Pulse-width modulation, is varying the duty cycle of a rectangle wave, usually with a constant frequency.

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36 views

How to choose what a power supply to drive 2 x 10watt RGB LEDS?

I'm trying to figure out how to determine what power supply I should be using for different types of LEDs for this and future projects. I have 2 x RGB LEDS: Forward Current: 350mA Forward Voltage: ...
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2answers
85 views

Help to design an amplifier

I need help designing an amplifier that is capable of providing 1 W to an 8 Ohm speaker. I have 3.3 V, 5 V or 18 V supply available to power it. I also have only one power supply available that has ...
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0answers
22 views

Calculating power draw for LEDs and driver (TLC5941)

I am designing a backlit keyboard with 61 white LEDs. These will be individually driven by a TI current limited PWM driver (TLC5941). LEDs: 61 x Osram LCW JNSH.PC (Datasheet) Drivers: 4 x Texas ...
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2answers
63 views

Amplifier design

I am having trouble calculating values for this audio amplifier. Input comes from AVR PWM operating at 44.1 kHz with high being at 3.3V. The speaker is 8 Ohm and speced for 1 Watt. First two ...
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2answers
77 views

Variable Voltage Using PWM and Low Pass Filter

I am trying to control a steady DC output voltage using a Micro controller with a PWM duty cycle. With the current schematic, the Voltage on Vout is pulsing along ...
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1answer
87 views

Controlling speed of motor through L293D using TLC5940NT

I am trying to control a DC motor through an L293D. Ultimately I am controlling it with an Arduino, but I am trying to use a TLC5940NT chip as an intermediary to increase the number of outputs that I ...
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1answer
29 views

PWM input voltage regulation

I have a 12V DC motor that I plan to run in one direction with PWM input at 21A. However, in the other direction I want to drop the voltage to limit the speed. Ideally. the regulator would sit between ...
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1answer
86 views

Capturing PWM Signal on an Oscilliscope

I have a stepper motor that is controlled by PWM. I am trying to analyze the signal coming out of the controller on an oscilloscope. Ideally, I would like to capture, maybe 2 seconds of wave form so ...
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3answers
50 views

Capacitor on line with high frequency digital signal?

Capacitors act as a short for high frequency signals. If I place a capacitor on a digital 5V PWM line or perhaps a motor encoder line does the cap still act as a short to ground for the square wave ...
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2answers
115 views

130V DC Motor Control

I am interested in building a control circuit for a motor. More specifically this motor. The model I want to control is the 130V model, 0.48A, which should make it at ~62W for the motor, and 1/17 ...
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1answer
55 views

PWM Dimming results in input ripple due to excessive inrush current

I use a constant current SEPIC boost regulator ([TI LM3410X) to run a 8.5V 400mA OLED panel from a single Cell Lithium polymer battery. I have noticed that the input voltage ripple is too much (~1V ...
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3answers
162 views

Can PWM be used for PID controlling…

I am was wondering if an IC like the PCA9685(Datasheet) that generates PWM signals can be used in a PID controller for controlling a heated bed on a 3D printer. My understanding of PWM is that it ...
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1answer
81 views

How does a true sinewave inverter work?

I am an Electrical Engineering student, and when we were taught about inverters (at a power electronics course) we studied inverters using Sinusoidal Pulse Width Modulation. My question is do the ...
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2answers
53 views

Complex LED drivers/circuits [closed]

Throughout my travels I've seen these very complex circuits that incorporate ICs for "i.e. dimming applications" that are included in designs with buck boost converters, etc. What makes LED driving ...
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1answer
48 views

How do I replace an existing servo with a geared DC motor?

I am a complete beginner, just getting into the world of electronics, in particular robotics. I have found a really nice open source set up that I want to build on and change for my own ends. The ...
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0answers
32 views

Comparator Selection for enhanching voltage level of PWM

I want to raise the voltage level of the PWM signal from 5V to 12V for that purpose i am using comparator. But when it comes to comparator selection i got confused bwt LM339 and LM324. Which one will ...
2
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1answer
66 views

How to build LED dimmer for room illumination - PWM, low pass filter?

