hybridfree/eevblog-posts huggingface dataset:
!HELP! Altuim Designer PCB Layout - Page 1
Forum section: electronics / beginners

author: YaSaRa_N
author_rank: Contributor
timestamp: July 17, 2019, 04:12:23 am
content: Hi!I am designing a Micro-mouse robot as a hobby project. I did the schematic using the EasyEDA online editor. that is because i can directly chose parts from LCSC.(I use LCSC because of the lowest shipping rates). however, after creating the schismatic using EasyEDA, I convert it to a PCB and then exported it as a Altium PCB ducument(.pcbdoc) to do the routing.Once I opened the file from Altium it works fine except for that there is a white box around each component. (as shown in the attached image. it only appears once i selected the component)it seems to be a clearance thing. as in the image 1 , I cannot move R48 or R50 closer to the SW5. when the components are in either horizontaly or verticly, this white box is basically the package outline and its ok.but when i rotate a component, it becomes bigger. How can i get rid of this ? i am using AD19.Thank uou.

author: YaSaRa_N
author_rank: Contributor
timestamp: July 17, 2019, 06:02:24 am
content: Quote from: blueskull on July 17, 2019, 04:14:43 amI disabled the component clearance rule but no luck.At the very beginning of the layout i was able to place the components such that the white box overlaps. but now i cannot.So it must be a setting that i changed ?

author: YaSaRa_N
author_rank: Contributor
timestamp: July 17, 2019, 04:11:18 pm
content: Quote from: blueskull on July 17, 2019, 06:10:25 amI tried that. no luck.however I installed AD18 and it seems to be working fine. I think it might be a bug in AD19. anyway problem solved. Thanks for the replies.now i can place components anywhere i want. even on top of another

author: Dave
author_rank: Super Contributor
timestamp: July 18, 2019, 04:56:23 am
content: If you want clearance rules to work correctly in Altium, you need to have 3D models embedded in the footprints. Otherwise it does what you've noticed: draw stupid rectangles around the footprint and claims everything is colliding. This often isn't a problem if all components are horizontal or vertical, but it's absolutely useless at any other rotation angle.
[ BJT amplifier circuit, v_be negative ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: March 04, 2012, 04:17:39 pm
content: Hi,I am learning about BJT transistor and I understand them quite well know... I guesseduntil I saw the following simple circuit:http://www.reconnsworld.com/audio_simplepreamp.htmlWhat I do not understand: passed the first AC coupling capacitor, the voltage can benegative. Usually, the transistor is base voltage biased in such a way there is an offsetso that negative voltages are not an issue. But in this schema, there is no offset. I builtit, and it works: I get some Vbe < 0 and get a correct Vc with no clipping...How is it possible, can someone explain to me what I am missing? I guess there issomething with a current involved from Vcc to C1 as the voltage accross C1 becomes< 0, and that it acts as the Vbe offset I do not see... but not clear at all to me.Thanks!Best regards,texane.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: March 04, 2012, 05:40:10 pm
content: HiTake out of circuit C1, and check, if then, you have around 0,6 Volts VBE, if not, or you have a faulty transistor, faulty R3/R2, or wiring error...

author: texane
author_rank: Regular Contributor
timestamp: March 04, 2012, 05:51:04 pm
content: Thanks for answering.I think I found my mistake... I left the oscilloscpoe to AC coupling and obviously was seeing'negative' voltages instead of the real one... for my defense, let say this is an old scopeOf course, having Vbe negative would have clipped the voltage on the other end.Best regards,Fabien.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: March 04, 2012, 05:54:10 pm
content: Happy End!!

