hybridfree/eevblog-posts huggingface dataset:
How to emulate a BLDC motor? - Page 1
Forum section: electronics / projects

author: helge
author_rank: Regular Contributor
timestamp: January 09, 2016, 11:47:37 pm
content: In an effort to modify two DLP projectors by adding LED light sources I got stuck at the point where the BLDC colour wheel drives should be removed.Here's what happened up to now:- remove short arc lamps- build discrete circuits to emulate HID ballast (basically an RC filter + schmitt trigger to pass sanity check)- disconnect and remove fans that were dedicated to the lamp and light engine coolingNow there is that humming, vibrating colour wheel that I'd like to get rid of.Both devices have slightly smart BLDC controllers (for reference A8902http://www.allegromicro.com/~/media/Files/Datasheets/A8902-Datasheet.ashx?la=en) so a simple "power good" signal won't cut it (the motor controller has a serial interface for configuration and the optical pick-up on the motor also feeds into the DSP for image generation synchronous to the colour wheel).So the question is:what is the least that needs to be done to make such a controller happy?I could imagine generating a 3 channel PWM output (fake back-EMF VCC/2 transition 30° between commutations) + 1 tachometer signal and generate a pattern according to the presence of OSC (commutation clock) and !BRAKE.One projector for example does a spin-up test at power-up. I'll have to experiment and see whether the device fails when one of the sectors is removed - you get the drift.Later on, a more general solution would be preferable because not all controllers work the same - but all colour wheel assemblies do.I just hope there is a way around three 4 quadrant DCDC converters and associated voltage / current sensing ADCs... because then I'd rather re-balance that bloody motor and put it away in a box where it can do its thing and that would be a disgrace.Comments and suggestions welcome!

author: station240
author_rank: Unknown
timestamp: January 10, 2016, 12:04:19 am
content: Perhaps replacing the BLDC motor with 3 iron/ferrite core inductors, see if that produces the correct back EMF.A 3 wire BLDC motor is wired the same as a 3 phase motor, eg coils go A-B B-C C-A

author: amyk
author_rank: Super Contributor
timestamp: January 10, 2016, 01:26:23 am
content: It doesn't seem like it'd be too hard to replace the controller with an MCU that just generates the right signals.

author: helge
author_rank: Regular Contributor
timestamp: January 14, 2016, 11:47:59 pm
content: Thanks for the replies so far.I'm lead to believe the controllers are generally a bit smarter than something you could trick by providing a static signal. They are designed to drive HDD spindles and a spin-up test is performed upon power-up. When motor or reflective speed pick-up are disconnected the projector enters a fault state. Will have to create some kind of 3 phase waveform locked to the commutation clock.
How to emulate resolver signals? (sin cos encoder) - Page 1
Forum section: electronics / projects

author: serco
author_rank: Newbie
timestamp: October 16, 2020, 12:04:45 pm
content: Colleagues, there is a task to emulate the resolver signals, е.g. tо generate a sine wave signal with the specified parameters.I am currently engaged in the automation of a forklift. This is necessary to control the angle of rotation of the drive wheel. According to the scheme, when the steering wheel is turned, the signal from the resolver mounted on the steering wheel goes to the control controller. There is no way to get through to the controller (no CAN, etc.) The onlysolution for automation is emulation of the resolver signal.Please advise how to correctly implement it.

author: Alti
author_rank: Frequent Contributor
timestamp: October 16, 2020, 01:30:35 pm
content: QuoteYou are kidding, right?Self-driving forklift?

author: serco
author_rank: Newbie
timestamp: October 16, 2020, 02:00:29 pm
content: Self-driving forklift, yes AGV robot
How to explain this Audio Headset Circuit - Page 1
Forum section: electronics / projects

author: kian0079
author_rank: Contributor
timestamp: September 29, 2024, 08:50:50 am
content: Hi all,I am looking at a reference design for an audio headset. The schematic is attached. May I know what is the purpose of the capacitors C78 - C81? Are they necessary and do they need to be placed closer to the headset jack or closer to the microprocessor? Also, are the ferrite beads and transient suppressors necessary?Thanks in advance!

author: Andy Chee
author_rank: Super Contributor
timestamp: September 29, 2024, 09:18:15 am
content: These components need to be positioned physically close to the socket. These components form a low pass RF filter, and stop RF from interfering with microprocessor function.You need to keep in mind that the fleshy human body can act as an antenna and static charge generator, therefore, any sensitive inputs that a human can touch with their finger, should be protected from these effects....if you want a robust and reliable design that is.

author: kian0079
author_rank: Contributor
timestamp: September 29, 2024, 02:16:47 pm
content: Following up on my question. I am also quite puzzled by how the headset detect works. The CDC nets(connections) on the schematic goes to an audio codec (as part of an android hardware development kit). I do not have the datasheet of the audio codec. But when I am trying to find out is how can I get the headset to be permanently detected regardless of whether a headset is plugged into the stereo jack or not.Looking at the schematics, when the headset is not plugged into the stereo jack, pin 5 is connected to pin 2 on the stereo jack. This essentially creates a 'short circuit' between the left speaker output and the headset detect pin. Conversely, when the headset is plugged into the stereo jack, pin 5 is disconnected from pin 2 of the stereo jack. Does that mean that if I leave the CDC_HS_DET net floating, the audio codec will think that a headset has been detected?

