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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81 views

Logic level for system lower than IC's recommended logic level

My system has a logic-level and logic-supply-voltage of 2.4V. I want to use a particular IC in it (which basically operates as a shift register), and the datasheet says the minimum recommended logic ...
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1answer
385 views

Multiplexer for low-voltage measurements

How does voltage leakage (or cross-talk) from a mux affect low-voltage (voltages on the range of 10s of microVs to mVs) measurements? I am building a measurement set-up consisting of a Keithley 2400 ...
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3answers
195 views

Detect voltage below 0.7V? [closed]

I have a LED in circuit which I want a circuit to detect whether it's on or not. I have found ground and +ve of the circuit. And I checked the voltage across +ve of LED and Ground, when it is ON, it ...
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1answer
120 views

What DC motor controller will work for a small toy train? [closed]

I'm thinking about modifying a battery-powered toy train to use a higher voltage battery so the toy can go faster. Like this: https://youtu.be/qK-IVIllOBY?t=30 The 9V battery has a nice form factor ...
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1answer
1k views

PIR (HC SR-501) not working

I'm working with ESP8266 Wemos D1 Mini and HC SR-501 (PIR sensor) in one particular project (please, see the circuit image in annex). The question is the HC SR-501 stay always LOW. I tried change the ...
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0answers
130 views

Specifying & operating a TRIAC with a low voltage load

I am looking to do a circuit to switch a 12 VAC of a device to the ground. I intend to use a microcontroller to drive the TRIAC. The goal here is only to short the 12 VAC of a device to its ground. ...
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2answers
173 views

PCB relays for switching 700-1000V analog signal [closed]

I'd like to switch the polarity of a differential high voltage line that carries up to a 750V (+/-375V per conductor) analog signal. The easiest way to do this appears to be to use a dual-pole dual-...
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2answers
781 views

Low voltage disconnect with no quiescent current

I'm a noob. Please correct my mistakes. I'm making a circuit where I'd like to protect my Li-ion battery (3.7V, 3500mAh) from discharging too much. The batteries have a protection inbuilt which shuts ...
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2answers
176 views

Calculating resistance when ohm law has no response

I have a 3v DC source and a 3v light emitted diode, i want power this led with just 5 mA . There is a formula : R = V/I But in my case V is 0 V[source] - V[LED] = 0 So R is 0 always!!! How can i ...
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3answers
9k 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 im not sure where to go to make it happen. Or if i ...
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1answer
85 views

How to convert 0.08 V of AC to DC

I am using an insulated wire as an antenna, which is picking up 0.08 V of AC. I want to convert that to DC. I know I need to use a rectifier, however my configuration doesn't seem to be working. I ...
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1answer
192 views

Switch off this single cell lithium hi-power LED driver with protection circuit

I've been goofing around the internet trying to build my own flash light with a single 18650, with low voltage protection circuit. For now this circuit can already achieve following ideas: Standby ...
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3answers
320 views

Isolated way to detect 240V contact closing

I want to create a small project with an ESP8266 that makes a server call when a thermostat is open or closed. My main problem is detecting the thermostat status. The electro-mechanical thermostat ...
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0answers
58 views

Unknown 2-pin weatherproof connector

We have a meteorological station (Made by the now-defunct Solar Millennium) next to our solar plant that has a faulty connector from its PV panel. It has a circular cross section and has a screw-in ...
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1answer
224 views

Using flyback diode with relay, load regulation faults occur

I'm having a problem with load regulation errors on my board. When I engage our load with a relay, it causes a metering chip in our system to reset. I've placed a picture of the relay with the flyback ...
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4answers
1k views

Low voltage cutoff circuit not working

I've spent the past 10 hours trying to figure out why my low voltage cutoff circuit won't work, and I'm at the point where I feel like I need to ask for help. The idea is to slap this circuit in ...
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2answers
5k views

Can I run a 12v fan off of a 9v power supply for LED lights and are there any side effects

I have multiple (9v 1500mA to 9v 3500mA) LED light fixtures that I have tested chaining a single fan (12v 5.2w and 12v 0.16A fans) and they seem to work under the brief test with enough air flow for ...
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4answers
2k views

AC vs. DC in Low Speed, High Torque application

My club is building a 1/4 scale utility tractor (around 800 lbs) and for the past couple of years we have been using an electric hybrid drivetrain. Our system has been a 32 hp gas motor powering a DC ...
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2answers
292 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 ...
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3answers
2k views

Do low voltage “Nixie tubes” exist?

