hybridfree/eevblog-posts huggingface dataset:
PCM4202 audio ADC - differential input buffer design - Page 1
Forum section: electronics / projects

author: Yansi
author_rank: Super Contributor
timestamp: May 29, 2016, 07:10:10 pm
content: Hello!I'd like to design something with a PCM4202 stereo audio ADC. But I have some design issues in the analog part before the ADC.I have a line level balanced audio input which I want to bring into the ADC. The ADC of course has differential inputs. So what I need is only a buffer for the ADC.In the PCM4202 datasheet there is a recommended circuit (Figure 13 on p. 22), using OPA1632 as a driver:http://www.ti.com/lit/ds/symlink/pcm4202.pdfAnd there is the schematic of the evaluation module on p. 14 here:http://www.ti.com/lit/ug/sbau103/sbau103.pdfIt is using the same circuit.First, I need the audio input to have 10 or 20k input impedance balanced. The circuit recommended has only 2k. Too low. The values could be scaled up 5 to 10 times, but that might violate recommended values for the OPA1632 (quite low impedance feedback loop is being recommended). Also, the original circuit has gain <1 which is fine but I might require more sensitivity. (Not decided yet).What is currently important is to make the input 10-20k input impedance, tolerant to all sorts of EMI (strong local MW radios, mobile phones,..). This circuit topology with no direct passive filtering on the input seems no brainer, unusable. The CMRR at MW frequencies and up will be shit, no doubt.The other very interesting thing in the recommended circuit for PCM4202 is how they DC bias the ADC input. They use a buffer for the commonmode voltage from the ADC - fine. They use quite expensive low offset/drift opamp - also fine. And then they place 1k resistor in series with the Vocm input of the OPA1632?! What the hell? The Vocm input has about 15k input impedance and is supply-centered by internal resistor divider (30k:30k). That external 1k resistor will introduce quite some offset error, so the ADC is not biased right and will produce data with quite some offset. Am I right?How do you recommend solving these three main issues? (Input impedance, EMI protection, DC bias)It seems to mu not much thought (if any at all) was put into the reference design. I might be missing something, but I don't understand much, how is that circuit supposed to work, correctly.Thank you for help,Yan

author: Chris Mr
author_rank: Regular Contributor
timestamp: May 31, 2016, 12:11:33 pm
content: Have you considered the Johnson Noise of the 10-20K input?
PCM5102 DAC noise issue - Page 1
Forum section: electronics / projects

author: cowana
author_rank: Frequent Contributor
timestamp: June 17, 2013, 06:36:56 pm
content: I recently designed and made a digital/analogue preamplifier.It supports multiple SPDIF sources (USB via a PCM2707, TOSLINK, Regular SPDIF). These are switched and converted to I2S by a CS8416, and then fed into a PCM5102 DAC.The output from the DAC, along with several analogue inputs, are switched by relays and summed and buffered by a pair of LME49710 opamps.This signal is then fed into a PGA2311 voltage control chip.This all works well. However, I seem to be having a slight issue with noise being introduced by the DAC.When there is no SPDIF signal being fed into the CS8416 (thus no I2S data going into the DAC), there is a small amount of noise on the output - as recorded in the attached file.Once valid SPDIF/I2S data is played, this noise disappears. Even if the data is silence (for example a muted youtube video), it still disappears.As soon as SPDIF data stops coming (and thus I2S data stops being generated), the noise returns.I suspect the issue is something to do with the internal analogue muting in the PCM5102? I have tried replacing the PCM5102, however this does not fix the problem at all.I'd very much appreciate any thoughts on the matter, and am happy to answer any questions you may have.Many thanks,Andy

author: jaycee
author_rank: Regular Contributor
timestamp: June 21, 2013, 10:37:08 pm
content: are you sure it is the dac producing the noise, ie have you measured it with a 'scope ? Is it possible the LME49710's are oscillating?

author: envisionelec
author_rank: Frequent Contributor
timestamp: June 22, 2013, 03:24:38 am
content: You have a voltage difference issue. I see a VDDa and VDDd and corresponding analog and digital grounds. What I can't see is your ground plane paths as they're greyed out. The noise is there when the outputs are muted to ground. The problem is...there is a difference in the analog and digital ground and it's audible. Did you try shorting the outputs to analog ground at the chip? How about tying all the grounds together? It seems like anathema, but you'll probably be surprised that it works just fine and it then noise free.Also, keep your ground tie far away from those relays.
PCM5102A in 1.8V mode. Separate 0.1 and 10uF caps for DVDD and LDOO? - Page 1
Forum section: electronics / projects

author: sidlauskas
author_rank: Contributor
timestamp: January 27, 2019, 01:46:56 pm
content: Hi,I found in the datasheet (33 page, 11.5.1) that when using PCM5102A in 1.8V mode, DVDD and LDOO should be both connected to external 1.8V. What's not clear to me is if I still have to put separate 0.1 and 10uF caps for both DVDD and LDOO pins as shown in the schematic provided in their datasheet. Here's how it looks like in my schematic:Is this correct? Thanks

author: dmendesf
author_rank: Frequent Contributor
timestamp: January 27, 2019, 02:06:49 pm
content: Pins are so near that this won't make a difference. You can put one of each without fear.