author: texane
author_rank: Regular Contributor
timestamp: March 04, 2012, 05:55:57 pm
content: yes, but I spent a lot of time thinking that my understanding of BJT was wrong or incomplete...still a lot to learn by the way

author: Tube_Dude
author_rank: Regular Contributor
timestamp: March 04, 2012, 06:03:33 pm
content: We all (almost all...), learn with our mistakes...
[ comparator with npn transistors ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: January 17, 2010, 08:36:50 am
content: Hi,I am working on a small project forwhich I need to compare a voltageto 2.5v. The compared voltage iscalled Vin. If Vin is more than 2.5,I need a Vout to 5V, otherwise to 0V.I do not want to use a comparator,but transistors for learning purposes.I was thinking about using the avoltage divider so that Vin is scaledfrom [0, 5 volts] to [0, 1.4] thus mycomparing voltage become 0.7v (ie.was 2.5v in [0,5] becomes 0.7v in[0,1.4]) which I plug to an opampwhich is linked to the transistor Basepin.< 0.7v wont switch the transistor ON,otherwise it will. I can replace the opampwith another transistor.Is the basic idea good? Any commentwelcome! I have read relying on theBaseEmitter voltage drop is not a goodthing...Thanks for helping,

author: Unknown
author_rank: Unknown
timestamp: January 17, 2010, 12:12:49 pm
content: You want to use an OpAmp, but not a comperator?I'll tell you a secret. A comperator is an OpAmp, just specially optimised for working as a comperator. So I don't see the learning experience here - replacing a comperator (which is an OpAmp) with an OpAmp, albeit one not specially suited for comparing.

author: texane
author_rank: Regular Contributor
timestamp: January 17, 2010, 02:32:43 pm
content: hi,forget about the opamp, and replace itwith a transistor providing the samevoltage (ie. Ve = Vb - 0.6) but with again in current. My question was aboutrelying upon the drop of 0.6v (0.7v) atVbe.Thanks,f.

author: Zero999
author_rank: Super Contributor
timestamp: January 17, 2010, 05:53:11 pm
content: You'll need several transistors, not just one.Google for 'differential pair' and learn the basics of differential amplifiers which is what goes into op-amps and comparators.Look at the datasheet for a comparator and op-amp IC and base your design on it.Accept, that your circuit will never be as good as an IC because none of the transistors are matched.

author: texane
author_rank: Regular Contributor
timestamp: January 17, 2010, 06:03:59 pm
content: ok, thanks for pointing me to the right direction.Thanks,
[ switching 5v on off with 3.3v command ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: June 09, 2013, 06:18:04 pm
content: Hi,I need to switch on off a 5v source using 3.3v command (ARM MCU GPIOs).The load can draw up to 2A, typically 500mA. In this application, frequency andrising times can be omit (the source is switched on or off by a human).One constraint is that the analog switch must be in serie between the sourceand the load (high side design).I planed to use a P channel MOSFET, but looking at various datasheets showtypical Vgs threshold voltages in [2 - 4]v. 2v is too close, as 5v - 3.3v = 1.7v, andI am looking for a Vgs threshold more in the [3.5 - 4]v range, or some dedicatedIC that specifically fits this purpose ... Have you any reference?Currently, what I do is to use a N channel MOSFET to convert the [0 - 3.3v] to[5v - 0v] and use it to control the second P channel MOSFET. But it makes 2FETs.Thanks for your help!

author: jmole
author_rank: Regular Contributor
timestamp: June 09, 2013, 06:21:03 pm
content: Why not use a low-side switch?

author: c4757p
author_rank: Super Contributor
timestamp: June 09, 2013, 06:22:56 pm
content: Quote from: texane on June 09, 2013, 06:18:04 pmOh no, two FETs!Sounds like a perfectly acceptable solution to me. Why would you rather use a dedicated IC than two cheap-ass FETs?Quote from: jmole on June 09, 2013, 06:21:03 pmI second this, though. Are yousureit has to be high-side?

author: texane
author_rank: Regular Contributor
timestamp: June 09, 2013, 06:34:43 pm
content: Hi,Thanks for your replies.Being high side is a requirement in this circuit. I thought some specializedand low cost ICs did exist for this kind of application, but the 2 FETs solutionis fine too.