author: Andy Chee
author_rank: Super Contributor
timestamp: September 29, 2024, 04:10:12 pm
content: Quote from: kian0079 on September 29, 2024, 02:16:47 pmMost probably, yes! The easy way to test this is by inserting a new plug with no cable, or a scrap plug with the cable cut off.Strictly speaking, the net probably isn't floating and is internally pulled up within the chip, or a resistor elsewhere on the schematic.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 29, 2024, 04:47:47 pm
content: In case you want to do that trick only to start the radio without a headset plugged, the radio can be made to start, but it won't work. The headset antenna is really needed for FM reception.

author: bson
author_rank: Unknown
timestamp: October 01, 2024, 03:40:11 am
content: They form LC filters with the ferrite beads, right?
How to find a replacement 7 segment 6 pin 6 digit LCD? - Page 1
Forum section: electronics / projects

author: jmaja
author_rank: Frequent Contributor
timestamp: October 23, 2014, 06:30:26 am
content: I'm trying to repair a tachometer with a LCD hour meter. It's a VDO rebranded as Volvo Penta from 2004 and they all have a problem with the LCD display, which can be solved by changing the front panel with the display, but then you need to buy a new tachometer to get one. The display is connected with a 6 pin ribbon cable. There are no markings on the display. Are there any standard protocols and pin configurations for these kind of displays? Any chanche of just putting some other display in place.Here are some photos of the unit and an instruction how to put a new hour meter in place of the old display. I would like to replace just the display.http://verl900.files.wordpress.com/2013/01/volvo-penta-tachometer-lcd.pdfThe display can show 6 digits or alfabets (as 7 segment) and a desimal point.On the main PCB there is a PCF8582C-2 I2C EEPROM and a 44 pin chip from NXP with a2c34128/wwg, cc6905 and tpg0437a, but I couldn't find what it is. Must be a microcontroller. The LCD ribbon is connected to the same I2C as the EEPROM, thus the LCD must be I2C.The pinout of the ribbon is:1. I2C SDA2. I2C SCL3. 5V VCC4. GND5. GND6. ??, it has a 180k pulldown resistor to GND and doesn't seem to be connected to anything else.
How to find Chinese ICs by specs? - Page 1
Forum section: electronics / projects

author: Benik3
author_rank: Contributor
timestamp: July 27, 2018, 05:21:36 pm
content: Hello.Does anyone have a tip, how to find ICs from China?I mean when I search something more local, I look on mouser, digikey, Farnell etc. but what if I'm looking for something special from China?Like I know, that there exist SOT-23 IC which is LED driver with linear drive of external MOSFET, dimmable by PWM and current sensing. But I don't know the type and I didn't find something like this from "big" companies (like TI, linear etc.)Thanks for any idea

author: senso
author_rank: Frequent Contributor
timestamp: July 27, 2018, 07:20:13 pm
content: http://www.ti.com/product/LM3405AOnly needs inductors and passives, integrated Mosfet, does everything you want.

author: RobK_NL
author_rank: Frequent Contributor
timestamp: July 27, 2018, 08:05:39 pm
content: https://www.diodes.com/assets/Datasheets/AL8860.pdfhttps://www.diodes.com/assets/Datasheets/AL8861.pdf

author: Benik3
author_rank: Contributor
timestamp: July 27, 2018, 08:23:32 pm
content: Yeah, I'm able to search like that.The reason why I said that it drive EXTERNAL MOSFET is, that I need 3A+Also I wrote that it's linear driver because of using 1 li-ion with 1 LED. So the Vf is pretty close to the voltage of battery and buck converter is not so efficient. Mainly on low currents (10-100mA).

author: senso
author_rank: Frequent Contributor
timestamp: July 27, 2018, 09:11:51 pm
content: If its linear you dont need any IC then.

author: Benik3
author_rank: Contributor
timestamp: July 27, 2018, 10:14:25 pm
content: Well it's simpler that you don't need to solve problem with filtering of the PWM to mosfet.Because LED has much lower efficient when you drive it with low duty cycle PWM then with constant current.Like this:https://led4power.com/product/ld-b4-2-12amp-17mm-constant-current-led-flashlight-driver/

author: analogNewbie
author_rank: Regular Contributor
timestamp: July 30, 2018, 01:50:13 pm
content: you can find Chinese LED driver IC herehttps://list.szlcsc.com/catalog/583.htmlhttps://lcsc.com/products/LED-Drivers_583.html

author: Poe
author_rank: Frequent Contributor
timestamp: July 31, 2018, 01:23:28 pm
content: 74HC595 at 1k pcs is $0.0017 USD or 0.17 cents!!!Add a 25% tariff and it's still two orders of magnitude cheaper than a reputable source like Digikey.

author: Benik3
author_rank: Contributor
timestamp: August 01, 2018, 05:39:59 pm
content: Quote from: analogNewbie on July 30, 2018, 01:50:13 pmThanks, I will look on it

author: PartialDischarge
author_rank: Super Contributor
timestamp: August 01, 2018, 06:07:43 pm
content: Quote from: analogNewbie on July 30, 2018, 01:50:13 pmAre lcsc and szlcsc the same webpages but one in chinese? same components?

author: analogNewbie
author_rank: Regular Contributor
timestamp: August 02, 2018, 03:59:30 am
content: yes,
How to find DCM or CCm  - Page 1
Forum section: electronics / projects

author: whatty
author_rank: Contributor
timestamp: February 16, 2023, 12:23:59 pm
content: HiI am using PWM controller uc3843 DOES THIS IC UC3843 WORKS IN DCM OR CCM HOW TO FIND IT OR HOW TO MAKE IT WORK IN DCM MODE.i didnt find anything the Texas instrument datasheet saying setting of DCM or CCM using the pins. i had attached the datasheet and even in application notes i couldn't find anything saying how make the ic to work in CCM or DCM mode.

author: Zipdox
author_rank: Regular Contributor
timestamp: February 16, 2023, 12:53:02 pm
content: Whether it runs in DCM or CCM is not a function of the PWM controller but of the inductor, switching frequency and load.

author: whatty
author_rank: Contributor
timestamp: February 16, 2023, 07:05:04 pm
content: yeah ok as you said i will design the ferrite core transformer according to the dcm calculations and procedures how would i set the frequency in uc3843 so that the circuit operates in dcm mode ....? in uc3843 we could change the frequency by adjusting R and C values across R/T pin how could this determine the DCM mode please can you explain in detail....?

