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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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1answer
747 views

Why use a ten-percent rule-of-thumb for a bleeder current on a voltage divider?

A book I am reading recommends "The 10 Percent Rule" as a method for selecting resistors for a voltage divider: The book claims it is a standard method. My question is: why choose a bleeder current ...
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1answer
106 views

Voltage divider network calculation

Hello I am troubleshooting a voltage divider circuit in which I know the output going to U28 pin 3 should be around 700mv. What I am measuring however is around 7.5v. How do I calculate the v out for ...
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2answers
317 views

How to effectively downscale input voltage of a device?

Oscilloscopes let us measure input voltage in a variety of input signal ranges (either AC/DC, +/- 500V or Gigahertz's of frequency). I am wondering: how they make it happen? Say, an oscilloscope has ...
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3answers
517 views

voltage divider circuit design [duplicate]

I am giving -8 to +8 V supply to the op-amp. So, output of the op-amp is varying from (-8 to +8) V. I want to give this to ADS1115 ADC module. But the ADC module's max. Vin is 5.5 V. I decided to ...
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1answer
153 views

Lower the voltage on a 5V PSU to 4.9V

I've been working on a mostly software based project that includes an addressable LED strip. I am powering the strip with an old ATX PSU and the LEDs seem to be vely unstable when at low brightness. ...
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2answers
743 views

Find resistance r1 and r2 using vin and vout

I have tried everything.I have tried all voltage divider rule but i need atleast r1 or r2. Can anyone help me understand to solve it? No need of solution just set me on right path.
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1answer
127 views

Filtering noisy buffer output

Please bear with me as this is my first time working with filters. I am trying to scale down the voltage from my piezo to a voltage which my ADC can read (from >100V on the piezo to 0-5V on the ADC ...
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2answers
367 views

Is it possible to measure the voltage and current of a load with this circuit and Arduino?

I'm trying to measure the voltage and current for a DC-AC converter in my car with Arduino. I know it would be easier, more accurate and cheaper to use breakouts with INA226 like this. But this ...
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2answers
329 views

Stepping Down Voltage to power DC motor

First post here, it's probably a very easy fix for most of you here. Right now I'm trying to use a digital potentiometer in a voltage divider to step down a voltage from 5v to a range of 3 - 1.5 volts ...
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2answers
3k views

How to calculate voltage divider transistor bias?

So I've been trying to learn how to calculate transistor bias, but I can't seem to find any appropriate equations. Let's say I have this (right) circuit which I can transform to the left circuit. ...
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4answers
505 views

Voltage divider ratio limitation applied to potentiometer

I'm trying to find the general formula or more like understanding of how to choose resistor values to limit the voltage ratio when using a potentiometer. A potentiometer is equal to a voltage ...
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1answer
49 views

Voltage divider in voltage mode control of Buck converter

What is the need of voltage divider in buck converter? I am not able to understand that why can't we connect output voltage as a feedback voltage to the error amplifier
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3answers
350 views

I have a 9V battery, but I only need to output 4.5V from it. How do I accomplish this?

This is the circuit I have so far: Falstad Voltage Divider Circuit simulate this circuit – Schematic created using CircuitLab As you can see, I tried using a simple voltage divider, but this ...
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1answer
99 views

how to calculate voltage divider [closed]

Is VDR applicable for R3 and R4? Why? I want to calculate the voltage divider across resistor R3 I do like this Vs*R3/R3+R4 Is it true?
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1answer
369 views

Sizing Resistors for Voltage Divider Circuit Feeding Solid-State Relay

I need some assistance in sizing the two resistors for a voltage divider circuit in order to drop from 48V DC to somewhere in the 4V-32V control voltage range of the Crydom DC100D40C solid-state relay....
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3answers
261 views

Reasonable resistor values for voltage divider

I'm getting an unexpected voltage from a voltage divider I created. Is it likely that the resistor values are too high to provide enough current for my multimeter to measure accurately, or do voltage ...
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2answers
3k views

Calculating Resistor Wattage for Voltage Divider?

