Questions tagged [voltage-divider]

A voltage divider is a circuit that produces an output voltage that is proportional to the input voltage. One typical configuration consists of a pair of resistors in series from the input voltage to ground, with the output voltage taken from the junction of the resistors. As an example two equal valued resistors will give an output voltage 50% of the input.

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Measuring battery life for Arduino device [duplicate]

I'm building a IoT thing based on Arduino. The thing will be powered by a 12V battery. The reason why I want to use a 12V battery is because I will also have motors on the thing. I would like my ...
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How to connect a W25Q64 3.3 SPI Flash to a 5V Arduino Mega?

I need memory to read from, for my project. I first intended to use an SD card, but I now found out a W25Q64/128 SPI Flash is more practical, since I don't need to write data. However, this W25QXX ...
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How to dynamically adjust voltage divider (90V) using a 3.3v microcontroller

I have a power supply that regulates its output by turning a potentiometer. It supplies the full 90V to the two leads of a 200k potentiometer. By sending a voltage in-between 12-90V to the wiper input ...
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SFH3310 Phototransistor read ADC value

I want to sense brightness via an OSRAM SFH3310 phototransistor by using an ADC (Vref 3.3V - teensy 3.1). I understand that I need a voltage divider to get a good ADC reading. In the past I simply ...
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43 views

safe negative voltage divider to GPIO pins

this question comes from this other, trying to implement the folloging circuit to measure a -3V battery pack (2xAA) (I've to measure in that way, cannot swap or move GND): Digital PIN 6 will be set ...
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reading a high negative voltage with attinys running on batteries

I need to read a negative input voltage from a camera flash capacitor that can charge up to -330V. I am using an attiny85V that is running on batteries and want to set the internal reference voltage ...
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Measure 10kV with 600V rated multimeter [duplicate]

My multimeter is rated for 600V but I need to measure a 10kV AC source. I was thinking of building a voltage divider but I wouldn't know how many resistors it would take to safely measure this high of ...
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measuring -3V with 3 resistors voltage divider

I know (or may be think) that I can scale the measurement of a 0 to -3.1V external battery to a analog pin ADC range of 0 to 3.3V, but I'm unable to calculate the resistors. I've been trying how to do ...
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5V 4-pin Noctua A4X10 on Raspberry Pi

I want to connect a NOCTUA NF-A4X10 5V PWM 4-pin fan to a Raspberry Pi 3B. The below is the circuit I'm planning to use. (EDIT: Flyback diode (such as a 1N4001) is not needed since Noctua already ...
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Help designing a voltage divider

I said voltage divider on the title, but could be anything. I have a DC source of 19.7V. I need an output that varies from 0V to 18V. I have: Resistors (1/8W); 1k potentiometer; 5k trimpot; 2N3904;...
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In this BJT circuit why can I apply a voltage divider in the resistors?

I presume that I can remove the capacitors since the circuit uses DC, but then I don't understand why I can apply a voltage divider in the 30K and 20K resistors since the base is connected between ...
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voltage divider driving PMOS with slow turn-off time

I have a voltage divider that is driving the gate of a high side PMOS switch. The voltage divider turns the PMOS on once the NMOS is turned on by a 5v logic controller. The PMOS turns on ...
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Problem with the reset circuit for a MCU

I need help by understanding the problem with an existing MCU circuit concerning the Reset PIN (STM32 Cortex M0+: STM32L071K8): It seems something in the circuit is wrong, since it works only when I ...
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78 views

Resistors scaling in voltage divider?

For my bench power supply, I am willing to make a voltage divider with two potentiometers (for coarse and fine tuning). I think I got the schematic right but what I am not sure about is the influence ...
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Measuring voltage on different grounds PV inverter

I'd like to create a voltage meter that can measure battery voltage and PV panel voltage. The only problem is that the PV input and Battery I/O doesn't share ground. I'm not sure if tying the grounds ...
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37 views

charge capacitor in two phases

i want to charge two 25F Supercaps (in series) in two stages: while their total voltage is under 5v, i want to charge them slowly via a resistor R3 of around 100 Ohm. After they reach the desired ...
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Which values for voltage divider [duplicate]

I just learned about voltage dividers and how to calculate the relative values for the resistors to use. For instance, to go from 5v to 3.3v I could use a 1 kohm and a 2 kohm resistor. However I could ...
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Are the results for Proteus simulation and hardware testing for same purpose using different controllers comparable?