author: mvs
author_rank: Frequent Contributor
timestamp: January 27, 2019, 05:06:29 pm
content: Quote from: sidlauskas on January 27, 2019, 01:46:56 pmI see no practial reason to cheap out on decoupling caps... It costs almost nothing and would not add any new item to your BOM.Put at least separate 100nF to LDOO, so if you decide later to use 3V IO levels, you can still cut the trace between LDOO and DVDD.

author: sidlauskas
author_rank: Contributor
timestamp: January 27, 2019, 06:19:14 pm
content: Quote from: mvs on January 27, 2019, 05:06:29 pmIn 3.3v mode LDOO must be connected to GND, so it wouldn't be enough to cut that trace

author: mvs
author_rank: Frequent Contributor
timestamp: January 27, 2019, 09:50:11 pm
content: Quote from: sidlauskas on January 27, 2019, 06:19:14 pmLDOO is output of internal 1.8V LDO voltage regulator and positive supply rail for internal logic... why on earth it needs to be grounded?

author: sidlauskas
author_rank: Contributor
timestamp: January 27, 2019, 10:06:04 pm
content: Quote from: mvs on January 27, 2019, 09:50:11 pmIt seems you're correct. Sorry for confusing and thanks for your input!
PCM9211 - How to configure pinmux? - Page 1
Forum section: electronics / projects

author: hitech95
author_rank: Regular Contributor
timestamp: December 07, 2020, 12:08:56 am
content: Hi, I would like to start working on a new project.Unfortunatly I cannot understand a Datasheet.In those cases I would contact TI via its forum but they decided to disable "personal" emails and my university email is not a valid one.I would like to implement the typical application of a PCM9211 (Datasheet).RXIN4 to RXIN7 are muxed with another function (i2s input). But I cannot find a way on how this MUX is set.On chapter 9.2.2.1S/PDIF Ports is talking about the typical application and it states:QuoteI've also looked for a Application Notes and EVB Notes but found nothing about.What am I missing?Did someone alrady tried to use this chip?

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 07, 2020, 01:43:59 pm
content: From the block diagram on page 17, you just select the mux for auxin0. Most likely you'll want to use the one for the DIT since the other two are basically passthroughs.

author: hitech95
author_rank: Regular Contributor
timestamp: December 07, 2020, 03:00:50 pm
content: Ok so you think that when auxin0 is enabled, the RXIN4 to RXIN7 are automatically pinmuxed to i2s instead of SPDIF?

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 08, 2020, 03:39:26 am
content: Yes.
PDB Design Review: Impedance Matching & Termination Resistors - Page 1
Forum section: electronics / projects

author: bogomips
author_rank: Newbie
timestamp: November 30, 2020, 08:14:40 pm
content: Hi, I hope you guys can help review my design-I'm working on a keyboard PCB design. I thought I was nearly done, but after happening accoss discussions on USB impedance matching of the data traces (and differential pair routing), I thought I'd better at least try and address this.Due to design constraints, I'm not able to place the USB plug near the MCU (Atmega32u4) - so I have to route the data traces a loooong way across the board.(appologies, I can't get the inline attachments working... images are visible below post)From what I read, to attempt to design to match an impedance value, you need to put a copper fill (GND) on the back of the PCB, have no interruptions to that ground plane under the traces, and set your data line traces to be a specific width, and a specific width apart - and - also try and keep the traces the same length.I've managed to get the ground plane in, uninterrupted from USB plug to MCU. I've also set my D+/D- trace widths and separation, as per this calculation - trying to reach90 ohms on differential impedance.(Values picked from the manufacturer:https://jlcpcb.com/capabilities/Capabilities)Since this is only a keyboard, I don't need high transfer speeds, so I guess that means my design does have to be 110% perfect in this regard... Due to the spacing of the USB connector pins and MCU pins, I had to compromise on trace width and taper it in..Here are a few close-ups:Here are theTermination Resistors:In the keyboard design world, itcommon conventionto put in 22 ohm resisters in the D+/D- lines:These are 0402 package resistors (so, tiny).Here is another chat about these termination resistors for USB:https://www.eevblog.com/forum/projects/why-usb-data-series-resistors/Questions:1) Do you think I've done a reasonable job at routing those D+/D- traces to try and match impedance? Any obvious things I could improve?2) I'm worried about the Termination Resistors - they cause the traces to diverge a bit... I think that will mess up the impedance matching efforts? I don't have JLCPCB specs for min distance for SMT assembly... So I don't know if I can move them closer... Any thoughts on this? Should I just try and make them as close as possible together?3) The veryvalueof Termination Resistors is a question... 22 ohm is the usual value cited... but I don't know how that factors into the overall impedance of the D+/D- lines?(I'm still learning...)Thank you very much

author: jonroger
author_rank: Regular Contributor
timestamp: December 02, 2020, 02:02:14 pm
content: Some good info here:https://www.silabs.com/documents/public/application-notes/an0046-efm32-usb-hardware-design-guidelines.pdf22 ohms is from the ATmel data sheet.
PDM MEMS Microphone - weird DC bias  - Page 1
Forum section: electronics / projects

author: davegravy
author_rank: Regular Contributor
timestamp: May 18, 2022, 03:35:53 pm
content: I have a PDM MEMS sensor (IM72D128V01,using this eval kit) connected to a STM32U5 NUCLEO board.(Background: it's connected to the ADF peripheral which I have configured to provide a 5th order CIC filter with a 32x decimation factor. ADF clocking is configured to output a 3,072,000Hz data clock to the MEMS sensor)Every time (or at least most) I start my STM32 program I have to power cycle the MEMS IC or else I get a DC bias in the data register - the most significant byte of the 24bits (which includes the sign bit) is constantly 0x0 meaning the integer sample values are all positive.After I power cycle the MEMS IC I immediately start getting a mix of positive and negative integer sample values as I would expect. This persists until I terminate and relaunch in CubeIDE.Why might this be? Is it common to need to implement switched power to a PDM MEMS IC to address this in a production design, or am I likely doing something wrong?

