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 resisors in series from the input voltage to ground, with the output voltage taken from the junction of the resistors. As an example two equal ...
7
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4answers
382 views
Zero or low-current voltage divider for switch identification
Is it possible to design a voltage divider circuit with switches that uses zero current, or very low current? Would it work to use a transistor to connect/disconnect the end of resistor string from ...
6
votes
4answers
1k views
Low power design - switch out voltage divider using transistor?
I have a very simple voltage divider circuit for measuring the resistance of a platinum 100 Ohm resistor.
I want to be able to switch out the voltage divider circuit from the power supply in order to ...
6
votes
2answers
128 views
Setting a part's VCC slightly lower than board's supply voltage
I'm interested in using the undervoltage detection feature (in addition to the primary function) of this chip. This IC draws 6 uA (microamps), and accepts any VCC between 1.6V and 5.5V.
The ...
6
votes
1answer
464 views
op-amps: where to split the rail?
I have been experimenting with op-amp audio amplifiers powered from a 9V battery. I am just wondering how I should go about splitting the voltage from the battery, as I have found 2 ways of doing this ...
5
votes
8answers
1k views
How does the electricity “know” the ratio of the resistance in a voltage divider?
I'm having a hard time conceptualizing what/how things are working in a voltage divider setup. I've read a couple other questions/explanations where the answerer has said to "not think about it in ...
5
votes
3answers
1k views
Measure Lithium ion battery voltage (thus remaining capacity)
What I am working with: I am running my self-made Arduino board (in the sense that I use the Arduino bootloader and code editor) at 3.3V, and powered from a Lithium ion battery, which is USB-charged ...
5
votes
3answers
171 views
When use Voltage divider in circuit analysis
I am trying to find the voltage in R2 with voltage divider, this is the schematic:
simulate this circuit – Schematic created using CircuitLab
but I can't, and I don't know how to apply ...
5
votes
2answers
96 views
Scaling voltage to meet two conditions at once
I am using an IC (STM6600) which, among other functions that I need, is also capable of Undervoltage Monitoring. It works like this:
The IC monitors VCC in comparison to two thresholds, V_Low and ...
4
votes
2answers
318 views
ADC reading 96V DC
I have a 96volt DC line, and I am trying to get it down to 3.3volts to put into an opamp, and then to put into an ADC so that I can read the voltage on the line. The 96volt line will be prone to ...
4
votes
2answers
151 views
Pull-down resistor value for FSR's voltage divider circuit connected to Arduino
I am working on a project which includes two FSRs (force sensitive resistors) connected to an Arduino Uno. I have each FSR setup as in http://www.instructables.com/id/FSR-Tutorial/?ALLSTEPS, but each ...
4
votes
3answers
343 views
Choose the resistence with voltage divider sensor
I'm on voltage dividers circuits for reading some sensors that changes their resistance (force sentive resistor).
With my tester (with input scale set on 200K ohms) I read 23 if sensor is not touched ...
4
votes
3answers
484 views
80's Cassette Line to Microphone Level for iPhone
This is a followup question to this one: Using an iPhone as a cassette recorder for 80's home computer
I'm trying to record from an 80's home computer (a Microbee) into an iPhone. Although I ...
4
votes
1answer
981 views
How does the input circuit on this oscilloscope manage to accept such a large range of voltages?
I recently bought this ($45!) oscilloscope: http://www.gabotronics.com/development-boards/xmega-xprotolab.htm. Looking at its schematic, I see the circuitry for one of the two analog input channels:
...
4
votes
3answers
154 views
Reduce and clip voltage of a 5Mhz ultrasonic signal from +-50V to 0-3.3 V
I know there are a lot of posts similar to this one but some differences make it worth posting it.
I’m working on a project where I have a 5MHz AC signal with the largest amplitude of +-50V. It’s an ...
4
votes
4answers
598 views
Set up an array of pressure sensors
I am working with a flexiforce pressure sensor 25 lb.
I have to run 6 of them in parallel and I'm using an Arduino Uno. I'm not an electrical engineer (read: I'm a computer science major) and this is ...
3
votes
5answers
7k views
What resistor values to use in a voltage divider?
