Questions tagged [low-voltage]

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

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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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0 answers
20 views

Rewinding the 12.5HP submersible pump to run at lower voltage [closed]

I have 12.5HP double cable 3 phase submersible pumpset and motor for irrigation purpose. In my area the voltage is very less which is 280V to 350V. This leads to MCB trip and cables get extremely hot ...
0 votes
2 answers
527 views

Effect of electrical arcing on the system voltage

What will be the effect of Electrical arcing (between phases or between phase and neutral) in a 415V three phase system in the downstream voltage... Will it just act as a load ( let's say the arcing ...
0 votes
1 answer
64 views

Millivolt logger with high sampling rate [closed]

I'm trying to find modern components for a design that would be able to record millivolt range samples at a high sampling rate (~30 kHz) for ~1 hr interval. Key components I can think of thus far are ...
2 votes
1 answer
706 views

Under-voltage disconnect on MCP73871

I've designed a circuit using an MCP73871 (link below) and some lithium ion 18650 cells. I'm confused by the under-voltage lock-out (UVLO) on that chip as it's not clear (to me at least!) whether it ...
1 vote
1 answer
44 views

Low power consumption/leakage tips and tricks (input NC magnetic reed switches)

I have an ATtiny412 that has 2 pins (PA1, PA2) set as internal input pullups. These 2 pins (PA1, PA2) sense magnetic reed switches with the NC setting. GND is active when closed on these switches. The ...
-1 votes
1 answer
37 views

Need help connecting 10 LED USB powered lights to one power source [closed]

I need help to connect 10 LED string lights into single plug. I wanted to make sure I have enough power, but not burn out the lights.
2 votes
2 answers
555 views

Biased single-source relaxation oscillator not starting

Vcc is 5 V , first op-amp LM358 provides 2.5 V ground for easiest possible relaxation oscillator build with MCP661 (2.5/5.5 V supply, 60 MHz operational range). I wanted to use it to measure values of ...
1 vote
0 answers
40 views

Symmetric PCh and NCh MOSFETs for variable resistors

I'm wanting to build a variable voltage-controlled resistor. The resistor would be in series with a 200 uA AC current source and need to be controllable between 1-20 ohm. My current plan is to take ...
1 vote
1 answer
68 views

Voltage stabilizer or voltage protection device for irrigation setup [closed]

I have an irrigation setup in a rural area with voltage fluctuations. The irrigation setup consists of a Hunter X2 Controller powering a pump start relay which in turn runs a 1.5 HP submersible motor ...
0 votes
1 answer
41 views

A stable very low-voltage reference generator (a very low-voltage LDO design idea) [closed]

Essentially, I have a voltage which varies between 0.15 VDC to 0.25 VDC, and this feeds into a system whose output is varying because of this variation at the input side. This is summarized in the ...
7 votes
2 answers
1k views

LED Fails to illuminate, what am I not seeing in my configuration(s)?

I'm working on a super simple circuit, I want to light the LED. Power Source 1: 5.5v from 9v battery through breadboard power supply module Power Source 2: 5.5v from lab bench PSU LED Info: Vf - 3v to ...
2 votes
0 answers
68 views

Philosophy of safety by Double Insulation

In a Class I appliance, when a fault occurs that brings dangerous voltage in contact with accessible conductive parts, the installation wiring fuse or GFCI will not only shut down the dangerous ...
1 vote
2 answers
86 views

Reading voltage across Christmas light wires, multimeter shows erratic readings

I am attempting to splice a simple on/off switch into a strand of Christmas lights. Previously, I separated the two wires and cut open the one marked with dots, expecting it to be the positive/live ...
1 vote
1 answer
83 views

Op-amp not increasing amplitude of signal

I was doing some LTSpice simulation with an op-amp to amplify a 1 millivolt 40 kHz sine wave. However, in the output signal, it had just raised the voltage of the whole waveform, it decreased the ...
0 votes
0 answers
60 views

Asking Question about Low Voltage Transistor, MOSFET or op-amp for a Conditioning Circuit

Which transistor, MOSFET or op-amp, can I use in place of the 2N2222 NPN transistor to turn ON the circuit for the lowest input voltage in mvolts. Explanation: I've obtained a voltage signal from a ...
0 votes
1 answer
95 views

Low Voltage LED Runway lights Part 2 [duplicate]

I will use 10 g 2 strand direct bury low voltage wire I believe that I need to run a loop and I am considering adding another 600 watt transformer to the opposite side of the runway that will turn ...
1 vote
1 answer
922 views

How to design a circuit to disconnect a battery charger automatically?

