Questions tagged [7805]

7805 Voltage Regulator IC is a member of 78xx series of fixed linear voltage regulator ICs.

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All in one PCB mount buck converter? Sounds like snake oil

I am on the hunt to power an ESP8266 and a relay from 12V while keeping the PCB as small as possible. I am trying to avoid having to SMD the parts and have been advised against the LM7805 route as ...
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BCD 7447 powered by 7805 drops voltage

I am trying to use a BCD converter 7447 to display numbers on a seven segment display. Even before I apply any inputs or outputs, I observe that the VCC voltage of the 7447 drops (which is powered by ...
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3 votes
3 answers
806 views

Which capacitors to use with voltage regulator IC such as 7805?

Many of the tutorials suggest to use a large smoothing capacitor (tens and even hundreds of uF) with a full wave rectifier but the datasheets of the voltage regulators and some tutorials suggest only ...
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External 5V sensors separate 5V regulator , Poly fuse or both?

I'm producing an Arduino project that has two 5V inductive proximity sensors placed outside the project box. The project is powered by a Meanwell 12V power supply then to a Murata 5V DC-DC converter ...
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7 votes
3 answers
2k views

7805 voltage regulator reverse polarity

I'm working on a project for which I need to use a 7805 voltage regulator. I feed 9V to its input pin and power a 5V board with the output. However, when the board is connected to a computer, the ...
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How would a using a resistor and regulator together affect a circuit?

I'm having trouble understanding a concept. Let's just say that I have a simple circuit made using a 15V power supply. If I have a linear 7805 5V regulator connected along the circuit, and then add an ...
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12VAC-5VDC regulator, but L7805CV doesn't work properly

Hi everyone. I am trying to make 12VAC - 5VDC power supply. However when plugged in, voltage between L7805CV in - ground was 4V while output was 1V. I have test 7805 separately and it works correctly ...
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1 answer
138 views

Protecting regulator from alternate power supply

I'm designing a module built around a Teensy LC MCU which can either run off of Eurorack power (+12/gnd/-12) or USB (mainly during development). The Teensy wants 5V and regulates down to 3.3V onboard, ...
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4 answers
280 views

Input voltage control by resistor, is this method is correct or not?

In my application I have a requirement to switch 40V to 5V with the help of a linear voltage regulator. My load circuit consumes approx 7 to 8 mA. Due to the unavailability of any specific model of a ...
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2 answers
129 views

Logic level switch controlled via ground (0v)

simulate this circuit – Schematic created using CircuitLab Hello, all. My goal: to convert a ground signal pulse into a +5v signal pulse. My question: How on earth do I do this? Backstory: My ...
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1 answer
757 views

LM7805 Voltage Regulator stops working when input voltage increases

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I designed the PCB, had it printed and now I am testing it. When I power it up the following happens: ...
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4940v5 drop-in replacement for LM7805?

I am a novice who purchased several TO-220 L4940v5 chips thinking they were drop-in replacements for the inefficient TO-220 7805s that I've been using. But not a single one seems to work. No heat, ...
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Regulated Power Supply

I am supposed to simulate this circuit (regulated power supply 5V), however I am not understanding what's the point of the resistor R. Is it a load resistor? Cause i thought these needed to be before ...
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1 answer
138 views

Feedback on astable 555 timer circuit to control MAC valve for turbo control

I have some questions and wanted to get feedback on this circuit I have put together. Basically to see if there is something I missed or obvious that I should change or should have designed ...
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2 answers
145 views

Can I use any digital component to avoid 7805 killing my microcontroller directly when its ground is disconnected (hence 12v goes to uC directly)?

My idea is to have an intermediate cheap component that will blow-up before my uC if the voltage goes above 5v from 7805 (or even some fuse, but I am not sure if a fuse will blow-up with over-voltage ...
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Circuit for stabilizing the mini - 3 phase wind turbine output to 5 Volt using 7805 IC

I am trying to get some stable output from a Brushless power generator/motor/turbine which i purchased from Aliexpress Mini Micro Small 3 Phase Turbine To check if it works i tried to rotate it and ...
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1 answer
160 views

Fluctuations in 7805 Regulator IC Output

I built an Arduino using ATmega328 on perfboard. To power it, I used an 8V adopter with a 7805 IC. But the ATmega328 IC started to reset randomly. After some efforts I figured out that the problem was ...
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1 answer
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Is it possible to use Ultrasonic sensor HC-SR04 in continuous power-on mode

I will be using Ultrasonic sensor HC-SR04 in water level measurement. I will be triggering the US sensor and getting back the time-pulse from it at very slow rate maybe once every minute. I want to ...
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1 vote
5 answers
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Is it possible to use 7805 regulator without capacitors at its input and output pins?

