hybridfree/eevblog-posts huggingface dataset:
Strange problem, help needed - Page 1
Forum section: electronics / projects

author: SJW2511
author_rank: Newbie
timestamp: October 20, 2014, 08:01:14 am
content: Ok bit of a strange one here, and bear with me because Im a little bit of a noob with electronics.Basically I have a couple of lasertag guns, they have 3 what I believe are IR sensors on them to detect the hits, what Im trying to do is extend the sensors away from the gun.the sensors themselves are black 2 pin IR receivers (I think)Anyway I removed the sensors off the pcb no problem, then I attached a 12inch wire to each point where it was joined with the sensor then attached on the ends of these wires.Tested it out and it received hits on the sensor perfectly, however the gun wouldn't fire properly, it was sometimes not firing at all, then sometimes it was taking a few seconds for it to fire after pulling the trigger. This is where it gets strange to me...Removed the sensor and left the wires the same length but with no sensor or anything on the ends, same problem. However if I cut one of the wires down to about an inch, or remove it altogether the gun works fine!?!? What is this voodoo? why would it matter how long the wire is especially as there is nothing even on the other ends of the wires?The only thing I can think is perhaps the wires are acting as some sort of aerial, or causing some sort of RF interference? in which case would using shielded wire help?thanksSteve

author: moffy
author_rank: Super Contributor
timestamp: October 20, 2014, 11:06:51 pm
content: Try twisting the wires together then connecting to the PCB and sensor. Not the best way to treat the sensor though.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 22, 2014, 11:22:14 am
content: Everything is an antenna. Your added wires are picking up ambient electromagnetic waves, and injecting them into the circuit. The background radio noise is variable, which likely explains why the symptoms are variable.It's a fixable problem, but requires someone who understands RF to look at the actual circuit and construction.Using twisted wires _might_ make a difference. Another idea is shielded twin-core, such as microphone cable. But then you have to figure out the right place in the circuit to connect the cable shield.
Strange problem with ngspice-25 - Page 1
Forum section: electronics / projects

author: Chryseus
author_rank: Regular Contributor
timestamp: June 12, 2013, 07:30:15 pm
content: I've been trying for hours to get the following netlist to output data into a rawfile, but it just will not do it for some reason.It works just fine for op, dc and tran.Code:* AC testVin 1 0 DC 0 AC 1R1 1 2 100C1 2 0 1u.AC DEC 10 10 100k.save all.endAnd the rawfileCode:Title: * ac analysisDate: Wed Jun 12 20:23:46 2013Plotname: AC AnalysisFlags: complexNo. Variables: 4No. Points: 0Variables:As you can see No. Points is zero.Either I'm doing something very wrong or ngspice is broken.Oh I found the problem, it wants me to use Meg instead of M, what the hell is this
Strange serial port on a router mainboard - Page 1
Forum section: electronics / projects

author: sam1275
author_rank: Frequent Contributor
timestamp: August 03, 2015, 03:43:49 pm
content: Hi everyone, I got a Mikrotik RB532 recently. When I power it on, I found it seems doesn't boot, the 2 LED (blue and orange) on the bottom of the six lit all the time, the WAN port LEDs lit a second when power on, no response to ping or any others.So I get a serial cable today but I found it's male connector... So I have to solder it to the RB532 with pin 2,3 and 7,8 reversed, however I get no real boot message but the following:Just after power on:After for a while:It seems it only send out space and "change to new line" in a loop. It doesn't respond to my commond, and I've tried connect/disconnect different pins, use different settings(different rate, change flow ctrl mode, change parity, stop bits, data bits)... None of them works.I'm blocked here... What could the problem be? Is it because the DB9 to USB cable is faulty? It's a Chinese product so I really don't trust it...(It passed my "manual loopback test") But I want to ask you guys first before try a new cable.Thanks!

author: technix
author_rank: Super Contributor
timestamp: August 03, 2015, 03:56:25 pm
content: Maybe this is not the UART that goes to the main processor. You can check the /dev/ttyS0 blog and the 40 minutes 20 roots video for tricks in finding available UART, pry into your device, and pwn it with your own firmware.

author: sam1275
author_rank: Frequent Contributor
timestamp: August 03, 2015, 04:03:24 pm
content: Quote from: technix on August 03, 2015, 03:56:25 pmThank you, but this port should be the console according to official document:http://routerboard.com/pdf/rb500ugM.pdf

author: technix
author_rank: Super Contributor
timestamp: August 03, 2015, 04:54:45 pm
content: Quote from: sam1275 on August 03, 2015, 04:03:24 pmThen I think you will have to go directly to the flash chip - maybe contents in that chip is messed up. Try JTAG it.

author: sam1275
author_rank: Frequent Contributor
timestamp: August 04, 2015, 04:08:04 pm
content: Quote from: technix on August 03, 2015, 04:54:45 pmIt do have a dedicated bootloader alone from OS, but it's not opensource, so if that brokes, I won't be able to recover it...Thank you anyway.
Strange shoot through in simple class AB Mosfet amplifier - Page 1
Forum section: electronics / projects

