hybridfree/eevblog-posts huggingface dataset:
3.3V LDO regulator circuit reverse polarity protection - Page 1
Forum section: electronics / projects

author: ilium007
author_rank: Frequent Contributor
timestamp: August 13, 2021, 11:07:36 am
content: Does this circuit look correct? I am building this power as a power supply for an ESP32 project and want to have both a USB-C power input and a 5VDC screw terminal input. I need reverse polarity protection on the screw terminal input.Q1 is a logic level P-channel mosfet (https://datasheet.lcsc.com/lcsc/1810180217_Alpha-Omega-Semicon-AO3401A_C15127.pdf) with a low -2.5 Vgs and relatively low 80mΩ Rds.Does this circuit look correct? Will this also give the USB-C input preference over the screw terminal input?

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 11:12:09 am
content: Since you are using LDO and don't need full 5V, you can just use a Schottky diode from each input and not overcomplicate things.EDIT: Your circuit is susceptible to ESD damage.

author: ilium007
author_rank: Frequent Contributor
timestamp: August 13, 2021, 11:15:09 am
content: Will do, thanks. I was trying to be clever

author: ilium007
author_rank: Frequent Contributor
timestamp: August 13, 2021, 11:26:58 am
content: This should work??

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 11:30:23 am
content: Yes but you don't need 10k resistor unless you are using VBUS detection somewhere else.

author: ilium007
author_rank: Frequent Contributor
timestamp: August 13, 2021, 11:38:15 am
content: Quote from: wraper on August 13, 2021, 11:30:23 amI missed that one. Thanks.

author: Peabody
author_rank: Super Contributor
timestamp: August 13, 2021, 02:21:57 pm
content: However, there is no preference in the diode circuit. The power source with the highest voltage will power the load. In your original circuit, if USB power is present, it will always power the load unless the screw terminal source is high enough to forward bias the mosfet body diode. But if preference is important, you could still use the two-diode circuit, but make the screw terminal diode a regular rectifier diode.
3.3v output boost and invert for piezo drive - Page 1
Forum section: electronics / projects

author: Psi
author_rank: Super Contributor
timestamp: August 18, 2016, 06:45:52 am
content: Does anyone have any tricks to cheaply convert a single 3.3v ouput oscillating at 4khz to a differential signal at >5v for driving a piezo?Need to be super low power when not active as this is for cr2032 powered device that lasts a year.So under 1uA when off.

author: Zero999
author_rank: Super Contributor
timestamp: August 18, 2016, 07:47:25 am
content: Google returned quite a few results for IC specifically designed to do that:https://www.google.co.uk/search?q=charge+pump+piezo+sounder+driver&ie=utf-8&oe=utf-8&safe=active&gws_rd=cr&ei=Ima1V7iJEojZgAaxnYMYhttp://ineltek.com/eolpcnpdfs/DA6240-004.pdfhttp://www.diodes.com/_files/datasheets/PAM8904.pdfhttp://www.njr.com/semicon/PDF/NJU72501_E.pdfThey're all in SMT packages with thermal pads though.Failing that. I'd use two 74HC00 CMOS oscillators: one with some Schottky diodes to make a charge pump, giving about 6V out, followed by another used to drive the piezo. The oscillators can easily be disabled when not needed, giving very low power consumption.

author: Psi
author_rank: Super Contributor
timestamp: August 22, 2016, 08:50:45 pm
content: Thanks! one of those looks perfect
3.3V Regulator Not Working On Custom PCB - Page 1
Forum section: electronics / projects

author: waymond91
author_rank: Regular Contributor
timestamp: February 10, 2022, 06:06:08 pm
content: Hello,I just received a custom board assembled from JLCPCB. However, I am having some difficulty with a 3.3V regulator.Its a little ESP32 board with some I2S and GPS peripherals.The first board I actually fired up had a short between 3.3V and ground. After spending an afternoon taking off components and cutting traces, I discovered that there was a short in hole for the mems microphone and the 3.3V pour. On a fresh board I've cut that connection and now I can program the board with my programmer (esp-prog) and power 3.3V directly from that.However, when I plug in a 1s lipo, no power comes out of the 3.3V regulator. When I plug in USB I only get 0.5v.Here are my schematic and top layer:And a link for the pesky part:https://www.lcsc.com/product-detail/Dropout-Regulators-LDO_MICRONE-Nanjing-Micro-One-Elec-ME6217C33M5G_C427602.htmlI apologize for the orientation of theVBUS(which is VUSB) line on the schematic...Any tips on how to diagnose and repair? Should I just ship a different component from digikey, or is likely there is a problem with the PCB itself?

author: fourfathom
author_rank: Super Contributor
timestamp: February 10, 2022, 06:25:10 pm
content: Look at your Pin-3 connection. You have it "NC" on the schematic and the layout, but on the regulator spec sheet it is "CE", and pin 4 is the NC. This would certainly explain the regulator being shut down. This is for the SOT23-5 footprint, which it looks like you are using.

author: waymond91
author_rank: Regular Contributor
timestamp: February 10, 2022, 06:51:49 pm
content: Wow, thank you so much! Apparently I just looked at the picture in the data sheet, not the table of pin assignments

author: fourfathom
author_rank: Super Contributor
timestamp: February 10, 2022, 08:04:32 pm
content: Yeah, that data sheet isn't the best I've ever seen!

