Questions tagged [circuit-design]

a term to describe how a circuit should behaved based on accomplishing a particular task. When designing circuits, one should consider how it works, the target specifications, efficiency, cost effective, code compliant, and ethics.

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Splitting a 50 Ω pulse signal into two gain stages

Given a pulse from a charge-sensitive preamplifier with 50 Ω, output impedance I'd like to split the signal into two separate conditioning circuits. Using an AD8009 as a buffer I've come up with this ...
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Connecting LED indicators

I have schematics of system that I design. When SW1 is closed, SW2 is open and the battery getting charged via the Charge Controller with around 6 V and 500 mA. ...
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1 answer
53 views

Second opinion: circuit for camping van

I am customizing a van to take on a camping trip and want to install some electrical applications. With only little experience on this topic I did my research online and drew up a schematic for the ...
1 vote
1 answer
71 views

Step down 100 V to 26 V with some specific requirements

I'm trying to repair an HP 8555A spectrum analyzer module which shows problems in the step-down power module. I'd like to replace the module which steps down the 100 VDC coming from the mainframe unit ...
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3 answers
60 views

How do I power an STM32 dev board with 9 V properly?

Dev Board: Discovery board with STM32F411VET What is happening in the MCU? I saw the datasheet with the 100-pin chip and and saw it has a bunch of VDD pins and a VBat pin but I'm not sure how the 5 V ...
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1 answer
33 views

Maximum capacitance on 12 V ATX PSU

I'm designing a fan controller for a PC. It will be controlling 6 fans. I want to start initially with 100 µF tantalum capacitor for each fan. Can 600 µF capacitance on the 12 V line (4-pin, 5.08 mm ...
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RP400N501A DC-DC regulator on PCB not outputting correct voltage

I have created a PCB that is powered by a 3.7v lipo, and has a 5v boost converter and then a 3.3v linear regulator. The reason for the 5v boost converter is that I have to drive some LEDs at 5v, but ...
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1 answer
23 views

ESP32MINI + MCP2221A + 3.3v, 5v, and 12v power supply circuit problems

I'm trying to design a circuit with an ESP32-Mini that connects to a CAN bus via an SN65HVD230. I've added an MCP2221A as a USB/UART interface to the ESP32 so that I can program the chip while on ...
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74HC595 shift register outputting data when it shouldn't

When I connect my Arduino with this 74HC595 shift register circuit, all the shift register's outputs go high, and any code I run doesn't seem to change this. Regardless of what I run, all outputs are ...
1 vote
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5 V to 500 V converter PCB review

After spending about an hour researching, I opened EasyEDA for the first time to make a circuit. It is supposed to convert 5 V from a USB port into 500 V in order to power a neutron detection tube. I'...
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TLP3556A MOS switch doesn't seem to turn on

We are using this photo MOS relay in one of our designs. This design is in production and we test every relay in QC. Recently I came across a failed unit with one relay not turning on. I checked the ...
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2 answers
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BJT phase shift oscillator

DC 5 V for input Three 10 nF capacitors One 2.2k resistor One 680k resistor Two 5.6k resistors My assignment is to make an oscillator using only the elements given above. This is the desired ...
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1 answer
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Digital system design in Proteus

Why doesn't it show anything on the seven-segment displays when it's running? It also shows grey areas at the connections.
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How to figure out equations for a signal flux diagram?

I have a signal flow diagram like the one below for a biquad NHK. I'm trying to understand how to derive the equations \$\frac{v_1}{v_i}, \frac{v_2}{v_i}, \frac{v_3}{v_i}\$ from it. I don't quite get ...
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2 votes
2 answers
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How can I modify a synthesizer with multiple voices to include a discrete line-out jack for each voice?

