Electronics lab electrical power

Here are some tips how to arrange electrical power distribution on a small electrical lab (for example home lab).

Grounded power outlet: The power that comes to your electrical lab should be grounded for your safety. Most everyone has 3-prong electrical outlets in their homes, with the third prong being called the “ground.”

Extension cords (with switches): You will have many mains powered lab equipment on your lab. Plug all you have to one extension cord because you don’t have enough mains outlets on your you need to have some way to get enough outlets. When you have all equipment plugged to one extension cord, you minimize the ground loop problems because you have essentially star grounded system on your table. When you have all equipment connected to one extension cord, you can easily turn everything on and off with one switch on your extension cord (or just pull the plug out) when you end doing your experiments.


Ground fault interrupter: Make sure that your mains power coming to you lab has a a ground fault interrupter for your safety. That ground fault interrupter could be on your mains panel, built into your outlet or a device that you plug between your outlet and your lab equipment. Ground Fault Protection of Equipment is a system designed to provide protection of equipment from line to ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted current.

Residual Current Devices (RCDs) and Earth Leakage Circuit Breakers (ELCBs) are terms used for circuit protection devices commonly used in Europe, Australia and other countries. They are considered personnel protection in some countries but not in the U.S.A. or Canada. Typically Earth Leakage Circuit Breakers (ELCBs) used in Europe detect 30 mA leakage current.

In USA for personal protection you should use Class A GFCI for personal protection. Class A GFCI is a device whose function is to provide personnel protection by de-energizing a circuit, or portion thereof when the fault current to ground exceeds 6 milliamps within a period of time established by the GFCI Standard (and the fault current to ground is less than 4 mA should not interrupt the circuit). Ground Fault Protection with higher current range (more than 6 mA) in USA is for equipment protection not personnel protection.

My advice is to aick a ground fault interrupter that matches the needs of you country. This means 5-6 mA Class A GFCI for USA and 30 mA or less for Europe (10 mA versions are available but harder to find).

Safety isolation transformer is a good thing to have if you need to service or build mains powered equipment. Electricity will flow through your body when you become part of the current’s path. A person can receive a shock by being in contact with:

  • Both wires of an electric circuit
  • One wire of an energized circuit and the ground
  • A metal part that accidentally becomes energized, for example, a break in its insulation.

Even low-voltage electrical shock injuries can manifest in the days or weeks following an event.

In electronics testing and servicing an isolation transformer is a 1:1 (under load) power transformer used for safety. With the transformer, as there is no conductive connection between transformer secondary and earth, there is no danger in touching a live part of the circuit while another part of the body is earthed.

Using PME (unbalanced) power with an isolating transformer: Bridging between either terminal and ground is safe because there is no circuit through which the current can flow.

Usually you do isolation for safety reasons, but sometimes you might need mains power isolation for ground loop solving, and the safety isolation transformer works for this as well.

Safety timer switch is useful for shutting down your soldering iron etc. after set time if you forgot it on. Set your timer to 30 minutes, 60 minutes to two hours what suits you. When you leave the room, you don’t need to worry that the soldering iron would be left on all and night (will make the tip bad quickly and is potential fire hazard). You can also put other equipment that could be dangerous when left on behind this timer. Select a simple timer that has a “restart” button so you can easily make the timer start from beginning (when you are working on table you just need to press it every now and then to have power all the time you need).

Those are some of the basic things you should have.


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  3. Tomi Engdahl says:

    The Essentials of AC Power Safety

    If you’re bringing ac power directly into your new product, then the implementation methods to get a safe device need to be carefully considered as part of the design. If you don’t, getting things wrong with ac power can lead to deadly devices, and smoke-filled outcomes.

    The multitude of devices now using low-voltage dc power provided from an external ac-dc converter allows many EEs to remain blissfully unaware of high-power safety considerations. Using external ac adapters allows designers to largely ignore many high-voltage product-safety requirements. Designing with power inlets under 25 V, where the “Extra Low Voltage” (ELV) concept is applicable, simplifies things a lot, putting safety issues largely in the hands of the designer of that ac adapter.

    Many older (especially prior to 1960) electrical products were inherently unsafe or could become deadly with a single fault failure. Metal enclosures (prior to the widespread use of plastics) and a lack of a ground safety made for a deadly combination. Thankfully, consumer electronic products have a fairly short life, so many of those devices are now obsolete.

    Most EEs deal with ELV devices that are subdivided into “Separated ELV” (no ground return path used) and “Protected ELV” (a ground earth safety is present). Recently, IEC 62368-1 (Safety Requirements for Audio/Video, Information & Communication Technology Equipment) has become the standard for ELV safety, and has more carefully defined ELV devices as the “ES-1 region” that limits both current and voltage. For ELV devices, safety requirements are very minimal, with some form of overcurrent protection and a non-conductive enclosure generally being sufficient.


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