Large Noise from Bridge Rectifier; Conducted Emission Measurement

Started by Klaus Kragelund in sci.electronics.design8 years ago 21 replies

Hi I am working on a high power frequency inverter (> 1kW) and have a "funny" looking emission graph The converter is the typical inverter...

Hi I am working on a high power frequency inverter (> 1kW) and have a "funny" looking emission graph The converter is the typical inverter type, EMC filter-> 3 Phase Rectifier-> DC Inductor-> DC Link capacitor-> 6 switch Inverter-> Motor Like this: www.electronicsdesign.dk/tmp/Inverter.jpeg We stripped down the circuits and isolated the noise to the EMC filter and bridge rectifier. T


Question regarding diac-triac lamp dimmers

Started by Anonymous in sci.electronics.design8 years ago 8 replies

Could some electronics guru please hekp ? Maybe this is a stupid question, but here we go. Simple AC kine based lamp dimmers use a diac...

Could some electronics guru please hekp ? Maybe this is a stupid question, but here we go. Simple AC kine based lamp dimmers use a diac triac pair with a capacitor that gets charged via a resistor chain that includes a potentiometer to control the charging rate. When the capacitor gets charged, it discharges via the diac, and this in turn triggers the triac. So far so good. But t...


Ideal vs. lossy transmission line model question

Started by Anonymous in sci.electronics.design8 years ago 25 replies

Could some electronics guru please clarify a few subtle questions regarding lumped parameter model of transmission lines ? The simple...

Could some electronics guru please clarify a few subtle questions regarding lumped parameter model of transmission lines ? The simple loss-less lumped parameter model consists of an ideal capacitor-inductor pair per unit length. OTOH, the lossy model includes a series resistance with the ideal inductor and an dielectric conductance in parallel with the ideal capacitor. Simil...


Voltage-variable capacitor doesn't work in LTSpice

Started by Joerg in sci.electronics.design8 years ago 92 replies

Gentlemen, Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or whatever. Works, always did. Doing the same with a capacitor...

Gentlemen, Setting up voltage-controlled resistors is easy: R=(V(X)+0.01) or whatever. Works, always did. Doing the same with a capacitor fails with this error message: Error on line 6 : c1 n002 0 c=(v(x)+0.01) Unable to find definition of model "c" * Unknown parameter "x" WARNING: Less than two connections to node X. This node is used by V4. Fatal Error: Missing capacitance ...


Colpitts crystal oscillator in LTSPICE

Started by bitrex in sci.electronics.design7 years ago 59 replies

I'm trying to simulate a low frequency Colpitts oscillator in LTSpice using an NPN darlington and a crystal, and I'm having a lot of trouble...

I'm trying to simulate a low frequency Colpitts oscillator in LTSpice using an NPN darlington and a crystal, and I'm having a lot of trouble getting it to start up. Does anyone have a working one of these? I'm just using a capacitor to simulate the crystal, the parameters I am working with are something like: motional capacitance: 5.3ff ESR = 11k ESI ~ 4500 henries EPR = 100 meg E...


Somebody had an idea for a lossless flyback snubber

Started by Anonymous in sci.electronics.design6 years ago 25 replies

Hey Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. I am working...

Hey Been trying to find the post with the lossless snubber, with AFAIR a capacitor from the drain node to a regenerative point. I am working on a 2 switch flyback and some other schemes, but would like to try that novel idea out.... Anyone knows a pointer to the thread? Regards Klaus


Phototransistor fed to a transimpedance amplifier

Started by SilverLeo in sci.electronics.design6 years ago 45 replies

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a...

Hi all. I'm running through some test of a phototransistor signal conditioner, and I'm facing with wild noise issues. The conditioning is a basic TIA stage: http://i.imgur.com/PcgglKZ.png Feedback resistor is 5K, feedback capacitor is 470pF, negative bias is -12V, and photocurrent is in the range 8uA-800uA. The bandwidth should be about 50kHz. Opamp is OPA2277UA. Problem is that phototrans...


How to make a bipolar electrolytic capacitor from what you have in your junk box.

Started by John Fields in sci.electronics.design6 years ago 15 replies

Let's say you need a > 10 microfarad bipolar cap rated to stand off 10 volts, right away, and and all you have in your junk box is a...

Let's say you need a > 10 microfarad bipolar cap rated to stand off 10 volts, right away, and and all you have in your junk box is a 50 microfarad monopolar aluminum electrolytic rated to stand off 50 volts. If you connect the cap, backwards, to a DC supply and limit the current into the cap to something which won't blow it up, the current into the cap will eventually fall close to zero as


Spice Model Needed...

Started by Jim Thompson in sci.electronics.design6 years ago 8 replies

Spice Model Needed... Does anyone know of a _device-level_ Spice model for a 74HC05 open-drain inverter? I could write one, but there's not...

Spice Model Needed... Does anyone know of a _device-level_ Spice model for a 74HC05 open-drain inverter? I could write one, but there's not a lot of accurate specification information out there. I need a device-level model since my client's application dumps a capacitor. ...Jim Thompson -- | James E.Thompson ...


200kHz oscillator

Started by Piotr Wyderski in sci.electronics.design6 years ago 11 replies

I would like to experiment a bit with magnetic parametric amplifiers. For that purpose, I believe I need a 200kHz sine wave generator with a...

I would like to experiment a bit with magnetic parametric amplifiers. For that purpose, I believe I need a 200kHz sine wave generator with a watt worth of output power. My obvious choice was to construct a current-fed resonant Royer oscillator. For a 1nF tank capacitor it implies a 633uH inductor (2x5 turns on a 6400nH/turn^2 way to big toroidal core), 2x ZTX851, a 100k base polarization resi...


