Testing with VFD

Started by EnigmaPaul in sci.electronics.design8 years ago 20 replies
PWM

Hi Folks - I need to setup a VFD in a workshop to test the accuracy of my AC voltage and current metering on the line side. VFDs often...

Hi Folks - I need to setup a VFD in a workshop to test the accuracy of my AC voltage and current metering on the line side. VFDs often disrupt the measurements of RMS due to harmonics, conducted, and radiated noise. I'm going to get a low cost PWM VFD and need to apply a load to it. I'd like to use a motor to most accurately simulate an inductive load but I was wondering: 1) Can I ...


High resolution PWM for fake DACs

Started by Phil Hobbs in sci.electronics.design8 years ago 4 replies

Hi, all, I've been working on an automatically-tweaked noise canceller design with my trusty code and layout Sherpas-in-training (my son and...

Hi, all, I've been working on an automatically-tweaked noise canceller design with my trusty code and layout Sherpas-in-training (my son and my younger daughter). I need about 10 slow but high resolution DAC outputs for the tweaks, and I was thinking about using PWMs run from the LPC1769 processor for at least some of them. I can close the loop on them with an on-board delta-sigma...


Simple MPPT question.

Started by Yzordderrex in sci.electronics.design3 years ago 21 replies

I enjoyed the conversation last week on MPPT chargers. It was well discussed If I am looking for MPPT point can I just use current into...

I enjoyed the conversation last week on MPPT chargers. It was well discussed If I am looking for MPPT point can I just use current into batteries? Dither the pwm around some and find the point of maximum current into the battery pack? I run a 2kW panel now and putting another 2kW up in May. regards, Bob N9NEO


Off-line LED drivers

Started by Adrian Jansen in sci.electronics.design9 years ago 27 replies

Many sources now for these devices, but the few I have inspected all have relatively large electro caps on the input side, to make DC from...

Many sources now for these devices, but the few I have inspected all have relatively large electro caps on the input side, to make DC from which the current controller PWM draws its supply for the LED drive. I strikes me that with the published figures for LED lifetimes of 50,000 hours, the electro caps in these are probably going to fail long before the LEDs and other associated circ...


Minimising EM noise from PWM switched fairly lights?

Started by Tim Watts in sci.electronics.design2 years ago 48 replies

Hi, This year's project is to drive 3 strings of 30V DC LED outdoor fairy lights from Raspberry Pi's[1] I've been on here before last...

Hi, This year's project is to drive 3 strings of 30V DC LED outdoor fairy lights from Raspberry Pi's[1] I've been on here before last year and took some greet advice with respect to H-Bridges and found some, along with DC-DC converters that will enable me to interface a 30V DC supply to the Pi and the Pi back to the lights. The only thing I am mindful of is not to inadvertantl...


UC3825 help with Pspice

Started by Waldes in sci.electronics.design13 years ago 1 reply

Hi all! I need simulation file for this IC. If someone has it, please share with me. I found here some files for UC3843, UC3842, but they...

Hi all! I need simulation file for this IC. If someone has it, please share with me. I found here some files for UC3843, UC3842, but they are current mode, and I want something with voltage mode for flyback converter, which has voltage regulated from 30V to 300V. So I will be gratefull for model UC3825 or information how to simulate in Pspice PWM modulator with Soft Start and limit max cur...


dc/ac inverter

Started by nescafe in sci.electronics.design9 years ago 5 replies

1.) How to change this design to 72V input 2.) If i look at the data table that is presented on the web page, 4500W should be reachable with...

1.) How to change this design to 72V input 2.) If i look at the data table that is presented on the web page, 4500W should be reachable with 72V. This is too small for me. I need to get 8kw at 72V input (i have battery bank 72V-135Ah) http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/ Can someone help with redesign ?


How to blow up an LM395

Started by George Herold in sci.electronics.design6 years ago 12 replies

http://www.ti.com/lit/ds/symlink/lm395.pdf I use these as "bullet proof" output pass elements. One is used to drive a 50 ohm heater. (~30V...

http://www.ti.com/lit/ds/symlink/lm395.pdf I use these as "bullet proof" output pass elements. One is used to drive a 50 ohm heater. (~30V p-p PWM) I had a few reports that the circuit would not turn off, it was always heating. I had one user ship the board back. Indeed the LM395 was toast. I tried everything to destroy another one, Short circuit the load, change the load... I le...


Attainable PWM accuracy?

Started by Phil Hobbs in sci.electronics.design2 years ago 84 replies

Hi, all, As part of the aforementioned cathodolumiescence system, I'm doing a bias supply for multipixel photon counters (MPPCs). MPPCs...

Hi, all, As part of the aforementioned cathodolumiescence system, I'm doing a bias supply for multipixel photon counters (MPPCs). MPPCs are extremely voltage sensitive--the gain of this one goes from ~0 to 2E6 between 52 and 55 volts' bias. (See .) Sooo, there's a bit of pressure to keep the bias very stab


3 phase motor drive current sanity check

Started by Clive Arthur in sci.electronics.design3 years ago 17 replies

Hi I have a client using a three phase brushless motor driven by H-bridges. I know little about it except that it uses high frequency PWM...

Hi I have a client using a three phase brushless motor driven by H-bridges. I know little about it except that it uses high frequency PWM to generate sinusoidal excitation. As I see it (and there's no possibility to look on a scope, it's on a different continent) each motor winding must take current as half a sine from one diagonal pair of H-bridge switches, then the next half from...