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: February 16, 2023, 07:15:54 pm
content: DCM and CCM are terms which are not very useful when you're talking about converters in a non-academic setting. Imagine this, if the load is extremely light, a single switching cycle of the UC3843 (or whatever the SMPS IC) would be adequate to uphold the output voltage rail and as a result, the feedback would be higher than the threshold for a long enough time that the inductor current would fall to 0A (viola! DCM). In contrast with a heavy load, the feedback will never be high enough to ever stop the switcher (CCM!!).As for setting the switching frequency, just have a read of the datasheet. It should give you everything you need
How to find maximum DC voltage allowable on a Schneider ic60n circuit braker - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: October 29, 2024, 05:25:23 pm
content: Looking for a DC disconnect switch for a solar array, Typically what is done in my area is they use a DC rated circuit breaker instead of using a solar disconnect switch (caused a few fires because of these failing) my problem is these DC "solar" breakers are usually chinese brands and none from a reputable brands (that i can get a hold of) so im a bit skeptical on those, im probably sure there are good chinese brands out there but finding which one is the problem.Anyway my hope right now is this breaker from schneider:ic60n seriesand the datasheet says its okay to use in a DC network, but my only problem is i do not see a maximum voltage rating especially for DC.There is though breaking capacity, although breaking capacity is important, i dont really mind having very low breaking capacity as the DC lines are fused, what i really care about is it able to handle 350V DC (my short circuit voltage).image 1image 2The breaking capacities seems to indicate a maximum 125V-DC and 450V-AC. If it can handle 450V-AC wont that imply that its internals are able to handle withstand 450V AC and DC? If current is the problem i can always get a higher Amp rated version as i dont plan on using it as a breaker but rather a disconnect, and the line is fused to a lower rating than the breaker so there is no problem of an overcurrent.

author: TimFox
author_rank: Super Contributor
timestamp: October 29, 2024, 06:19:58 pm
content: The datasheet file:///C:/Users/fox50/Downloads/Schneider%20Electric_Acti9-iC60_A9F74220.pdf is explicit on its breaking capabilities on AC and DC (separate lines).All DC breaking values are at 125 V DC. AC breaking voltages are higher, since the voltage goes periodically to zero and it's harder to make a contact-damaging arc across the opening switch.
How to find the LT1575 pole capacitor and zero resistor by using LTspice - Page 1
Forum section: electronics / projects

author: andrewsh
author_rank: Newbie
timestamp: March 24, 2024, 02:22:15 pm
content: Hi! Can I know how to find my pole capacitor and zero resistor by AC open-loop. The stability : AC open-loop Bode plot has at least 45 degrees of phase margin at both 1% and 100% of the assigned Maximum Load Current.I don't know how to get C3, C4 and R4.
How to find the transfer function of this low pass filter & Volt divider circuit - Page 1
Forum section: electronics / projects

author: ajoseph88
author_rank: Contributor
timestamp: July 23, 2015, 01:43:20 pm
content: I got the desired output voltage, by changing the voltage divider resistors and also eliminated the high frequency noise in the signal. I got an output voltage of 5.65 V, which goes to op amp, from op-amp it goes to MCU with proper voltage scaling and diode clamp protection.But I having confusion of how to find the transfer function of this circuit, Can someone with much knowledge on this topic advice me how to find the transfer function, or is there a software to draw this circuit and find the correct T.F...

author: ajoseph88
author_rank: Contributor
timestamp: July 23, 2015, 01:49:10 pm
content: I just realized op-amp will have its gain and all, so that will affect the transfer function, but ignoring the op-amp, just till Vout, how to find the T.F...Vin is 100V D.C with frequency around 2.2 KHZ and i got Vout as 5.65V dc with frequency switching around 3 to 30HZ.

author: ajoseph88
author_rank: Contributor
timestamp: July 23, 2015, 02:48:06 pm
content: OK, I was just stupid... I found out how to find the T.F of circuits... its all here in the link below..."http://www.egr.unlv.edu/~eebag/Chapter14.pdf"So this is resolved...

author: retrolefty
author_rank: Super Contributor
timestamp: July 23, 2015, 04:23:01 pm
content: Wow, a first for me to see on a posting.Same user asked, then comments, and then solves the problem with no help required by anyone else. Is this the future we are seeing, artificial intelligence skynet taking over?

author: tombi
author_rank: Regular Contributor
timestamp: July 24, 2015, 01:31:52 am
content: I think it is the electronics form of Rubber Ducking.https://en.wikipedia.org/wiki/Rubber_duck_debugging
How to find the voltage rating of an unknown capacitor - Page 1
Forum section: electronics / projects

author: trevwhite
author_rank: Frequent Contributor
timestamp: November 14, 2015, 11:40:32 am
content: Hi, I have found a strip of ceramic smt capacitors but I do not know what their voltage rating is. Is there a test that can be done to understand their rating?

