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.
247 questions
6
votes
5
answers
1k
views
How can I measure a 0-3.3V analog signal through an isolation barrier?
I am running into an issue where I have to be able to receive an analog DC voltage that will vary from 0-3.3VDC, but I need to be able to isolate the signal before I run it through an amplifier and a ...
- 69
1
vote
4
answers
76
views
Measuring the voltage in low voltage side of a mains powered device (that is non-isolated)
I have a task to measure voltage fluctuations provided from a non-isolated power supply. The voltage is around 3.3 volts but it fluctuates heavily.
The problem is that I need to be able to log these ...
1
vote
1
answer
47
views
Running a wall wart at 24VAC
I'm working on a HVAC project and I need 6-30VDC to power a XY-J05 module. 24VAC is everywhere, but one side is also "common" and used as a reference for a DC measurement.
Anyway, after ...
- 11
-1
votes
0
answers
28
views
How to calculate maximum PWM for MOSFET with 3.3v/5v power supply?
How to calculate the maximum PWM frequency of a MOSFET switch circuit?. However, it is not clear from this question what to do when you have a maximum of 40mA (ESP32-S3) from the GPIO. The load can be ...
1
vote
0
answers
48
views
Ring Video Doorbell / ghost rings with 16 VAC solenoid chimes [closed]
I have:
Ring Video Doorbell
(x4) solenoid chime operating on 16 VAC
The chime is a pre-2000's analog device. Presumably it uses an analog circuit to ring the solenoids in a pattern to make a ...
- 137
0
votes
2
answers
50
views
Solar emergency LED Night light control design: Solar panel, 5 V : 3.7 V 18650 Li-ion or similar as Vref. No negative voltage. Only GND. Which Op-Amp?
Solar charging daytime with 0 V battery output to micro LED chain.
At nightfall, solar voltage drops to 0, activating Vout: 3.7 V or alternative Lithium chemistry to power 30 ft (100×) white LED rope ...
- 11
0
votes
2
answers
64
views
Effect of high voltage electric field on the motion of charged particles in an isolated tube
Please refer to the image for a visualization of the schematic.
I feel I am trapped at this stage. I am trying to understand the following:
In a closed container, charged particles are moving from the ...
- 3
1
vote
3
answers
119
views
Voltage regulator with polarity depending on input
I'm pretty new to electronics, I have some very basic notions, and I need help with a little project I'm working on, basically I have an input that can vary between 4 and 13 volts and I need to keep a ...
- 11
0
votes
0
answers
61
views
Troubleshooting a Low Voltage Cutoff (LVC) Circuit for Overdraining Prevention
I am attempting to design a Low Voltage Cutoff (LVC) circuit to safeguard against overdraining my 12V rechargeable battery. The objective is to halt circuit power once the battery voltage drops below ...
0
votes
1
answer
66
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 ...
1
vote
1
answer
77
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 ...
- 179
-1
votes
1
answer
56
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.
- 11
1
vote
0
answers
66
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 ...
- 11
1
vote
1
answer
71
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 ...
- 13
0
votes
1
answer
74
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 ...
- 41
7
votes
2
answers
2k
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 ...
- 181
2
votes
0
answers
85
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 ...
- 23.4k
1
vote
1
answer
115
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 ...
- 35
1
vote
2
answers
252
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 ...
- 113
0
votes
0
answers
62
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
99
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
0
answers
72
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 ...
- 428
1
vote
2
answers
138
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 ...
- 701
0
votes
2
answers
230
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
253
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 ...
- 3
0
votes
1
answer
73
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
246
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 ...
- 173
2
votes
2
answers
130
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 ...
- 21
0
votes
4
answers
146
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
334
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 ...
- 639
2
votes
1
answer
266
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 ...
- 21
2
votes
1
answer
60
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 ...
- 2,657
1
vote
1
answer
152
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. ...
- 2,657
1
vote
1
answer
151
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 ...
- 11
2
votes
3
answers
219
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 ...
- 21
1
vote
1
answer
36
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 ...
- 11
4
votes
0
answers
973
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 ...
- 191
2
votes
2
answers
528
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 ...
- 21
0
votes
0
answers
105
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 ...
- 303
1
vote
1
answer
88
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 ...
- 11
0
votes
2
answers
259
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 ...
2
votes
2
answers
199
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 ...
- 21
0
votes
1
answer
79
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 ...
- 65
1
vote
1
answer
110
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 ...
- 35
0
votes
0
answers
95
views
Low voltage to drive LED flash (not successful in simulation, but works on breadboard)
I first did this circuit on a breadboard, except I originally used a light-sensitive resistor, which is around 1 kΩ at daytime and above 160 kΩ in darkness.
It oscillates with LED as capacitor adds up ...
- 71
1
vote
3
answers
115
views
7-meter cable between gas meter and microcontroller: too long?
My gas meter has two GND / PULSE pins that trigger a short pulse (probably +3V or +5V) each time 0.010 ㎥ has been used, for use with domotic equipment. There is no power plug in this basement, and I ...
- 2,178
1
vote
1
answer
101
views
Battery over-discharge protection
I am studying NiMH battery charging and using such a battery on a board to feed other circuits. I would like to add a protection circuit that provides protection for over-discharging the battery at ...
- 39
-1
votes
1
answer
272
views
Fusing power injected LEDs from both sides [closed]
I am involved on a project where we will be installing thousands of LEDs (WS2812B Addressable strips) on the floor. I have a question about about fusing and if there is a more efficient way to go ...
- 21
2
votes
4
answers
1k
views
Low-voltage vacuum tube amplifier design
Amateur radio HF frequency amplifiers using transistors commonly can be powered with around 12 to 14 VDC, or even lower voltages, for QRP transmitters.
Tube amplifiers seem to require DC power ...
- 4,851
1
vote
1
answer
74
views
Thermoelectric EMF problem for low voltage measurement load cell
The resolution of a load cell is highly dependent on its capacity. That's because the higher the resolution and the higher the capacity, the smaller the voltage change. For example, many companies ...
- 39