author: c4757p
author_rank: Super Contributor
timestamp: June 09, 2013, 06:40:18 pm
content: I'm sure there are specialized ICs for this, but it's hard to beat the price of a little FET. Out of curiosity, why high side?

author: texane
author_rank: Regular Contributor
timestamp: June 09, 2013, 06:54:44 pm
content: This is part of the specs: currents not returning to the ground mustalso be switched off. That is why the switch is high side.

author: David_AVD
author_rank: Super Contributor
timestamp: June 09, 2013, 09:45:26 pm
content: You could also check out some of the "load switch" ICs that are around. Some of them should be in the current range you want.

author: texane
author_rank: Regular Contributor
timestamp: June 10, 2013, 05:43:03 am
content: Thanks for the tip, it helps a lot. The ICs I see all have a voltage drop betweenthe gate and source of max. 0.2V ... it can be an issue.

author: AndyC_772
author_rank: Super Contributor
timestamp: June 10, 2013, 06:07:00 am
content: Is the pin of your MCU 5V tolerant? If so, perhaps you could pull it up to 5V with a resistor, connect it to the gate of your P-FET, and program the pin into open drain mode.

author: texane
author_rank: Regular Contributor
timestamp: June 10, 2013, 06:33:10 am
content: Thanks for the advice. I will have a look at the datasheet to see if GPIOs are 5v tolerants.
[ ttl output to cmos input ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: November 14, 2009, 01:42:03 pm
content: Hi,I am to interface an old TTL based device withthe PIC18f. The device has roughly 20 pins comingfrom TTL based gates I have to read at a given time.I did not know, but reading the PIC18f specs, someof the GPIOs are CMOS Schmitt trigger input buffer indigital IO mode. So I guess I have to translate the level,from TTL to CMOS, because the TTL level may be toolow for the CMOS Schmitt trigger to switch correctly, Iam right?In that case, do you know about a chip doing so?Cheers,Fabien.

author: jimmc
author_rank: Frequent Contributor
timestamp: November 14, 2009, 03:50:02 pm
content: A pull-up resistor from the TTL output to VCCwill ensure that VOHis CMOS compatible.Value is not critical, say 4k7 lower for high speed operation. Minimum value is set by IOLmax of TTL device.For ultimate speed use 74ACT series device (eg 74ACT04 hex inverter) as a level shifter, the ACTseries has TTL compatible input thresholds.Jim

author: texane
author_rank: Regular Contributor
timestamp: November 14, 2009, 05:52:58 pm
content: Hi,Thanks for replying. I do not really care aboutspeed in this application. I did see the trick ofadding a pullup resistor, but I do not understandit... I understand what a pullup resistor is I mean,but could you explain why it raises the voltagein this case? I mean 2 voltages from differentsnodes do not add...Thanks for helping,Fabien.

author: septer012
author_rank: Regular Contributor
timestamp: November 14, 2009, 06:06:20 pm
content: Maybe you need something like this?!http://www.sparkfun.com/commerce/product_info.php?products_id=8745I used one for a 3.3v GPS to 5v PIC/Shmidt Trigger Input

author: texane
author_rank: Regular Contributor
timestamp: November 14, 2009, 07:07:05 pm
content: Thanks, I will have a look. At a first glanceit seems a bit undersized since I would needat least 6 pins, thus an octal buffer converter.Cheers,fabien.

