# All Questions

117,872 questions
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### Turn on a device if voltage drops below a configurable level?

Consider a Li-Po battery that has to be protected from damage by going below 3V. What would be the easiest, lightest, smallest ways to e.g. turn on a warning LED or buzzer (using the same battery ...
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So I've done this so far, and know one of the components is a 50ohm resistor. However I dont know where to go from here. How do i decide if its an inductor or a capacitor? This is a past paper exam ...
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### Location for placing ESD components for UHD video

I am implementing ESD protection for HDMI video input. The HDMI video goes through a custom cable of ours, into a connector board attached to our enclosure, through an edge card connector, into our ...
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### What chips can be used to design an Anti-Counterfeit /Authentication circuit?

I am an intern within the R&D branch of a company that designs tools that must operate with low noise at extremely high external temperatures (upwards of 175C). My boss asked that I look into ...
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### OBD-II Device, Simulate Car Alternator (emulate “on” state) / Voltage Levels

I have a device which plugs into the OBD-II port on a vehicle. This device includes some sort of ADC or other voltage detection mechanism on the main power pin. In order to determine if the vehicle ...
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### How much battery power for LED and how to make it flicker

I am trying to figure out what configuration of battery(ies) I need to power this LED. I am only using one (specifically the warm white 1-up). I am also looking to make it flicker like a candle with ...
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### How to filter/clamp/suppress positive voltage spikes from IC

I need to work with an IC or more specifically a PCB (RFID reader) that is feeding back positive voltage spikes into my supply line. What is the generally accepted solution of isolating noisy IC's ...
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### MOSFET switching on

I have a doubt. Consider an N-MOSFET: which is the voltage that can switch on it? The voltage between Gate and? Sometimes I read "between Gate and Bulk", sometimes "between Gate and Source", sometimes ...
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### Peak Detector with Reset

I'm trying to make a N.Peak Detector with reset functions. I've tried various modification to the classic peak detector without any success. What I'm trying to accomplish is: Detect the negative peak ...
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### What happens if you only energize one pole in a 2-pole 240v circuit?

I have an Intermatic pool timer box that has two 120v poles. The LINE has two pins (Pin 1 = L1, Pin 3 = L2), and the LOAD side has two pins (Pin 2 = Load 1, Pin 4 = Load 2). Currently, I have two ...
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### Does anyone know of a soldering iron that gets to 900 Fahrenheit? [on hold]

I'm looking for a new soldering iron that will get as hot as the old Hakko 936, but I haven't found anything. All that I've found have the temp range 200-850 F. Does anyone know a reputable brand ...
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### Rc ac parallel circuits:-

can someone, simply explain why does the capacitor current leads the resistor current by 90 degree in an rc ac parallel circuits, pls be simple. I thought about it but found no answer.
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### which one is preferable encoder or decoder for optimal solution?

while study the topic of encoder decoder in the subject of DLD my teacher ask a question that is which one gives optimal solution many of students give answered it's depend upon the circuit design but ...
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### what does the “UL” means when specifying the clock speed for AVR MCUs

So I am using the ATTiny10 for the first time, and I noticed that even after setting the clock pre-scaler register correctly (0x00 in my case) I had to define a value called ...
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### Input impedance calculation - antenna + transmission line [on hold]

Question: If an antenna with an input impedance of Z(a) = (50-j10) Ω is connected to a 50 Ω transmission line of length 1λ. What is their input impedance? Here is my attempted solution: Is it ...
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### Low voltage shutdown with regulator using microcontroller

I'm using a lithium polymer battery with an LDO regulator. I want the regulator to shut down when the battery voltage gets too low. I'd prefer to monitor the battery voltage using a microcontroller ...
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### ESD Diode - clamping voltage

I'm trying to replace an existing ESD diode(PESD1CAN) in my application CAN circuitry due to some reasons, I've found an alternative ESD diode(RSB27C2), but compared to the diode that I already have ...
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### Variable declaraton with extra in C

I am reading some C code and came across this declaration in the program: unsigned char serv_ctr @0x0002; Can someone point me to documentation or explain what ...
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### What could be causing an unreliable output for 3 different IS31FL3731 chips

I have a board that uses the Adafruit breakout of the IS31FL3731 to control 81 illuminated switches. I have some code that runs on an Arduino that should turn all the lights on, but only about half ...
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### Comparator loses voltage when connected to mosfet

I want to make a discharger for 18650 batteries so I can store them at a specific voltage. I built a comparator (LM393) with a voltage reference to 3.8V at the inverting input and the voltage of the ...
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### question about bjt voltage gain

Input voltage triangular wave signal with 12.7Vmax and 9.1Vmin passing thru a NPN BJT, assuming if the forward voltage of the BJT is 0.7V then why is the output Vmax is not 12.0V but way lower like 11....
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### Identifying a zener diode

This board is from a Ford 2004 F-350 instrument cluster (speedometer, tachometer, fuel gauge etc..) Ford has epoxied the chips down along with the solder. I tried removing one of them and well not ...
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### If battery negative lead is negative voltage(conventional current) or zero volt (ground)?