author: waymond91
author_rank: Regular Contributor
timestamp: February 10, 2022, 08:33:41 pm
content: Yeah looks like the ins and outs are also in the wrong position, so with any luck I can find a different part that fits

author: fourfathom
author_rank: Super Contributor
timestamp: February 10, 2022, 08:45:58 pm
content: For testing it looks like you can bridge R8 (or replace it with a zero-Ohm resistor), then jumper Pins 3 and 4 (connecting pins 1,3,4 to Vin). This assumes that pin 4 (NC) is truly not connected to anything internally. Your pin 2 (ground) and pin 5 (Vout) are connected correctly.

author: waymond91
author_rank: Regular Contributor
timestamp: February 10, 2022, 09:18:20 pm
content: We did it!

author: fourfathom
author_rank: Super Contributor
timestamp: February 10, 2022, 10:23:24 pm
content: Congratulations! Now on to the next mystery!
3.3v Zener in series with 78L05 regulator - why ? - Page 1
Forum section: electronics / projects

author: TomKatt
author_rank: Frequent Contributor
timestamp: March 27, 2025, 03:24:21 pm
content: I'm building a project based on anOlimex AVR-MT128controller board. It has an onboard 5V regulator for the 9VAC - 12VDC input that has a 3.3V 1N4728 zenerin seriesto the 78L05 input terminal. I'm definitely no expert, but I don't recall coming across a similar design before. I'm thinking that this may be some kind of protection or voltage reduction for the 78L05 so that it doesn't have to drop the full 7 volts from the 12 volt power input?

author: TimFox
author_rank: Super Contributor
timestamp: March 27, 2025, 03:34:48 pm
content: Yes: reducing the input voltage to the 78L05, while keeping it high enough to avoid dropout, reduces the power dissipation and, therefore temperature rise, of the regulator IC. The 78L05 is in a small package: the TO-92 TH package is rated for 158 K/W temperature rise from ambient air.

author: TomKatt
author_rank: Frequent Contributor
timestamp: March 27, 2025, 03:43:28 pm
content: That's what I was thinking. While it helps, I'm guessing that you're still capped to the 100ma limit the 78L05 has? Which kind of stinks - even though the ATMEGA128 and few active components don't consume a lot of current, you could easily go over 100ma by adding a few leds etc. In fact, I noticed that the lcd display on the board did not have it's illumination led pins connected - I considered wiring them to the 5V bus, but then realized that would consumer another 40+ma.If all you need is the functionality on the board, the design is more than sufficient. But as a developer platform I'm going to replace the 78L05 with something a bit more capable.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: March 27, 2025, 03:46:32 pm
content: In some HP equipment that I repaired, the engineers seem to use quite a few in series zeners on well controlled voltage lines to achieve the needed voltage. I was surprised when I initially found them but looking at different HP TE from the past, it seems quite common.

author: TimFox
author_rank: Super Contributor
timestamp: March 27, 2025, 03:51:36 pm
content: Quote from: TomKatt on March 27, 2025, 03:43:28 pmPer the TI data sheet, the maximum recommended continuous operating current for the 78L05 is 100 mA, and the typical peak output current is 140 mA. The 78M05, in a larger package, has higher current ratings.
3.5 mm 5-conductor TRRRS phone - Page 1
Forum section: electronics / projects

author: ebclr
author_rank: Super Contributor
timestamp: June 08, 2019, 01:48:06 am
content: What is the search name of the female of this 3.5 mm 5-conductor TRRRS phone connectorI need an smd connector for a project where can I find this?

author: mariush
author_rank: Super Contributor
timestamp: June 08, 2019, 02:16:17 am
content: You mean these?https://www.digikey.com/short/pmbfrtIf it's not for audio, you could probably get a better connector in the same general size (or maybe wider)... like for example something like mini/micro USB with a 5th pin (OTG)
3.5" touch display solution suggestions? - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: March 04, 2022, 07:48:01 pm
content: Hi,I have to develop a custom system/PCB with a 3.5" touch display but is the first time working with graphic touch displays and am looking for pointers/suggestions.The fixed requirements are only 3.5" 480x320 with integrated resistive touch panel and refresh at least 40Hz and it would have to be a parallel interface.Any suggestions for:- the display controller. Which ones are the most common or industry standard controllers? I came across for example the ILI9486L but no idea how "standard" it is and what other part numbers it might be available as (just in case given the global components situation).- the micro I am leaning towards is an ARM - which one specifically I am open to suggestions but not sure if there are perhaps some with hardware-dedicated peripherals?Less important, any recommendations for software tools that allow simple fast development?Many thanks
3.5mm headphone jack 3p/4p temperature sensor standard? - Page 1
Forum section: electronics / projects

author: mairo
author_rank: Unknown
timestamp: June 03, 2020, 05:06:23 pm
content: Hi all,Is there a standard for the pin-out of a 3.5mm headphone jack 3p/4p when used with temperature sensor, particularly in the power wiring? Mainly 1-Wire based digital sensors, but if there is something for analog ones (e.g. MCP9700 based ..), I am also interested to know.The only information I found was from iTead on some Sonoff probes:https://www.itead.cc/wiki/Sonoff_Sensor_Si7021and some tread in which the circuitry for the power seems flipped when compared to the one from iTead/Sonoff tread above:http://rants.dyer.com.hk/rpi/1wire.htmlThank you

