Questions tagged [low-voltage]

Low voltage refers to voltages in a range from 1) 50–1000 Volts AC [Vᵣₘₛ, rms…root mean square] and 2) 120–1500 Volts DC according to standard IEC 60038 of the International Electrotechnical Commission.

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Replacing button switching 1.3V with microcontroller

First, sorry, I am a total hardware beginner (and 20 years since I had some electronics classes on the uni). I want to replace a mechanical switch (well two switches…) with something driven by a 3.3v ...
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How can I select a suitable cable with these characteristics: 690 V, 550 A, 1 km long, AC three phase underwater cable

How can I select a suitable cable with this characteristics: The cable is connected at one end to a 690 V power generator that is between 6 and 40 meter below the surface of a big river and converts ...
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55 views

Two battery control

I have two Li-ion batteries in my system. (7.4 V 12000 mAh and 7.4 V 2200 mAh; also they have BMS). The larger one of the batteries can be easily removed and installed from my system, so I can charge ...
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High Voltage & Low Voltage PCB Design

I am trying to make a PCB that acts as a "Raspberry PI HAT" and allows me to connect the raspberry to different sensors. Specifically, I'm having difficulties in defining the design rules ...
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10 votes
3 answers
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Is it okay to charge a deeply discharged Li ion cell below 1V?

I accidentally discharge my lithium cell to 0.45V. Is is okay if I try to revive it by charging with 10mA of current till it reaches 2.5V? cell capacity is 4000mAh.
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Blocking oscillator, Slayer exciter drawing too much power

I am trying to build one of these using an air-core coil. I got it oscillating but have to cut power off after 4 seconds as it starts to heat up (can't hold it with my fingers.) The transistor is not ...
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-3 votes
1 answer
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12V-only (and no 110V/220V) household electrical installation [closed]

Power outlets are in 220V/110V in houses for historical reasons (light bulbs and other appliances probably required >100V voltage) but nowadays as: we use a USB charger 220V->5V for phones, ...
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Single vs two pole breakers - Single phase loads on IT power with distributed neutral

Are two-pole breakers required on single-phase 230 V loads when connected to a 3-phase supply with IT earthing system (with distributed neutral) in Germany? Where in the standards is this requirement ...
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3 phase low voltage signal generator

I want to create my own 3 phase signal. However, instead of it peaking at 230V AC it must peak at 5V AC. This generator will be used to feed a secondary unit that uses this signal to perform its own ...
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Low voltage asymmetric duty cycle oscillator

I'm designing a low voltage (1.6 V and less) LED decoration. The source voltage is a low power, high impedance energy harvesting source. With the following characteristics: deliver between 0.8 and 3 V ...
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3 answers
104 views

Can I use a 1kV capacitor for a 5V circuit?

In a different question, it was asked if you could use a relatively higher voltage cap in a 5V circuit (35V cap). It seems that's ok, but I want to know if that logic is still applicable towards the ...
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Regenerative Drive VFD when drive is a major % of network load?

I'm in the process of designing a new facility with about 50-60 VFDs in the 5-10 HP range, another 5 VFDs in the 100-225 HP range, and then one burly beast at 1000 HP. I've been looking into various ...
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Why do we not see multiple or parallel DC PSUs?

A friend mentioned that his home router had blown its 12V PSU recently and had to be replaced. That got me wondering - Servers and routers can have isolated dual PSUs for exactly this condition, but ...
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Design a flashing circuit that uses PWM signal and MCU signal to control when it is on and off

My team and I are working on the low voltage systems of a solar car and have an issue with figuring out how to flash the turn signals on the car. The options we are exploring include: Using a 555 ...
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2 answers
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Help with constant current load hysteresis

The circuit above is a constant current load based on an LM358 comparator. It is very useful to measure the capacity of lithium-ion batteries. The original circuit I found online had a 5V supply but ...
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Low-Voltage Unidirectional Ground-Level Shifter

Greetings, electronics Mavens! I'm trying to interface the status LEDs of a third-party device to the GPIO of my ESP32. I am using internal pull-ups on the ESP32 inputs, and trying to trigger on the ...
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-1 votes
1 answer
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What will happen if I use RCBO where there is no neutral in the system?