author: TC
author_rank: Contributor
timestamp: May 20, 2022, 12:42:57 am
content: Look at section 3.4 Auto DC Bias in the microphone data sheet and check your startup state.

author: davegravy
author_rank: Regular Contributor
timestamp: May 22, 2022, 03:07:30 am
content: Thanks that was it. I thought I had the select pin tied to ground but turns out it was floating, and I missed that little section in the datasheet.
PDM Microphones - Page 1
Forum section: electronics / projects

author: itdontgo
author_rank: Regular Contributor
timestamp: June 23, 2017, 04:59:56 pm
content: To quickly get some audio out of these microphones I used a PIC16 as follows:PWM @2.67MHz to generate the clockTimer1 increment on clock positive edge (so connecting T1CKI to the PWM output)Timer1 Gate connected to the DATA pin on the mic.My idea was to count the pulses with timer 1 when the data pin is high using the gate. When data is low it won't count the pulses. I then read and reset timer 1 giving me the number of pulses in the 125us 8kHz window I am looking for.That all worked but the sensitivity of the mic is too low. It works fine when it's right next to my mouth but produces no measurable change when a couple of foot away. The mic is a 120dB AOP mic. Not the most sensitive but I would expect to be able to get some background noise out of this mic. Do you see any value in this method of decoding or will it always be insensitive?

author: itdontgo
author_rank: Regular Contributor
timestamp: June 24, 2017, 02:46:45 pm
content: Well I did some work and... Yeah it's OK for loud noises to do it that way but to get the full range needs a bit more signal processing.Using the timer 1 with gate I managed to get basic 8-bit data and then used the recommended CIC filter which gave the results I was looking for. It works nicely.
PDN impedance test board - what to include? - Page 1
Forum section: electronics / projects

author: jmw
author_rank: Frequent Contributor
timestamp: February 02, 2023, 07:15:00 pm
content: I want to make a PCB for familiarizing myself with the two-port shunt-through method for measuring power distribution network (PDN) impedance. I've made a common-mode choke transformer by winding coax around a ferrite that's a hopefully a good clone of the Picotest J2102B. This evaluation board would have several isolated modules, each one with two neighboring coax ports, and then some connected network to simulate the PDN.What kind of configurations should I put on this board? So far, I was thinking of the following:precision shunt resistor, like 1 or 10 mΩ, for testing the effectiveness of the common-mode chokebunch of 0603 + 1206 footprints, connected with traces only, and at various lengths away from the pair of ports to visualize importance of placing capacitors close to bypassed parts, use of decade capacitors, and effect of tantalum/higher ESR capssame as above, but with power and ground planesWhat else?For coax connectors, I was thinking to use compression-mount SMA connectors. They're expensive, but if this board has many sections that need two ports each, it may end up being cheaper than buying several SMT or through-hole connectors, and I can just unscrew and move the connectors around to make measurements.Picotest app note about the method:https://www.picotest.com/measurements/images/download/the%202-port-shunt-through-measurement-app-note_REV1_073118.pdf

author: jmw
author_rank: Frequent Contributor
timestamp: February 05, 2023, 04:46:21 am
content: This is sketch of the layout I'm thinking of: put one capacitor ACAP between the connectors, then have several open footprints at various distances. Haven't yet added via stitchings or a version with power and ground planes.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 05, 2023, 06:15:22 am
content: You might want to make that center conductor a bit more thicker. The goal here is not to reach 50 ohms impedance, but to keep the series impedance of the probe as small as possible. This helps when you are measuring PDN impedance of few milli ohms.I assume that you have an SMA calibration kit and the calibration would be performed till the end of the cable. That still leaves out the SMA connector from your calibration. It will add some uncertainty, unless you de-embed them as well.It would be worthwile to have a coupon with the 2x thru, which enables you to de-embed the SMA to SMA structure.Compression mount SMA always adds some milli ohms of contact resistance at low frequencies. Use soldered connections to avoid this contact resistance.
Peak detector is not linear at millivolts level - Page 1
Forum section: electronics / projects

author: ryantran
author_rank: Newbie
timestamp: November 03, 2020, 05:12:55 am
content: Hi Guys,I have been struggling with the issues with the peak detector at low level but could not find answer anywhere. The mechanism of a peak detector is well presented in many resources but not many address the process of how to to select components such as op-amps , diodes , caps values etc..I am having a peak detector as shown belowADG1222 is a switch to reset the peak detector. In my application ,the input is a Gaussian curve and frequency is around 400MHz but I use a sine wave in LTspice for simplicity. The detector works fine at high level signals but it loses its linearity and accuracy at millivolts level (and I'm talking about 1 or 2mV or even down to hundreds microvotls). For example, I feed a 2.4mVp input and the output is only 1.3-ish mV and if I double the input to 4.8mV, the output is about 4.2mV which is about 3 times larger. Note: all the results were obtained by probing with a Rigol oscilloscope.I appreciate your feedback.