author: aix
author_rank: Regular Contributor
timestamp: June 04, 2020, 06:17:19 am
content: It looks like the first link uses a 2.5mm, not a 3.5mm, connector.I've seen meat cooking probes also use a 2.5mm connector for the thermistor, but I'm guessing that's not the type of temperature sensor you're after.
3.5mm TRS audio jack with integrated mini TOSLINK optical receiver - Page 1
Forum section: electronics / projects

author: Sparky
author_rank: Frequent Contributor
timestamp: July 15, 2024, 07:08:09 pm
content: Hello enthusiasts!I'm trying to identify a3.5mm TRS (stereo) audio jack that also accepts mini TOSLINK plugs. Its a receptacle that combines analog and digital audio inputs -- obviously only one at a time.See photos attached of an actual part. I've been unable to identify a part numberObservations:- The black section appears to be a standard 3.5mm TRS audio jack. I believe there is an integrated switch so the accompanying circuit can distinguish between a mini TOSLINK plug or standard analog plug.- The pink section is the optical receiver (not transmitter). It apperas to be an optional "clip on" to the main body of the receptacle so that the analog jack can be used by itself, or with the optical receiver (factory fitted option probably).Something similar I've found on DigiKey is astereo jack with LED built in.Instead of light emitting diode there must be the version with a photodiode instead.Is anyone familiar with the part attached or could help identify?Thank you! Have a great week!

author: wasedadoc
author_rank: Super Contributor
timestamp: July 15, 2024, 08:44:01 pm
content: Such sockets were quite common on higher end portable MiniDisc recorders.

author: Sparky
author_rank: Frequent Contributor
timestamp: July 15, 2024, 08:59:55 pm
content: Quote from: wasedadoc on July 15, 2024, 08:44:01 pmInteresting -- I did not know that. This device is much more recent (2018), and I'm aware that some computers used the combined analog/digital output. There are many cables that convert the normal size TOSLINK to mini TOSLINK, e.g.from Monopricewhere they write:QuoteMini TOSLINK adapters and cables seem readily available, but I cannot find any manufactuer of the jack

author: Niklas
author_rank: Frequent Contributor
timestamp: July 15, 2024, 09:11:00 pm
content: The pinout is not a 100% match, but Cliff has both a transmitter and a receiver in similar packages.https://www.cliffuk.co.uk/products/optical/opticaljacks.htm

author: Sparky
author_rank: Frequent Contributor
timestamp: July 15, 2024, 09:32:58 pm
content: Quote from: Niklas on July 15, 2024, 09:11:00 pmAmazing! Thank you! The "ORJ-4 Single optical receiver jack. Low profile, right-angle PCB mount." seems like just the thing I'm looking for!Hopefully from this I can find alternative options. I don't mind the pin out/package is not a 100% match as I'm designing from scratch.
3.7V BLDC Driver - Page 1
Forum section: electronics / projects

author: i_am_fubar
author_rank: Regular Contributor
timestamp: March 09, 2020, 01:29:33 pm
content: I've made a few BLDC motor drivers before using off the shelf MOSFET drive IC's. Usually around 12v.I have a new requirement to make one that runs from a single Lithium cell (3.7v) At about 5A (10A peak I imagine).Does anyone know of any gate drive ICs that run at this voltage? Are there any other options I should/could consider?And no, I can't buy one pre-made. Need to package it with a load of other circuitry and put a load of motion control stuff in.Cheers,Fubar
3-Electrode sensor potentiostatic circuitry - Page 1
Forum section: electronics / projects

author: timkoers
author_rank: Contributor
timestamp: February 19, 2021, 09:21:28 am
content: I'm designing a circuit to read out the C2H4-CA10 sensor (datasheethttp://www.membrapor.ch/sheet/Ethene-Gas-Sensor-C2H4-CA-10.pdf).Following the typical applications document (https://www.membrapor.ch/sheet/Application_Note_MEM1.pdf)I designed the following:To verify the schematic, I created a new TINA simulation:When probing VM1, I get a output value of 999,952953mV with IG1 @ 350nA (which equals the starting current for the sensor.)When the sensor is at 10ppm, the current value should be 1550nA, and the voltage over VM1 rises to 1,000000V.I've got a few questions.Do both OP1 and OP2 need to have a power supply connected? It's not part of the schematic in the MEM1 document.If yes, how do I need to connect them? I've searched around on Google and didn't find a single potentiostatic circuit with an external power supply connected.If I remove the power supply from OP2, the output value drops to 20uV, so I suppose OP2 does need it.Why is the output voltage limited to 1V@1550nA? I connected it to a 5V supply.When realising the circuit once the design process has been completed, I want to make Rgain disconnectable from C2 to allow for better tweaking, is the circuitry affected if I use two headers with jumpers to connect/disconnect Rgain?EDIT:I just noticed that changing the simulation to the schematic listed below, generates an output voltage which complies to I = Isensor * RgainOP1 and OP2 both receive a supply voltage of -1V at it's negative pin and 1V at it's positive pin
3 PH PWM BLDC Motor Control Board - Page 1
Forum section: electronics / projects

author: TBone1946
author_rank: Newbie
timestamp: July 12, 2023, 06:29:14 pm
content: I originally posted this request earlier today. When I went back to look at the attachment I found that it was not as I had intended. So I am resubmitting this same request with the proper attachment.I have the above mentioned board that is shown in the attachment. (3PH PWM BLDC Motor Controller 2.jpg) It is made to drive a 24 volt DC three phase bldc motor. The power terminals are noted. (POW) I have a 24 volt DC supply. There are 5 control terminals for the controller. (Blue terminal block) The added lines on the board show the second layer connections that are made on the bottom of the board. I see the connections that are made to the ATMEL ATF16V8CZ. The controller drives the motor from a slow speed to a top speed in both the forward and the reverse directions. I assume that a PWM signal is used on one of the two terminals leading to the ATMEL but I am not sure which one and I do not know how the direction determined? Any help is greatly appriciated. The project is to use the worm gear driven motor for a miniture elevator. Thank you in advance for any advice.