author: wraper
author_rank: Unknown
timestamp: November 14, 2015, 11:54:47 am
content: Nothing too serious, mostly you can only guess. Most low value caps will be 50V rated. But even 16V capacitors usually will withstand even 100V for a quiet long time.

author: dom0
author_rank: Super Contributor
timestamp: November 14, 2015, 05:08:07 pm
content: Measure capacitance and look up what voltage ratings in the package are available typically. As wraper said most small caps (100 nF and the like) are almost always rated for 50 V. Only MLCCs with much larger capacities go down significantly with their voltage rating.

author: Someone
author_rank: Super Contributor
timestamp: November 14, 2015, 06:07:54 pm
content: It will depend if they are class I or class II.For class I parts it will be based on leakage/failure, you will need to apply high voltages while measuring the leakage of a representative sample from the reel.For class II parts the best test is to measure the capacitance as you increase the DC bias, then you have a qualified part that the characteristics are very well known. Failure will be a long way from the -3dB point, and you could try taking them to failure. Most ceramics are HALT tested at 3x (sometimes 2x) the rated voltage and will pass that test with some maximum leakage, but the class II parts will have a tiny fraction of their capacitance left by this point so unless you need an unusual part with a large peak voltage rating just use the capacitance -3dB point.

author: lemon2015
author_rank: Newbie
timestamp: November 14, 2015, 08:55:57 pm
content: you could pulse the cap. with high voltage (up to 100Volts) and measure the variance of capacity.

author: bktemp
author_rank: Super Contributor
timestamp: November 14, 2015, 09:11:50 pm
content: It is impossible to "measure" the voltage rating.Most ceramic capacitors fail at more than five times the rated voltage, but it can be also be much higher (I tested some 10V 10uF Y5U 1206 caps and half of them did not fail at 400V until I stressed them mechanically). So this method does not produce useable results.Using the capacity reduction at higher voltages also does not work:https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527If they have less than 1uF, the voltage rating is at least 25V or 50V. 50V is the most common voltage.
How to find where signal enters an amplifier? (specifically in an organ) - Page 1
Forum section: electronics / projects

author: Wheres_my_chippy
author_rank: Newbie
timestamp: February 12, 2015, 06:57:56 pm
content: I bought a chord organ recently and I wanted to do some modifications to it but I need to know how to find where the line level signal enters the amp. (Sorry, it might be a simple question but I usually rely on schematics and instructions).What I am trying to do is put an effects loop (for reverb and other audio effects) in the circuit right before it hits the amplifier. I was also wondering what 1/4 in telephony jacks that bypass when nothing is plugged in are called.Thanks!

author: Andy Watson
author_rank: Super Contributor
timestamp: February 12, 2015, 07:07:15 pm
content: Quote from: Wheres_my_chippy on February 12, 2015, 06:57:56 pmI would look at or around the volume pot (assuming it has one).QuoteSwitched jacks? Usually stereo 1/4 inch with break-contacts. Be careful about specifying "telephone jacks" - the end terminal (tip) is often reduced in diameter compared to the standard musician's jack plug.

author: Wheres_my_chippy
author_rank: Newbie
timestamp: February 12, 2015, 07:13:22 pm
content: Thanks, it does have a volume pot (foot controlled) which I was considering replacing with a variable resistor. Also I had no idea about the jacks, that's really helpful.Is there any way I could use a multimeter to confirm that I found the audio source? i.e. Would checking for voltage spikes when I press down keys work?

author: atferrari
author_rank: Frequent Contributor
timestamp: February 12, 2015, 11:22:00 pm
content: I would use the DMM to measure continuity first, to see who connects to whom.

author: Andy Watson
author_rank: Super Contributor
timestamp: February 14, 2015, 10:02:46 pm
content: Quote from: Wheres_my_chippy on February 12, 2015, 07:13:22 pmPossibly, depends on the meter. I would try measuring the voltage across the pot on both A.C and D.C. If it's an A.C signal (the one you want) it will not show much when the meter is set to D.C. (although it probably won't show a great deal on A.C.). If the meter says there is no D.C. potential there then connecting to, or in place of the pot should work. However, if the meter shows there is a continuous D.C. potential, you probably need to look elsewhere. It's difficult to be certain.
How to flash a USB flash - Page 1
Forum section: electronics / projects

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 15, 2021, 08:25:20 am
content: Hi,I have a 32GB flash, Unfortunately during a format, flash is not detected by my PC, I think maybe the firmware inside the chip is lost, so do you know any way to re-flash the firmware? I think maybe they have a common chipset and there should be some way to bring it back to life.

author: coromonadalix
author_rank: Super Contributor
timestamp: June 15, 2021, 11:04:52 am
content: you have tool like : SD card formater 5.0.1 from Tuxeraa normal format should not brick you usb key even if its linux or mac file(s) format, windows should pop this device need to be formated ...or this usb dongle is sh@%$% "crap" I have found in the past many faked sizes usb dongle, an 1tb size for 8$ usd lolll was an 8 gb lollFor the firmware(s) you need to know the maker chip inside and if possible to find any related tools for that makerChipGenius v4 .... to identify it if possibleOr see usbdev.ru website in some cases ...