author: moffy
author_rank: Super Contributor
timestamp: November 03, 2020, 06:20:30 am
content: You have finite gain, gain bandwidth and slew rate of the opamps. You have delay (100R/1nf) in the loop as well as parasistic capacitances and leakage currents. Considering the design you are getting good performance.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 03, 2020, 12:38:22 pm
content: With a low input signal the 1st OP just needs too long to overcome the step from the 2 diodes (D2 and D3). The capacitor C1 additionally slows down the OP.For a high speed chances are the memory cap should be smaller than 1 nF, more like 20 pF to 100 pF. If drift is a problem add another slower stage.

author: ryantran
author_rank: Newbie
timestamp: November 03, 2020, 04:41:35 pm
content: So how can I determine the required GBW or Slew rate? Sorry it's quite fuzzy to me how small signals matter a lot here.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 03, 2020, 04:54:49 pm
content: The critical parameter for use with a small signal would be the GBW if there is no additional capacitor to slow down the OP. With the extra cap it may be that bandwidth. The point is slewing some 1.2 V for the 2 diodes with a small error signal. The rate of voltage change for OP is input voltage (accepted error) times GBW time about 6 (2 pi in simple theory).The hold capacitor and resistor set a limit on how fast the OP can be. it does not help much to have a faster OP and than artificially slow it down.If small signals are relevant one could consider a 2 nd parallel channel that works with an amplified signal. Small peaks would be caught by the amplified channel and large peaks would use the normal channel. Intermediate peak that still just fit the amplified channel may be used to check the gain if needed.
Peak detector with discharge - Page 1
Forum section: electronics / projects

author: Harvs
author_rank: Super Contributor
timestamp: October 31, 2012, 03:48:49 am
content: Gday all,I'm designing a new ignition module for the old Ducati 2V engines, primarily for interest’s sake.At this stage the plan to use a uC to control everything (PIC32 at the moment), with a pretty standard inductive/flyback setup using an ignition coil driver IGBT.However, rather than just use the maximum internal current limiting of the coil drivers (which isn’t suitable under a number of circumstances), I've been putting together some circuits to add:- Variable peak current limiting to the coil primary set by a DAC output from the uC,- Feedback to the uC of when it has hit that current limit (so the uC can actively manage dwell time),- An ADC input of the peak primary coil current, so the uC knows what current was reached if it is not hitting the target current.Anyhow, for the third point I’ve been experimenting with a peak current detector circuit that came out of the TI datasheet. Works well for the application with careful selection of diodes and cap for low discharge. However, what I want to do is add a uC controlled discharge to the cap. So the idea will be, after the uC turns off the IGBT, wait a hundred or so uS’s for the main peak spark to occur (as it generates a pile of EMI), then sample the peak current, then discharge the detector for the next coil charge cycle.Obvious thought was to add a small FET across the Cap. However I’m struggling to find anything with a small enough off state drain-source leakage current. Particularly when you look at the higher operating temp leakage current. Needs to be in the order of several nA for the cap values not to end up too large for the opamp to drive, and still maintain reasonable accuracy.So I’m hoping for some better ideas? Maybe a completely different peak detect & hold circuit? Or am I looking at the wrong type of devices to discharge the cap?

author: Harvs
author_rank: Super Contributor
timestamp: October 31, 2012, 09:46:47 pm
content: Sorted... I think. Increased the holding cap to 12nf, added a 300R resistor to the output of the first opamp stage for stability and put a 2N7002 mosfet across the cap. At this stage, all appears well.I guess the real test will be once I warm it all up in an oven and see how that effects the leakage rates.
Peak Hold: Keithley 2000 - Page 1
Forum section: electronics / projects

author: k1mgy
author_rank: Regular Contributor
timestamp: February 07, 2018, 09:24:58 pm
content: My Keithley 2000 (I have two) are lovely meters and have a boatload of features. One that I need presently would capture peak values. I am monitoring a DC rail for any excursions of interest. As the sample rate of the Keithley is very good, I hope to catch transients. But, how? There seems to be no peak hold feature.Anyone built such a feature using the meter's programming?

author: xani
author_rank: Frequent Contributor
timestamp: February 08, 2018, 12:50:23 pm
content: Dave might help you:Aside from that you could just control it via scpi and just dump data then find the highest one but honestly protoboarding simple peak detector will probably be faster.

author: hwj-d
author_rank: Frequent Contributor
timestamp: February 09, 2018, 05:36:10 pm
content: Maybestore/recallwill help you?Store1024 readings (max). Depending on your reading rate, it tooks time (watch the star in the display). After that, withrecall, andarrow-key'scycle through your readings,rdg #1, std dev, average, min at, max at(right arrow for value), and so on. Automate this with programming.hth
Peak Repetitive Reverse Voltage and others differences - Page 1
Forum section: electronics / projects

author: abdulbadii
author_rank: Frequent Contributor
timestamp: October 14, 2021, 07:45:52 am
content: What are, of a diode characteristics, the main differences among:Peak Repetitive Reverse VoltageWorking Peak Reverse VoltageDC Blocking VoltageWhat importance in distinguishing them while that seems trivial?