author: DavidAlfa
author_rank: Super Contributor
timestamp: July 12, 2023, 07:10:54 pm
content: Probably one the pins by setting it high or low.The ATF16V8CZ is programable logic so there's no easy way to figure out how it works.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 15, 2023, 11:32:52 pm
content: The ATF16V8 is programmable, but it is simple and you can work backwards.The CLK is always on Pin1, which strangely seems firmly +5V connected here, so that leaves a ROM/Table usage.eg with 4 lines, they may have a 3 bit lookup for 6 driving phases and a PWM modulate, which should be easy to decode with just 5V applied and a 4 bit binary switch & multimeter.
3 Phase 4 wire Wye system, Fluke iFlex current probes - Page 1
Forum section: electronics / projects

author: mpauster
author_rank: Newbie
timestamp: July 22, 2025, 10:15:54 pm
content: HelloNew to the Forum. Thanks to those who contribute. There is a wealth of knowledge here!I own an Electrical Testing Company which performs Surveys/Tests on electrical/mechanical equipment in Industrial Processes.I recently purchased a broken/for-parts-only Fluke 1735 and managed to buy parts for the 1735 to make it operable. I do this often since early stage of the business and can't always afford new equipment.The 1735 has a 7-pin plug input for the ammeter probes. I also purchased 4 used Fluke iFlex 2500 probes. I will cut-off the molded special Fluke connectors and wire each probe (twisted pair with bare ground) into a terminal box which will connect to the 1735.pic 1- voltage and amp-probe input pin connectors (amp probe 7-pin on right)pic 2 - PCB with internal connector for amp probes (7 wires)pic 3 - PCB with circuitry going to to only 6 pins (I think)So the question/request is wiring the 4 probes(3 phase 4 wire config) to the 6 or 7 pin outs.4 probes with a common excitation wire and independent signal wires equals 5 wires. The 6th and/or 7th pin is not clear to me.Any insight/help appreciated

author: Poroit
author_rank: Frequent Contributor
timestamp: July 23, 2025, 07:30:30 am
content: G'day mpauster,Your pics were not attached.The attached shows the Voltage and 7 pin Current Probe Connector.

author: mpauster
author_rank: Newbie
timestamp: July 23, 2025, 12:11:35 pm
content: thanks Poroitpics addedregards

author: Poroit
author_rank: Frequent Contributor
timestamp: July 24, 2025, 09:07:08 am
content: I suggest you research Rigowski Current Sensing and see if assists you with indentifying the connector pinout.https://www.powerelectronictips.com/options-current-sensing-part-2/

author: mpauster
author_rank: Newbie
timestamp: July 26, 2025, 04:35:44 am
content: Thanks PoroitI started researching. I think you're dead-on regarding Rogowski Coil.Thank You!
3 phase AC to DC Buck converter  - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: January 18, 2024, 10:57:33 am
content: Hi folks,I want to build a big battery charger with an output voltage of 50-60V and a working current of 50-100A3 phase 230V AC is available and I can get off with having one output terminal referenced to the N terminal.So I was thinking about halfwave rectification followed by a simple buck stage.It seems to me that it will be better to avoid bulk capacitors at the input side and just follow the voltage.At this power level, it will be probably reasonable to have the buck stage as multiple phases. But then is here the question if it is better to treat it as 3 separate buck converters fed by separate half wave rectifiers or to combine rectified mains to bus and fed bucks stages from this.With a combined bus, I will get a nice 120-320V feed voltage, can have just a small filtrating capacitor, and all buck phases are utilized all the time (plus can have any number of them). So this option seems better to me.Separated phases can have a little higher power factor, but probably not that much, and will be utilized just 40% of the time with high peaks, so it will probably decrease efficiency.The main goal is to reach the maximum possible efficiency without going crazy complex with something like an LLC and complicated active mains rectifiers. And this setup will probably be unbeatable even without much optimization as there are basically just two semiconductors in the path from mains to output.As for safety concerns, there will be a contactor at the output (closed only when the battery is detected and charging is active)and probably a crowbar circuit (even when the battery practically unlimited current sink). This with fast fuses shall be safe enough for my requirements.It will use a digital controller based on one of my commercial designs.Did any of you build something similar?
3 phase matrix - Page 1
Forum section: electronics / projects

author: midasgossye
author_rank: Contributor
timestamp: April 29, 2013, 06:20:12 pm
content: Can anyone help me with the following problem please?Recently, I took an old external CD player apart. I hacked the draw opening system and hooked it up to an arduino with a motorshield.Also I wanted to control the "spindle". The motor that spins the CD.After some research I discovered it was a small 3 phase motor.The chip that was driving this used a 3 phase matrix. Chip N° BD7902FS (datasheet in attachment)I don't know what that means.Is it possible to drive this kind of motor with an arduino?Greetings,Midas