I've got this vintage synth called the Suzuki Omnichord OM-84. It's principally an electronic autoharp, with a metal ribbon you can strum or tap to make notes as though you're playing strings, but it ...
1 vote
1 answer
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Manual switch override for solid-state relay

I'm using an SSR controlled by an Arduino to control a bulb. I'd like to wire a manual switch also in case the Arduino or the SSR isn't working. Basically, it should be OR logic. Either switch or ...
3 votes
2 answers
368 views

Power drain meaning

I came through the following circuit in PIC microcontrollers datasheets, and I did not understand the highlighted statement: If T1OSI pin is an input of a clock signal (square wave), and the inverter ...
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Help with circuit behavior

(All transistors are of the same size) (Both signal transitions occur at the same time) case 1: (initial stored value is 0) The PMOS transition didn't really matter, the X-coupled INVs were capable ...
2 votes
2 answers
72 views

Low quiescent current boost converter for battery application (Io < 200 μA)

I am designing a PIR sensor alarm. It must be able to run on batteries for about a year. I am using 3.7 V Li-ion batteries to power an ATtiny24 directly. Although my PIR senor needs 5 V as recommended,...
2 votes
0 answers
54 views

About MOSFET circuit behavior

When I look at the waveforms of simulated circuits, how do I know when their behavior (for example flipping value stored on a node, or an unexpected drop in strong level value...) is due to MOSFET ...
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Increase boost converter power

I am looking to build this DC-DC boost converter. I know what parts were used to build a 150 W version of this design. I would like to build a 500 W version which basically has the same input and ...
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1 vote
2 answers
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Why does MOSFET driver IC (FAN7392N) keep breaking when motor is connected?

I am creating an ESC for a BLDC motor. Here is my schematic: I'm still in the testing stage to make the motor spin with this ESC and while I'm testing, somehow the FAN7392N ICs always break and I ...
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Multiplexer voltage reference

There is a potentiometer on a circuit board that I want to simulate with a DAC. I want to be able to either use the original voltage from the potentiometer or simulate the voltage from the DAC, hence ...
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Circuit using a D flip-flop and logic gates

How do I create a circuit with two inputs A and B and one output Q using only one D flip-flop and logic gates? The circuit should perform the following when the clock ticks: ...
2 votes
2 answers
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Adding an external switch and external LEDs to this circuit

I'm building an arcade cabinet, and would like to incorporate two different gaming systems (PC and a FPGA). I have the overall setup functioning (PC + FPGA --> KVM with external switch --> CRT ...
1 vote
0 answers
37 views

How to prevent grounding issue on Mini DisplayPort

I am attempting to design a board that has a Mini DisplayPort output. When I plug a Mini DisplayPort cable into the board and measure the ground (system ground against Mini DisplayPort shield,) I get ...
1 vote
1 answer
97 views

What is this sheet-like part in this circuit? Can I cut through it?

I have this remote-control circuit (front and back.) What is this sheet thing where I put a red question mark (?) on? The reason I ask is because I want to cut a hole in the circuit board where you ...
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1 vote
1 answer
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Photodiode detector 2-stage amplifier design

I found the post with circuit diagram I wanted to build: circuit diagram. The resistors values, gain and filter frequency are enough for me. I wanted to measure light intensity as DC voltage, so ...
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1 answer
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Better design for a shunt resistor load on a voltage divider

A bit new to circuit design. I'm designing a helper circuit that monitors incoming current. For testing purposes, we'll be taking inputs of max ~5 V and dropping this down to the millivolts, and pass ...
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2 answers
76 views

Golf cart battery fuel gauge? [closed]

I've got a 10 segment golf cart fuel gauge meter that shows full at 36.9 volts and empty at 31.77 volts. My problem that at full charge my golf cart battery reads 39.19V and when it won't go up an ...
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31 votes
4 answers
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Why put a 10k resistor between VUSB and GND?

I recently came across Yet Another RP2040 Trinket (the Beetle RP2040.) In their linked schematic something caught my attention: It is R10 below - a 10k resistor ...
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4 answers
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With a standard key-matrix, how many IO pins are required for N keys?

Using a standard key-matrix such as this: What formula stipulates the number of IO pins required for n number of keys?
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2 answers
149 views

Need help with a seemingly simple RC circuit with a Schmitt trigger inverter

I've been struggling with getting this circuit to work. My objective to try to use low-power (3.3 V/μA), low-cost, jellybean components. The idea of this circuit is that we have six latching buttons ...
1 vote
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110 views

What is the purpose of these capacitors in series with LEDs?