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: October 01, 2022, 08:07:57 am
content: After inventing the class abD, I decided to put an end designing analog amplifiers. So this is my ultimate one. It is not brilliant in THD numbers, 0.01-0.03%, but it features a unique open loop response the shift only -5° at 20khz instead of habitual -90° which requires 60db NFB at 20khz for perfect sound. This amp has only 36db NFB flat to over 100khz.The problem I have is on transient square wave, instead of having the active side to be commanded inactive, on the contrary it gets commanded to over act for a short period. The scope shows for positive and negative slopes with 2us scale.Any idea what is the problem?

author: magic
author_rank: Super Contributor
timestamp: October 01, 2022, 08:19:41 am
content: Probably it's Miller feedback.The upper driver can sink significant current. It turns on the 9240 which pulls the output up, sending significant current through the upper capacitor, which is easily sunk by the driver.An equal current flows through the lower compensation cap, but the low side driver can't sink it being an NPN.Probe the bases and emitters of the drivers and see what happens.If EF drivers are used in front of a common source stage, compensation should be routed back to the bases of the drivers, not to the gates. Generally, global Miller compensation is normally routed all the way back to the output of the input stage.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: October 01, 2022, 08:37:49 am
content: Thank you.I halved the millers, nothing happened, I compensate from the bases, the shoot through greatly reduced but the double LTPs are still commanding wrong, you can see the red curve when increased, the green should start falling. It doesn't, it goes also for a while increasing.By putting the miller on the outputs, this transconductance amplifier doesn't require Zobel, now it does.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: October 01, 2022, 08:51:42 am
content: Yes, yes, I now understand. It is the miller that is injecting opposite command from the output, nothing wrong with the LTPs.Thank you magic, thank you very much.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: October 01, 2022, 11:08:00 am
content: I inverted the polarity of the drivers, as I lost 1.4v on the base resistors hence bias current of the ZLTPs, I lost 3db on the NFB. Good point is it doesn't need millers to be stable. The shoot through has totally disappeared. I have a phenomenal slew rate to get 1Mhz power bandwidth.
Strange size of a DC barrel connenctor  - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: August 03, 2020, 07:10:11 pm
content: Hi,I have been spending over an hour trying to "reverse engineer" a simple dc connector and also find the mating part for a Acer monitor but cannot find any matching size on any of the distributors.Attached screenshot of 1) connector 2) PSU label (doubt it can be of any use) and 3) monitor label (again probably pointless)The PSU side is the only one I can measure because the mating one on the monitor side is too deep into the plastic enclosure. The PSU connector (see attached picture) has an OD of 5.50 to 5.55mm. The ID I can only measure by inserting various drill bits at increments of 0.1mm. I can insert the 1.6 by pushing with acceptable force. Maybe it could go as far as 1.7mm if the drill bit was rounded and polished like the pin of the mating part. But I cannot try I don't have 1.7mm diameter.Bottom line when I look on Digikey, Farnell etc all the 5.0 and 5.55mm OD connectors have the ID of 2mm minimum.1) Am I doing something wrong in measuring it?2) How do I find the right one and it's mating part (both for in-line connection i.e. cable mount)?BTW... I doubt it is of any use but just in case... the monitor is an Acer monitor is a G246HL.Many thanks

author: magic
author_rank: Super Contributor
timestamp: August 03, 2020, 07:41:42 pm
content: Try web search for "barrel jack 1.7/5.5" or "dc jack 1.7/5.5".I'm getting some hits, although they are mostly adapters to the common 2.1/5.5 or 2.5/5.5 systems. With some patience maybe you will find bare connectors too.I also tried 1.6/5.5 and got exactly nothing.editIf you need to repair an unobtainium plug, scrap the rubber mold from it, solder the new cable and isolate it with tape or hot glue.

author: ricko_uk
author_rank: Super Contributor
timestamp: August 03, 2020, 09:46:09 pm
content: Thank you Magic,

author: glentek
author_rank: Regular Contributor
timestamp: August 04, 2020, 04:57:57 am
content: Available on Aliexpress are 4.8/1.7, but what you want is an Acer exclusive. Search for Acer DC plug - I've ended up buying molded cords, the plug itself doesn't seem to be available.www.aliexpress.com/item/4000316828928.htmlAlso look at:https://en.wikipedia.org/wiki/Coaxial_power_connector

author: ricko_uk
author_rank: Super Contributor
timestamp: August 04, 2020, 11:02:51 am
content: Thank you glentek!For all those who are interested, this is also a good solution:https://www.amazon.co.uk/gp/product/B07F7776T6/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1It is a full set of adaptors between the classic 5.5 x 2.1 to every other size.
Strange Victoreen tube? - Page 1
Forum section: electronics / projects

author: KJ-90
author_rank: Contributor
timestamp: June 14, 2017, 04:14:00 pm
content: I have a strange Victoreen Corotron high voltage regulator tube that I found from my father's estate. The tube is about the same size as a 6V6GT tube, with the numbers GV9A-2800. It has a clear glass envelope, with a single top cap, and a black bakelite base. Inside the tube are four cold cathode elements. Each element's anode is connected together to the tube's top cap, but I'm not sure about which base pins the cathode elements are connected to. I have been completely unable to find any data on this tube online, even after at least 2 hours of searching. It doesn't appear either in any vintage Victoreen catalog online, either. Does anyone know the technical specifications for this tube?