Background: I am monitoring the voltage of a 4 cell LiPo battery (max voltage 16.8V, maximum advertised current output = 60A) using a sensor with a maximum input of 3.2V. I am using a 2-resistor ...
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2answers
42 views

powered led generator works but with other power source with voltage divider at same volts don't

As the title say I have a small motor used as generator that generates 0.5ma at 1v that power up my led (slighty). I don't have the data sheets from led(it's a 5mm red led), I suppose the forward ...
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1answer
69 views

Making a voltage drop while providing high current - how does this work?

I have a USB power source at 5V which needs to power a chip at ideally 4V (4.4V max) - but I need to be able to supply 2A of current for the "spike" current draws for the chip. In general the chip ...
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2answers
227 views

Voltage Divider Equation [closed]

I want to create a Voltage Divider Equation that gives Vout in the three places in the ratio 5:5:7 of Vin. I have tried many times but because of lack of expertise and a bit not good in Mathematics, I ...
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1answer
108 views

Single Ended Precision Variable Amplitude Square Waves and Charge Injection

I love to hear any thoughts about a good break-before-make analog switch with low charge injection or even even better any thoughts on generating precision amplitude square waves in general. As to ...
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1answer
752 views

Problem with voltage divider

simulate this circuit – Schematic created using CircuitLab I have a problem with a voltage divider circuit. I'm not an electrical engineer, so I am having some trouble finding a solution. I ...
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2answers
53 views

Charging my cellphone with a 18V DC source

I have received a 18V 2.5W photovoltaic panel and want to use it to either charge a cellphone (or even two at the same time) or power some Arduino projects. In both cases I need a 5V source, but mine ...
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1answer
144 views

Step voltage down safely for a LED

I have a 127VAC -> 24VAC transformer to power a project and I want a LED to light when my electronics is ON. I rectify it and pass through a smooth 2200uF ...
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1answer
69 views

Connecting a PhilipsHue led output to a relay

I followed an Instructables tutorial to get some understanding of what pins can be used from the Hue light bulb. Out of all the "exposed" pins, I focused on ...
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4answers
289 views

Voltage drop across a resistor

I have been trying to figure this out, kinda a amateur question actually! Looking at the above circuit diagram am wondering why there is no voltage drop across the resistor R1? A part of voltage ...
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2answers
5k views

BJT Voltage Divider Bias Circuit problem

Let's say we have the following circuit: The known values are: \$\beta=100\$, \$Vcc=2.5V\$, \$V_A=\infty\$ (meaning the Early effect is not taken into account), \$V_{BE}=0.7V\$, \$I_S=8\cdot10^{-16}A\...
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2answers
173 views

Why am I seeing a low voltage when the switch is open?

I'm building a battery test circuit to check the voltage of the source battery and I've added a Sziklai pair of transistors in as I need to be able to shut off the voltage so that I don't have a low ...
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0answers
148 views

Current limitation to capacitive voltage divider

For an AC capacitive voltage divider, I would think the amount of current that could come from the divider would be limited by the absolute size of the capacitors. The flow of current should be a ...
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1answer
62 views

neat voltage divide sequence [closed]

I am learning voltage dividing and created an array of different values to get a broader perspective and found this repeating sequence. Can anyone explain why the combo of r1 as 6000 ohm and r2 of ...
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1answer
91 views

logic voltage divider problem

https://www.partsim.com/embed/#102528 I made the following cirucit. Pin 1 2 and 3 are connected to microcontroller output pins. Pin 4 is where I want to measure a voltage. Only one pin (1,2,3) is ...
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3answers
766 views

voltage divider with 2 power sources, Vout?

simulate this circuit – Schematic created using CircuitLab If V2 is NOT present(VB=GND) i can solve it easily using voltage divider formula: I know the steps: I = V1/(R1+R2) Vout = I * R2 =>(...
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5answers
2k views

Does this circuit problem have a solution without an Op-Amp?

I was going through the definition of a voltage follower in this site http://www.learningaboutelectronics.com/Articles/Voltage-follower And a basic problem was presented, and an op-amp voltage ...
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4answers
449 views

Easy way to get 12v DC from 32v DC bus?