I want to illuminate a room. This will be done by two LED strips 60led/m, each 5m long, located along the tops of opposite walls. In order to get full light power, they together consume 4A@12V. ...
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2answers
92 views

What is the reason my ULN2003A overheats?

I'm driving some 12v fan motors from a microcontroller using ULN2003A Darlington array. Both total wattage and per-channel wattage are way below ULN2003a limits. Still, I found that when PWM duty ...
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0answers
62 views

Voltage Sag with PIC24 PWM Open-Drain Configuration

I'm experiencing some major voltage sag with an open-drain PWM output into an RC servo. I'm pulling up to +5V with an external pull-up resistor. I've tried using everything from a 1k-100kOhm resistor, ...
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1answer
42 views

555 servo controller “modulation input”?

Exactly as the question says. On the TI 555 Rev. C data sheet, what is the modulation input for the PWM circuit? Also, can I round the resistor and cap. to 10k and .022uf, respectively?
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1answer
82 views

PWM understanding

I am giving PWM to a MOSFET (50% duty). It switches about 8.5V to be fed to a phase of a motor. There are 3 such phases. Now, I am looking at voltage measured from these phases as well. I have ...
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0answers
57 views

How to drive Worldsemi “smart” LEDs

Let's get to it: The issue is about these cheap 6-pin 5050 package LEDs from Worldsemi. These LEDs contain an IC with a simple serial interface running at 800kHz. You can daisy-chain those LEDs ...
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0answers
20 views

Variable load using PWM

I am trying to design a variable load by PWM. From what I have understood I need to feed the base of a BJT (for current amplification) with my PWM signal. The maximum voltage that we need at the ...
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1answer
78 views

Arduino PWM pin vs digital pin PWM simulation

Do I understand it correctly from this thread, Why do some pins have `~` signs next to their numbers?, that the PWM pins generate a square wave signal independently from what the code uploaded to the ...
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3answers
136 views

Complementary H-Bridge Motor control

I have some concerns in a motor control board I designed. Sometimes the MOSFETs unexpectedly start to burn. I suspect one of the reasons is the thin track (0.2mm) I have in my flexible board (0.2mm), ...
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1answer
40 views

Using both PWM and Timer2 interrupt in PIC18F25k50

Background I'm working on lead-acid battery charger and experimenting with battery desulfation. I want to draw current vs time graph on graphic LCD and see: how high current spikes I have measure ...
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1answer
93 views

EMI suppression low frequency

I'm dealing with a PWM generator which drives a load at 12V with pretty high currents (5-10A) The PWM frequency is in the band of 100-200 Hz. Which is the best choice and right configuration of ...
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0answers
67 views

Trying to use SPI to communicate between dsPIC (33EP) and LED driver (LT8500)

I'm trying to setup SPI to generate PWM signals on the LED driver LT8500. Below is my code: ...
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3answers
78 views

PIC18F25k50 - 10-bit PWM resolution with 8-bit timer?

Im messing around with PIC18F25k50 standard mode PWM. I found something weird. Datasheet says, that PWM is 10-bit, and timer is 8-bit. How that can be? Is that datasheet is wrong, or my english ...
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2answers
64 views

Simple PWM regulator, current measurement without high-side current sensing

I have a very simple Lead-Acid battery charger with slow (1kHz) PWM regulator. I would like to add current and voltage measurement (with PIC18F ADC - 200kSPS). I have no problem with voltage ...
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1answer
41 views

PWM photodiode bias circuit control voltage

Cant the photodiode bias regulator described here, Fig 6 be controlled with a PWM input? The RC loop right at the control input seems to filter PWM frequencies, but I am not sure if there are any more ...
2
votes
1answer
56 views

PIC24 Open-Drain Config for 5V PWM Operation

I'm running a PIC24HJ series processor with a supply voltage of 3.3V. I need my PWM signal to be 0-5V, not 0-3.3V. Can I simply connect the PWM line to a 5V supply with a pull-up resistor? Or do I ...
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3answers
147 views

BJT switch vs amplifier mode

I'm getting really confused about a specific BJT circuit. I want to control LCD brightness and contrast as suggested here. Apprently a capacitor is used to filter PWM output to the contrast pin, ...
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1answer
61 views

