Questions tagged [7805]

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

0
votes
6answers
133 views

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 ...
0
votes
0answers
22 views

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 ...
1
vote
1answer
82 views

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 ...
0
votes
0answers
20 views

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. ...
0
votes
2answers
124 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 ...
1
vote
3answers
211 views

H-bridge with 7815 regulator

Could anyone explain to me why my 7815 regulator gets hot and eventually blows up ??
1
vote
1answer
125 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... ...
5
votes
1answer
433 views

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 ...
4
votes
1answer
581 views

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 ...
2
votes
3answers
186 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 ...
-2
votes
1answer
342 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 ~...
0
votes
2answers
4k 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 ...
0
votes
2answers
192 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 ...
1
vote
1answer
214 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). ...
0
votes
0answers
22 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. ...
-1
votes
1answer
138 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,...
0
votes
3answers
129 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 ? ...
2
votes
4answers
306 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 ...
0
votes
3answers
1k 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 ...
0
votes
1answer
225 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 ...
4
votes
4answers
1k 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 ...
0
votes
2answers
638 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 ...
6
votes
3answers
3k 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 ...
1
vote
2answers
5k 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 ...
20
votes
7answers
19k 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?...
2
votes
3answers
3k 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 ...
0
votes
2answers
1k 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 ...
0
votes
2answers
349 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 ...
4
votes
2answers
976 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. (...
0
votes
2answers
62 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)? ...
1
vote
2answers
561 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 ...
0
votes
1answer
463 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 ...
0
votes
1answer
74 views

Circuits And Voltage [closed]

simulate this circuit – Schematic created using CircuitLab Please help.... I have an input of 7.5V but when it goes out of the circuit the voltage drops in 2.5V but i want 5V of output voltage ...
3
votes
1answer
311 views

Choosing bypass capacitors for successive linear regulators

Background: I am reviewing my prototype PCB to iron out previous issues. The PCB is a Bluetooth data capture unit for liquid levels and flow. I am a software programmer by trade and I have some ...
0
votes
2answers
885 views

External power supply design (12V to 5V and 3.3V) for arduino based system

I am designing an embedded system having following components: One arduino uno (~300-500mA 5V=2.5W) One nodemcu (esp8266) (~300-500mA 3.3v=~2W) One PAM8403 based audio amp board (3W output, so on 5V ...
0
votes
1answer
190 views

Controlling NiMH charging with power MOSFET: MOSFET before or after the linear regulator?

I am starting a project where I want to make a simple, Arduino-controlled NiMH battery charger. I imagine several iterations, but the first one will be really simple. It will charge at a constant ...
0
votes
2answers
2k views

Why 7805 regulator gives output 6 volt?

I am using 7805 and 7815 for the voltage 5 V and 15 V respectively. I provide 24 V to 7815 it is giveinng me output voltage 18.5 V instead of 15 V. According to 18.5 V to input to 7805, its output is ...
1
vote
1answer
3k views

Is this an appropriate way to test a 7805?

Trying to check some 7805 voltage regulators. I do not have a DC power supply and do not want to test with the circuit hooked up to mains. That leaves me and my multi-meter. http://www.androiderode....
23
votes
7answers
12k views

Optimize heat sink design - connect cooling pad on PCB backside by vias

In one of my current projects I'm using an MC7805 in a D2PAK package to generate my logic supply of 5 V from an available 24 VDC supply. The current required by the circuit is 250 mA. ...
22
votes
3answers
17k views

Why is there always a capacitor on input and output of a voltage regulator?

Looking at the datasheet I can see that the voltage regulators are not just a zenner diode inside, they are complex devices. I have noticed that there is always a capacitor at the input and another ...
0
votes
1answer
103 views

Battery voltage drops when connected to PCB

I have a circuit containing an atmega328p microcontroller with hc-05 bluetooth module. microcontroller is powered via 7805 regulator. When 7805 is supplied the source voltage by a 9V battery, the ...
0
votes
2answers
89 views

Solar cells with 5v regulator: would it supply more current than available?

I recently bought online three solar panels rated 6v x 500 mA for some circuits I had in mind. What I got instead were 12v cells, and I am certain they are rated 250mA, since the seller had those too. ...
2
votes
0answers
210 views

What is the purpose of the 7805 output capacitor?

How does a cap on a regulator output improve transient response? Is this cap not more appropriately drawn next to the load where it is not being defeated by intervening trace inductance? Or does this ...
6
votes
5answers
3k views

What is the purpose of the 7805 input capacitor?

Most 7805 datasheets specify an input capacitor of 0.33uF or so. This one (the LM340 http://www.ti.com/lit/ds/symlink/lm340-n.pdf) at least specifies that the cap is only required if the regulator is "...
5
votes
3answers
1k views

Can a 7805 ever oscillate?

I see many references to input and output caps helping with "stability" and some outright references to preventing oscillation in both answers on this site, and even in some data sheets. I also have ...
-4
votes
1answer
1k views

How much current does IC7805 device draw? [closed]

How much current does a IC7805 regulator draws, when it drives a 1.5A load?
-1
votes
2answers
691 views

Please help me to elliminate mistakes in linear power supply design or improve it! (LM723/7805))

So I decided to build power supply unit for my modular synthesizers. 2-in-1 Design: +/-15V (3A each) and +5 (1A) for TTL logic ICs modules. I started from enclosure, learning the SolidWorks in the ...
0
votes
1answer
637 views

Voltage regulator Current regulation

I want to understand the concept of current regulation in the circuit, In my research I came across the following link Boosting Regulator Current for IC 78xx by MJ2955 where in the circuit schematic ...
1
vote
1answer
3k views

7805 for 4-20mA current injector

I'm trying to setup a low cost current injector for testing certain I/O modules. I found a rather simple design for a current source using 7805. simulate this circuit – Schematic created using ...
1
vote
1answer
25k views

How to unhide hidden pins in proteus?

Recently I was designing a PCB for my project using 89c51. I am using a 12V battery to run motor and 7805 to give 5V to 89c51. When going to ARES for PCB designing I realised the VCC pin of 89c51 is ...