If the ground is zero volt and we consider battery negative terminal as ground. Then why does the negative voltage affect the circuitry.
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### Cheap signal amplifier for school physics lab [on hold]

I would like to buy a signal amplifier, and am looking for advice on make and model. It should have either 3.5mm or 4mm input and output, and can increase a signal around 10x (or more). It doesn't ...
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### Source Conversion: Combining series current sources

I have done 1.1 and gotten 9V and 3k Ohms for the equivalent source. I am trying to do 1.2 without first converting to voltage source and I come across this situation: How would I combine the two ...
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### SCR triggering in LT Spice

I have been trying to trigger a SCR in my circuits but an error shows up every time. Unknown subcircuit called in xu1 n002 n001 n003 scr This is a screenshot of ...
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### DC-DC converter not simulating correctly

I am trying to design a solar charge controller to charge a 12V battery, my solar panel is made of 9 cells that are 5W and 0.5V per-cell. I would like to make a booster circuit to get the voltage up ...
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### 13.56 MHz on chip wave rectifier

I would like to ask you if you now any on-chip half wave (or full wave) rectifier for 13.56MHz. I am considering whether to use nmos or pmos chip for wave rectification.
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### How to protect against line transients?

I am designing a circuit that can detect if a cable is connected to mains voltage (e.g. via an external relay or switch). The device will be installed in electric cabinets. The circuit is tested and ...
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### Drawing a line with a triangular aperture in Gerber

So, I`d like to output a rounded equilateral triangle in Gerber format. The first method I tried was to pick a large triangular aperture (%ADD11P,8X3*%, that is) ...
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### Problem with PSPICE simulation

I am having a problem replicating some lab results in the PSPICE/capture CIS program for an assignment. I have this circuit right here: which is an oscillator using the uA741 op-amp which is supposed ...
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### Energy lost in in Peltier device?

Suppose I power a Peltier device to heat up/cool down some water. Then I later use the same Peltier device, in reverse, to convert the separated heat energy back into electricity. I have read ...
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### Solving Thevenin’s equivalent circuit

Solving the KCL from these two nodes of this circuit doesn’t yields a result.The circuit is given below I tried this KCL method but since these two linear equations are unsolvable- In the book they ...
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### Finding the voltage across a inductor in a charged RLC-circuit

Well, I've the following circuit: simulate this circuit – Schematic created using CircuitLab In the circuit I want to find the voltage $\text{V}_{\text{Y}_1}\left(t\right)$ as a function ...
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### ATTiny84 is not working and freezes [on hold]

I have uploaded the program for several ATTiny84, some of them working perfectly and the rest are not sending any signals. I checked the Fuse sitting, it is right because I compared with the other ...
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### How to connect these relays together?

I have 4 relays as shown. I have created a small connection flow diagram with these relay.-->shown Is these connection ok for control four relays? Any current/voltage issue come? Any ...
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### Inrush Current effect on a Relay

I am confused about inrush current for a relay. For example, if I had 12A as the inrush current due to a motor, if the contact rating of a relay is only 6A, does a new relay need to be chosen? As in ...
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### Powering 12 volt DC engine with arduino [on hold]

For my mechanical engineering project I need to power an engine and a solenoid with 12v using relay module and arduino. I have a hcsr04 ultrasound sensor that gives out values and I need to power two ...
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### LED strip power supply 12V 2A vs. 12V 25A [duplicate]

I am using a white light LED strip in my 3D printer enclosure. And I would like to use the power supply of my 3D printer to power this LED strip. The original power supply of the LED strip is 12V/2A ...
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### Uneven LED Lighting Wired in Series

I’m struggling with six 11.5-watt LED cans wired in series. With a 75-watt incandescent at the end, the other five seem to function properly, though the incandescent is dull. With an LED in its place, ...
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### What is the purpose of using the transistor in the circuit?

Current sensor using an instrumentation amplifier: Image source: Texas Instruments INA139, INA169 High-Side Measurement Current Shunt Monitor, Typical Application Circuit (datasheet page 1) Could ...
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### How are and what are the sources coupled to a 3-wire RTD leads? [duplicate]

I can understand two or four wire connection for RTDs. But I don't get where they apply voltage or current and how they measure the resistor values for 3-wire connection: Here is a page about these ...
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### Infrared burst/gap rate and ratio for TSOP1236

My transmitter consists of this exact IR LED, with an 180 ohm resistor, operating at 5V, that is being pulsed by an ATTINY13 using this code: ...
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### Need LM324N non-standard logic converter

I have a background in electronics but am very rusty and need a circuit to monitor my security system. I would like to monitor the voltages at my security system board for each of the door contacts, ...
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### Problems with capture cis simulation

I am trying to run some simulations on capture(PSPICE) for a school assignment and then compare the results of them with the results that i got when trying these circuits in the lab. However the ...
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### A very basic question about response time of an instrument

Regarding a temperature transducer, what is meant by response time in this context? It says it can be set to < 30 ms or < 300 ms. Is there any trade of between choosing low or high response time?...
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### Connect charger to device first or to power first? [on hold]

What reduces the chances of frying a device? Connecting the charger to the power plug first or to the device first?
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### How to connect a device to ground using negative signal with high impedance

simulate this circuit – Schematic created using CircuitLab I have a device that enables a ground connection when I press a key on a remote control. This negative signal used to control other ...