author: Caleb_P
author_rank: Newbie
timestamp: May 01, 2013, 07:32:26 pm
content: Hi Midas,The chip in question is a purpose built chip for CD/DVD players and can control every motor one would use.On the second page of the datasheet there is an application circuit. If your CD player is built similar to this application circuit you may be able to access the control logic to power up the CD spindle. Try cutting the trace leading to pin 24 and add a wire from your arduino. You may be able to toggle that pin and it get it to spin. If that doesn't work pins 22 and 23 may need to be accessed as well as they perform some kind of standby/break operation.Can you find some application notes on the chip? The datasheet you linked is more of a product advertisement.Cheers,Caleb
3-Phase Motor Controller - Page 1
Forum section: electronics / projects

author: Nkrause
author_rank: Newbie
timestamp: February 07, 2022, 03:30:29 am
content: Hello, I'm a recent EE graduate (August of 2021) and I've been working on a hobby project on evenings and weekends to improve my skills. The project is a 3-phase motor controller for a turbopump, I've designed and laid out my own PCBs before but nothing of this complexity and I was hoping to get some coaching and mentorship. It's a 4-layer PCB and I can try attaching the KiCad files for anyone who wants to take a closer look. I have a number of questions as well.1. Is there a rule of thumb for controlling trace size given the power running through them? I've made the traces going out to the motor much bigger, but I have 5V, 15V and then motor power traces all running on this thing, and I haven't changed either the 5V and 15V traces2. For a 4-layer PCB I've made one of my planes the ground plane, and was planning on making the second some sort of power plane. I assume I should make it the power plane for the power traces supplying the motor, is this correct?3. Is it generally acceptable to put component labels inside the outline of a component? I'm having trouble getting all the labels to be visible.4. How do I size vias for different trace sizes, so far I've just been using the default settings in KiCad, but that clearly won't work for my thickened high power traces5. Any general constructive criticism about the layout of the board and the traces would be much appreciated!
3 phase motor drive for low voltage high current (not a hobby esc) - Page 1
Forum section: electronics / projects

author: qwaarjet
author_rank: Regular Contributor
timestamp: March 05, 2015, 02:51:28 pm
content: I'm looking for a 3 phase drive that can operate in open loop or use feedback like back EMF or encoder or both preferably. This need to drive bldc motor from a quadcopter for a bench experiment for a school lab so low voltage but fairly high current. I don't want just a regular ESC because I cant control the feedback parameters but most VFDs require a encoder and cant be run open loop. Building a custom solution is an option but I would rather not it there is commercial product that could be used. Anybody got an idea?

author: Seekonk
author_rank: Super Contributor
timestamp: March 05, 2015, 02:58:17 pm
content: Hobbyking has plenty cheap.

author: qwaarjet
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:20:46 pm
content: I can't control the feedback on a regular hobby drive almost all of them use back emf for feedback. I want one that can run true open loop

author: eneuro
author_rank: Super Contributor
timestamp: March 05, 2015, 05:37:46 pm
content: This interesting sensorless BLDC driving TI technologyInstaSPIN™-BLDC, however not sure if HobbyKing has already something which implements this.There is quite nice introduction - maybe something more than kits are commercially available?Definitelly will put my hands on this technology after a few other projects are finished, while need drive a few BLDCs in another projects and it could be nice use cheaper BLDC motors without Hall sensors

author: mazurov
author_rank: Frequent Contributor
timestamp: March 05, 2015, 10:09:28 pm
content: Quote from: qwaarjet on March 05, 2015, 03:20:46 pmIf you attempt to run BLDC open loop you'll get a stepper with very large step. Any hobby ESC runs open loop at startup with characteristic jerking motion of the rotor. You can rotate a BLDC like that with 3 switches by energizing 2 windings at a time in a certain sequence. I made a controller once using Allegro A4960 (http://www.circuitsathome.com/diy-2/advanced-brushless-dc-motor-controller); if you screw up the settings of the chip you will get open loop.
3 phase motor hall effect sensor - Page 1
Forum section: electronics / projects

author: thefamilyman
author_rank: Regular Contributor
timestamp: February 04, 2016, 02:33:53 am
content: Good afternoon gents.I've got bit of a question about rotation encoding for a PM generator.I have a 3 phase to DC converter that also is a VFD drive that will be used to start the small diesel motor using the PM generator as a motor.the problem i have is that the controller needs a 3 phase hall effect sensor to detect rotation and speed which my PMG does not have.Could i use a novel and reliable way to use the 3 phase AC out of the PM generator in place of a 3 phase hall effect sensor?

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 04, 2016, 02:51:41 am
content: I know it has been done, even commercially, but I don't know how to do it

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: February 04, 2016, 03:04:00 am
content: I'm not sure what you're asking exactly, but it sounds like you want "sensorless" sensing, this is done in low-cost RC stuff, it's part of the controller using the un-energized winding for feedback, but the motor needs to be running for it to work.Therefore the controller doesn't know which way the motor will spin on power up; this can be dangerous if you can't tolerate a powerful kick in the wrong direction on power up.