author: danadak
author_rank: Super Contributor
timestamp: June 14, 2017, 04:55:13 pm
content: http://www.radiomuseum.org/tubes/tube_gv9a-2800.htmlhttp://www.ase-museoedelpro.org/Museo_Edelpro/Catalogo/tubes/records_nw/GV9A-Series/GV9ASER.pdf
Strange Vintage Transistors - MHT8035, T.I. SP6024, PIRGO 1248 7113 - Page 1
Forum section: electronics / projects

author: KJ-90
author_rank: Contributor
timestamp: March 09, 2017, 01:32:58 am
content: I have recently found a few strange stud mount power devices, that I think are all power transistors, but I'm not sure. They are all in gold plated cases and date from the late 1960s - early 1970s. One of them was made by Solitron in the late 1960s, and marked MHT8035, in a TO-63 case with 3 pins. The other is marked T.I. SP6024 in a TO-111 case, with 3 pins as well. The last device is marked PIRGO 1248 7113, and is also in a TO-111 case, but with 4 pins. There are no data sheets on the Internet on these devices. Does anyone have any idea what their technical characteristics are?

author: Cliff Matthews
author_rank: Unknown
timestamp: March 10, 2017, 06:51:32 pm
content: I think many stud devices back then were more often rectifiers and thyristors. Gold? Maybe military spec. Google image "Solitron stud" shows-off some sweet looking vintage items..

author: calexanian
author_rank: Super Contributor
timestamp: March 10, 2017, 11:25:00 pm
content: Those sound like either custom numbers or supplier specific numbers. Sometimes second source suppliers would change the 2N oa 2SA, etc, to something else specific to themselves.
Strange voltages on Headset Jack in Android hardware development kit - Page 1
Forum section: electronics / projects

author: kian0079
author_rank: Contributor
timestamp: October 01, 2024, 12:43:31 pm
content: Hi all,I have this android hardware development kit from here:https://www.variscite.com/product/single-board-computers/var-sd410customboard/I am looking at the schematics for this dev board and cannot understand some strange voltages and connections that are appearing on the headset jack. The schematics can be found here:https://www.variscite.com/wp-content/uploads/2017/12/VAR-SD410CustomBoard-Schematics.pdfI am looking at the audio headset section of the schematics (see attached) which has the following signalsCDC_MIC_BIAS2 - Unused for my application, R80 is not connected in the dev kitCDC_MIC2_P - Connects to positive terminal of microphoneCDC_HPH_REF - Headset Ground SensingCDC_HPH_R - Connects to positive terminal of right speakerCDC_HS_DET - For detecting if a headset is connected to the stereo jackCDC_HPH_L - Connects to positive terminal of left speakerThe signals are connected to a System On Module (SOM) chip (see attached). Here are the things that I do not understand and hope to have a good discussion.Firstly the CDC_HS_DET pin on the SOM is an analog input. Looking at the stereo jack connection, CDC_HS_DET connects to CDC_HPH_L when no headset is inserted. I measured the voltage between CDC_HS_DET and CDC_HPH_REF to be about 0.2V. When a headset is inserted, CDC_HS_DET disconnects from CDC_HPH_L, and I assume its floating (I checked and there is no connection between pin 5 with the rest of the pins on the stereo jack) I measured the voltage between CDC_HS_DET and CDC_HPH_REF to be about 1.8V!! How can this be possible possible?Would anyone be able to figure out why?My second question is regarding the CDC_HPH_REF signal. In the schematics, there is no direct connection between CDC_HPH_REF and GND. However, when I used a multimeter to check, CDC_HPH_REF and GND is shorted together!! CDC_HPH_REF and GND is not connected internally inside the SOM. The only possibility of CDC_HPH_REF having a connection to ground is through the 120R 1.2A ferrite bead and ESD protection diode. So how did these 2 signals have a short circuit on the dev kit?Hope someone can help to figure this out! Thanks in advance!
Strategies for reducing THD in ADCs/DACs - Page 1
Forum section: electronics / projects

author: ezalys
author_rank: Frequent Contributor
timestamp: November 23, 2018, 02:53:26 am
content: I’m curious how Audio Precision reaches such low THD in their signal chains. Has anyone disassembled an apx555 to see what ADC or DAC is used? Can you put multiple ADCs/DACs together in some configuration to cancel second or third order distortion somehow? Can you perhaps characterize the distortion and compensate for it? How stable is the distortion with process, voltage, and temperature? I know ESS and Cirus make some very well specced chips which seem like they might fit the requirements of the AP units... maybe it’s “just” these? Any additional thoughts?

author: David Hess
author_rank: Super Contributor
timestamp: November 23, 2018, 04:19:42 am
content: Part of it is removing common mode distortion from any non-inverting amplifiers by using inverting amplifiers instead. This is a big problem when trying to make a Wein bridge oscillator pure enough to check the performance of an audio ADC.

author: udok
author_rank: Regular Contributor
timestamp: November 23, 2018, 07:54:26 am
content: The low THD generator is an anlog state variable oscillator.The analyzer uses a notch filter before the ADC. The ADC convertes the residual after the notch filter.Older devices use standard audio DACs (AK5354A) and ADCs (AD1955), but i do not knowwhich parts are in the APx555.