author: jimmc
author_rank: Frequent Contributor
timestamp: November 14, 2009, 07:09:49 pm
content: The standard TTL output stage is the 'Totem pole' shown here:http://www.siliconfareast.com/ttl.htmas you can see that, on its own, the output cannot rise above 2 diode drops below VCC.Adding the pull-up resistor enables the output to rise to VCCwhen the lower transistor (T4) is off.Under these conditions the diode is reverse biased and T3 has no effect.If you're not interested in speed the a higher value resistor may be used for the pull-up, it only has to overcome leakage in the TTL output stage, 22k will still give 4v with almost 50uA of leakage.I am assuming that you are running the PIC from the 5v, the TTL only operates at 5v.A quick Google on 'TTL to CMOS' gives this as one of the top results:http://www.fairchildsemi.com/an/AN/AN-314.pdfJim
[ ucurrent gold 2 amplifiers question ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: May 24, 2014, 12:42:24 pm
content: Hi,I am implementing a current / voltage logger, whose design will be opensourced. The current monitoring part is similar to Dave's ucurrent golddesign. I read the initial article:http://alternatezone.com/electronics/ucurrent/uCurrentArticle.pdfThen, I read the new design here:http://www.eevblog.com/projects/ucurrent/In the new design, there are 2 amplifiers both with a gain of x10instead one with a gain of x100, as it was done in the previousdesign. Can anyone explain the reasons of doing so ?Thanks for helping !Texane.

author: kizzap
author_rank: Unknown
timestamp: May 24, 2014, 01:23:52 pm
content: He did a whole video on this...

author: texane
author_rank: Regular Contributor
timestamp: May 24, 2014, 01:37:36 pm
content: Missed this video, thanks !
[ window voltage comparator ] - Page 1
Forum section: electronics / beginners

author: texane
author_rank: Regular Contributor
timestamp: October 17, 2009, 10:25:42 am
content: Hi,As a beginner, I am reading the following book: practical electronicsfor inventor, from Paul Scherz.For a light sensor project, I need a window voltage comparator. I useone from the above book. I attached the schema.What should happen:Vout is +5v when 2.3v<Vin<2.7vVout is 0v otherwise.However, I get the opposite...:Vout is 0v when 2.3v<Vin<2.7vVout is 5v otherwise.I use a lm339 quad comparator, so that I actually has only onecomparator. I tested the comparator inputs/outputs independentlyto see if it works, and I get right measures. Maybe there is somethingI didnot understand regarding the above schema...Any idea?Thanks for helping,Regards,Fabien.

author: texane
author_rank: Regular Contributor
timestamp: October 17, 2009, 10:40:03 am
content: I think I misunderstood something... the schemaactually works as expected, sorry for posting

author: Simon
author_rank: Unknown
timestamp: October 18, 2009, 08:41:46 pm
content: if you get a similar situation again (thats if it really happens) reverse the inputs on the comparators
(almost) silent micro switches - what brands? - Page 1
Forum section: electronics / beginners

author: arekm
author_rank: Unknown
timestamp: November 09, 2013, 11:02:14 pm
content: Are there any brands of silent (or close to silent) micro switches? The typical ones are very loud and thus aren't good candidates for mouse-like equipment.Micro switch type I'm looking for

author: ConKbot
author_rank: Super Contributor
timestamp: November 10, 2013, 12:12:46 am
content: Those are generally called "Tatctile switches" because they are (almost) silent, just mainly felt when you push the button. Almost any tactile switch you can get from farnell or ebay in that form factor would be near silentMicroswitches on the other hand are louder, though my mouse has microswitches instead of tactile switches, but it does make a nice audible click as you push the button.

author: wraper
author_rank: Unknown
timestamp: November 10, 2013, 12:29:03 am
content: Tact switches like on the picture are very bad idea for "mouse like applicatoans" as they work not so stable as should, have short life and overall feeling while pushing them won't be good. Only right choice is proper microswitches like thosehttp://www.ebay.com/itm/2Pcs-Micro-Switch-OMRON-D2FC-F-7N-10M-For-Mouse-New-/251336866229?pt=LH_DefaultDomain_0&hash=item3a84d839b5

author: arekm
author_rank: Unknown
timestamp: November 10, 2013, 08:24:09 am
content: It needs to be the same type as shown on the photo, so that omron won't fit.Googling for tactile switches then -- found Omron B3F-1002

author: G7PSK
author_rank: Super Contributor
timestamp: November 10, 2013, 09:28:08 am
content: My Hama twister mouse has just died as well due to the use of tact switches but as it was 7 years old I wont hold a grudge against it, the tact switches were not of the usual type either so I could not find replacements. Just ordered anothe wireless mouse meanwhile I have to put up with a rat that I keep just in case.

