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# 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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144 views

### High Power Variable Potential Divider

I have a DC high voltage (>270V) high current (>40A) circuit which needs to power a standard LED along the way to a heater. The LED is to indicate whether or not the heater is activated. I'm ...
1answer
86 views

### Voltage Divider Configuration of Transistor

I have a voltage divider configuration for biasing my transistor. The gain of transistor is lets say 150 which is typical value for BC547. What I want is limit the current flowing through the base to ...
2answers
228 views

### Measure LiPo Battery Cells with Voltage Divider?

First, I am new in this topic, so please excuse unnecessary questions. I want to measure the (four) cells of my lipo battery. The connector of the battery has a plus pole and four minus poles. (Image)...
3answers
60 views

### How to reduce voltage from shift register to ESP32 MISO pin?

In this circuit I have sensors that are rated for a minimum of 6V connected to a 74HC165 which passes its output to the MISO pin of an ESP32. I was hoping a simple divider to convert the 6V from the ...
2answers
85 views

### 3 Resistor Voltage Divider Formula

I'm trying to analyze this circuit and spend almost 2 days to make a formula for it but I don't get it , anyone know what it's called or how can I make formula for it ? I want to calculate I1,I2,I3 ...
3answers
232 views

### Arduino oscilloscope voltage divider design

I'm building an oscilloscope with arduino, but I have some questions about how to design the input voltage dividers without ground. The problem is the oscilloscope only needs one input to measure ...
1answer
66 views

### Cascading/multiple voltage dividers

Could someone explain the voltage readings on the following "oscilloscopes" of the simulated schematics below: (I understand the concept of a voltage divider but it seems something less ...
3answers
82 views

### How to interface a C64/Atari joystick port with the ESP8266 (level shifting from 5 to 3.3V)?

I'm working on a device based on an ESP8266 (Wemos D1 Mini) that shall be connected to a C64 or Atari 8-Bit computer's joystick port. At the same time, a normal joystick could be connected (signals ...
2answers
210 views

### How to calculate resistor values for a VGA DAC

I have an FPGA and want it to drive a VGA monitor. I want more than 3 bits of color so I need a DAC of some sort. So I want to make a resistor dac. My plan is to have 3 bits per subcolor. So total of ...
2answers
115 views

### Reducing 3v supply to run 2.4v laser diode

I am setting up a laser trip wire system, this question revolves solely around the laser itself. IMPORTANT: The laser is always on (it will have an on/off switch) Supply voltage is 3v (2x aa's) ...
3answers
177 views

### Optocouplers vs Voltage Dividers

I have a device that has a terminal that goes to 5v at certain times. I wish to sense that voltage with an ESP32. I have built this circuit using an optocoupler: simulate this circuit – ...
2answers
3k views

### Why do we need a voltage divider when we get the same voltage at the output as the input?

I am using a voltage divider circuit of 100 Ω and 10 kΩ resistors, and using their output for the (IRF740) transistor's input. I'm trying to figure out why do the resistors have those specific values....
3answers
173 views

### Convert 24V to 12V @ 30mA

I have a device, Neptune Apex, that has programmatically controlled 24VDC outputs. Using the 24V I would like to trigger a relay that is built into another component, that has the specs of: 3-12VDC, ...
2answers
116 views

### Voltage Divider Multiplier Value Too High?

After constructing a voltage divider to reduce the voltage from my power supply (Output 10kV, 30mA) an oscilloscope probe was used in hopes of measuring the output voltage of the system. Due to the ...
0answers
33 views

### 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 ...
1answer
322 views

### 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 ...
2answers
103 views

### 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 ...
2answers
88 views

### 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 ...
1answer
60 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 ...
1answer
58 views

### 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 ...
3answers
136 views

### 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 ...
2answers
90 views

### 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 ...
2answers
981 views

### 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 ...
3answers
252 views

### 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;...
1answer
68 views

### 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 ...
2answers
70 views

### 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 ...
2answers
125 views

### 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 ...
1answer
129 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 ...
0answers
28 views

### 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 ...
1answer
38 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 ...
4answers
934 views

### 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 ...
1answer
55 views

### 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 ...
1answer
90 views

1answer
102 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 ...
1answer
58 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 ...
4answers
138 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 ...
0answers
79 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 ...
1answer
105 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 ...
2answers
504 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 ...
2answers
78 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 ...
3answers
206 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 ...
1answer
110 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 ...
2answers
87 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 ...
2answers
159 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 ...
1answer
98 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 ...