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 16, 2021, 05:53:07 am
content: QuoteThanks for the hint, the flash was working fine and I have used it for several months,After this last time format, windows can not detect itit would say thisQuote

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 16, 2021, 05:57:15 am
content: ChipGenius v4 report the flash has this info, do you have any Idea what controller it has and how to reflash it?Quote

author: viperidae
author_rank: Frequent Contributor
timestamp: June 16, 2021, 06:52:52 am
content: Sounds broken.This websitehttp://usb3speed.nirsoft.net/?vid=2316&pid=8192shows many different brands and sizes with varying performance all sharing the same vid and pid

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 16, 2021, 07:18:13 am
content: Is there a way to flash the chip inside?

author: coromonadalix
author_rank: Super Contributor
timestamp: June 16, 2021, 09:43:40 am
content: You have to find the maker software if there is .... check usbdev ... sometimes based on the VID PID you can find some hints
How to generate a 230V sine wave with maximum 0.01A current output - Page 1
Forum section: electronics / projects

author: SmartFoxElectronics
author_rank: Newbie
timestamp: June 28, 2023, 08:35:45 am
content: Building a test rig for a UPS logic board & was kinda shocked to see that the reference voltage for the 3ph input, output and bypass lines hadn't been stepped down at all & it was just the full 230V sine wave with resistors limiting the current. Obviously I could just recreate this circuit but it doesn't feel particularly safe in terms of potential short circuits etc.I'm looking for some kind of small electronic module that could convert a DC supply voltage (preferably 15V, though not crucial) into a 230VAC reference voltage with current limitation of 0.01A or less. If the voltage can be adjusted that would be awesome but I can build a separate circuit for that if not.Thanks in advance!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 28, 2023, 08:44:48 am
content: Audio amplifier and mains transformer wired backwards.

author: Psi
author_rank: Super Contributor
timestamp: June 28, 2023, 09:51:47 am
content: Or get two motors. A low voltage adjustable speed DC motor and a 230V AC motor and mechanically couple their shafts together.Just have to be sure your AC motor can actually act as a generator, no induction motors.But a small audio amp, 50/60hz tone generator and backwards transformer is easier.Add a current limit resistor and seal all the areas before that resistor.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 28, 2023, 03:35:02 pm
content: 230 VAC 10 mA may be achieved in different ways and several were mentioned.One of ways: step-up DC-DC converter as HV power supply (there are ready-made Chinese modules), an oscillator, and HV amplifier. I posted HV aplifiers circuits several times somewhere here (can't find at the moment).

author: wilhe_jo
author_rank: Regular Contributor
timestamp: June 28, 2023, 03:54:22 pm
content: Quote from: mikeselectricstuff on June 28, 2023, 08:44:48 amThat'll be my choice as well... Some small 230/6V transformer and a 10W@8ohm class-D amp should work beautifully.Btw: using a 1.8kW audio amp gives you 110V directly. Adding a cheap 110/230V autotransformer gives you a nice and capable grid simulator...73
How to get good isolated / idiot proof 9VDC supply from +/-15VDC rails? - Page 1
Forum section: electronics / projects

author: K3mHtH
author_rank: Regular Contributor
timestamp: October 30, 2019, 09:10:02 pm
content: So I have a modular synthesizer with a +/-15VDC power supply and I'd like to power something (guitar effects pedal) that requires 9VDC.I was initially planning to just use a 7809 off the +15 rail to get my 9V power supply, but realized that several of my pedals actually ground the positive rail to get a -9V internal supply. My thoughts was to run the 7809 through a 1:1 transformer, but I've never specced out a transformer before for isolating a DC supply and have no idea where to start.I'd be looking at supplying about 250mA max.I'd also like this supply to be idiot proof.. so if I short something out, or draw more than 250mA - I don't want to damage anything, or take down my +/-15VDC supply.Maybe there's even IC's designed to deliver a 9VDC isolated supply, etc... I'm totally OK with the supply being switchmode too.

author: Buriedcode
author_rank: Super Contributor
timestamp: October 30, 2019, 10:04:18 pm
content: You can get off-the-shelf DC-DC converter modules, often these are unregulated, and *can* be quite noisy, have fairly poor regulation, but isolated. It can be common practice to follow the output of these with a linear regulator, even a cheap 7809 (as you mentioned) will do, as this can clean up the line and provide short-circuit protection. An example would be 12V in 12V out DC/DC module, with a 7809.The 250mA output current means 9*0.25 = <2.5W, but I would go for at least 4W for headroom. Aside from digital/multieffects or boutique reverb pedals, most draw very little current. I suppose if you can get them cheap enough you could use one DC/DC module per pedal output, in which case you could go with the lower 2W.If you're ordering from Farnell or Mouser, I would buy a few from different manufacturers (if they're fairly cheap like $4) just to test them and see how noisy they are - the noise on the output can be sorted with a regulator and/or filtering, but EMI, radiated noise, would require shielding so is harder to sort.There are indeed IC's designed purely to provide isolated low voltage supplies, often just simple push-pull oscillators, but the transformers they are designed for can be difficult to source. Also I can't see to find any part numbers. As this isn't for high volume, I would go with modules.
How to get Raspberry PIs to Internet? - Page 1
Forum section: electronics / projects

author: LM21
author_rank: Regular Contributor
timestamp: November 29, 2022, 05:00:46 pm
content: We have RaspBerry Pi board, and we want to connect it to Internet (wireless). Are there any Chip sets or modems for that.

author: themadhippy
author_rank: Super Contributor
timestamp: November 29, 2022, 05:07:09 pm
content: plenty of usb wifi dongles,for examplehttps://thepihut.com/products/usb-wifi-adapter-for-the-raspberry-pior if its 4g your after maybehttps://thepihut.com/products/4g-hat-for-raspberry-pi-lte-cat-4-3g-2g-with-gnss-positioning

author: eugene
author_rank: Frequent Contributor
timestamp: November 30, 2022, 07:07:33 pm
content: Which RPI board? There are many. Most of them have wifi built in...
How to get temperature reading using MAX6603 - Page 1
Forum section: electronics / projects

author: joniengr081
author_rank: Regular Contributor
timestamp: April 11, 2024, 08:40:31 am
content: I found MAX6603, a Dual-Channel, Platinum, RTD-to-Voltage Signal. I have couple of questions.If we connect PT100 or PT200 then, the output is a voltage signal proportional to the temperature at RTD, right ? How much current actually run through PT ? Is that constant ?https://www.analog.com/en/products/max6603.htmlIs that possible to set a gain ?What is the voltage to temperature relation ?How PT100 can be used with MAX6603 ? As the datasheet suggest to use standard PT200.