author: trobbins
author_rank: Frequent Contributor
timestamp: October 14, 2021, 05:41:13 pm
content: Why do you ask?

author: thm_w
author_rank: Super Contributor
timestamp: October 14, 2021, 10:05:17 pm
content: https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/diode-ratings/QuoteQuoteQuote

author: magic
author_rank: Super Contributor
timestamp: October 14, 2021, 10:22:51 pm
content: Yeah, still gibberish. This is meaningless without specifying frequency, pulse width and shape, duty cycle, you name it.I wouldn't be surprised if it's supposed to refer to 60Hz rectification.Maybe there is a JEDEC standard on it, somewhere...

author: David Hess
author_rank: Super Contributor
timestamp: October 15, 2021, 02:12:22 am
content: https://www.electricalclassroom.com/diode-ratings-diode-datasheet/

author: magic
author_rank: Super Contributor
timestamp: October 15, 2021, 05:57:51 am
content: Still meaningless without specifying frequency, pulse width and shape, duty cycle, you name it
peaking 2nd order filter in speaker filter - Page 1
Forum section: electronics / projects

author: Ryjuuuhn
author_rank: Newbie
timestamp: October 26, 2017, 09:41:32 am
content: Hi all,I wanted to design a subwoofer in addition to my bleutooth speaker, this had to be a portable subwoofer of approximately 4liters in size.After some testing with a thousands of speaker drivers I found out that a new version of Winisd was available.In this version i messed around with some speaker filters until I found the option of a peaking 2nd order filter.I am quite familiar with calculating filters and simulating them in Matlab.But I could not find any information regarding the use in speaker filters, to use them to create a peak.Because this filter allowed me to push a speaker downto 40 Hz(-3dB point) in a closed enclosure with 3 liters of volume.I wanted to make this filter before the amplifier, which I already designed in Eagle, an TPA3116D2 bridge design.So I wanted to have a gain with this filter at 45 Hz 8dB peak high pass filter.Off course all filters and sources are going to be isolated by opamps for cascading.Because a third order low pass filter (over damped) should also be added.So my question is actually if this is a good idea to make this peaking 2nd order filter for subwoofer us?I am aware of the phase change and delay which it creates, but this seems to be equal to a subwoofer in a bass-reflex enclosure without filters attached.I wanted to design this just with filter RCL, with 0805 resistor and a 1 uF film capacitor and a coil.I did not ask this question on a hifi forum, because hifi enthusiast seem not very familiar with making the filter at the input of the amplifier.And i wanted to have it before the input, so I could cascade filters with the help of opamps instead of getting nasty filter interference by cascading.
Pease constant current source - Page 1
Forum section: electronics / projects

author: timelessbeing
author_rank: Frequent Contributor
timestamp: January 11, 2014, 05:36:05 am
content: What circuit is Bob painting? I wish I could see the whole thing.Is it a well known, or reference circuit, which is available somewhere? It looks similar to one of the example application circuits in the LM399 data sheet, but there are some differences.

author: Dave
author_rank: Super Contributor
timestamp: January 11, 2014, 05:51:02 am
content: Click.

author: timelessbeing
author_rank: Frequent Contributor
timestamp: January 12, 2014, 04:51:58 am
content: Thanks
Peavey Deca 528 Class D output question - Page 1
Forum section: electronics / projects

author: CaptDon
author_rank: Super Contributor
timestamp: October 05, 2022, 01:43:06 am
content: I have a question about how Peavey did the Class D output on the 528. There are two Mosfets to pull the center point up to +75vdc. Those are IRFP9240 and are P-Channel. But they only use one Mosfet (IRFP240) N-Channel to pull the center point down to -75vdc. This seems very strange. It isn't one of those oddball bridges where a diode is in place of a Mosfet. It isn't an H-Bridge, only a half-bridge. Those Mosfets are Q409 and its mate Q411 and on the lower side is the lonely Q410. Sorry I can't upload the schematic but it is readily downloadable from several sources. Any ideas or opinions of why they did two for pull up and one for pull down? Thanks!!

author: CaptDon
author_rank: Super Contributor
timestamp: October 05, 2022, 01:57:58 am
content: I see one possible clue. The IRFP240 which is alone in its function has an RDS of .18 ohm at 10vgs. The IRFP9240 which has a parallel partner has an RDS of .5 ohm at 10vgs. Perhaps they felt it was best to have a lower total RDS and paralleled up the pair?? This unit can drive 140vpp or 70vp or 49.5vrms (with zero headroom) into a 4 ohm load. The amplifier is however rated at 250 watts RMS per channel into 4 ohms both channels sinewave driven. These were single rack space amps noted for low end transient available power and admired by bass players for thump without the weight.