I want to use an AC to DC 14.4 V adapter to supply both my circuit and its battery. The circuit works with 12 V and I use a battery during power outages (blackout time). I have prepared the below ...
1 vote
0 answers
60 views

Electrical Standards for Exposed DC Connections

We are trying to make a slide lock connection between two parts and thus need to have some sort of connector between them. I am wondering if anyone is aware of a IEC standard relevant for connecting a ...
2 votes
1 answer
948 views

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 ...
1 vote
1 answer
114 views

Using skin to close low-voltage circuit

I am trying to create a ping pong ball sized light-up ball that should light up when held in my hand, as in the 80's toy inspired by the movie/television series "Star man". The circuit must ...
1 vote
2 answers
112 views

If the current through a welder is hundreds of amps to melt metal, how does the welder circuitry cope

A pretty simple question but i have no idea. My logic is if the current is so high where something as low resistance like a metal slab can be heated to melt. How on earth does the components in the ...
0 votes
2 answers
98 views

Single pulse generator

For my 10V model train's signals and switches I need a ~500msec power pulse (AC; low Amp). I already have an electronic switch that provides power when triggered. However, the power should be brief, ...
0 votes
1 answer
63 views

Is there a way to tell if I have MLV or ELV transformers driving my 12V 50W LEDs? [closed]

Is there a way to tell if I have MLV or ELV transformers driving my 12V 50W LEDs? I want to dim a small row of ceiling downlights with 3-Way Lutron Maestro dimmers. The actual fixture is a Nora NL-301 ...
0 votes
1 answer
59 views

1950s Era primary and secondary low voltage intercom system [closed]

I have a 1959 low voltage panel right next to my 120 volt panel in my laundry room. This panel controlled an Old intercom system as well as the lights for the house. Inside of the panel there seems to ...
0 votes
0 answers
115 views

Variable voltage control from an ESP32

First, the background context: I have a pair of these TCS-300 landscape lighting controllers which have a cloud-only control interface, which cannot be integrated with my local home assistant. My goal ...
2 votes
4 answers
20k views

Circuit with 10 LEDs with 9V battery

I know that a 9V battery can only power so many LEDs. I need a 9V battery to power 10 of them maybe less or a few more and keep brightness and I am not sure where to go to make it happen, or if I need ...
2 votes
2 answers
81 views

Looking for Low Noise High Shielding BNC [closed]

I am doing some research looking at low voltage signals, on the order of 100nV. Due to the usage of other equipment such as a current source there is spurious pickup noise in the cables carrying this ...
2 votes
1 answer
171 views

What assumptions are made by UL when they equate 30Vrms to 60Vdc for LVLE circuits?

UL defines Low Voltage Low Energy circuits as "A circuit involving an alternating current voltage of not more than 30 volts, rms (42.4 volts peak) or a direct current voltage of not more than 60 ...
0 votes
4 answers
118 views

I have a solenoid rated at 24 volts AC, but at a trickle voltage of 1-9 volts the solenoid stays pulled in when it shouldn't be

I have a solenoid that pulls in at 24-30 volts ac to control water flow. It opens at 24 volts ac, but stays pulled in at a trickle voltage of .75 -1.0 volts. How can I stop this from happening?
2 votes
1 answer
128 views

Simple LED Low Voltage Indicator for Li-ion cell (3.3 V threshold)

I'm working on a handheld project that runs off a single cell 3.7V Li-ion cell. I would like to trigger an LED to turn on when its voltage drops down to 3.3 V. I have seen other answers with a TL431 ...
0 votes
0 answers
108 views

High swing (Low-voltage) cascode current mirror pole

I have been trying to figure out extracting the exact derivation for the poles, I am only struggling with figuring how the author got pole 8. I am using the small signal for the high swing cascode ...
1 vote
1 answer
247 views

Reducing the start-up voltage of a low voltage cut-off circuit

I just built this circuit, with the intent to use it as a low-voltage cut-off switch for a single li-ion cell. It works great, but once it's triggered it needs about 7 volts to turn back on, so I ...
1 vote
2 answers
10k views

How to calculate actual hfe for low voltage source?