Placing Tesla Coil Capacitor WITHIN the Secondary

Started by Robert Miller in sci.electronics.design5 years ago 7 replies

I intend to build a classic spark gap Tesla coil. I understand the value of the timing cap must be selected with reference to the resonant...

I intend to build a classic spark gap Tesla coil. I understand the value of the timing cap must be selected with reference to the resonant frequency of the coil. I was wondering what would happen if I was to custom build (wrap) a tubular cap, from al foil and mylar, and slide it _within_ the TC's secondary so both are on the same axis. Would this configuration tend to make selection ...


Analog MUX using discrete MOSFETs for flying capacitor cell measurement BMS

Started by P E Schoen in sci.electronics.design5 years ago 20 replies

My latest project is a battery management system (BMS) that can accurately measure cells in a lithium battery pack, and also perform shunt...

My latest project is a battery management system (BMS) that can accurately measure cells in a lithium battery pack, and also perform shunt balancing and possibly charge shuttling to balance the pack. I would also like to be able to use it for a pack of four 12V SLA batteries. A DG408 could be used to select up to 8 cell voltage taps from nominal 3.2V (LiFePO4) or 3.7V (Li-Ion), with a ma...


Buck regulator chips

Started by Phil Hobbs in sci.electronics.design5 years ago 27 replies

Modern buck regulators seem to have way too many features that I can't turn off or customize. The otherwise very nice AOZ1282-1 snookered me...

Modern buck regulators seem to have way too many features that I can't turn off or customize. The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed short-circuit protection interval--it wouldn't start up into a 220 uF capacitor, even with a very light load. Fortunately, switching to 22 uF fixed it, and I had some with the right footprint. And then many go into stut...


How to select transistor for oscillator ?

Started by Anonymous in sci.electronics.design4 years ago 45 replies

Could some electronics guru here please help ? What is the best way to select a transistor for an oscillator ? Consider a Colpitts oscillator...

Could some electronics guru here please help ? What is the best way to select a transistor for an oscillator ? Consider a Colpitts oscillator running at 5 MHz. The following are the analysis steps. 1. Select a value for the LC tank capacitor C1 = C2 = C 2. Select a load e.g., R=50 Ohm 3. To start oscillations, gmR > C2/C1. In this case gmR > 1 4. Using the oscillation frequency and


How to stop electrical whining noise?

Started by John Doe in sci.electronics.design4 years ago 40 replies

https://youtu.be/FSwZQtqWyHw Can that whining noise be easily eliminated? I am assuming its origin is easy for some to guess. It uses...

https://youtu.be/FSwZQtqWyHw Can that whining noise be easily eliminated? I am assuming its origin is easy for some to guess. It uses brushless motors controlled by an "electronic speed control" (ESC). There is a large cap across each ESC supply plus and minus. I tried adding a 1000 ?F low ESR capacitor on the battery input but that didn't help. Thanks.


AC offline to low-V supply, with a cap

Started by Winfield Hill in sci.electronics.design4 years ago 77 replies

Years ago we had threads about the ugly but seemingly simple scheme to get 12V DC at 5mA, etc, with a film capacitor straight to the AC ...

Years ago we had threads about the ugly but seemingly simple scheme to get 12V DC at 5mA, etc, with a film capacitor straight to the AC line. We said, gotta have a series resistor to minimize the startup inrush current. Does anybody recall a specific instance of this scheme being used commercially? Paul and I are days away from turning in the manuscript on our new x-Chapters ...


Common collector amplifier and amplitude modulation

Started by Anonymous in sci.electronics.design4 years ago 20 replies

Could some electronics guru here shed some light on this Could a single stage common collector amplifier exhibit amplitude modulation ? I have...

Could some electronics guru here shed some light on this Could a single stage common collector amplifier exhibit amplitude modulation ? I have the SPICE model of a simple common collector amplifier consisting of two base bias resistors, a collector resistor and an input and a output DC blocking capacitor, as well as a source and a load resistor of 50.0 Ohm. The BJT collector is connected to ...


Bitscope (Micro BS05) and 32bit Linux

Started by Johann Klammer in sci.electronics.design3 years ago 4 replies

I got one of those. Today, I tried to set up two oscilloscope probes. (the frequency compensation capacitor) I noticed the following...

I got one of those. Today, I tried to set up two oscilloscope probes. (the frequency compensation capacitor) I noticed the following things in bitscope-dso: when adjusting the cap, the waveshape doesn't change, but the amplitude does. at 250kHz it's almost triangles regardless of capacitor setting. 50kHz looks acceptable. I am also not sure what sort of filter it has and how to turn i...


Film capacitor as power-supply filter

Started by Anonymous in sci.electronics.design3 years ago 200 replies

Is there any reason not to use a 20-uF 900-volt film capacitor as a power supply filter? I'm updating a vintage Heathkit capacitor checker that...

Is there any reason not to use a 20-uF 900-volt film capacitor as a power supply filter? I'm updating a vintage Heathkit capacitor checker that I use regularly for re-forming electrolytics, and its power supply filter is currently two 40-uF 450-V in series, without balancing resistors; applied voltage is nominally 600 V DC. This hasn't given any trouble, but I'm uneasy about its future. Now...


Things that go boom? Need to present to some kids

Started by Anonymous in sci.electronics.design3 years ago 36 replies

Hi Every year I teach a class in 7th grade about electronics and space stuff I normally end the presentation with a reverse power capacitor...

Hi Every year I teach a class in 7th grade about electronics and space stuff I normally end the presentation with a reverse power capacitor that goes boom, just so they at least get excited about that. But, any other component that makes a large boom? (I would like to avoid the cap, since it spills electrolytics and smells bad DPAK2 FET, with 30W disipated? Tantalum reverse biased? ...