LCD brightness and contrast control with PWM

Is it reasonable to control LCD brightness and contrast directly with the PWM pins of an Arduino, or would it be advisable to use a capacitor/filter to get a constant analog voltage? I assume human ...
0
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1answer
68 views

Using L293 H-Bridge to drive DC motor with PWM

I want to drive an DC motor with ability both to change direction, and torque. Obvious solution: PWM + H-Bridge. I've been planning to use a PSoC4 for controller, and L293DNE for the H-bridge, which ...
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1answer
139 views

Difference between two 12V PWM signals/circuits (PIC and NE555)

I'm trying to understand the difference between two 12V PWM circuits I've build and tried. The PWM signal is intended to control the speed of a motor. Only not in the way you would expect. The motor ...
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1answer
97 views

Supply voltage for MOSFET driver in high-voltage (110v) PWM regulator

I am designing PWM speed control for 110v DC motor. Since it is 110v, I am going to power it from bridge rectifier connected to mains, with MOSFET on low side for switching. For driving MOSFET I plan ...
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1answer
36 views

pwm or gpio for pled display on beagle bone? [closed]

Wondering which adafruit bbio library i should use. I know nothing. My sense is that GPIO will be simpler to communicate the display info to the screen. The screen is a 128x32 adafruit pled
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2answers
81 views

Can I use pwm to control speed of at motor driver?

Ive got this motor driver from Sparkfun, https://www.sparkfun.com/products/9670. Where I get it that setting ENA and IN1 to high will enable connected motor 1 to og full speed in one direction. But, ...
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1answer
40 views

Vex 393 motor with 12V supply

Have a Vex 393 2-wire motor and I'm using a 6-40V PWM driver @ 5A max. My question is this... The Vex was spec'd at 4.8A stall current and 0.37A no-load current at 7.2V. From what I've read here ...
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1answer
121 views

Proper configuration of a PWM fan which should be stopped when the controller power is cut off

Recently I am working on a controller to drive a PWM fan (datasheet). I am using a atmega32u4 and it sends a 25khz PWM signal to the fan and it's working well. I want the fan to be off when I cut the ...
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1answer
79 views

PWM driven LED array over a shift register

I am trying to drive 8 LEDs connected to a 74HC595 shift register with PWM. I want to be able to set each LED to a different brightness. The PWM signal is connected ...
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1answer
62 views

Using PWM to generate analog output

I am trying to understand this application note from Microchip about using PWM and a low pass filter to generate an analog output. I have a few questions regarding to the article: In the example ...
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1answer
74 views

How to choose a correct LED PWM driver?

I would like to control an RGB LED via a (vendor specific) microcontroller. However its maximum output current is 60mA whereas my LED requires 100mA. I have seen number of LED driver solutions with ...
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1answer
41 views

Motor rated 7.6AMPS. How will motor behave if driven with PWM controller with 4A output?

Firstly, I apologies for having to ask such a basic question. I'm looking to buy a controller for a permanent magnet motor. The specs of the motor are: 200VDC, 1.5HP, 5700RPM, 7.6A, form factor: 1.0 ...
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2answers
164 views

RGB LED flickering with PWM

I just have issues with the RGB LED flickering under low duty-cycle like 10% on time with 780 Hz. I tried changing the PWM frequency to lower and higher rate but I still see flickering at low ...
2
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1answer
60 views

Arduino: Generating time critical signals with interrupts

I have some problems to fully understand how interrupts on e.g. Arduinos/AVR are used in practice. Lets assume I want to generate a time-critical signal like PWM and at the same time be able to ...
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1answer
161 views

Isolating PWM From H-Bridge

I have a H-bridge based on FAN7392 drivers. This bridge works at 350VDC to output a approximately 240V 50Hz waveform. This circuit is isolated from rest of the board and I would like to maintain the ...
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3answers
100 views

Stereo to High Speed LED for Data Transfer

I am currently doing a project on optical data transfer using LED. The first hurdle I need to overcome is the LED driver circuit. I have little to no background in circuits. I do know a fair amount of ...
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2answers
45 views

Finding required maximum current rating for a diode which will run in PWM mode

Consider a diode rectifier which will transfer a PWM signal. The duty cycle rate of this PWM signal is \$D\$ (\$0 \le D \le 1\$). The diode on state current is \$I_{ON}\$, and no current will be drawn ...