I need some help. Could you please go through the scenario and try to answer my query below? This system is installed in a ship where there is no neutral connection available. A 440V/220V step-down ...
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2 votes
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Isolating low-current, low-voltage digital signals

I'm working with a battery-powered sensor that allows reading its measurements using two digital signals - a clock and a data line. The clock speed is abount 3kHz. In addition to those two signals, ...
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216 views

Low voltage MOSFET gate drive

What is the best way to drive a MOSFET with low voltage? I have encountered several projects where power from a battery is used to drive motors or source a DC/DC converter. In most cases, we used an ...
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1 vote
1 answer
303 views

Can I use a multimeter to verify if RX/TX of a device is working?

To summarize a problem: My electricity meter uses a HAN interface (via M-bus) to transmit the meter's data every 10 seconds. Apparently this HAN interface can be enabled/disabled by my energy provider....
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2 votes
1 answer
47 views

How to wire two open-drain logic outputs to a three pin bi-color LED

I am very new to working with electronics; my main experience is in programming. I am working on a project and intend to use this MCP73833/4 Li-Ion Charger. It has two "Charge Status Output" ...
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How to block low voltages in a very low current circuit

I have a circuit circuit fed by a 48V nominal lithium battery source. I'm using a few simple resistors to divide the voltage down to a suitable range to drive a p-channel mosfet gate. When the battery ...
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1 vote
1 answer
120 views

How can I block low voltage?

I have added a picture about my circuit. Please look at the picture. How can I safely provide the logic in the image? What kind of circuit should be in low voltage control block? I have to cut off Vo1 ...
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Update very old, very low voltage (10V) Nutone doorbell system to new 16V chime

I have a Ring video doorbell that is connected and functioning to the old doorbell wires, which I measured at 16V. I also have a old Nutone Scoville 10 V, 5 VA transformer tucked in a very hard to ...
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Safety with low voltage high current safety

For my work, I’m working on a project that uses a power supply that outputs 42A DC at 5V limit. While I know that 5V is nothing if I were to come into contact, poor grounding can still cause flashes ...
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Can I power a 35 Watt light fixture over a thermostat 5-wire?

I would like to add this light fixture to my ceiling in an area that only has a thermostat 5-wire coming out (something like this). (The other end of the thermostat wire travels about 15 feet, ending ...
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Can an Adjustable Circuit Breaker be adjusted while Energized?

For a Low Voltage Circuit Breaker, such as the Legrand DPX3 630, 3x400A, 36kA, 400V, we have adjustment dials to change the properties of the magnetic (Magnetic adjustable from 5 to 10 In) and or ...
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DC-DC boost converters in parallel to run DC motor

Our aim was to power the motors of our bot (which were selected according to the torque requirement of our bot) using a single AAA Battery but due to limited time and and the difficulties in ...
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Relay: wetting contacts before using sub-wetting current

I'm considering using small signal relay for my application since I need to switch shunt resistors to measure currents from 1uA to 10mA (two shunts) with voltages from 0V to 5V. Now, it's clear for me ...
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Modifying the MT3608 DC-DC Boost convertor

I am using the DC-DC boost converter MT3608 for a project where my input ranges around 1 V. Is there a way to modify the circuit so that the boost converter can operate at voltages less than its ...
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How to protect low-voltage hardwired device against 120 V AC miswiring ? (I need a resettable solution)

I need to protect a hardwired device, made for AC low-voltage transformers (e.g. doorbell), from miswiring to a 120 V AC power line. It actually occurs no matter how many warnings I put everywhere. ...
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Low voltage beak away/tension release connectors for building to building overhead cables

Are there low voltage breakway or tesion release connectors that should be used for overhead, building to building applications? The background is we are running a single pair of speaker cable, and a ...
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Low voltage directive

I just want to check my understanding of LVD. I have a portable device that operates on a 30V DC input. Its output is less than 30V DC and is powered by a wall plug (UK 240V) that I supply. Am I ...
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1 vote
1 answer
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low voltage radio frequency amplifier [closed]