I have used Proteus design suite for simulating sensors (such as temperature sensor) interfaced to LPC2138. The sensors which were not available in the software, for them I have modelled them as ...
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Reference voltage changes when connected to inverting input of op amp comparator

The capacitor C2 keeps the value of a slow varying signal for some time. The capacitor discharges through the two resistors R3 and R4 with a time constant of \$\tau = RC = 10\mu F \times 1M\Omega = ...
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367 views

Voltage divider does not work with LM393 sound sensor

I have a sound sensor which I want to connect to a RaspberryPi. RaspberryPi input voltage on GPIO is 3.3V and this sound sensor output gives 5V. I've made voltage divider that looks like this: It ...
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280 views

How to calculate the node voltages for this circuit using the voltage divider rule

I am working on the following circuit: Simplifying the circuit: After simplifying, my answers do not match that of values I get from simulating the circuit in multisim. Here's my calculation: $$...
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How to calculate current in voltage divider with load?

Say, I have this circuit (please ignore the zeros, and the diode should be some load that draws 10ua): So, V_in be 12V. I would say that D1 gets R2/(R2+R1)*12V as voltage. Then, as I know that it ...
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78 views

Capacitor in series with voltage divider

I am trying to understand the dynamics in the following circuit: I have a voltage source here. Now, I measure current at C1 and voltage at C1/R2 and the result is this: So, what I understand so far ...
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Which resistors to use for high current (10A) voltage-divider? [closed]

I'm having a problem determining resistor specs (especially wattage) for my voltage divider circuit [ 27 V to 17.5 \$+-\$ 0.5 V ] on 10 ampere DC supply. I have an AC (220V 50Hz) to DC (27V 10A) ...
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71 views

Dynamic voltage divider

I'm trying to build an ESC (electronic speed controller) for three phase brushless motor. I found some intresting circuits but I am trying to build something very easy to do, with mosfet and pc817 and ...
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57 views

I have a 2 A 12 V regulated power supply and I want to use it to emulate a 9 V battery for a breadboard

I have a 2 amp 12 volt regulated power supply and I want to use it to emulate a 9 volt battery for a breadboard. However, I need to protect the power source and the components used in my breadboard ...
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4answers
95 views

Voltage error when connecting a zener diode

I am working on a project where i need to measure the battery voltage and send the measurement to a uC, which is powered by 3.3V. The voltage divider is projected as shown before: As input we have ...
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52 views

How to get output of 12V from a 15V output without dropping the current

I am planning on using NI myDaq to power a motor and encoder which requires 12V, but myDaq outputs 15V. How can I reduce the voltage to 12V without dropping the current? I was planning on using a ...
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64 views

Differential Amplifier to Scale Down DC Voltage

I'm using a 3.7V LiPo to power a device that normally runs on 3V (and draws about 100-200mA). I've determined that my device can run properly if I can achieve an output voltage that scales the input ...
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233 views

How do I implement a simple and efficient voltage divider for battery level readings for a ESP32 board?

I'm trying to design a simple device based on ESP32 board, which will control stepper motors from a battery pack (26650 series). I'm struggling with the battery level control part (red/blue colour ...
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63 views

Voltage drop and voltage dividers

First, I'm not interested in numbers or the general math behind this. I know how to split voltage into some particular value(s). But what is actually going on? I get Kirchoff's Voltage Law, or at ...
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187 views

Why doesn't this battery voltage measurement circuit work? [closed]

So, I built this simple circuit for measuring voltage from a battery pack to an Arduino. The thing is, I want to measure the first cell and then the voltage from the whole battery pack: using two ...
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1answer
62 views

How to make a battery level indicator for arduino (The battery is powering the arduino also) [duplicate]

Hi I am building a pocket altitude, temperature and humidity meter with 1.8" TFT display. I have a 1000mah 3.3v Li-ion battery to power the whole system. I also need to display the battery level in ...
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2answers
72 views

Using an analogue multiplexer to control a motor controller?