I have to drive a magnetic buzzer whose current is 50mA and max. voltage is 6V. I will use 7805 regulator to drive it as my supply voltage is variable 9V to 24V DC. There will be another small load ...
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0 votes
0 answers
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Voltage drop on system activation

My question is generic in nature about electronics system design. I am trying to put together an RC car which is powered by an AVR Atmega168 chip. It communicates through an HC-12 module and has a ...
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1 answer
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Current-limit circuit for 78XX voltage regulators

I need to find the value of Rsc and R1 in the following circuit: In this circuit, Q1 is the high-current pass transistor. Its emitter-to-base resistor has been chosen to turn it on at a given load ...
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NodeMCU with JHD162A Lcd module display issue

I have uploaded a program to NodeMCU, to print "hello, world" on JHD162A 16x2 LCD module. But the text doesn't appear on the LCD display. Instead just black blocks appear on the first row on the LCD. ...
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2 answers
927 views

Why peak output current is greater than short circuit output current in 7805 voltage regulator?

This is the datasheet of 7805 voltage regulator produced by "Continental Device India Limited". Question: Why is the peak output current greater than short circuit output current? Shouldn't the ...
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3 answers
487 views

H-bridge with 7815 regulator

Could anyone explain to me why my 7815 regulator gets hot and eventually blows up ??
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1 answer
254 views

3 terminal regulator max input voltage with zener at adjust pin?

Quick question: If I stick a zener at the adjust pin of a 3 terminal linear voltage regulator, the allowable maximum input voltage will also increase by the breakdown voltage of the zener used... ...
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7805 sense resistors

In this answer, there is a schematic showing the internals of a 7805 voltage regulator, reproduced below: First of all, what is the sense pin in the first place? Every 7805 I've ever seen had three ...
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4 votes
1 answer
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Using two voltage regulators (780x) in series to prevent heat sink

(updated due to remark of ChrisStratton). I am wondering if it is a good idea to use two regulators in series. What I want: using 2 12V Nema17 motors (using 12V, 1.7A each). Using a microcontroller ...
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2 votes
3 answers
337 views

Capacitors for 7805CV?

I have some questions about using capacitors with an L7805CV According to the datasheet, on page 4, it shows I need: C1 = 0.33 uF C0 = 0.1 uF I bought a few sets some time ago with 'common' values ...
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-2 votes
1 answer
794 views

7805 Voltage Regulator powering astable 555 Timer yields LOW voltage as input to timer circuit

Hello stack exchange, So, I have two batteries powering a circuit and I want to only use one. 12.7V comes from a lead acid battery, and the smaller one is a stack of 4xAA that yield around 6.4V. The ~...
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2 votes
2 answers
12k views

how to fix Heating issue of 7805?

i am using LM7805 whose output voltage 5V and Output Current 1A i have used this to feed 5V supply for my application Circuit and my application circuit draw 125mA current , even tho 125mA current ...
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2 answers
405 views

How is the input of 7905 determined?

I have read that the max input voltage for this IC is -7V and max output voltage is -15.6V. According to it's name, the output voltage should be max -5V. I read this here. But for 7805 IC, the max ...
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1 vote
1 answer
491 views

Atmega328P - PU Not Working Properly (Instability, goes to sleep mode after some usage)

I have successfully designed & tested a circuit using arduino uno for controlling a dc motor (MAX 50A,12V,SHORT-DUTY) By using a relay module and current sensor (configuration given in schematic). ...
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0 votes
0 answers
26 views

Minimal ripple, minimal fuss

I am in need of a stable 5v source, max current around 200mA for a pocket oscilloscope. I have tried a powerbank, but the step-up converter puts through too much ripple that messes with the Scope. ...
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-1 votes
1 answer
149 views

stable DC converter for PH analog reading [closed]

i have purchased a small board to measure pH with a MCU. I am using a ADS1115 as ADC that have an internal Vref, that should be precise enough for my purpose. Now, if i connect my Vin to the ADC pin,...
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0 votes
3 answers
162 views

will my linear regulator overheat?