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 11, 2024, 09:28:28 pm
content: If we connect PT100 or PT200 then, the output is a voltage signal proportional to the temperature at RTD, right ?YesHow much current actually run through PT ?1 maIs that constant ?YesIs that possible to set a gain ?NoWhat is the voltage to temperature relation ?Vout = (VCC * resistance) / 1000How PT100 can be used with MAX6603 ? As the datasheet suggest to use standard PT200.You can use PT100, output voltage is lower due to the lower resistance.

author: joniengr081
author_rank: Regular Contributor
timestamp: April 12, 2024, 08:07:44 am
content: Thank you for answering these questions.From the attached Figure 2, the supply voltage VCC can be the same for MAX6603 and also for MCU/ADC. Can we use VCC as 5 V for both MAX6603 and also for MCU/ADC ?Our temperature range is 0 to 150 C and we need to find a PCB mount PT in SMD 0603/0805/1206 etc package. According to the datasheet Figure 1, they have shown PT200. Do we have PT200 available in SMD solder able packages ?OrBecause the MAX6603 is characterized for PT200 according to Figure 1 in the datasheet. Can we just connect two PT100 in series to make them PT200 ? Connecting two PT100 in series at 0 C will result in to 200 Ohm, right ?
How to get the most accurate inductance value for inductive ballast? - Page 1
Forum section: electronics / projects

author: roxanne may
author_rank: Newbie
timestamp: September 25, 2015, 09:08:21 am
content: I am currently working on my thesis prototype AC and DC circuit trainer. This includes inductor component and I used inductive ballast. But I cannot get the real value of its inductance. The measured and computed value has large percent difference. I am using LCR meter and what I obtain from the measurement is far less than the computed value. Please help me.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: September 25, 2015, 09:16:02 am
content: You probably need to explain how your computed value is computed.An inductor ballast is very far from an ideal inductor as it is probably partly working in a non linear region due to saturation.So accordingly your model may need some more complexity.Or go for a different inductor if you can.

author: roxanne may
author_rank: Newbie
timestamp: September 25, 2015, 09:29:40 am
content: I measured the internal resistance of the ballast and I have a 220 V 60 Hz AC source. The measured inductance I gained from the LCR meter is twice the computed value

author: SeanB
author_rank: Super Contributor
timestamp: September 25, 2015, 09:56:01 am
content: DC resistance is not inductive reactance, just the resistance of the copper or aluminium wire used to wind it. The LCR meter ( provided the test frequency used is 100/120Hz) will be a lot closer to the value, but the only way is to run in circuit and measure the voltage drop and RMS current through it, to get an impedance under actual operation.As said above the inductance will vary, as the choke is running in a partly saturated state of the core, and thus will have a non linear inductance with applied voltage.

author: Berni
author_rank: Super Contributor
timestamp: September 25, 2015, 10:24:21 am
content: As people said ballasts sometimes employ some magnetic trickery to get them to work at its best.The laminated iron core might have large eddy current losses at frequencies any higher than 60Hz and LCR meters often use higher frequencies. The basalt might be designed to run in to saturation on 220V. It might have a carefully designed air gap inside its iron core to control how it behaves in saturation etc.In general if you want an inductor that behaves closer to a textbook ideal inductor then you probably want something with a low loss ferite core and decently thick wire to minimize the resistance. But beware in that area too. There are ferite core inductors that are designed as power supply chokes. Those might contain a high loss type of ferite core that is designed to dampen down its Q at high frequency to prevent oscilations.If you only need one then winding a few 1000 turns on to the core of a TV flyback transformer would give you a pretty good inductor.
How to hand solder SO-8 with thermal pads? - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: August 03, 2015, 06:11:34 pm
content: Related to the GPS module question since it is from the same board. I have a TP4056 on that board (also LIR2032, the rechargeable Li-ion version of CR2032, so the purpose of TP4056 is pretty obvious, and LIR2032 lasts for longer than the supercap that usually goes with the GPS module,) which featured an exposed pad for heat dissipation. I hand solder almost everything, so how to solder this properly? Vias on the back? Or apply a bit of solder paste beneath the chip before soldering it down and take it to a trip of hot air gun later?