I am designing a control circuit for a Sabertooth 2x60 motor controller. When this controller is in analog mode, it runs in full reverse (0v control signal) until my software starts and applies 2.5v ...
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2answers
121 views

using pressure sensor with 0-10v output for 0-10bar using arduino but pressure value won't cross 4bar. so is a voltage divider required in this case?

I have a pressure sensor working at 24V dc whose output is analog 0-10V for 0-10bar pressure. I am using this sensor with Arduino Uno. I know that the pressure value will never go beyond 4bar. So do I ...
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75 views

Voltage divider for ADC

Can anyone tell me why we use a voltage divider circuit with an LDR for an LDR robot? For example, why can't we directly take the LDR output and feed it to the ADC port in an ATmega controller? Why ...
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Are my calculations wrong for the capacitance?

In an earlier post i discussed about the effects of voltage derating on a capacitor. From here i measured the output with DC and AC applied to a highpass filter and found the cutoff frequency with the ...
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132 views

Voltage divider resistance/wattage sizing

I am working on a small project currently -- I recondition hybrid car battery packs with a grid charging system, and I am working on a voltage sensing circuit that's monitored and available via a ...
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50 views

Effects of a voltage divider on an audio DAC

Background: I'm planning on using a TI TS5A22364 SPDT Switch with Negative Signaling to connect AGND to the Left and Right Channels of the TI PCM5102A Audio DAC when the DAC is powered down as an ...
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44 views

Power off detection circuit to close opened latching solenoid valve

The image above is referred from this SO link. My use case is the following: A latching solenoid valve, which would be run using 4 AA batteries (6V) Solenoid Valve (9 Ohm) operates at 6V under 40ms ...
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56 views

Does anyone know the UL standard related to resistors and isolation on AC mains?

I have a circuit that is attempting to measure AC line voltage 120-240V but I was told by the certification test lab that my voltage divider resistors would require an expensive 3 week soak test. The ...
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93 views

Fuel sender - need something to convert ohms to volts?

I need to connect a cars fuel sender(ohms) to a analog input on a GPS tracker (volts) Here's the catch, in our tests most fuel senders we worked with seem to send the data as ohms/resistance However,...
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2answers
280 views

Battery Voltage Monitoring

I have designed a simple battery voltage monitoring circuit to monitor a 3.7V Li-Po battery. My microcontroller (ESP32) uses a 3.3V supply. simulate this circuit – Schematic created using ...
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1answer
78 views

Voltage divider and LED

I want to measure voltage presence when an LED lights up (i.e. the IC_Output goes LOW, LED is common anode). The -Ve of LED is ...
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1answer
63 views

Best way to shift automotive logic to Arduino TTL

My vehicle ignition switch voltage is 9V when the vehicle is not running. It is 6V when button is pressed. I need a way to convert this to TTL Arduino digital logic levels. I thought I could use a ...
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175 views

What is the purpose of diode in parallel with the resistor divider in MOSFET gate driving circuit

I have built several 200W AC dimmers using Microchip 8-bit CPU and the illustrated back-to-back MOSFET circuit. I have seen on Internet schematics with the D1 diode in parallel with the R1 resistor, ...
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207 views

How to combine a LPF and a Voltage divider?

I have to connect a 5V analog signal to a 3.3V MCU analog GPIO input as shown in the attached image. I wonder if its possible to combine the 2 blocks of voltage divider and RC-LPF into a single block? ...
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83 views

How can I calculate voltage drop on non resistors?

I understand that calculating voltage drop with two or more resistors in series is easy because we can apply ohms law and divide up the supply voltage relative to the resistance of each individual ...
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Finding the voltage of base Vb

I wanted to know if Vb in the trasistor in the photo is equal to the formula in red circle: Vb=R2*Vcc/(R1+R2)
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Change range of data acquisition system

I have a DAQ with many inputs that can measure within +-10 V, and I want to go up to +-30 V. Using a resistor voltage divider could be an option, but this lowers the input impedance. I would prefer ...