author: pmbrunelle
author_rank: Regular Contributor
timestamp: February 04, 2016, 03:35:09 am
content: I have used the Timken M15 stuff here:https://www.anaheimautomation.com/marketing/encoder/rotary-encoders.phpIf you can get one to fit (endplay spec is not too good, bore size means that you'll likely need access to the end of the shaft) then it would be pretty inexpensive.Comes with the three UVW Hall open-collector outputs... pretty idiotproof.You may need to play with the clocking of the magnet disk and/or PCB to get the right phasing between the rotor and the magnet disk.Sensorless is interesting, but I think it would have to be built into the drive from the design stage, not added on after.
3 Phase power calculation for backup generator - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: November 12, 2020, 05:24:41 pm
content: I've never had to learn how to calculate the power of a 3 Phase machine until now.Is it the same as single phase 220 V but just multiplied by three? Not sure if I should use the neutral to line (220V) or line to line (400V) voltage for the power calculation.Any clarification would be great as I need to purchase a diesel generator to run my 3 phase machines in my new shop and need to know how to size it up in terms of KVA.I've estimated that I would need a maximum of 50 A on each phase to run my shop at full capacity so would that mean 33 KVA unit would be enough or do I need a 60 KVA generator?

author: ejeffrey
author_rank: Super Contributor
timestamp: November 12, 2020, 06:52:02 pm
content: Take the power of the three phases independently measured line-to-neutral. However for true power (vs apparent / kVA) the phase angle can be more compilated than a single phase system.For instance, if you have a resistive load in a single phase system the load is in phase and power factor is 1. For a resistive load connected line-to-line, the current will be in phase with the line-to-line voltage but not the line-to-neutral.Example: you have a 20 amp resistive load connected phase to phase:Apparent power = 20 A * 220 V * 2 = 8.8 kVA (the '2' is because you have 20 amp on each of two phases)Real power method 1: 20 A * 220 V * 2 * cos(30) = = 8.8 kVA * cos(30) = 7.6 kWReal power method 2: 20 A * 380 V = 7.6 kWIn "real power method 1", the cos(30) comes because the current waveform is 30 degrees ahead of one phase-to-neutral voltage and 30 degrees behind the other.Now lets say you put identical 20 amp loads on the other phases. Now, the real power is 3*7.6 kW = 22.8 kW. However, because the currents through each load are not in phase with each other, they don't add exactly and instead of 40 A phase current you get around 35, leading to a total apparent power of 22.8 kVA -- unity power factor.You need a 33 kVA generator.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: November 12, 2020, 08:06:52 pm
content: Quote from: ejeffrey on November 12, 2020, 06:52:02 pmThanks for the clear explanation. Makes sense now that I think about it
3 phase to DC regulator SCR vs Bridge with buck stage - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 17, 2021, 07:56:48 pm
content: Hi just wonder what is a better solution those days.I need moderate power 2-4kW with about half the voltage sux pulse rectifier give me.Is there any reason to use SCR with plenty of low speed switching noise and terrible waveform? When is available (hopes so) IGBTs and SiC for small buck stage with easy to filter ripple.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 17, 2021, 08:19:07 pm
content: I mean if you need something simple and done, SCRs probably aren't a bad idea still. The electronics can even be fairly compact... save for the stonking huge choke you need after it.If you need anything at all -- compact  size, PFC, higher efficiency, faster load response -- it's got to be a modern-conventional design, some combination of PFC and buck or inverter stage.Tim

author: trobbins
author_rank: Frequent Contributor
timestamp: July 18, 2021, 12:28:42 pm
content: Miyuki, you haven't identified why the waveform is a concern? It sound like you have an existing SCR regulator that provides a DCV level that is half the what a simple diode bridge would provide - if so then is that regulator not performing properly?
3-pin Power Supervisors - Suggestions? - Page 1
Forum section: electronics / projects

author: Benta
author_rank: Super Contributor
timestamp: August 30, 2022, 10:59:02 pm
content: Hi, I've run into an issue.I like the MC34064/34164 supervisors, but am unable to find SPICE models for them.This set me on a wild goose chase for other devices: TL7757 (TI), LM809 (TI et al), MIC120/130 etc., but no joy.I need a reset trigger at around 4.5 V and an operating voltage of at least 6.5 V. Current consumption is not a big issue, neither is precision.Can someone please either:1: point me to a SPICE model for the MC34064, or2: suggest a part that can do the above and is supported with a SPICE model?Thanks in advance.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 31, 2022, 05:04:38 pm
content: I'm thinking there are a few ref+comparator ics out there. eg MAX40000 which does have a model.

author: Benta
author_rank: Super Contributor
timestamp: August 31, 2022, 06:32:23 pm
content: Solved, found the LM809 from TI. Very nice part.Thanks.
3 pin TO220 "house numbered" semi's by Texas Instruments" -- help needed - Page 1
Forum section: electronics / projects

author: rodd
author_rank: Regular Contributor
timestamp: March 19, 2017, 08:39:06 pm
content: Hi folks,I am not sure if this is the correct place to post this question but here it goes:I bought a lot of TO220 parts and while classifying them I came across a lot of "house numbered" 3 pin parts.I tried to figure out the device type using the Atlas PEAK DCA55 (transistors, FETS, etc) and the SCR100 (SCRs and TRIACs) but unfortunately they showed up as no device connected.In my experience, the Atlas components testers usually identify 90% of the 3 pin devices I have tried so far.Any suggestions?ThanksRoger

author: rodd
author_rank: Regular Contributor
timestamp: March 19, 2017, 09:37:26 pm
content: Hi,thank you for the replies.These two component testers are capable of identify transistors, FET's and double diodes.I have used them in the past with very good results.They will NOT id voltage regulators, though.I checked this possibility with a variable DC power supply and a DMM.If I assume the pinout of a 78xx positive regulator, the output follow the input than drops to zero than goes up again.When I try the 79XX pinout the input current is very high (probably a forward biased diode).I could not figure out which 3 pin semiconductor would have this "signature curve".Ideas?

