# Tagged Questions

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 ...

373 views

### Why should we need DAC ICs?

Please look at the schematic below. This is a very simple resistive adder that works fine with any standard ! (TTL,CMOS,...) or any arbitrary voltage that is fed into it. On the other hand as there is ...
2k 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 ...
565 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 ...
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 ...
10k 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 ...
149 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 ...
3k 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 ...
401 views

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 ...
748 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 ...
716 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 ...
559 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 ...
170 views

### Voltage divider ambiguity

considering the following circuit : ...
104 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 ...
604 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 ...
818 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 ...
258 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 ...
1k 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: ...
417 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 ...
4k 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 ...
128 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 ...
1k 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: ...
208 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 ...
231 views

### Using/Charging a backup battery in a 12VDC circuit

EDIT: I've revised the circuit in response to comments from Andy aka. I have also updated my questions to make it more clear what I am asking. I'm leaving the top paragraphs for completeness' sake. ...
217 views

### 7-segment output: 4-6V, LCD input: 3-5V. How to convert?

Problem: I am thinking of using a chip that gives out 4-6V on 7-segment output pins but the LCD only wants 3-5V input, so I need to convert somehow. The display is a TN type, drawing virtually no ...
3k 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 ...
769 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 ...
737 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 ...
275 views

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 ...
179 views

### Which one is better as voltage divider: resistive, capacitive , low pass filter,…?

There are different types of voltage attenuators for AC signals ( a short explanation is here). The most well known is a resistive one. Others like capacitive, inductive or low pass filters are ...
113 views

### replace buttons in voltage-divider with mosfets

I have this voltage divider (each press of a button generates a different voltage) I want to be able to enable the buttons with a +5V signal. I tried to replace the buttons with 2N7000 n-channel ...
192 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. ...
158 views

### Generating a 10 volt rail from a High Voltage Supply with unknown Ground Potential

I have a sticky situation where my power supply is coming from a charged capacitor with 200 volts across it. Because of the way it was charged, I can't guarantee that the negative side of the cap is ...
2k 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 ...
115 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 ...
467 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 ...
85 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 ...
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 ...
191 views

### Using an Op-amp as comparator

I have a dual op-amp that I want to use as a comparator: Vin should be compared to Vref (1/2 VCC). This is the circuit that I am using (as I have a dual op-amp, I am using a voltage follower on the ...
411 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 ...
1k 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 ...
99 views

### PIC - How to skirt around low maximum ADC input impedance?

Reading a 9V battery on a PIC is nothing new. The most simple and straightforward way is with a voltage divider. I'd like to keep the divider resistances cranked up into the hundreds of kohms so I'm ...
172 views

### Effect of a transistor on a voltage divider? (or vice versa)

I'm learning about transistors and am trying to make a basic circuit that uses a photoresistor as a sensor to turn an LED on and off depending on light conditions (the 150kOhm resistor is where the ...
604 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 ...
261 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 ...
378 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 ...
257 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 ...
238 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 ...
2k views

In the past to create voltage dividers or protect against back emf I have used resistors, but reading about signal diodes those situations are given as examples. I can't really comment on the inductor ...