author: Marco
author_rank: Super Contributor
timestamp: November 26, 2018, 04:16:29 am
content: There is actually a way to remove distortion from DACs to generate near pure tones. You switch a low distortion low pass filter into or out of the chain and loop it back to an ADC. The harmonics caused by the ADC stay the same, the harmonics from the DAC change according to the transfer function of the filter. Thus you can calculate them and correct them in the signal you send to the DAC, iterate that a couple of times for a near pure tone. Of course the resolution of the DAC sets a lower limit, so you should do this with a high resolution DAC, though it can be a pretty shitty one, as long as it's consistently shitty.See the paper "Low Cost Ultra-Pure Sine Wave Generation with Self Calibration", they used two 16 bit DACs resistively combined for a 140 dB THD sine generator AFAIR.
Strategy for reverse engineering a simple PCB - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: December 22, 2018, 06:11:14 pm
content: Please see attached imageI would like to draw a schematic for the following PCB (I also have a scan for the bottom layer)...It is a simple 2 layer board from the 1980s which replaces some custom Konami silicon which is now unobtainiumAre there any tools that allow me to draw a PCB but then go backwards to the schematic?Thanks in advance

author: helius
author_rank: Super Contributor
timestamp: December 22, 2018, 06:24:54 pm
content: Quote from: NivagSwerdna on December 22, 2018, 06:11:14 pmMore seriously, I think some EDA programs do have the ability to link layout and schematic editors, but they are not designed to be used to infer a schematic from a layout.

author: soldar
author_rank: Super Contributor
timestamp: December 22, 2018, 07:51:41 pm
content: I have successfully done this by taking photos or scans of both sides and then working with them with a graphics program like Photoshop but you still have to do a lot of manual work confirming paths, connections, etc. It is very time consuming but it can be done.

author: amyk
author_rank: Super Contributor
timestamp: December 22, 2018, 07:55:45 pm
content: Post both sides, someone may help.What I do is put the parts in the same relative position in a schematic editor, then draw the traces in the same way.Besides the top left component (which appears to have been sanded), everything else there looks like standard TTL.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: December 22, 2018, 08:04:07 pm
content: Thanks. Maybe DaveCAD is a good approach.The circuit should be logically divided into three... but I haven't worked out the detail yet
Strategy to limit inrush current - Page 1
Forum section: electronics / projects

author: aurmer
author_rank: Regular Contributor
timestamp: March 12, 2019, 07:31:51 pm
content: I have been reading up on inrush limiting, but the advice I found was conflicting.Here is the hardware I am working with.VIAIR 275C Compressor ----- 12V 18AmpProtek Power supply #PUB250-12 ----- 12V 20.84Amp(We have a Duracell Deep Cycle 12V SLA which turns on the compressor no problem.)What component(s) are best to help reduce the peak inrush current and allow this 20A power supply to get the compressor running? Or am I going about this the wrong way? Do we actually need a supply with more power?

author: Ian.M
author_rank: Super Contributor
timestamp: March 12, 2019, 08:10:26 pm
content: A DC motor's stall current can be as much as ten times its nominal max running current. Unfortunately, unless you are using a motor controller with current limiting, or can otherwise ramp up the speed slowly, every time you start the motor, its rotor is initially stationary, so it *will* attempt to pull its stall current, which may well be over 100ATo fix this without rewiring the compressor so its pressure switch sends an ON signal to an external motor controller would be very difficult.Linear current limiting would have to dissipate up to 216W every time the motor starts, and have negligable voltage drop when the motor's drawing 18A. You could probably get there with a whole bunch of paralleled power MOSFET + OPAMP constant current sinks on a*BIG* heatsink.The best external option would probably be a large high current supercap bank to supply the surge, with a time delay relay to short out a 1.2 ohm 100W resistor once its fully charged from the PSU and also operate a >100A contactor to keep the load disconnected till the cap bank is charged. You could also probably replace the relay and contactor with really beefy PMOSFETs and a 555 timer.

author: David Hess
author_rank: Super Contributor
timestamp: March 12, 2019, 10:47:46 pm
content: Current limiting during startup can also be implemented with a switching regulator which avoids the problem of high dissipation in a linear design. Or a buck converter can have its output voltage ramped up. A more interesting solution would be to put an open loop pulse width modulator and filter between the power supply and motor and ramp up the duty cycle; this avoids any requirements for closed loop stability.
Strong metal detector  - Page 1
Forum section: electronics / projects

author: salvazero
author_rank: Newbie
timestamp: January 13, 2017, 06:14:36 am
content: Hello,I would like to make a metal detector strong enough to detect a piece of stainless steel tape in the cable that we make.We make electronic/electric cable, for example, sometimes this cable is bad and from the 50,000 feet we make, we have to cut it 3 times (we call that splices) because cable had a cosmetic defect so we cut that part out, now, we solder these splices to make one single cable so we can put the final plastic cover to make it one single piece without setting it up 3 times because of the splices.I was thinking to make the detecting coil around a 2" or 3" PVC pipe so the cable/wire goes through and it will be easy to detect. It has to be strong enough to detect a 1/4” inch tape with 0.004” thickness that we want to put around these splices so they can be detected, make a beep and turn a red light, connect it to an 110 volt.It needs to detect on 18-8 stainless steel tape, no iron, no copper, no aluminum, no silver, no gold, There are so many tutorials to make one online but I need this one to be strong and able to detect it.Any help will be appreciated.Thanks in advance

author: Kleinstein
author_rank: Super Contributor
timestamp: January 13, 2017, 11:31:24 am
content: Stainless steel near a thick copper conductor could be difficult to detect with a normal type of metal detector. At least the search coils would have to be formed to work for short distance - as opposed to large distance with normal metal detectors. It really depends on the configuration, so where the extra piece of metal is. So a drawing of the approximate configuration would help.If the extra metal is more to the outside, it might be easier to detect it as a capacitive change, not by magnetics as in normal metal detectors.

