The shocking power supplies

Transformerless power supplies are showing up a lot, especially in inexpensive products where the cost of a transformer would add significantly to the BOM. But transformerless power supplies are a double-edged sword. You can get yourself easily electrocuted if you don’t understand them and take proper safety precautions. Poking around in a transformerless-powered device can

Differential oscilloscope probes

By far the most used oscilloscope probes are the passive 10:1 attenuation probe. Next step in probe categories are active probes. Active probes succeed in practically eliminating reactive loading of the circuit under investigation by means of a small solid-state amplifier in the probe body adjacent to the tip. There are two main classes of

Fire and Smoke Alarm Systems

Smoke and fire alarms can save lives. The occupant and the housing company are responsible for the acquisition and maintenance of smoke alarms in Finland. It is the duty of the occupant of the flat, i.e. the resident, to buy a smoke alarm and to keep it in good working order. Smoke alarms must meet

European mains power

This post is about European mains power. Electricity in EU countries conforms to the European standard, coming out of the wall socket at 230 volts alternating at 50 cycles per second. While the voltage and frequency are fixed, the mains connectors and wiring practices can vary between different countries in Europe. One thing to note

Coiled mains cable heating and inductance

What is the problem of using a coiled extension cord? When the power cable passes a considerable load current, it will definitely heat up noticeably. As the load current increases, the temperature of the cable surface will be higher. A cable loaded near it’s rated current can feel that it is warm to the touch,

USB C vs US outlet

Have you noticed that the size of the USB C plug is such that it is possible to insert it to an US outlet. The USB C connector just fits to the wider prong hole in the US connector (slightly too big for thinner prong hole). It is even possible to make the USB connector

US electrical power dangers

Any form of energy, when not properly controlled or harnessed, can result in serious danger to those who use it. Electricity at any voltage can be dangerous and should always be approached with caution. Direct Dangers of Electricity include a variety of hazards that include Electric Shock, Physical Burns, Neurological Damage and Ventricular fibrillation resulting

Measure mains voltage with oscilloscope

Sometimes there are needs to measure mains voltages with oscilloscope. You must be very careful when measuring voltages on the mains with any measurement instrument. The mains voltages are absolutely deadly. Measuring mains voltages with multimeter can be dangerous. Trying to do the measurement of mains voltage with oscilloscope is potentially more dangerous, because typically

Friday Fun: Speaker to mains power disaster adapters

This is an old recipe for a disaster from 1990′s. This converts NEMA mains connector to 1/4″ plug. Offers a nice set of possibilities for unexpected show disasters like electrocution or over kilowatt of constant 60 Hz bass line without an amplifier. It seems that some company really tried yo push this potentially extremely dangerous

Under the 110 kV power line

Radiation is the emission or sending out of energy from any source. Generating, transmitting, distributing, and using electricity all expose people to ELF radiation. Power lines, household wiring, and any device that uses electricity can generate ELF radiation. How much electromagnetic radiation you are exposed to depends on the strength of the electromagnetic field, your