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 03, 2015, 07:06:21 pm
content: 1) remove solder from all pads2) apply a small amount of paste to center pad *only*3) reflow with hot air to solder center pad (optional - apply a slight downward force during reflowing to ensure IC leads touch their pads)4) hand solder IC leads with iron
How to ID small packages stripped from a board? - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: July 07, 2015, 07:44:14 pm
content: I disassembled a battery bank (since the controller board is not working properly, and missing a chip anyway) and here are some chips that I cannot ID. Hope you guys can give me some pointers:* "KL4" SOT-23-3* "A152" SOT-23-5* "CD=E24" SOT-23-5* "F3K" or "F3KI" SOT-23-3* "GRJH" SOT-23-6* "A13HB" SOT-23-3* "HXN-AP" SO-8 with thermal pad* "8205A Z1J05" wide-body TSSOP-8* "TQ7604 42CHG" TSSOP-8 with thermal pad (difficult to read under a magnifying glass even with 20/20 vision)

author: Yansi
author_rank: Super Contributor
timestamp: July 07, 2015, 08:12:49 pm
content: thishttp://www.marsport.org.uk/smd/mainframe.htmor google or ... bad luck.the 7604 is probably this:http://www.mouser.com/ds/2/200/irf7604-298600.pdfMaybe 30 seconds of google. Have you tried yourself?You haven't done your homework. UTFG please!I've just tried another one (KL4) and IDed it on the first try:http://www.farnell.com/datasheets/1317753.pdf

author: amyk
author_rank: Super Contributor
timestamp: July 07, 2015, 10:08:16 pm
content: You seriously couldn't ID a8205A?Agree with the poster above, do some more Googling first and come back with the ones you can't find...

author: technix
author_rank: Super Contributor
timestamp: July 08, 2015, 06:13:35 am
content: Quote from: Yansi on July 07, 2015, 08:12:49 pmGoogling those SOT-23 packages and the "HXN" frustrated me out as those always turned out fruitless, either flat out no relevant result or the packaging does not match the one I have at hand. If I should Google it then how?

author: technix
author_rank: Super Contributor
timestamp: July 08, 2015, 06:17:19 am
content: Quote from: amyk on July 07, 2015, 10:08:16 pmNope the "8205A" is a TSSOP-8 package and obviously the one from the linked datasheet is not one. I asked here because Google turned out fruitless.

author: amyk
author_rank: Super Contributor
timestamp: July 08, 2015, 01:04:39 pm
content: Areyouseriouslytellingmeyoudidn'tnoticeanyofthese!?

author: technix
author_rank: Super Contributor
timestamp: July 09, 2015, 06:10:46 am
content: Quote from: amyk on July 08, 2015, 01:04:39 pmI did notice a few of them but none of them mentioned the exposed pad. Like the one above you, wrong package!
How to Identify Counterfeit Adjustable regulator LM338??? - Page 1
Forum section: electronics / projects

author: Gurumurthy
author_rank: Regular Contributor
timestamp: June 15, 2017, 03:13:56 am
content: Hi to all!!!Last week i bought LM338K manufactured by STMicroelectronics , It went to breakdownload while working.I have searched thorough the market(Chennai) but i cant find LM338 TO-3(manufactured by TI) package any where. Some seller say product is obsolete. I think i have bought Counterfeit IC, that why it went to breakdown before giving Rated current..Also Say me a method to test adjustable voltage regulator. SO teach me the way to test Adjustable voltage regulators and to identify Fake Regulators of this type.

author: danadak
author_rank: Super Contributor
timestamp: June 15, 2017, 04:51:27 pm
content: In the TO3 package you can always grind off the top of the package and look atdie markings using a microscope.No easy way electrically to ID this type of part unless it has a very un-usual characteristicthat could test for. a characteristic no other regulator manufacturer has in the market.Regards, Dana.

author: w2aew
author_rank: Super Contributor
timestamp: June 15, 2017, 05:12:06 pm
content: These devices include several forms of self-protection - current limiting, thermal overload protection, and safe operating area protection. Depending on how you used/tested the device, it could have shutdown due to thermal overload or SOA conditions, long before the maximum output current is reached.See the datasheet for details:http://www.ti.com/lit/ds/symlink/lm138.pdfThe TI datasheet was revised 6 months ago, so I doubt the device is obsolete.

author: rdl
author_rank: Super Contributor
timestamp: June 15, 2017, 05:39:13 pm
content: They aren't obsolete yet. Mouser has plenty in stock. However, it must be a lot of trouble to put them in the steel TO-3 package because those cost over $50 each. The TO-220 type are a more reasonable $1.90 for single quantity.

author: alm
author_rank: Super Contributor
timestamp: June 15, 2017, 05:53:31 pm
content: How about just testing the datasheet specs you care about? Carefully read the datasheet, make sure you are within all stated limits (input voltage, Vin-Vout, current, temperature, dissipation) and see if it exceeds the datasheet bare minimum specs at the point you care about.If you have a large quantity, then cutting one open makes sense. Less so if you bought only three.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: June 17, 2017, 12:31:49 am
content: I can issue a warning on this: when used with a too small heatsink, the protection features of the LM338 do not work and the component will die faster than you can say dang! I made this experience 30 years ago with parts that were beyond reproach! Even for breadboarding, use it on a heatsink that will support your application.
How to identify input, output of DC-DC converter--blind? - Page 1
Forum section: electronics / projects

author: iXod
author_rank: Frequent Contributor
timestamp: July 24, 2020, 07:47:05 pm
content: I've got an old car DC-DC converter for a laptop, 12v in, 24 out. I've long since cut off the cables and was going to recycle it but now could use it.The PCB is well-potted inside an extruded aluminum "tunnel" so access isn't practical. The cable stubs are identical so I can't identify which had a cigar-lighter (remember those?) plug and which had the barrel connector.Using the diode test measurement (and swapping DMM probe polarity) on these two 2-wire cables, I get:* 0.8v / 0.5v* 0.6v / increasing to infinityIs the one with 0.6v / infinity measuring the output rectifiers and filter caps?How can I verify which is which?Thanks.- - -EDIT: "Just buy another" isn't an option. This is a project, a challenge. I have this and want to use it.