20 mA LED SMPS buggy

Started by Bernhard Kuemel in sci.electronics.design9 years ago 31 replies

Hi sed! I want to illuminate our hall with 7 white LEDs so we don't have to turn on the main light at night when we want to save energy or...

Hi sed! I want to illuminate our hall with 7 white LEDs so we don't have to turn on the main light at night when we want to save energy or avoid too much light. I started to build a SMPS with a TL494 PWM controller salvaged from an ATX SMPS [2]. Image/video gallery [0]. Before I hook it up to 230V AC (325V rectified) I'm testing it with 12V and something is wrong. When I decrease t...


Overexcitable fan

Started by Anonymous in sci.electronics.design7 years ago 23 replies
PWM

A PC cpu fan in an 8 core AMD system is very noisy at full tilt, and is rather excitable. CPU temp only need go up by an imperceptible amount and...

A PC cpu fan in an 8 core AMD system is very noisy at full tilt, and is rather excitable. CPU temp only need go up by an imperceptible amount and it revs up (idling for a minute.) I want to quieten the thing somehow. I'm thinking the control system is presumably pwm, and a series doide or 2 should help, and probably not cause problems. Am I right? I wish the control system could be


capacitor gets hot in a HF-HV resonant circuit

Started by blisca in sci.electronics.design6 years ago 28 replies

Hi i was asked to help some friends in a task that is unusual for me: I have to generate a 100 Vpp -150 KHz ringing on a single turn of a...

Hi i was asked to help some friends in a task that is unusual for me: I have to generate a 100 Vpp -150 KHz ringing on a single turn of a transformer secondary. I generate an adjustable PWM with a microcontroller,then a driver drives a N MOSFET connected to VDD via a couple of turns(the primary of the transformer),paralleled by a capacitor** With a pulse width of about 7us i have ...


TL494

Started by Pimpom in sci.electronics.design4 years ago 18 replies

OK, we've all been bitching - silently or vocally - about the low SNR at SED. Here's a real, albeit small, design question. The venerable PWM...

OK, we've all been bitching - silently or vocally - about the low SNR at SED. Here's a real, albeit small, design question. The venerable PWM controller TL494 was widely used in older computer power supplies. It differs from the similar SG3524 in that, in addition to two error amplifiers, it has a dedicated dead time control (DTC) pin. It allows minimum dead time at 0V and zero duty c...


OT: PIC16F648A interrupts

Started by Robert Baer in sci.electronics.design6 years ago 4 replies
PWM

I have a simple program that runs the (timer2) PWM reliably, scope measurements confirm timing of pulse width and the rate as well. I add...

I have a simple program that runs the (timer2) PWM reliably, scope measurements confirm timing of pulse width and the rate as well. I add a simple 256 location lookup table to change the PW on a cyclic basis. Still OK but not exactly verified with scope on a dynamic basis, tho verified that i get the proper PW at setting of CCPR1L. Now, here is when i get into trouble; addin...


DC/DC converter - 8KW

Started by test in sci.electronics.design10 years ago 29 replies

Hi. I need some simple low cost schematics how to make 8KW converter that can convert from 72 to 460V . The basic idea is to wind some strong...

Hi. I need some simple low cost schematics how to make 8KW converter that can convert from 72 to 460V . The basic idea is to wind some strong transformer and to rise the frequency to 200 - 300 HZ + IGBT. There is no need for riple and stable voltage or for PWM control because the inverter is connected to DC link of micromaster and mm is connected to AC 8kw motor. The motor should not p...


isolated synchronous flyback topology idea

Started by bitrex in sci.electronics.design4 years ago 11 replies

I was reading about various isolated synchronous flyback topologies and the schemes used to sense and optimize dead time of the switches; I was...

I was reading about various isolated synchronous flyback topologies and the schemes used to sense and optimize dead time of the switches; I was thinking why not use a cheap 8 pin micro (like 50 cents) with onboard fast PWM and 10-12 bit ADC on each side, along with some kind of gate driver to drive the switches. Then communicate across the isolation barrier with each other via i2c to "kn...


Engine injector control ICs

Started by Cursitor Doom in sci.electronics.design5 years ago 19 replies
PWM

Gentlemen, Does anyone know of a readily available chip to control the timing and duty cycle of engine fuel injectors? Or a PWM chip that...

Gentlemen, Does anyone know of a readily available chip to control the timing and duty cycle of engine fuel injectors? Or a PWM chip that could do the job equally well? Most of the ICs I'm finding seem to be entire engine management chips that do far too much other stuff whereas I only want injector control. Thanks.


Microcontroller phase locked loop, ping Tim Wescott et. al.

Started by bitrex in sci.electronics.design6 years ago 27 replies

Has anyone successfully implemented a phase locked loop on a microcontroller? The frequency of interest would be somewhere in the 200kHz...

Has anyone successfully implemented a phase locked loop on a microcontroller? The frequency of interest would be somewhere in the 200kHz range, and the objective of the PLL would be FM demodulation. So I'd have an input for the FM modulated frequency, and an external VCO in that range that the uC would hopefully control via filtered PWM. Other than that, this is mostly hypothetical ...


Floating impedance simulator idea

Started by bitrex in sci.electronics.design8 years ago 2 replies

Use 4 optoisolated current sources/sinks under microprocessor control, and sense the terminal voltage/current at each of the two ports. Apply...

Use 4 optoisolated current sources/sinks under microprocessor control, and sense the terminal voltage/current at each of the two ports. Apply the appropriate passive device defining equations in software to simulate a floating inductor, capacitor, negative impedance, etc. Something like this maybe: http://i.imgur.com/i8nSruE.png PWM output goes to the NPN current sources, op amps s...