it lets you quickly make a number of Fn settings changes in succession, without having to drop down a menu level for each, or being forced out of the Fn menu between choices. The few exceptions to this are those items with a second level of control, such as multi-shot ISO or the tweak adjustments for white balance settings. In those cases, you need to explicitly select the menu item via the OK button, and then use the left/right keys to make the needed adjustment. The only exit at that point is to hit the OK button again, which unfortunately drops you out of the Fn menu entirely.

I recently had a home inspector ask me how hot is too hot when it comes to circuit breakers and switches. Many home inspectors, including all of the inspectors here at Structure Tech, use infrared cameras during home inspections. These cameras can’t see through walls, but can often alert us to problems with a house that can’t be seen with the naked eye.

As far as litigation goes? I know enough about Chinese law to know that it’s really up to Fotek and whether Fotek applied for trademarks in China or not, and whether they did the rest of the intellectual property legwork in China (which is really tricky because China doesn’t use common law like Western countries do, so it’s a harder system to navigate). If they did, then yea, the counterfeiters could probably be sued although it’s a whack-a-mole game, the counterfeiters come up faster than they can be whacked down. But if Fotek didn’t go through the China IP process to protect their brand, then the counterfeiters may have actually applied for the trademark themselves in China, gotten the right to use the name, took the likeness and everything, legally (at least in China). Best Fotek could do at that point is try to keep them from being imported into the USA (similar to the Sparkfun fluke-colored DMM’s a few years back) but again that’s a whack-a-mole game that they wouldn’t win.

Storage and battery. The Sony Alpha A33 offers a single flash memory card slot, but it’s compatible with two memory card standards, each with various permutations. The first is Memory Stick PRO Duo / PRO-HG Duo, Sony’s own proprietary media format. As an alternative for those who prefer more standardized media, Sony also supports three flavors of Secure Digital cards — standard SD, SDHC, and SDXC.

Grip comfort/security is greatly aided by the deeply sculpted thumbrest on the camera’s back. Combined with the textured rubber used over the whole right half of the body, it provides a very secure gripping point for my thumb, and does a lot to make up for the small size of the front grip. The rubber coating also contributes to a feel of solid build quality, by damping the body vibrations that often make small and light cameras feel tinny or cheap.

Yup, switched off but still plugged in, that way the case is still earthed. Assuming a sensible 3-pin plug, or whatever the hell they do in places with just 2.

The one thing some users might find distracting about the Sony A33′s EVF is the RGB "rainbows" you can see when either your eye, the subject, or the camera is moving rapidly. Each pixel of the display shows its red, green, and blue information sequentially, so if the viewfinder image is moving rapidly relative to your eye, you’ll see red, green, and blue ghosts or trails around bright objects. I didn’t notice this at all until someone pointed it out to me, but after they did, it became unreasonably annoying for a while. After a couple of days of shooting with the camera, though, I again became largely unaware of it and now have to deliberately look for it to be aware of the effect.

Yes you can use those high voltage safely, BUT your typical DIY people don’t even bother to read or understand datasheets. These people need the proper training, but aren’t likely to be bother to go beyond the typical monkey see monkey do watching youtube and think they know it all. I have seen enough of bad layouts of the average projects that doesn’t even understand that the creepage space between the primary and secondary side of an optoisolator aren’t meant to be for routing!