author: Pawelr98
author_rank: Regular Contributor
timestamp: July 25, 2020, 02:36:43 am
content: It's a boost converter so you can just try to apply a current limited voltage source on either side.If you connect it to output then it should just charge the output cap, nothing more.When connected to input it should just start up.It would be that simple, provided you know which one is positive and negative.Which is simple to check. Negative is common so it should measure as a short when probed between input and output.If you look at the schematic of a boost converter with a mosfet switch then it becomes fairly obvious, how should the DMM react.Output should just go to high resistance over time as the output diode is blocking current from flowing back.On input it will be mosfet diode drop at reverse bias and in other direction it's an unknown really, depending on the circuit itself.

author: iXod
author_rank: Frequent Contributor
timestamp: July 25, 2020, 05:00:12 pm
content: Thank you Pawelr, that worked.Using current-limited PS, connected first to what turned out to be the output and got a tripped current limit immediately. Reversed polarity and ran up to 12v with no indication, and no voltage appearing on the other pair of wires (which turned out to be he input).Applied the 12v to the input and magically(!) I have 24v on the output.Thanks again for helping think out this solution.
How to identify Kynar (PVDF) insulation? - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: January 14, 2017, 05:32:14 am
content: (Originally posted in Beginners, but didn't receive any replies)I bought some cheap wire wrap wire which claims to be PVDF insulated.The insulation is easily damaged and can be stripped just using fingernail pressure and turns white if you stress it.If real PVDF slippery like PTFE and difficult to strip?

author: filssavi
author_rank: Frequent Contributor
timestamp: January 15, 2017, 12:24:56 am
content: The simplest method that i can think of is to use a temperature controlled soldering iron to find the softening/melting point of the insulation tht should narrow It down, pvdf is also quite chemically stabile, so there might be some chemically that attacks most plastica but leaves intact pvdf( you should ask someone with more of a chemistry background than me if you want ti take the route TBH)

author: jpanhalt
author_rank: Super Contributor
timestamp: January 15, 2017, 01:10:30 am
content: Kynar is in my opinion easy to strip. It is a little slippery compared to PVC, but not nearly so slippery as Teflon. Its finish is duller than Teflon and it feels harder than PVC. In my experience, the main distinguishing feature compared to PVC is that it doesn't shrink back and char nearly as much. I can't recall ever causing it to char.It is the only wire I use (24 awg) when I am using a solderable breadboard.John
How to identify part from numbering - Page 1
Forum section: electronics / projects

author: FrankT
author_rank: Regular Contributor
timestamp: August 21, 2020, 01:46:56 am
content: I wanted to buy some ACS70331EOLCTR-2P5U3 chips (SOIC-8 hall effect 0-2.5A current sense chips), but I couldn't find them in any of the main suppliers (in small quantities) but I did find them on Aliexpress, but I'm not sure they are what they say they are.Before I solder them up and try them, is there any way I can tell from the numbering on the chip?It shows 3 lines...A70331(Alegro Symbol) 1806042kI've checked the datasheet but can't find any codes.Is there another place I can look?Thanks,Frank

author: Phoenix
author_rank: Frequent Contributor
timestamp: August 21, 2020, 04:31:14 am
content: Quote from: FrankT on August 21, 2020, 01:46:56 amPage 25 of the datasheet with package details also gives marking details.Line 1: Part NumberLine 2: Logo A, 4 digit Date CodeLine 3: Characters 5, 6, 7, 8 of Lot Number

author: FrankT
author_rank: Regular Contributor
timestamp: August 21, 2020, 06:52:18 am
content: Gee, that sucks. Looks like I'm going to have to test it.Thanks for the extra set of eyes.
How to identify with oscilloscope noise or ripple that affects ADC accuracy - Page 1
Forum section: electronics / projects

author: Red_Micro
author_rank: Regular Contributor
timestamp: October 27, 2021, 02:29:02 am
content: The circuit attached is a 1.65V buffer that has the following purposes:1- It provides a 1.65V DC offset to four op amps to measure AC signal with STM32 ADC.2- It is directly sampled by the MCU also.3- It provides a reference for other op-amp circuitsBoth circuits work, but the one with the shunt reference makes the AC measurements more accurate, thus ADC measurements more accurate. So it seems that there's some factor around the 3.3V supply that it's eliminated by the shunt before going through the buffer. The buffer seems quite robust so I thought the shunt would not be needed. You can see that in the circuit with the shunt reference I had to change the upper resistor of the divider to 5.1K to keep the 1.65V since the shunt provides 2.5V.I tried to watch with the scope what's happening around the 3.3V and 1.65V points but could not catch anything. I set the probe to 1x, AC coupling, 5mV division but did not see anything other than the scope noise floor. I even got rid of the scope ground clip and got the ground loop as short as possible. Either my scope is not suited to see such things or I'm doing something wrong. At the end I want to explain myself what is the shunt reference eliminating that makes the ADC measurements more accurate.

author: David Hess
author_rank: Super Contributor
timestamp: October 27, 2021, 03:36:16 am
content: It is very likely that the noise level in either circuit is lower than a typical oscilloscope can measure.

author: harerod
author_rank: Frequent Contributor
timestamp: October 27, 2021, 05:26:12 pm
content: What David said.In addition:- you supply the OPAMP somehow? Interesting CAD system, I am curious about the layout.- Some STM32 ADCs show several bits of periodic noise from other subsystems (e.g. ART on STM32F407). Best build-in ADC performance can only be reached by disabling those subsystems during conversion.