author: Heszu
author_rank: Contributor
timestamp: January 13, 2017, 09:48:03 pm
content: That sounds perfectly doable.. With IB detector (Induction Balance). IB uses two coils TX and RX, and measures differences between coils.. When first setup with coil close to the cable, cable doesn't need to go through, balance as equal.. When cable goes By, at the exactly same distance, detector dont react. When the splice arrives the detector reacts on the difference in metal amount, which disturb the balance..Yes quite doable.WBRHeszu

author: Brumby
author_rank: Unknown
timestamp: January 14, 2017, 06:31:11 am
content: It would seem there is some hope for your cause - but it would really help if you could provide a drawing showing the normal construction of the cable (with dimensions) andwhat the difference isat the point you want to detect.
Strong ZVS Induction heater seen on YouTube - Page 1
Forum section: electronics / projects

author: hichm19956
author_rank: Newbie
timestamp: September 08, 2021, 07:24:53 pm
content: Hello every body,here i want to know the details how that "Baby first power electronics" seen 2:24 inhttps://youtu.be/wKFnk4R54ZQso i disturb with those green and blue wire where did they go? the other things i know how to join them like gate driver, the three Colis , I'm not use that to boil the steelbecause that consume lot of currentand can do some problem in my counter, but use it to melt small things like silver, gold recovery, and copper ... and work just at night where the human activity is low in electricity.and thanks to kevindk9 "Kevin" to give schematic of Control Board (SHRIGMA DRIVER V2)https://easyeda.com/kevindk9/pll-induction-heaterthe Q: the green where go? and blue where it go?
Struggles Understanding Control of an Active Rectifier - Page 1
Forum section: electronics / projects

author: Cirro
author_rank: Newbie
timestamp: November 16, 2022, 11:14:41 am
content: Hi All,I am currently trying to teach myself about single phase active rectifiers (voltage source based) however I am having a hard time understanding how to generate a PWM pattern for the MOSFET's.I have been playing around with the switching pattern on simulation software (PLECS). I have attached an image of my sim below, component values and inputs are shown.The load voltage is also attached.My question to you guys is how do I go about controlling an active rectifier, additionally can people sign post me to some useful resources, I've found it incredibly hard to find any explanations out there on this topic! Any help would be greatly appreciated!Regards,Cirro

author: Zero999
author_rank: Super Contributor
timestamp: November 16, 2022, 05:03:17 pm
content: The MOSFETs are not PWMed. Look at the diodes in parallel with them. The MOSFET should be turned on when the current flows in the direction, when the diode will conduct and turn off again, when it reverses.FETD and FETD2 need to have their gate voltages higher than the peak mains voltage to turn on properly.Why are you doing this? It's not worth it for such a high voltage. The MOSFETs will need to be very expensive and over-rated to have lower conduction losses than silicon diodes. It's only worth doing for very low voltages, under 24V, or so.
Struggles with simulation in LTSpice - Page 1
Forum section: electronics / projects

author: Ravi
author_rank: Newbie
timestamp: March 22, 2020, 08:38:52 pm
content: Hello!I'm relatively new to LTSpice, I have a project to simulate in LTSpice. I appreciate any help you guys can afford. the project is a distance measure using ultrasound transducers. I have a timing generator which generates a square wave to start TX to send an ultrasound signal and a sawtooth signal wich feeds Sample and Hold circuit. When RX recieves an echo signal, it sends it to an amplifier wich enables Hold state. The voltage that is held is sent to VCO (using 555 timer) wich generates a proper signal according to Hold voltage, see attached block diagram and LTSpice file.My headache is the transmitter TX which it generates a 40 kHz signal when it simulated only with the timing generator but when it is simulated with the whole circuit, it generates a 20 kHz! And i don't have a clue of why!thanks in advance!

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 22, 2020, 09:20:58 pm
content: you have a couple of sub circuits that you should upload too..LIB C:\Users\Rawi\Documents...\Prosjekt\LTspice-extra-\lmc6482a.sub.lib C:\Users\Rawi\Documents...\Prosjekt\LTspice-extra-\lm324.sub

author: Ravi
author_rank: Newbie
timestamp: March 22, 2020, 09:41:42 pm
content: Hi HackedFridgeMagnet!Thanks for the fast response!I tried to upload them but it was not possible with .sub files so i changed to .txt. I hope it is okay?