I've got a 32 volt DC regulated bus. I also need about 30mA at 12 volts (DC). Is there an easy way to tap some power from the 32v bus? My first thought was just put in a 12v linear regulator. But ...
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4answers
1k views

Using a digital potentiometer in a voltage divider

I'm using an MCP3008 ADC and an MCP4131-103 (10k) digital potentiometer to try and create a sort of "adjustable voltage divider." For the project, the resistance I'm measuring will vary, and I hoped ...
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2answers
389 views

Why is my voltage lower than expected?

I'm designing a voltage measurement device and I i'm testing it and the front end voltage divider and it has a much lower voltage than expected. Circuit is below. simulate this circuit – ...
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2answers
186 views

Is it possible that the BJT will work in active mode even if emitter base junction is reverse baised? [closed]

I was going through voltage divider bias configuration of BJT and then i encountered two problems:- The above two problems are nearly same except that the emitter terminal is grounded in case of (b) ...
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2answers
423 views

How can we provide a stable reference voltage to a voltage regulator if we don't have a stable source to begin with?

In voltage regulator circuits i always see a "reference voltage", that is supposed to be used to tune the regulator to the voltage we want to regulate the output to. But since we don't have a ...
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1answer
389 views

Adding voltage divider in line to stereo speakers

New to site. Vintage hi-fi enthusiast. I have a pair of bi-polar speakers I want to modify. I would like the ability to lower the volume on the REAR drivers only so they are at 50% volume of the front ...
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1answer
112 views

Over-voltage prevention not working [closed]

I have an system that has a signal that swings to logic level 0(on)-12v(off). That i'm reading with an Arduino. The signal is normally held at 12v. Using a simple circuit like so: The blue line is ...
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2answers
150 views

What are the critical characteristics of an op-amp for buffering reference voltages?

So, let's say I have a precision voltage reference with the output fed to a voltage divider which is tapped at two places for voltages A and B. I've made sure to use precision resistors (or calibrate) ...
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1answer
77 views

Generating 14V, 12V, and 5V for winbond 8051 chips such as w77e58

I'm trying to make a way without error to use the fewest digital inputs possible to provide an output of 14V, 12V and 5V on the VPP pin of the winbond microcontroller. The model I will be using is ...
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2answers
266 views

mathematical equation for parallel voltage dividers?

As a followup to my previous question it turns out there was more to it than I thought. It seems that between my voltage divider and the ADC on the ESP there is a second voltage divider to step down ...
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1answer
558 views

Down-converting voltage

I'm trying to reduce the voltage of a power supply for a certain load without affecting the current the load draws. Since the op-amps I could find were not able to provide sufficient current, I added ...
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3answers
513 views

Voltage divider/reduction with no current draw

I am trying to measure the voltage on an LED in an open circuit (awfully shown below) using an arduino, however the voltages are too high for its inputs. I have tried: Using a voltage divider (~10K ...
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0answers
100 views

Debugging implementation of low current battery monitor

I have tried to implement the circuit in this answer in order to measure the voltage of an external battery using an Arduino. However, I am not sure if I have wired it correctly. Here is the diagram: ...
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1answer
2k views

Low power battery voltage monitor

I would like to measure the battery usage of my ESP32 device. As my device runs in deep sleep mode 99% of the time, it's important that the battery monitoring circuit does not add too much to the ...
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2answers
392 views

How Does A Pull Up Resistor In Parallel Work?

I've been playing with a Raspberry Pi and working with simple circuits. I thought I had a decent understanding of pull up/pull down resistors, but then I purchased an Infrared Break-Beam sensor (https:...
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2answers
302 views

How to get ADC input with high resistance?

EDIT: Original post was phrased as XY problem. What I need to do: Determine if power at "Switched power" is being turned on by SW1/FET combination or other power sources not pictured in the diagram ...
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1answer
230 views

Arduino ADC values change after USB disconnect

I using an Arduino uno analog read function to read a voltage divider circuit for a voltage range from 0-70 VDC. On the voltage divider, I am using 2.7Kohm and 36kohm to reduce to voltage range from 0-...