author: SeanB
author_rank: Super Contributor
timestamp: November 10, 2013, 10:02:56 am
content: Grab those out of an old cheap mouse, you will probably find one that has the right switches if you look through a pile of them in a ewaste pile.

author: wraper
author_rank: Unknown
timestamp: November 10, 2013, 02:45:30 pm
content: Quote from: arekm on November 10, 2013, 08:24:09 amI have some B3F-1050 which are same as B3F-1000 just taller. Seem to be quieter that average. And they are with lowest operating force (0,98N) in B3F series. B3F-1002 is 1.47N however. Take in account that lower force switches have longer life than high force ones. B3F-1000 has 1 000 000 operations durability, while B3F-1002 only 300 000

author: Stonent
author_rank: Super Contributor
timestamp: November 11, 2013, 03:55:27 am
content: I prefer the click. But that's just me. I used to use a Model M keyboard for a little while at one job. I loved it.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: November 12, 2013, 05:32:02 am
content: Anyone knows where I can find this type of switch, but normaly closed. Means, it opens when pressed.
(another) Pulse generator with Si5351  - Page 1
Forum section: electronics / beginners

author: stcoso
author_rank: Regular Contributor
timestamp: February 20, 2020, 11:03:09 am
content: Hi! I'm trying to design a pulse generator.I need adjustable 1-10 ns pulse with adjustable frequency (ideally 10kHz/50MHz).Si5351 has 3/8 clock outputs with adjustable 333ps/step phase offset. So I'm thinking to generate 2 clock signal ( same frequency but out of phase) and feed them into a fast comparator (with reasonable rise/fall) to obtain the pulse that I need.Where am I wrong?

author: radiolistener
author_rank: Super Contributor
timestamp: February 20, 2020, 03:25:33 pm
content: si5351 already has 1 ns rise/fall time. So, there is no need for comparator, you can use it's output directly.

author: stcoso
author_rank: Regular Contributor
timestamp: February 20, 2020, 03:31:50 pm
content: Ok... but it's 1ns 20/80% and that wouldn't allow 1ns pulse width

author: radiolistener
author_rank: Super Contributor
timestamp: February 21, 2020, 09:43:50 am
content: Quote from: stcoso on February 20, 2020, 03:31:50 pm1 ns pulse width is 500 MHz. But you're mention that you're needs 10kHz...50MHz frequency with 1..10 ns rise time. si5351 allows to produce 5 kHz...200 MHz with rise time 1 ns. Which ideally fits your requirements, isn't it?

author: stcoso
author_rank: Regular Contributor
timestamp: February 21, 2020, 12:18:41 pm
content: 1 to 10 ns pulse width. Rise/fall need to be good enough to get 1ns pulse with decent shape (this signal will be fed into a gan driver). For a 1-ns pulse width 1ns rise/fall time are clearly not enough. Also, si5351 has fixed duty cycle and is limited to 200MHz so can't use this directly to generate 1ns pulse width.I'm wondering if there is a clever way to achieve what I need.I could also use a AND gate with the clock signals from the si5351 shifted (starting from 180°) to achieve overlap.
[ARM] Does a USB device need a driver on the Host Microcontroller to get power? - Page 1
Forum section: electronics / beginners