author: JohnG
author_rank: Frequent Contributor
timestamp: October 05, 2022, 03:06:56 am
content: You are probably right about the on-resistance. Depending on how much feedback there is, having unequal resistance can give some substantial even harmonic distortion.Using a p-channel for the high side makes the drive easier since the source reference is the positive bus. Some designers even used capacitive coupling to drive the high side.The problem is that now you have a lot more capacitance for the high side switch, and this has its own problems, not the least of which is cost. It seemed like a reasonable idea in the 1980s, but designers have access to better high-side drivers for n-channel FETs, and you don't see so many p-channel power MOSFETs these days.John
Pedestrian Walk Signal - Internet Controlled - Page 1
Forum section: electronics / projects

author: JBionics
author_rank: Newbie
timestamp: July 26, 2014, 05:23:34 pm
content: I picked up a pedestrian walk signal from a surplus store for $30. It had previously been used in Cortland, NY. Using a Spark Core WiFi module and some interface electronics, I have made this into an internet connected and controllable display.You can check it out here:http://jbprojects.net/projects/walksign/The live stream requires flash, so won't work on mobile.There is a live stream of the sign and it can be updated and controlled through the website. The website interacts with the sign through Spark's device cloud infrastructure. You can change the hand/walk signal and scroll simple messages across the countdown timer's two 7 segment displays.The Spark Core is connected to two MCP23008 8-bit I2C IO Expanders. The IO Expanders are connected to two ULN2803 darlington transistor arrays.There's also a brief project write-up and some pictures on the site.

author: CrabxCore
author_rank: Contributor
timestamp: July 27, 2014, 04:36:17 am
content: Half drunk, sitting here playing with a sign remotely for 45 minutes. Thanks! This is a really cool project!

author: JBionics
author_rank: Newbie
timestamp: July 28, 2014, 07:35:06 pm
content: Glad you liked it!It's back online. There was a live streaming server issue. Fixed now.

author: stef_r
author_rank: Contributor
timestamp: July 28, 2014, 07:48:51 pm
content: Cool!And it works / updates real fast too!(Even from the little country The Netherlands!)

author: SeanB
author_rank: Super Contributor
timestamp: July 29, 2014, 06:08:59 pm
content: Tried it and it works nicely. Intersting just how much needs to be enabled to actually get it to work.
Pedometer with data storage and website uploads - Page 1
Forum section: electronics / projects

author: ngkee22
author_rank: Regular Contributor
timestamp: July 27, 2010, 03:43:32 pm
content: I found this project listed on another website (not my project) and was curious what kind of ideas people here had on how to solve it. It looks interesting. Leave your thoughts.Here is a brief overview what what the people were looking for:We are looking for a wi-fi (some standard) pedometer that can transmit daily data to a website.We would like to produce a pedometer/physical activity recording device to be used by physical education/fitness professionals.Produced for less than $10 per unit and sold for $60 per unit.The device needs to be small, lightweight, durable, and attractive as close in size to a typical pedometer.The device should be fully enclosedThe device needs to transmit packets of data when within 150 feet (via Zigbee) to a PC instantly and automatically.Battery powered rechargeable or replaceable should last at least a year or so.The device needs to measure activity/steps - light, moderate, vigorous physical activity - and be accurate (plus or minus 3%) using 3-axis accelerometerMust be able to calculate if the user has been physically active at least 60 minutes a day; a minimum of accumulated steps as the data output; stores data over multiple days; transmitted data has unique user identifier as to sync with existing user data base by date/time.Ideally, this device would be worn by students as they enter the gym and pass an internet active computer or other device that instantly downloads data from the device and uploads it to the website for student/parent viewing.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 27, 2010, 08:47:33 pm
content: TI MSP430 with integrated wireless connected to a low cost accelerometer. Then run it from two AA batteries, no regulation needed.
Lab Power Supply circuit questions. - Page 1
Forum section: electronics / projects

author: Hobgoblin612
author_rank: Contributor
timestamp: August 23, 2012, 02:11:29 pm
content: Hi, This is my circuit for a lab power supply based on the early schematic in Dave's first power supply video.I am looking for feedback on the design and any other comments or suggestions.I will be using these CX101B panel meters:http://www.futurlec.com.au/Panel_Meters.jspThe schematic (KiCad did that weird thing with the polarized caps when exporting as .svg.)http://oi45.tinypic.com/oa67g8.jpgThe main questions I have are: Are the main filter caps big enough? I cant find any decent rules of thumb to use.Have I set the feedback of the voltage control op-amp correctly?Is the LT1013 a good choice of op-amp?What order should the binding posts on the front panel be? There will be main out+, main out-, 5V and mains GND.(the 5V shares a common ground with the main output.)I will be adding output switches for both the main and 5V out.The current meter will have a small toggle switch next to it to select between monitoring the actual output current and the set current limit.Thanks, Timothy.
Peltier Cooler on pulsating DC - Page 1
Forum section: electronics / projects

author: sonnytiger
author_rank: Frequent Contributor
timestamp: October 07, 2013, 11:19:46 pm
content: Would it be a problem? I was thinking vaguely of a drink cooler thing using them. Wondering if I could just power a bunch in series off of rectified mains (120V RMS)

author: ConKbot
author_rank: Super Contributor
timestamp: October 07, 2013, 11:23:03 pm
content: IIRC low frequency PWM causes rapid thermal expansion and contraction at the joints, which causes stress and premature failure. How low frequency is low frequency? I'm not sure. 120hz (or 100) from mains may not be too bad compared to something running at 1-5 hz.