I understand that the output voltage is determined by the ratio between the two resistor values, and that two 1 kΩ resistors will output the same voltage as two 1 MΩ resistors (correct me if ...
3
votes
2answers
2k views
Is this 7805-based design correct?
I found this design on internet:
It is said to be a regulated power supply with variable DC output 5-15 V, 400 mA. My first question: Is this design around 7805 correct? I am asking because it ...
3
votes
2answers
654 views
Voltage divider for Xbee's ADC - what resistor values?
I have an analog sensor which outputs a value in range 0-3V depending on soil moisture.
The Xbee's ADC requires a value between 0 and 1.2V.
I was thinking about using a simple voltage divider:
...
3
votes
1answer
120 views
How do I calculate the voltage at these locations?
I'm wondering how to calculate the voltage on the following charts (series circuit and parallel circuit). I'm interested in the math process involved, not the answer.
I'm mostly confused about how ...
3
votes
2answers
156 views
3
votes
2answers
86 views
How can I get 17 VDC from 25 VDC with current may up to 10 A?
I'm new in electronic and electrical circuits, so maybe my question will be naive.
I have an electrical transformer that gets 220VAC as an input and gives 25VAC as an output, and can produce 20amp ...
3
votes
3answers
297 views
Choosing a transistor and resistor for PIC input pin protection from Car Power
Further to my previous question,
Using a PIC to perform switch on and timed shutdowns in automotive environment
I've been pointed at zener diodes and voltage dividers, but I'm now confused by the ...
3
votes
1answer
37 views
Replicate thermistor behavior for second sensor
I'm working with an R/C electric motor that has a 10K thermistor sensor built into it, which is connected to a speed control that has basic thermal protection. I would like to build a secondary sensor ...
2
votes
4answers
1k views
Lowering 3.3V to 3V
I am attempting to lower a 3.3V source to 3V for use with a sensor (which has a rating of 3V +/- 0.1V). Based on the other answers in here, I believe that placing two resistors in series would achieve ...
2
votes
5answers
516 views
If I'm going to use a potentiometer as an adjustable voltage divider, does the tolerance or resistance matter?
Here's what I working with. I'm researching some three terminal potentiometers for use as adjustable voltage dividers. The outer terminals are connected to 0V and 5V respectably, so as I turn the ...
2
votes
3answers
661 views
LPC2148 ADC problem with voltage divider for battery
edit: solution found with our new board revision; outside of careless mistakes, buffering the signal with an op amp seems to have resolved the issue (as suggested by Joshua below).
I am working with ...
2
votes
2answers
341 views
Measuring Power Amplifier with Sound Card
I'd like to measure the frequency response of my power amplifier, while it is connected to a loudspeaker.
The power amplifier outputs at +- 50V, and I think the maximum input of the sound card is ...
2
votes
3answers
153 views
Low current battery monitoring
I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the ...
2
votes
2answers
131 views
Increase resolution of voltage divider
I have a lead-acid battery on which I am using a voltage divider to measure the remaining charge.
Its my understanding that an example battery could discharge from 100-0% over say 10.5V - 12V.
...
2
votes
3answers
237 views
Current Drain on ADC
I am looking at a MCP3008 datasheet and it says that it has a maximum current drain of 150uA, and a typical current drain of 100uA.
I am building a voltage divider to knock down 96V to 3V. As this ...
2
votes
3answers
298 views
Whats up with my photoresistors! (Wonky readings, non-stable, I'm missing something)
I'm working on a photoresistor array with my arduino, and I'm having a little trouble getting stable readings.
I'm driving 7 rows one at a time with arduino's digitalWrite(pin,HIGH) command and ...
2
votes
6answers
102 views
Switch transistor with a low voltage and current
I'm designing a circuit that will use a combination of switches and resistors to allow a microcontroller to identify which switch was pressed based on the voltage read and perform a switch-specific ...
2
votes
1answer
213 views
Circuit Nodal Voltage
I have a voltage divider feeding into an op-amp voltage follower buffer circuit. I'm trying to calculate the voltage level at the non-inverting input of the op-amp vs. the source voltage. The possible ...
2
votes
1answer
62 views
Finding values of LRC circuit when frequency is given
I am trying to solve the following question. The original question is:
The given impedances of the series LRC circuit are established at an
angular frequency of 2000 rad/s.