author: SeanB
author_rank: Super Contributor
timestamp: March 20, 2017, 04:53:32 pm
content: Have you tried connecting them as LM317, they might be that. Otherwise try the $20 component tester, it generally will show up voltage regulators, or at least use a DMM and diode test for all combinations of pins.
3 state me memory cell - Page 1
Forum section: electronics / projects

author: DestinySpork
author_rank: Newbie
timestamp: May 16, 2015, 09:01:51 pm
content: Could someone help with circuit design? What I need is a circuit that will toggle the state of 3 leds with 3 pushbutton switches. If it can be designed with cheap and common components it would be even betterI know i t seems like a pretty simple thing, but help would be greatly appreciated.The attached is what I have for switching 2 outputs, which will hopefully show what functionality I'm looking for as well as componentry

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2015, 09:46:52 pm
content: Is this the sort of thing you're after?https://www.eevblog.com/forum/projects/discrete-logic-design-vs-a-super-cheap-micro/msg624939/#msg624939Obviously you need to add some series resistors and LEDs.

author: Rerouter
author_rank: Super Contributor
timestamp: May 16, 2015, 10:13:14 pm
content: or if you want it in descrete components, here you go,each cell has1x NPN transistor1x PNP transistor3 1K resistors1 switch to ground1 dioden-1 diodes, where n is the number of memory cells,1 led,This design is fairly immune to transistor gain variances,

author: Someone
author_rank: Super Contributor
timestamp: May 16, 2015, 11:25:03 pm
content: Quote from: DestinySpork on May 16, 2015, 09:01:51 pmQuote from: Hero999 on May 16, 2015, 09:46:52 pmThe 3 way solution I showed in that thread uses the same design pattern as the original here, adding ORing diodes to extend it. You could even use some of the ORing diodes as the indicators here saving a few more components.

author: DestinySpork
author_rank: Newbie
timestamp: May 17, 2015, 12:44:07 pm
content: Thanks everyone for your contributionI will use rerouters design as it uses nice discreet components which I already have
3 to 8 Decoder with both I2C and TTL control - Page 1
Forum section: electronics / projects

author: Sariel
author_rank: Regular Contributor
timestamp: February 23, 2024, 08:53:31 am
content: Hello,I am looking for an IC that allows to decode (I/O expender) 3 to 8 bits.There are several devices as this with I2C interface such as PCF8575.But I am looking for a device, that has I2C interface and also an option to configure the 8 output bits manually usuing TTL or pullup/pull down resistors on 3 input bits.Are there any such devices ICs?

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2024, 09:07:53 am
content: Why would there be? The assumption ever since Philips came up with I2C is that there is a MCU or CPU 'in the loop' to handle configuration, so if it *is* possible to configure an I2C device to power up standalone in a particular selectable state, that configuration will be done over I2C .If you *need* that functionality, you are probably going to have to roll your own I2C slave on a MCU or FPGA with enough I/O pins to let you have 'override' inputs.

author: mikerj
author_rank: Super Contributor
timestamp: February 23, 2024, 09:15:42 am
content: Quote from: Sariel on February 23, 2024, 08:53:31 amA 3 to 8 line decoder (e.g. 74LS138) will not allow you to configure 8 output pins separately, a 3 bit code only permits selecting one of 8 possible pins at a time. This would be an extremely unusual requirement, I don't think you'll find anything off the shelf. You could create this function with a bus expander, a separate 3-8 decoder and some selection logic to tri-state the decoder when not used.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 23, 2024, 02:49:45 pm
content: Time to roll a small MCU. Code an I2C slave, add the combinatorial logic. I’m doing about the same, as I run out Holtek LED drivers, and a small MCU to replace it.
3 Transistor latch with 2 inputs - How can this be done in logic? - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: May 26, 2021, 08:58:20 am
content: The requirement is that 'reset' latches power ON only if /ENABLE is low, but if /ENABLE goes high, the latch resets.I am unsure how to do this in logic in a way that works for sure at turn-on. I think an RS latch could start in either state. I do not want timers etc to cover startup.Below (which looks to have too many resistors), /ENABLE = low turns Q2 on. So Q2 is part of an 'AND' action.If Q2 is on, thenresetcan activate the latch.If /ENABLE returns high, this 'pulls the plug' on the latch.(A) /ENABLE falls during reset = 1: Latch --> 1(B) /ENABLE rises: Latch --> 0 (despite reset=1). That is "/ENABLE overrides reset".(C) Reset rises during (/ENABLE = 0): Latch --> 1(D) /ENABLE rises: Latch --> 0