author: Andreas
author_rank: Super Contributor
timestamp: October 08, 2013, 06:20:23 am
content: Quote from: sonnytiger on October 07, 2013, 11:19:46 pmLook for some application notes to TEC devices.Thermal efficiency depends largely on the voltage ripple at the input.Usually you will have to use a well regulated DC source with low ripple.Pulses should be either less than 1 per minute or switching frequencies > 5kHz.With best regardsAndreas

author: johansen
author_rank: Super Contributor
timestamp: October 08, 2013, 06:59:52 am
content: Quote from: Andreas on October 08, 2013, 06:20:23 amGiven that to get low ripple from a buck power supply it makes no sense for anything less than 50Khz, current ripple can be lower than 5% very easily.anyhow, its very simple to understand why current ripple is bad: heat is transferred by average current flow, while waste heat is generated according by RMS current.you can do rectified mains to TECs, but i recommend a buck converter.the UCC28019A might work.

author: sonnytiger
author_rank: Frequent Contributor
timestamp: October 09, 2013, 11:54:27 pm
content: Ok thanks for the info, i didn't see anything mentioning series connections = bad, I have many different DC power supplies I could use one. Are series connections alright?

author: johansen
author_rank: Super Contributor
timestamp: October 10, 2013, 03:36:09 am
content: Quote from: sonnytiger on October 09, 2013, 11:54:27 pmbetter than parallel connections actually, because it forces current sharing.

author: SArepairman
author_rank: Frequent Contributor
timestamp: October 10, 2013, 08:20:32 am
content: so to clarify so long you use a PWM at a frequency greater then 5KHz, so the peltier does not experience a temperature transient, it is good?

author: johansen
author_rank: Super Contributor
timestamp: October 10, 2013, 05:35:35 pm
content: Quote from: SArepairman on October 10, 2013, 08:20:32 amno, pwm regardless of the frequency is bad because the rms current is very high.. at 50% duty cycle your rms current is 1.41 times the average current..so that means your peltier is running twice the waste heat it would be if it was supplied from constant current dc.you need a properly designed inductor and filter capacitorgoogle "buck converter"
PEN (Earth) reactance - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: September 21, 2020, 03:36:54 pm
content: I found this page, which discusses the issuehttps://alltecglobal.com/articles/ground-system-resistance-vs-impedance-system-and-electrolytic-ground-electrode-comparison/As I see it, a broken PEN (combined earth & neutral cable) can act/look good if there exists a piece of 3-phase equipment on the same section having equal impedances to N. For example, 3 equal R (any value) from L1, L2, L3 to N/PEN are at 0V at the common point, the same potential as earth.The common of the supply company's transormers are also connected in a Y/star, and they are tied to actual soil (earth) at the star centre also.So I can create a reference derived from L1, L2, L3 then measure the PD to the PEN and verify they are the same. I assume I would have to check the PEN resistance also. But if the other machine is say 3 inductances in a star, returned to our locally-compromised piece of PEN, transient protection can still be poor - even if it looks good at DC and 50Hz.Or, if there are 3 large, equal capacitances then at AC or a short test at DC might not spot that. But for a DC fault, eventually the 3 capacitors would charge up to fault level.The link statesQuoteand I see no mention of DC either.What do the regulations say about acceptable PEN impedances?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 21, 2020, 05:51:47 pm
content: the ground/earth requirements depends also on your house installation,so if you have a TN or TT installation; a TT requires a much lower impedance than a TNolder TN installation here in Switzerland still depend on water tubing as PEN earth reference in the house installation, what would be completely insufficent for a TT installation.the impedance refers to 50Hz and maybe its harmonics; earth/ground reference in an electric installation can never serve as an appropriate RF-earth - these two things always get messed up, but have to be strictly separated
Pendant Lamp Wire Question  Super Mini Current Carrying Audio Coax Source? - Page 1
Forum section: electronics / projects

author: LaserSteve
author_rank: Super Contributor
timestamp: April 13, 2022, 10:04:38 pm
content: My place of worship has a metric ton of Led Ring Pendant Lamps. Please help a stumped Graybeard technician find the very difficult to find. Because guess who the leadership called when one lamp died, then later two were killed when a heavy person grabbed them during cleaning? I need a spool of the specialized miniature coax used to power the lamps. Two hours of the best of my Google-Fu failed.The constant current sources were standard modules. That part was easy. The cable however, has me baffled.The Led current from the constant current sources in the mounting box flows down to the LED rings via a sort of mini-coax about 1.5 mm in diameter with a center insulated stranded core carrying the 350 mA. I need it in bright silver/or clear with silver braid. The very well made outer winding is a twisted braid that is also structural, it carries the weight of the lamp. There are three coax coming down, one for upper led array power, one for lower led array power, and one that is just structural.Push to release fittings in the mounting box have the cable passing down their centers. This sets the hanging distance of the lamp. It also constrains the diameter. I'll have measurements in the morning.One thing I do know, the cable in question would make a really good subminiature audio cable for apps where you need tiny and tough. It is immensely flexible.I'm guessing this is readily available in China as a standard part, and not anywhere else.Anyone have any ideas? Outer jacket must be the right shade of silver, or I would never hear the end of it from the Ladies.In the lamps we have, unlike the picture, the clear wire with the center conductor does not exist. All current flow is in the structural coax.Thanks,StevePlease see attached pic.

author: thm_w
author_rank: Super Contributor
timestamp: April 14, 2022, 01:36:24 am
content: https://arstechnica.com/civis/viewtopic.php?f=53&t=1443943If its low voltage, maybe you can get away with insulated non-coax stainless cable.