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2020, 11:19:07 pm
content: Quote from: Ravi on March 22, 2020, 09:41:42 pmNo, don't do that. Paste them into the .asc file, as SPICE directives, that way it's all one file. I don't have time to try to get it to work at the moment, but here's your .asc file, with all of your models embedded. I tried skipping the initial operating solutiion and starting with power supplies at 0V, but it didn't work.

author: Ravi
author_rank: Newbie
timestamp: March 22, 2020, 11:24:43 pm
content: Thanks Zero999!Appreciate that!

author: Zero999
author_rank: Super Contributor
timestamp: March 24, 2020, 10:10:43 am
content: I've had a look at the simulation. The problem is it was generating convergence errors. I got it to simulate by changing the op-amps to generic models with the slew rate, bandwidth and input impedance set to match the data sheets.I don't think the circuit does what you want it to though.You should break it down into sections and simulate each individually, rather than plugging the whole thing into the SPICE.

author: Ravi
author_rank: Newbie
timestamp: March 24, 2020, 10:22:49 pm
content: Hi Zero999!I really appreciate what you have done!As you mentioned, i should break it down to smaller circuits.Have a nice day/evening!
Stuck on a project, need some help - Page 1
Forum section: electronics / projects

author: mgwalker95
author_rank: Contributor
timestamp: August 11, 2021, 04:01:56 am
content: I am out of my depth of knowledge working on a project of mine. I have run into a issue that I can not seem to solve with my Qi Wireless transmitter board and NXP will not provide support for this chip because I am a hobbyist. I have read all the material about the device posted online and followed all of their design guides, but cant seem to make much progress. How do you all deal with a situation like this?The issue seems to be that the wireless transmitter is triggering a FOD error when trying to charge a device but the FOD error is there even after tuning the software following NXP's guide.I could try to contract out to an engineer who is more experienced in this area, but do not know how to find such an engineer who is experienced in wireless charging. Where do you find someone who is open to contracting? Linkedin? Craigslist? Any help or ideas would be appreciated.
Stuck on the digikey merrygoround trying to find LCD Connector - Page 1
Forum section: electronics / projects

author: MatCat
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:06:40 pm
content: I am trying to find a descent LCD connector, 0.5mm pitch, 40 pin, anyone have a good link to one on digikey or mouser? I am not even sure what to look for.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:14:31 pm
content: Do you mean 0.050" 1.27mm?

author: hagster
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:16:48 pm
content: Something like this FPC connector. Very common on TFT displays.http://uk.mouser.com/Search/m_ProductDetail.aspx?qs=Ux3WWAnHpjANOPB31cr/Jw==

author: hagster
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:20:30 pm
content: FH12A-40S-0.5SH(55) manufacuters part number.http://www.digikey.co.uk/product-detail/en/FH12A-40S-0.5SH(55)/HFK140CT-ND/1110402

author: MatCat
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:31:47 pm
content: Quote from: hagster on January 05, 2014, 06:20:30 pmThat looks like what I am looking for! Thanks!
Stuck when using 2 LCD panel meters in parallel - Page 1
Forum section: electronics / projects

author: efron
author_rank: Contributor
timestamp: February 24, 2014, 01:53:42 pm
content: Hello,I'm working on a DIY power supply project and I'm stuck with a problem since long time ago now.The issue is that I want to display the output voltage and current of the power supply. To do that, I use 2 LCD panel meters.Currently I'm using these ones:http://www.circuitspecialists.com/pm-128e-backlit.htmlThese panel meters can be configured in 5Vdc with common ground. This is the option I chose, although I also tested them with 9Vdc isolated power supply.In any case I use isolated power supply, so in practice there is should be no problem with any common ground.Both panels are powered in parallel and connected following the schematic below.In this configuration, LCD2 is not displaying correct measurement. However, if I disconnect LCD1, LCD2 works fine (when standalone).From this schematic, it can be seen the Vin- of LCD1 is directly connected to the Vin+ of LCD2. My best guess is that LCD2 does not appretiate this for some reason.How should I proceed, keeping in mind that I would like to avoid to power both panel meters with 2 separate power supply?I understood that, when using panel meters that don't accept the comm on ground, the Vin- is somehow linked to the V+ of the power supply. Is there something similar in a common ground configuration?Any suggestion will be appretiated.

author: Neverther
author_rank: Regular Contributor
timestamp: February 24, 2014, 03:09:08 pm
content: The input of the panelmeters are not "true" differential inputs.I can assume that when you measure ohms from the voltage meter in- to the power ground, it is short or very close to it.The current meter most likely does the same so you are basically running parellel wire with the shunt resistor, as the power grounds are tied together.Couple options:1) Move the in- from voltmeter to ammeter ground and suffer 0.1V/A error in the reading.2) Run ammeter from common ground with the supply, power voltmeter from isolated source.3) Run both meters from their isolated powersupplies (kinda overkill).4) Run ammeter from common ground, run voltmeter trough the shunt and trim the current used by the voltmeter out of the ammeter if allows it (I'm using this method on mine as it doesnt require isolated power for either of the meters).
Studio condenser microphone and low impedance preamp ? - Page 1
Forum section: electronics / projects

author: GreggD
author_rank: Regular Contributor
timestamp: October 31, 2017, 05:05:36 pm
content: I can not find the url that lead me to Elliott Sound Products website. It was a home build sound recorder using two one inch studio condenser microphone capsules with super low self-noise of about 5dbm.It used a mp3 player in the voice record mode and incorporated a ultra low noise preamp "if I remember correctly"htt.. sound.whsites.net/project66.htmWell the microphone capsules require an applied voltage 15-48V and have a very high output impedance. The preamp is looking for a low input impedance about 200 ohms and does not want to see the 15-48V.The builder of this project wanted to be able to record the sound of leaves rustling in a light breeze and it worked quite well for this.Q; Can this mic be interfaced to this preamp without much compromise ?
Stunningly consistent complementary differential amp circuitry - Page 1
Forum section: electronics / projects

