Inside A Circuit Breaker With MikesElectricStuff | 19mm Momentary Push Button

The stakes are much higher when you’re connecting your project to the house mains, though, as [Mattias Wandel] recently learned when the solid-state relay controlling his water heater failed, with nearly tragic results. With aplomb that defies the fact that he just discovered that he nearly burned his house down, [Mattias] tours the scene of the crime and delivers a postmortem of the victim, a Fotek SSR-25DA. It appears that he mounted it well and gave it a decent heatsink, but the thing immolated itself just the same. The only remnant of the relay’s PCB left intact was the triac mounted to the rear plate. [Mattias] suspects the PCB traces heated up when he returned from vacation and the water heater it was controlling came on; with a tank full of cold water, both elements were needed and enough current was drawn to melt the solder build-up on the high-voltage traces. With the solder gone, the traces cooked off, and the rest is history. It’s a scary scenario that’s worth looking at if you’ve got any SSRs controlling loads anywhere near their rated limit.

Seriously, it looks rather sparse inside, does it not? Perhaps some of you more electrically inclined/engineering types can chime in and let us know if $750 seems reasonable now that we know what’s inside?

公司自成立以来始终坚持以纯电子商务模式运营、缩减中间环节、为客户在第一时间提供优质的产品及满意的服务、为您的生产以及采购工作提供‘安全 快捷 方便’公司拥有完善的物流供应系统、现已与众多国外知名品牌生产厂商建立了良好的合作关系。

You are right, FR-4 has a glass transition temperature of around 120°C, so if you heat up your traces above that, and take into account the mechanical stress from expanding copper traces, delamination is something waiting to happen sooner or later (especially if you design corners in your traces). Add to that the fact that you usually don’t measure the temperature directly on the traces to regulate input power, you could go way beyond 120°C in your copper traces. I don’t think a lot of DIY guys actually know that there would be high-TG materials on the market better suited for PCB based heater applications…

Also I have seen opto-couples where the pins have been spayed out to gain an extra 0.1″ between the rows of pins.

Japan is odd for another reason. The two “halves” of the country are on different frequencies. I believe the West is at 50 Hz and the East and North is 60 Hz. They have a collection of DC interconnects in the middle of the country to facilitate power sharing across this otherwise intransigent gap. Since the shutdown of Fukushima, those interconnects have been under quite a bit of strain, but that’s a whole ‘nother story.

It’s not voltage that kills you, it is current acoss the chest ie heart. Hence so called medical coils of the 19th century and high frequency tesla coils and drawing arcs to your skin that do not kill you. I knew a TV engineer that tested high voltage triplers for CRT TV’s by drawing an arc to his finger. The path is the issue and the current available.

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.

By the way, the plug-in Kia Niro appears very similar to the now-discontinued plug-in Ford C-Max. I wish Kia better success with their product offering than Ford had with theirs.

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But saws only bite in one direction, which is why the working stroke has to be in phase. Doesn’t matter which way the dudes are facing, they have to apply force to it in the same direction at the same time, and the other stroke is just returning back to starting point.

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