I want to make a small clock using Nixie tubes (for the cool/retro/steampunk look of them), I have some basic knowledge of electronics, but I have never done anything with more than 12V DC and ~10A. I ...
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1answer
102 views

Low Voltage AC to Dual DC supply

I have a special power supply requirement for Agro Based Applications.. After stepping down conventional primary 230VAC, 50Hz Single phase single line supply to secondary 80VAC (4Amps to 6Amps), I ...
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1answer
212 views

Measurement of highly resistive samples with Keithley 2182a nanovoltmeter

In our laboratory we are measuring transport properties of various materials. Currently we have deployed Keithley 2182a nanovoltmeter. When measuring bulk mineral (tetrahedrites, Cu12Sb4S13 Peru) ...
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1answer
60 views

LED Power Box Design

I am designing an LED power supply unit, using off-the-shelf constant current drivers (Phillips Xitanium). The system will include a 0-10v dimmer, and I need to connect the Xitanium to both 120v for ...
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3answers
3k views

Can I make a VCO full audio range with only one capacitor?

I'm trying to make a VCO with a low voltage setup (3.3V), and i 'm using a mcp6002 op-amp. I'm controlling the frequency with an MCP4822 (dac). The problem is that i get a limited range of frequencies....
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4answers
215 views

How to indicate Low voltage(2.7kV) and normal voltage(above 2.7kV) in 3.3kV 10uA power supply through LEDs

I have a power supply which gives 3.3kV 10uA output. Now what i need to do is to turn ON a Green LED when the voltage is above 2.7kv and turn red LED ON when it goes below 2.7kV. Could anyone guide me ...
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2answers
424 views

5 mA low dropout voltage, current source [closed]

I want to power two signal LEDs in series, about 3 V in total from a 3.3 V supply. The on current is 5 mA and I can switch either the positive or negative rail. Using only a resistor will not be ...
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3answers
6k views

How can low voltage, high current (kA) power be dangerous?

Aluminum refineries use electricity to separate aluminum from minerals it naturally occurs in. This electricity typically takes the form of low voltage DC ("low" meaning 4 to 6 volts), at very high ...
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1answer
578 views

Braiding 3 Phase Wires

I'm working in the 50V, 10A range with un-shielded wire to drive a brushless DC motor. Are there any advantages to braiding the 3 phase wires? will it reduce EMI and spiking?
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1answer
1k views

L298N (via 74HC595) motor control - unexpected voltage & motor not spinning

(Corrected version as last text was somehow corrupted) I have made a circuit with L298N in order to control direction of 2 DC motors. When I power the circuit I noticed that voltage between 2 output ...
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4answers
268 views

Filter-Amplifier circuit for Low Voltage I/P circuitry

I'm designing my first ever circuit for a hobby project. I've 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 the ...
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1answer
38 views

Powering an SN754410E from Arduino logic pins

I want to run a very small stepper motor using a 5V source (specifically, a stepped-up Lipo battery). Since both the stepper I have and the SN754410E are rated to operate from 5V up, I figured this ...
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1answer
2k views

Using a relay to turn on and off really low voltage circuit

I want to build a thermostat for my fireplace. I want to use my Arduino to turn it ON and OFF. The fireplace has got a switcher on the wall and I have measured it and the voltage different from one ...
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3answers
187 views

Right kind of resistance wire for near-skin heater?