author: Franki
author_rank: Regular Contributor
timestamp: March 19, 2011, 11:31:38 pm
content: I just found a really beautiful and consistent complementary differential amp circuit that I just wanted to share with everyone.Usually I'm not into spamming people with unrelated circuits, but this one looks just gorrgeous *SteveIrvine*, just look at its delicate yet consistent current mirrors, even these are complementary!I have no idea whether this circuit actually works, but it would be a pain in the ass if it didn't. On the other hand, there is just one way to find out...full sizehttp://www.freepatentsonline.com/6778014-0-large.jpghere's the link, unfortunately, it's patented, but hopefully, there is a variant in the doc that is prior art:http://www.freepatentsonline.com/6778014.htmlI feel like I need to put that in a simulator somewhen just for the fun of seeing how it works.

author: Zero999
author_rank: Super Contributor
timestamp: March 20, 2011, 08:51:39 am
content: The only way to prove it works, is to etch it onto silicon. It won't work when made from discrete components because they won't be matched.I wonder they have an op-amp based on this design?

author: scrat
author_rank: Frequent Contributor
timestamp: March 20, 2011, 10:00:43 pm
content: I agree with Hero, and (although I'm not an integration designer) I think there are many differential stages like this on the ICs we use every day. BTW, I don't see what that inverter on the output stands for...

author: Franki
author_rank: Regular Contributor
timestamp: March 24, 2011, 12:42:56 am
content: Quote from: Hero999 on March 20, 2011, 08:51:39 amstrictly speaking, you are right, but for testing purposes, one may use a pot to cancel out manufactorung differences.Quote from: Hero999 on March 20, 2011, 08:51:39 amI haven's seen any in ICs.There are a few power amps using complementary differential circuitries, but I haven't seen any using FETs or MOSFETs for that, they all use bipolar transistors and they only use it in some intermediate stages. Just like this one:source by some unknown audio hobbyist:http://www.littlefishbicycles.com/poweramp/

author: Zero999
author_rank: Super Contributor
timestamp: March 24, 2011, 07:52:44 pm
content: The CA3160 was almost entirely CMOS.http://www.intersil.com/data/fn/fn976.pdf
Stupid mini-christmas tree idea. Choosing the right components. Or trashing it - Page 1
Forum section: electronics / projects

author: Moriambar
author_rank: Unknown
timestamp: December 01, 2018, 01:34:39 pm
content: Hi.I was just wondering about creating a small circuit as a gift for some friends of mine: a triangle made of 0805 LEDs (I was thinking about 15 of them) arranged alternating rows of green ones and red/yellow ones. I was thinking about powering them with about 10mA each.The first problem arises, though, because I have no frame of reference for the mcd of a single LED, so I really cannot say whether those are bright or not (eg. a jellybean 5mm green LED is how many mcd usually?).This was not the worst part, though, because I was thinking about making the red/yellow rows light intermittently via a 555 timer (which is not a problem), but which will increase my battery consumption.Originally I was thinking about powering everything through a Cr2450 battery, via a smd holder: all of the non-led components would go one side of the board, and the led are mounted on the opposite side. I was thinking about coin cell because they're quite compact and thus my tree would be really small, but I don't know whether the battery can hold all of the power consumption (I mean it's around 150mA + the 555 consumption, way above the 0.3mA for which these are rated).So I guess my question is: is my project feasible? Should I just make it bigger in order to accommodate 2 standard aa batteries, instead? (I think I would need more LEDs then, though)Thanks for reading this.Cheers

author: Gyro
author_rank: Super Contributor
timestamp: December 02, 2018, 04:16:39 pm
content: 10mA sounds quite high for modern smd LEDs, you ought to be able to get reasonable light out at around 1mA. Being point sources makes them look brighter. The other thing is to use the CMOS variant of the 555, not the bipolar one - supply current is much lower.Regarding supply, you need it to be higher than 3V for the 555 to operate (I can't remember the minimum supply of the CMOS ones off hand*) - an alternative might be to make something with 74HC logic.Current consumption of the LEDs is much lower if you can arrange them in short series chains - if in parallel then you may need to allow individual current limiting resistors, which wastes power. You may want to look at a 9V battery for your application (physically smaller than two AAs anyway).EDIT: *My mistake, the LMC555 will operate down to 1.5V

author: Moriambar
author_rank: Unknown
timestamp: December 02, 2018, 04:29:36 pm
content: Thanks

author: girts
author_rank: Contributor
timestamp: December 02, 2018, 06:44:59 pm
content: 5 volts from MicroUSB.This allows to use any phone charger or powerbank.
Sub $200 DIY Fume Extractor - Page 1
Forum section: electronics / projects