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 26, 2021, 11:39:18 am
content: So, RS with a power-on state, and presumably, ENABLE dominant?Power-on reset is often done with an RC network.Tim

author: 741
author_rank: Frequent Contributor
timestamp: May 26, 2021, 12:40:07 pm
content: Yes - I'd like to avoid that RC really.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 26, 2021, 02:54:22 pm
content: An analog RS can be made unbalanced, so that it preferentially starts in one state. Strictly in digital synthesis, I don't know that you can do anything without a timer (or a reset generator, which uses, guess what), or abuse of the underlying (analog as above) technology.Possibly something can be done like an edge-triggered reset, where the "clock" is the supply itself; but the edge is in relation to previous history -- state, i.e. whether the signal was previously a stable level or something. I'm not sure that that state would be meaningful during startup (it just reduces to the above problem?), or that it would be reliable in the presence of non-monotonic voltage (a momentary dip might be misinterpreted as another clock cycle?), or that it wouldn't simply be another analog hack (e.g. a level comparator -- again, another kind of reset generator).Do you have any particular reason to avoid the traditional solution?Tim

author: 741
author_rank: Frequent Contributor
timestamp: May 26, 2021, 04:32:41 pm
content: Thanks for thinking about it, because I wondered if I had missed something obvious.I prefer the transistors because I'm a bit wary of RC reliability, and - passing the logical buck - I recall a comment in H&H that they tended to avoid monostables.So basically a feeling that the transistor design - in spite of extra parts maybe - can be made to work more reliably.I could be so wrong
3 Voltmeter method for measuring small power consumption - Page 1
Forum section: electronics / projects

author: nightfire
author_rank: Frequent Contributor
timestamp: December 31, 2022, 08:07:24 pm
content: In continuation of the thought already discussed inhttps://www.eevblog.com/forum/projects/measuring-ac-low-power-consumption-with-multimeteroscilloscope-combo/msg4530914/#msg4530914,I have done some research and realized that there are better ways of getting to the desired result.I did some homework on the "3 Voltmeter method", as described herehttps://www.giangrandi.org/electronics/cosphi/cosphi.shtmlAlso some teachbooks for university describe this method.Question here: Does anyone has experience with this setup and the achievable accuracy of the measurements? Especially when mentioned that this method is not as precise as of that of an oscilloscope with proper equipment attached? Or does this refer solely to the measurement of the Power Factor/cosPhi?My take would be something like this at the example of a small LED lightbulb:Adapter build with a E27 socket and some 4mm jacks to accommodate for the meters.Usage of good quality DMMs with TruRMS (because of the expectation that LED bulbs have non-sinusodial backfeed)DMMs have an ACV accuracy of say 0.5% or so.Before measuring the setup, I would qualify via a Oscilloscope (have some entry level Rigol 1102Z-E available) that in operation the waveforms (which I would expect to be some distorted sine wave) are constant and consistent after some warm-up timespan.I would put/detach the DMMs to that circuit and look for changes to the waveform to check for effects of the attached DMMs due to their internal resistance if it makes some difference to the behaviour of that circuit.My calculation is like: 230V-235V gets delivered to my apartment to the power strip I would use for attaching my DUT including adapter. In the german standards a voltage drop of 10% should be acceptable, so I would assume that I can safely produce a voltage drop over the needed resistor of up to 10 Volts in order to get some values in a range with the best accuracy of my meter(s).In the example of a 7W Osram Ledvance Parathom bulb, it is stated that there is a 7W nominal consumption, 52mA current, 6.3A inrush current, and "Netzleistungsfaktor λ (cosPhi)" of >0.5Including starting time of <0.5sMy calculation so far: i would use a metal resistor of 47 ohms, 0.6w and therefore get.47 Ohms*0.052 A= 2.44V voltage drop over the resistor to get some good signal ratio (or adjusted to get into the best range for the multimeter that measures the drop)Verification of signals that size should also impose no problems to a scope.Power dissipation should be around 126mW in this scenario, so no problem with this 0.6W resistor.I would then expect something like this:U1=mains voltageU2=voltage drop over resistorU3=voltage drop over lightbulbI2=current over resistorcosPhi=(U1²-U2²-U3²)/(2*U2*U3)andI=U2/RP=U3*I*cosPhiComments?
300mhz opamp gain control? - Page 1
Forum section: electronics / projects

author: BiOzZ
author_rank: Regular Contributor
timestamp: February 21, 2014, 06:57:40 pm
content: I'm using 3 THS4211 1ghz opamps with 10 gain each and they will pass 300mhz but i want the final stage to be able to be unity gain or 10x ... whats the best way to go about doing this? i was thinking either a RF relay across the output and negative feedback BUT there will be 1k parallel impedance to groundOR having a transistor interrupt the ground of the 1K resistor (a 1k and 9.9k pair achieve the 10x gain) but this will cause 99k series impedanceboth work in theory but im curious if there are any effects i should be looking out for by doing any of this?thanks in advance!

author: Bored@Work
author_rank: Super Contributor
timestamp: February 21, 2014, 07:58:03 pm
content: Well, at 300 mHz you can get out of the car, walk near the waveform and bend it into shape with your bare hands.

author: w2aew
author_rank: Super Contributor
timestamp: February 21, 2014, 08:42:21 pm
content: Quote from: BiOzZ on February 21, 2014, 06:57:40 pmAssuming that you really mean 300MHz, not 300mHz, then you have a problem. This op amp has a 1GHz gain-BW product - it will NOT have enough BW for your 300MHz signal with a gain of 10x. Take a look at page 4 of the datasheet. It shows a typical small signal bandwidth of 35MHz when using a gain of 10 and power output of -16dBm. Check out the small signal frequency response curves, figure 2, on page 10.http://www.ti.com/lit/ds/symlink/ths4211.pdf

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 22, 2014, 06:10:31 am
content: one candidate probably THS4021

author: nctnico
author_rank: Super Contributor
timestamp: February 22, 2014, 06:11:10 pm
content: Always amplify 10x and attenuate with resistors and a relay. Besides that most small signal relays work nicely at several hundred MHz. No need for a fancy RF relay.