The datasheet for a transistor (said 2N2222) give us the hfe assuming a Vcc in the 30V range. For uses like Arduino projects, the Vcc is usually 5 V, and under that condition, the actual hfe is lower. ...
27 votes
3 answers
14k views

Why do many electronics operate on 5 and 3.3 volts?

Many modern appliances use a 5V power connection, but internally they work with 3.3V. Wouldn't it be easier to have 5V everywhere? Examples are many USB devices or routers (they use 5V for power but 3....
2 votes
1 answer
49 views

How to achieve the lowest noise configuration from a differential setup

I want to be able to capture a differential output from a shunt resistor. The shunt resistor differential voltage will range from 2.5mV to 50mV at 50Hz. My initial idea was to send this signal through ...
1 vote
1 answer
134 views

How to design an accurate (1 μV error) meter

I want to design an accurate LV meter. The range is from 2.5mV to 50mV both AC, with a 5uV accuracy. This comes from a shunt resistor that is connected to AC main (230V AC). Hence it will go below 0V. ...
2 votes
3 answers
170 views

I need help designing a low voltage DC to AC circuit

Can anyone help me design a circuit that will perform low voltage DC to AC conversion? Ideally, I would like to have 3 to 6 VDC input (using AA batteries) Approximately 1 VAC output (less would be ...
0 votes
1 answer
89 views

Can not get maximum torque (stall torque) when current reach peak current

I am using FOC to control torque of 220V AC servo (SPMSM) with 36V power supply at low speed (100-200rpm). I tested with some servos (different manufacturers) which has specs as the below table. But I ...
1 vote
1 answer
34 views

Low voltage shut off [closed]

I have some temperature controllers that run on 110V. They get 110V from a generator pushing 480 three phase through a transformer to get 110V. The controllers have issues if the voltage drops too low ...
4 votes
0 answers
573 views

What is a short-circuit proof cable?

German norms and standards (VDE 250 Teil 602) specify, that wires and cables, rated for 3kV can be considered as "short-circuit proof" and "earth-fault proof" in low-voltage ...
2 votes
2 answers
329 views

I need to build a high current, low voltage buck converter

I am trying to power a 14 mΩ resistive load at 0.3 V 21.5 A to add some buffer to the design I'm trying to design for 30 A, since the load can change. Without going too in depth the load is a new ...
0 votes
0 answers
102 views

Why is a spliced USB extension cable frying USB Drives?

I cut a functional USB-A extension cable in half, reconnected the wires, and plugged a USB drive into it. This cable killed three USB Storage Drives. Why? The above photo shows the cable. I know, I ...
0 votes
1 answer
342 views

How to identify a low voltage transformer

Not 100% sure this is the correct forum for this question. If not, I apologise. I am trying to identify this transformer. It comes out of a Paradigm PDR-10 subwoofer amp. I believe it is bad as ...
1 vote
1 answer
83 views

Switching low voltage with high accuracy

To do some discharge tests, I want to connect 1.5 V batteries to very low resistances for a short amount (10 - 200 ms) of time, then have them disconnected for at least a couple of seconds. What would ...
0 votes
2 answers
185 views

LED light data issue

This has been driving me insane for some time now. I can't seem to figure out why my LEDs have issues with communication. They have plenty of power supplied. I broke down my entire circuit to the most ...
0 votes
2 answers
221 views

Low-Voltage Unidirectional Ground-Level Shifter

I am 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 voltage drop that occurs when ...
0 votes
1 answer
69 views

Low voltage boost-converted versus high voltage on capacitor

Let's say I have a 7.4 V Li-ion battery that I boost-converted to 36 V, and I have a 36 V Li-ion battery. I want to know if a charged capacitor from a boost converter would release energy like a ...
1 vote
4 answers
323 views

Filter-amplifier circuit for low-voltage I/P circuitry

I'm designing my first ever circuit for a hobby project. I have a sensor that outputs in mV (1 to 2) and a controller with ADC. The ADC is 16 bits, VDDA = 3.0 V, Temp = 25°C, fADCK = 1.0 MHz. Since ...
1 vote
1 answer
80 views

Are there any substitutions for depletion PMOS transistors?

I am currently building a low-voltage cut-off circuit. When the battery is under 10 V, the microcontroller should pull the battery power to ground which will blow the fuse with high current and cut ...

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