I am making a new design which I use a 4S 18650 batteries with total voltage of 14.8V in my design I need to have 9V and 5V using 7809 and 7805 regulators are these regulators going to overheat ? ...
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2 votes
4 answers
839 views

Is there an adapter for a TO-220 part to go into a TO-3

We have an old board that we do not want to redesign because it is near end of life. However, there is a TO-3 5V regulator that we can not source and when I do find it, it is for $13. I am wondering ...
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0 votes
3 answers
2k views

How to limit current for voltage regulator/decrease power dissipation?

I need to power a 5V device that needs more or less 1.2A in order to work correctly. I'm using a 13.8V power source with two diodes in series (1N4007) to limit the voltage to roughly 12V. I tried ...
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0 votes
1 answer
266 views

Why is this circuit letting the smoke out?

Using this circuit as a proof of concept to run a 12v motor off a 12v wall wart and ultimately use the 5v from the 7805 to power a Particle Photon through Vin pin. This circuit is letting the smoke ...
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5 votes
4 answers
2k views

Reducing voltage drop over 7805 regulator?

I have several projects (clocks) that require 12V and 5V supply. The 5V is for TTL ICs and the 12V powers a SMPS(Switching Mode Power Supply) to give HV(High Voltage) for a tube. The 12V pulls less ...
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0 votes
2 answers
1k views

Power supply fluctuations. Bypass capacitor needed?

I am powering up a 5V device using a 12v DC 1A SMPS power supply. The 12V supply is connected to the 5V device through a 7805 voltage regulator. The device draws about 30mA when idle, but when it ...
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6 votes
3 answers
5k views

L7805 destroyed - why?

I used a L7805 to power a Raspberry PI and it worked for about 10 seconds then started to smoke and die. L7805 is rated for 1.5A and 35V DC input. Power supply was 24V DC (was actually two plugin 12V ...
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1 vote
2 answers
8k views

How to measure AC and DC with oscilloscope

I'm a newbie with the oscilloscope. I have a digital RIGOL with two probes. I'm testing a simple 12V AC to 5V DC converter. I'm trying to measure the effect of the 7805 on the DC signal in output ...
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26 votes
7 answers
35k views

Can I use two 7805 ICs in parallel to get double current capacity?

I use a 7805 for a project where the circuit needs a higher current (~2.8 A) at 5 V. So I assume that if I use both ICs in parallel I can increase the maximum current capacity. Would it work?...
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7 votes
3 answers
13k views

Selecting the correct input/output capacitors for a 7805

So I've got a 7805 Regulator and I've been looking it up and each website says different info. I am using an input of 12V DC 1A Wall Adapter as an input supply. www.adafruit.com Says This ...
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2 answers
2k views

LM78H05K How to use

I have bought the LM78H05K 5 V voltage regulator , for the 5v output. My input voltage is 17 V DC. but unfortunately this component is in different shape. I have uploaded the image of the module. I ...
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0 votes
2 answers
1k views

Voltage drop in Vin of 7805 regulator when used with a Bridge rectifier and CT(Current Transformer)

I have a voltage regulator circuit powered by a CT. I rectify the output AC voltage to DC voltage and provide that as an input to the regulator L7805CV. My input voltage is about 7.20V When I connect ...
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4 votes
2 answers
1k views

2N2222 experiment is indicating incorrect gains

Okay, so I put a 20kΩ resistor between a 5V supply and the base of a 2N2222 with the collector connected directly to the 5V rail and emitter to ground. What I'd expect is that, roughly, 220μA (i.e. (...
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0 votes
2 answers
78 views

Going under specs for a linear regulator?

I have a Microchip PIC board (18F46K22) which has a VIN pin to connect to a power source (7vdc + supply). What happen if I feed 3.3V to the VIN which goes through the 5V linear regulator (ST 78M05)? ...
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1 vote
2 answers
881 views

Connecting the linear regulator directly to AC line

There are several out of the shelf solutions: LR8 from Microchip (formaly known as Supertex product) and NCP785 from ON-Semi. The last one is able to handle up to 700 volts at the input which is ...
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0 votes
1 answer
805 views

Powering two circuits from a 9v battery

I am building an experimental percussion instrument. I have two circuits in it which are not connected to each other. One is a small linear fan speed regulator controlling a small motor, which ...
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