I'll be up-front and say I know jack squat about electrical engineering aside from "conductors heat up when you run current through them." I'm looking in to building a low-voltage (~12-24 volts) ...
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3answers
1k views

Opamps used in low voltage applications

How is it possible to use op amps on a supply of (+3v), for example: mp3 player and other battery operated devices? What type of op amps do we use in low voltage applications? How is it possible they ...
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1answer
51 views

Voltage for RGB Strip Lighting

I'm looking at building a hobby project featuring led strips. I'm looking at 5v RGB addressable LED strips The Strips. I've already more or less figured out how much I need to cut for each section and ...
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2answers
217 views

12V LED dimmer burning out after several weeks of usage [closed]

We have changed the lighting in our room, but after several weeks the dimmer just puffs in smoke and stops working. This already happened twice. Basic setup is like this -> 2 way switch goes to 220->...
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2answers
340 views

Can you use a motor to run a transformer? [closed]

I asked a similar question earlier where I was not very specific. Here is the improved question (I hope). Can I use a brushed d/c motor to power a transformer when the motor creates 0.5VAC when the ...
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2answers
173 views

Can a transformer run on low voltage ac?

Can a 0.5 VAC power supply be stepped up to a higher voltage with a transformer?
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9answers
38k views

How safe is 48V DC?

In many Power over Ethernet (POE) setups the transmission voltage is 48V or slightly more. While higher voltage has obvious efficiency advantages, how safe it is? Is there any risk of electrocution ...
2
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1answer
516 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 ...
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2answers
88 views

Switch ON with PushButton, Switch off with GPIO

I am looking for a schematic which is capable to switch ON a power Supply to supply a micrcontroller. Then switch off the power supply with a GPIO of this microcontroller. I have found a lot of ...
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2answers
379 views

Low Voltage limiter circuit with fast recovery time

Hello I am having trouble building/finding parts for a circuit that I need to limit the peak voltage of a signal coming from a photodetector. My problem is that an amplifier I am using will not ...
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2answers
6k views

How to calculate actual hfe for low voltage source?

The datasheet for a transistor (said 2N2222) give us the hfe asuming a Vcc in the 30V range. For uses like Arduino projects, the Vcc is usually 5V, and under that conditions, the actual hfe is lower. ...
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1answer
94 views

LDO outputting low voltage. LDO or auxiliary components fault?

I burned a circuit by applying reversed polarity voltage. I measured the LDO that is supplied with 5 V and should output 3.3 V, however it only outputs ~2 V. Now what can I deduce from ...
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1answer
294 views

What is an extra low voltage circuit?

I am a novice in power electronics. I don't know when we can call a circuit an extra-low-voltage circuit. for example a circuit in which there's a power supply that converts 240V AC to 24V DC and ...
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1answer
47 views

Low Voltage Disconnect and 2 negatives?

I am looking at something like this LVD 12V and am confused as to the purpose of the two negative terminals. On the BATT side I will have the + coming from the + side of the battery and the - going to ...
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3answers
149 views

Electronic device that is open for 6V and passes current once it reaches 12v? [closed]

Please excuse the way I am this question as I do not have much of an electronics background... I am trying to upgrade the headlights in my car to HID projectors. One of the issues I'm running into is ...
2
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0answers
44 views

Centre contact clamping in coaxial barrel connectors

Barrel connector plugs seem to have two different methods for keeping the centre contact under pressure. Some plugs have a rigid circular inner contact which relies on the socket to have a split pin ...
4
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1answer
517 views

Step-up converter for 20 mV input

For an experimental thermo-electric generator (TEG), developed by a colleague for low-power energy harvesting, it is possible to achieve an output power of 400 uW at the maximum power point. The ...
2
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2answers
278 views

viability of idea for low voltage signal clipping (distortion) for guitar effect

I want to create an guitar distortion effect. What I want is a unity gain buffer op-amp that clips the signal. In the drawing below there is a circuit found on this forum here which will clip a very ...