author: LaserSteve
author_rank: Super Contributor
timestamp: April 14, 2022, 03:00:08 pm
content: You are my new hero for finding the Ars Technica post. Ours are indeed some form of Griplock.Kind Regards,Steve
Performance differences between large and small caps/resistors - Page 1
Forum section: electronics / projects

author: shadewind
author_rank: Frequent Contributor
timestamp: November 07, 2011, 05:21:05 pm
content: Are there any differences in the performance of, let's say, a 0402 resistor and an 0805 resistor with all things being equal such as tolerance with the exception of power handling? I'm wondering the same about caps. To sum it up, is there any drawback in going down in size except for assembly and perhaps reliability issues?

author: Unknown
author_rank: Unknown
timestamp: November 07, 2011, 09:17:34 pm
content: Voltage rating will be lower for smaller parts. With capacitors, the dielectric may also be inferior (eg. high K) to achieve the same capacitance in a smaller package.

author: w2aew
author_rank: Super Contributor
timestamp: November 07, 2011, 09:27:31 pm
content: Quote from: shadewind on November 07, 2011, 05:21:05 pmThe parasitics will differ, thus the high frequency behavior will differ between them. You'll have to consider things like equivalent series inductance, shunt capacitance, self-resonant frequency (for caps), etc. if you are operating at high frequencies.For caps, larger values aren't going to be as available in the smaller size. For example, a given value of capacitance might be available with an X7R dielectric type for a larger size, but only available with a Y5V or Z5U dielectric in a smaller size (higher dielectric constant, but poorer tempco).

author: mobbarley
author_rank: Regular Contributor
timestamp: November 08, 2011, 02:48:05 pm
content: The end of this is a great intro to the inductance of package sizeshttp://www.intersil.com/data/an/an1325.pdf
Performance test and review of 0.9V-5V to 5V 600mA boost converter - Page 1
Forum section: electronics / projects

author: HKJ
author_rank: Super Contributor
timestamp: August 21, 2015, 01:29:50 pm
content: This time I am testing a small boost converter. This test shows how the module performs, I do not try to improve any performance with extra capacitors.The full result can be seen here:http://lygte-info.dk/review/Power%200.9V%20to%205V%20600mA%20boost%20converter%20UK.htmlThe module is supposed to work from 0.9 volt, but do not expect any current from it at these low voltages.At 1.5 volt it is usable, but a single AA cell cannot supply 1.5 volt, at least two is needed.The output voltage is on the high side for a 5 volt module.Here I killed the module and had to use another module for testing.Idle current increases significantly at low input voltages.Loading with 200mA and varying the input voltage.Ripple with 300mA, more output capacity would be a good idea.

author: SharpEars
author_rank: Unknown
timestamp: August 21, 2015, 01:40:09 pm
content: A solid volt of P to P ripple? I call shitte on this one

author: bktemp
author_rank: Super Contributor
timestamp: August 21, 2015, 01:52:41 pm
content: The high ripple is due to the bad pcb layout:The output of the stepup is next to the IN+ terminal. The trace goes on the bottom side to the USB connector, but the capacitor (C2) is connected at the top side! All the stray inductance of the trace from the USB connector to C2 produces this ripple.Whoever made this layout did either not care at all, or had absolutely no knowledge on how to make the layout for a switching power supply.
Performance test and review of mains to 5V 0.6A Hi-Link HLK-PM01 - Page 1
Forum section: electronics / projects

author: HKJ
author_rank: Super Contributor
timestamp: August 29, 2015, 02:48:10 pm
content: I got the above module for test. It takes mains input and delivers 5 volt out with up to 0.6A continuous.Doing a load sweep shows that it can deliver much more for a short time (Specifications say 1A).Running it for 45 minutes at 600mA load makes it warm, but it is still acceptable.There is not much noise in the output at 0.5A load.For the full review/test see here:http://lygte-info.dk/review/Power%20Mains%20to%205V%200.6A%20Hi-Link%20HLK-PM01%20UK.html

author: Hixfield
author_rank: Contributor
timestamp: February 20, 2017, 06:02:03 pm
content: What fuse would you recommend for the mains input?

author: thm_w
author_rank: Super Contributor
timestamp: February 20, 2017, 10:45:33 pm
content: Good results, since the rating is up to 60C I suppose it makes sense it is capable of quite more than 3W at lower ambients.Module is $2 on aliexpress if anyone is curious.edit: good teardown as well
Pericom clock buffer -- power consumption - Page 1
Forum section: electronics / projects

author: blueskull
author_rank: Unknown
timestamp: February 02, 2018, 05:06:37 pm
content: Hi all.Is there anyone who had experience with Pericom (now Diodes) clock buffers?Their datasheets are not very clear at all, there't no mentioning about power consumption, which is a figure that I need to design power architecture for it.Is there anything I missed form the datasheet?https://www.diodes.com/assets/Datasheets/PI6C49X0208.pdfFYI, the clock frequency is 122.88MHz, output load is 8 channel, each channel 20pF (totally 49mA at 2.5V).The problem is, what's the internal power consumption?I would assume the datasheet max Idd is at max frequency, as such value matches value of similar products (CDCLVC1310, LMK00101).However, how do I calculate Iddo at a given frequency when enable=1?Thanks.

author: amyk
author_rank: Super Contributor
timestamp: February 03, 2018, 02:31:38 am
content: Easiest way might be to get one and measure it, if asking them directly for more information doesn't help.