I am planning on building a device that sends IR light into a head at a specific intensity and detects the intensity that is measured by a photo diode. I know that ...
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Digital and analog supply voltage for amplified half-bridge strain gauge and ADC - MSP430G2995

I am working in a project to extend a pressure transmitter with a second pressure sensor (half-bridge strain gauge). This extension will use an op-amp (MCP6N16T-100) to amplify the signal and a ...
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2 votes
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USB detection with MCU

I have USB on a circuit board that I'm working on and it powers up a part of the circuit. I also have my main MCU, SAMD21G, which is not connected to the USB. I want the MCU to know when the USB is ...
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Is it possible to program from I2C to SRAM and boot from SRAM on STM32G0?

In one of our projects, we want to program SRAM of STM32G0 slaves by using I2C from a master STM32G0 and boot them from SRAM. Is this possible? If possible, how can I do it? I could not find enough ...
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1 vote
1 answer
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SOA and varying VDS

In a hot-swap application the FET spends some time in the linear region/Saturation region before it moves into the ohmic region. Here is a snippet of the turn on waveform seen for a FET: Yellow is ...
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1 answer
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What is a circuit I could use to generate valid analog TV signal?

What is the simplest valid analog TV signal and what circuit is required to generate it?
-1 votes
1 answer
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Sensitivity characteristics of MQ-7 [closed]

When we look at the sensitivity characteristic graph of MQ sensors, Let's take MQ-7, which is a log_log graph, we find the definition of R0 at 100ppm, this resistance is defined to be The sensor ...
3 votes
1 answer
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Interference between buffer/driver and WS2815 LED strip

What are your thoughts on how to correct this waveform? The pulse should be a 410 ns wide and 5 V high square wave. The driver is a 74HCT365 push-pull buffer, supplied from the 5 V rail. The input (3....
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0 answers
39 views

LM4910 headphone amplifier noise source

I built a headphone amplifier using the LM4910, following the typical application schematic in the datasheet. The noise floor of this IC is specified at around 50uV for a 32 Ohm load, while my circuit ...
2 votes
1 answer
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Workings of single constant-current source with four MOSFET-switched LEDs

Background I have several hundred RGB+White LED lights which are controlled by a driver circuit which is no longer manufactured, and trying to plan some maintenance and possible replacement of the ...
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3 answers
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How to add a DOWN limit switch to a Harbor Freight (Pittsburgh) hoist [closed]

I am using a pittsburgh hoist to raise and lower a large curtain. The hoist has a built in limit switch to stop when it raises to a certain point. I need to add another limit switch to stop the hoist ...
4 votes
1 answer
111 views

Delay power-off for a 12 V circuit powering a Raspberry Pi

I started a project to embed a Raspberry Pi in an old radio. One of the challenges is that the radio has a hard power-off button, so I want the Pi to have power for another 10-30 s so it can shutdown ...
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Electronics Lab - Not measuring voltage drop across resistor connected in series with capacitor

I'm working on an RC circuits lab for school, and it stated to connect a circuit as follows: 15VAC in series with a 470-ohm resistor and 4.7uF capacitor and measure the voltage drop across the ...
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1 answer
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Calibration of MQ sensors and programming logarithmic function in MCU [closed]

I'm developing a microcontroller-based project for a gas sensor. I want to use MQ2 or MQ6, so I looked at the following sites: https://circuitdigest.com/microcontroller-projects/gas-detection-and-ppm-...
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Simple way to mix stereo output (from HifiBerry Amp) to single speaker?

I have an old radio case with a single speaker, which I want to turn into a bluetooth & spotify player by putting a Raspberry Pi with Hifiberry Amp inside. The solution will be very Low-Fi as the ...
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1 answer
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Controlling LEDs with I2C

I'm trying to connect about 4 LEDs to an MCU (SAMD21G) to power on when specific things happen, but all the pins are being used. I was thinking that I could connect some kind of LED strip through I2C ...
2 votes
1 answer
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What is the function of the feedforward capacitor on the LM2596-ADJ?

I'm looking at the LM2596S datasheet and notice that on page 7 (figure 3) it recommends a "feedforward" capacitor for the adjustable variant. The example schematic on page 9 shows a ...
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