author: ScottBLAM
author_rank: Contributor
timestamp: February 09, 2019, 10:36:20 pm
content: First off, I would like to thank Hakko. Thank you for the $100 soldering iron and thank you for asking for $800 for the fume extractor so I don't die from the fumes from the soldering station.I found this on Amazonhttps://www.amazon.com/dp/B06XFRNPR8it's a ventilation and filter kit for green houses in case you're growing smelly plants but I figured this is the exact type of rig you need for a fume extractor too. The small 4" one is just under $100 and says it does 200cfm which is more than the Hakko(168cfm) with the trade off being that the filter probably isn't as nice but it's probably enough to filter out flux, metal, and other fumes. The 8" large kit rates itself for 740cfm so unless you're Tim Allen and that's like your thing you probably just need the small one.The other problem is that the pipe is just flexible semi rigid duct tubing. I bought thishttps://www.amazon.com/gp/product/B077Q99PPVand hated the AC electrical wire(I was able to abrasion it with my fingernail!) so I don't endorse it but if you tape or ziptie the duct in the right places on it or another clamping flex arm lamp you can use it to control the position of your ducting. If you do end up buying that adjustable fan I linked do yourself a favor and upgrade the wiring so it doesn't burn your house down!Happy Healthy Soldering and happy Lunar New Year.
Sub for TS274 - Page 1
Forum section: electronics / projects

author: cncjerry
author_rank: Unknown
timestamp: August 28, 2020, 11:11:52 pm
content: I need a thru-hole sub for a TS274 used in an RF app up to about 20Mhz. I can probably get a TS274 off ebay but thought I would check here first.ThanksJerry

author: magic
author_rank: Super Contributor
timestamp: August 29, 2020, 06:17:38 am
content: TLC274 is a direct sub AFAIK. Check if TI still sells them in DIP.And.... 20MHz? Not sure if either chip will do that.
sub forum for manufacture of hybrids and such? - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: March 21, 2018, 03:57:54 pm
content: I am wondering if a subforum related to things like DIY vapor deposition of resistors, wire bonding, laser trimming etc would promote growth of these very seldom done activities.The current manufacturing forum seems oriented with large scale production, and use of industry accepted things. Not really high vacuum, plasma systems ,etc.I'm sure this forum has a decent portion of people that know about that kinda stuff, working in fabs and shit.
Subharmonic oscillations in DC/DC Converters - Page 1
Forum section: electronics / projects

author: tree
author_rank: Regular Contributor
timestamp: August 04, 2014, 02:56:47 pm
content: On page 72 ofhttp://cds.linear.com/docs/en/application-note/an19fc.pdf,it's stated that subharmonic oscillations occur for a duty cycle greater than 50%. Why don't they occur for a duty cycle less than 50%?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 04, 2014, 06:03:20 pm
content: A convenient approximation (and design choice), I think. What matters for a peak current mode controller is if there is residual current in the inductor; if the system is designed so the flyback (or recoil or whatever) voltage equals the supply (so the switch switches Vs*2, and etc.), then current becomes continuous at >= 50% duty.As for the oscillations themselves, the fundamental downside to a peak current mode converter (even with slope compensation and an error amplifier) is it exhibits chaos; duty cycle acts like the feedback parameter in the logistic map, and an identical bifurcation diagram can be generated from the circuit.Tim

author: tree
author_rank: Regular Contributor
timestamp: August 04, 2014, 11:23:27 pm
content: Quote from: T3sl4co1l on August 04, 2014, 06:03:20 pmYou just enjoy confusing me to death!

author: David Hess
author_rank: Super Contributor
timestamp: August 05, 2014, 12:54:16 am
content: I thought the application note described it pretty well. Reread the part at the beginning about S1 and S2.

author: tree
author_rank: Regular Contributor
timestamp: August 05, 2014, 01:03:05 am
content: I finally figured it out. The change in duty cycle corresponds to a decrease in time for the positive slope and an increase in time, of the same amound, spent for the negative slope. The equality I1/S1 = -I2/S2, where I1 and I2 are the deltaI for the positive and negative slope, respectively. The equality is saying the exact same thing that I described in words. I2 = -S2/S1 * I1. The current perturbation will continuously increase if S2/S1 is larger than one, i.e. DC > 50%

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 05, 2014, 02:31:27 am
content: Yup, and for higher duty cycles, it bumps into a 4-cycle, then a slight bit more into 8, and so on... Hence, bifurcation:http://en.wikipedia.org/wiki/Logistic_mapThe bifurcation diagram shows the discrete points (for the map, the numerical values; for the converter, the pulse widths) that are cycled through, on the Y axis, with (average?) duty being the X axis. It looks strange and beautiful, and doesn't make much sense at first (you can't plot it on an oscilloscope).Tim

author: David Hess
author_rank: Super Contributor
timestamp: August 05, 2014, 03:14:25 am
content: Come to think of it not only does my DSO support roll mode but also a "scan" mode where the display record is updated in real time at slow timebases and a cursor shows the current scan position.
Submerged CAN bus - Page 1
Forum section: electronics / projects

author: Harvs
author_rank: Super Contributor
timestamp: May 20, 2016, 06:57:21 am
content: I'm building an instrumentation system for a test rig that ends up being thrown in the ocean. Basically a number of sensors along a large metal pipe structure, about 10m in length, maybe 10 sensor sites along that.My current thought is a waterproof box with a single board computer (probably BBB), and a CAN bus running down the length of the structure.However the question I haven't been able to answer yet is what effect will the cabling being submerged have on the bus?I have no doubt the capacitance on the bus will increase, but will it be enough to cause issues at say 500kbps bus speed using an off the shelf shielded twist pair CAN bus cable?

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: July 08, 2016, 12:32:02 am
content: No, it won't have any detectable effect.