Calculate the ...
2
votes
1answer
59 views
How do I measure the characteristics of a voltage divider in a QUCS simulation?
How do I measure the characteristics of a voltage divider in QUCS?
Below is what I have tried thus far, using Qucs 0.0.15 on Ubuntu 10.04
I want to measure how the voltage at the center of a ...
2
votes
1answer
157 views
Opamp topology without a stable voltage reference
I have an opamp configured as a constant current sink like this:
As you can see, the reference voltage for the SENSE pin is set by the voltage divider on the left. This requires a stable voltage on ...
2
votes
2answers
2k views
What is the voltage divider rule?
Can anyone explain what the voltage divider rule is? How has the author of this book used it for analyzing the Voltage Divider Bias circuit for transistors?
And can anyone explain how the two ...
2
votes
2answers
956 views
Combined ADC scaling and offset with variable input voltage ranges
I am trying to create a circuit which will allow me to scale and offset a voltage (be it AC or DC) to within the range of the Arduino ADC.
The voltage could be anything between + and - 250V, but I ...
2
votes
1answer
183 views
Can I use a voltage divider circuit instead of a level shifter here?
I am trying to hook up an LCD module to my microcontroller, and was following this tutorial.
Notice that the three signal wires all go through a level shifter, which drops the voltage from 5V to the ...
2
votes
1answer
95 views
Arduino Pro Micro: how to access A1
I have an Arduino ProMicro 5V 16MHz board from sparkfun.
I have a 3Cell LiPo powering the entire thing (via the relevant regulator bringing it down to 5V). This is part of a TriCopter. I tap the 12V ...
1
vote
4answers
228 views
Characterizing raw op amp gain
I thought as a first exercise in op amps, even before setting up a feedback circuit, I would determine the gain of the raw op amp.
I tried with an LM324 and an LM358 which should be essentially the ...
1
vote
3answers
87 views
Measure current on a constant current source
I need to measure current on a constant current source(LM317), because I am using a 3v3 chip I also need a voltage divider to read it. Will this circuit work Or will it wreak havoc trying to increase ...
1
vote
3answers
101 views
Driving three LEDs in series with different Vf at 700mA
Given LED1: Vf = 3VDC for 700mA ---- and ---- LED2: Vf = 4VDC for 700mA
If I put LED1 + LED1 + LED2 (in series) and apply 10VDC across them, will I have 700mA flowing through them?
1
vote
2answers
421 views
Confusion with voltage drop equation
I had never really thought of resistors causing a voltage drop, I have only used them to limit current to say an LED.
Using something such as E = IR I can use a ...
1
vote
4answers
844 views
Voltage Divider vs. Resistor in Series
What is the difference between having a voltage divider vs just using a resistor in series.
So for example, I have an input voltage with 12V, and two resistors in a voltage divider, R1=10k, and ...
1
vote
1answer
151 views
voltage divider circuit for dc motor
I would like to run a 6V dc motor using a 9v battery supply. The motor specification states that current is 150mA at 6V which I calculate to be a resistance of 40 ohms (when I measure the resistance ...
1
vote
2answers
1k views
Postive input ==> Positive and Negative output
I was watching some tutorials on thesignalpath.com and came across something that I didn't quite understand (even after it was explained).
toddrharrison
August 21, 2011 at 6:29 PM
Answer ...
1
vote
1answer
306 views
how to reduce 24v to 0- 2.5v through a pot
I have a 24v dc supply and I need to give a heater a 0-2.5v variable input. I have a very limited understanding on electronics but I've read here about voltage dividers. I used a 10k pot (and the 2 ...
1
vote
3answers
160 views
Connecting 3.3 and 5 V devices
The requirements are different from similar questions I've found here.
TXB/TXS are expensive for my needs.
Sparkfun's logic shifter is bi-directional, while I need two uni-directional conversions, ...
1
vote
1answer
244 views
how to find minimum acceptable current through voltage divider driving transistor
I'm using a BC557 transistor to control a LED and a uC to control the transistor. The transistor itself is controlled using a voltage divider.
It was suggested to me to use resistors around 100K + ...