Is it possible to build an RF transmitter final amplifier that can be powered by a single lemon as a battery? (maybe 0.9 Vdc at 1 mA, with suitable electrodes, when fresh) Desired operating frequency ...
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Voltage Limitations of a header being used as a voltage selector

I have an application that takes a reference voltage. These voltages could be considered 'low voltage' as they range from 0 to 1000 V. Below is a reference schematic of what I'm trying to accomplish, ...
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1 answer
164 views

What to use for neutral protection

I need information on "the protection of distribution system through effective grounding techniques." I want to know the possible protection schemes for neutral as fault current or return ...
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1 answer
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How can I electically isolate two sprinkler controllers 24VAC working on the same output (master valve)

I have an old 24 zone sprinkler controller and I'm trying to move 16 zones to a "smart" sprinkler controller. I have a master valve that has to be switched on to provide water downstream to ...
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how to calculate hysteresis resistor value TL431

I'm creating a small ESP32 based robot controller board. Partially as a self learning experience (mech engineer, self taught on eletrical front but this is for hobby use :P) and partially because it ...
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2 answers
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back gate effect in low volatge circuits

1- In some circuits (Low voltage ones) the body of the pmos is connected to the gnd and nmos to the vdd. i wanted to know the reason behind this technique or in others words what's the idea behind ...
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6 votes
2 answers
120 views

270a DC inrush, 130a DC nominal load. 14 vdc supply. Ways to limit circuit to no more than 11.5 vdc?

What device can be installed between the glow plug relay and the power leads to the glow plugs, to allow ANY voltage under 11.5 vdc, but allow no more than 11.5 vdc, regardless of how much higher the ...
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Nodal voltage magnitude properties of electricity distribution networks

I am wondering how to know about an electric bus according to its measured voltage magnitudes (possibly and its corresponding real power injection profile). Following assumptions can be made: One ...
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4 votes
2 answers
464 views

Solution for how to drive a P-Channel MOSFET when Gate/Source voltage is too low?

I have used this forum to lookup solutions and suggestions from time to time but this is my first ever post! There are many great P and N-Channel MOSFET Questions and Answers in here, but I cannot ...
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1 vote
2 answers
91 views

Is upsized reactor allowed for the comparitively less motor HP?

We have a LV-MCC in our commercial outlet having a 480 VAC, 15 HP VFD with line and load reactors in series with it. The VFD is sized for 22.0 A (normal duty), the motor has a horsepower rating of 10 ...
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2 votes
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Controlling 120v line with a 12v switch on a different line

I have 10a 120v power sockets in my garage that currently doesn't have any switch on it and powers some overhead lights that I have plugged in. Separate to that, I have a 12v circuit powering various ...
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4S Lithium Ion Low Votlage Cutoff

Disclaimer: I'm not an electrical engineer, and most of what I've done so far has been from researching similar designs on the interwebs. I'm just a tinkerer with a soldering iron, so please excuse my ...
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2 votes
2 answers
70 views

Combine voltage sources [closed]

I have a Baldor DG6E generator. It must produce 120V/240V but I bought it and it has three wires as outlets - every one produces 120V. I want to combine two wires to produce 240V. How can I combine ...
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145 views

How to drop the voltage slightly (~100mV) for a MCU mostly in deep sleep?

How to drop the voltage by a low value (let's say <150mV) without wasting current to supply a microcontroller that spend most of its time in deep sleep mode? I'm working on a board with a ...
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Regulatory considerations for 500W, 400V DC power tether

I'm working on a robotics project where we intend to deliver ~500W of power over a 1000 ft tether. The current plan is to run ~400VDC down the tether on a pair of 16 AWG wires. These power wires will ...
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1 vote
3 answers
299 views

Plate current use of 12Ax7 vacuum tube at low voltage

Does anyone know the current used by at 12Ax7 (or similar) vacuum tube when in normal (triode) operation using a plate voltage no more than 10VDC? I'm not considering the heater current (~300mA at 6....
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5 votes
1 answer
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Using a JFET as a voltage limiter

I have a circuit that runs on 1V up to 15V DC. I want to attach a low-power battery-level (1.5V) device to this supply rail, and have it work over the broadest input range possible (yes, it will cut ...
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