author: robotwizard
author_rank: Newbie
timestamp: January 12, 2018, 06:39:57 pm
content: I've recently transitioned from arduinoes to ARM devices[Noob Alert]. I'm trying to make a maze solving robot - 'micromouse' and I'm trying to use an optical mouse's sensors to track the movement of the robot on the maze floor.So I got this free NXP development board from Hackster - a FRDM-K82F board; This Board has USB support. So I saw the USB demo drivers and they're fairly complicated and add to that my puny knowledge of the USB stack - So I decided I would setup the hardware first; so I'm making a prototype and I connected two optical mice to a USB hub and tried connecting it to the USB port on the microcontroller via a cheap micro USB cable. Before powering the microcontroller up, I read in the documentation that there is a jumper in the FRDM-K82F that is supposed to be 'jumped' to give power to the USB port and allow the board to act as a USB hub. I connected the jumper properly.Now to check if the hardware is working properly, I connected the optical mouse + hub setup to my laptop computer and the laptop is reading both the mice. But when I connect the hub to the microcontroller and power the microcontroller, The light on the USB hub doesn't light up; neither does the light on the optical mouse.So this is my noob question - Does a USB host need to be running driver code for it to supply power to the devices? Or could there be something else wrong with my setup. Will I have to write the driver code before plugging in the optical mouse setup?Also it would be nice if someone could direct me to a nice tutorial other than the documentation on setting up USB devices on NXP or ARM cortex M4 devices.This is the link for the Development Board I have.https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/kinetis-cortex-m-mcus/k-seriesperformancem4/k8x-secure/freedom-development-platform-for-kinetis-k82-k81-and-k80-mcus:FRDM-K82F?&&tab=In-Depth_TabI've also attached the Datasheet for the Board.Please tell me if you need more information. Thanks for your time!

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 12, 2018, 06:45:00 pm
content: As far as I know a USB 1 or 2 (and 3 too?) host should provide up to 500 mA @5v even when/if there's nothing connected to the data+ and data- pins.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 12, 2018, 06:48:04 pm
content: OTOH, it may well be that your mouse won't lit its led until after it has negotiated properly with the host, you know, the enumeration phase and all that jazz.

author: robotwizard
author_rank: Newbie
timestamp: January 12, 2018, 06:49:38 pm
content: Yes that is what I was wondering about.
[ASK] Converting typical Buck switcher into split rail power supply - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: November 13, 2016, 08:28:58 pm
content: Just curious if is it that simple to make a typical Buck switcher to generate positive and negative rails using this method ? Any other considerations ?TIAEdit : Some corrections

author: Paul Price
author_rank: Super Contributor
timestamp: November 14, 2016, 02:51:41 pm
content: No.If the circuit you show is very lightly loaded both the Virtual-Ground and V+ outputs would have about the same output voltage refereced to V-Negative.

author: chris_leyson
author_rank: Super Contributor
timestamp: November 14, 2016, 03:25:16 pm
content: You could also us a single switch in a combined SEPIC and Cuk converter, see Analog Devices app note AN-1106.http://www.analog.com/media/en/technical-documentation/application-notes/AN-1106.pdfAnother option is a "flybuck" converter and wire up the coupled inductor to the negative rail, a word of warning though the rail generated by the coupled inductor has NO short circuit protection.

author: BravoV
author_rank: Super Contributor
timestamp: November 14, 2016, 03:45:48 pm
content: Quote from: Paul Price on November 14, 2016, 02:51:41 pmAre you saying the V-Ground and V+ must be loaded all the time, or both rails V+ "and" V- must be loaded at the same time and all the time ?I got the idea after reading TI's app note ->SLVA369A - Creating a Split-Rail Power Supply With a Wide Input Voltage Buck Regulator, and thinking if I can apply the example like this one below at "other" buck switcher ?

author: BravoV
author_rank: Super Contributor
timestamp: November 14, 2016, 03:47:06 pm
content: Quote from: chris_leyson on November 14, 2016, 03:25:16 pmThanks Chris, never read that b4, noted on the short circuit weakness.
[ASK] Stacking up multiple TVS in series - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: November 03, 2015, 09:20:46 am
content: Currently I have only 5 Volt rated TVS in stock, plan is to protect power mosfet's Vgs (non logic level Vgs@20V max) by using 3 of these 5 volt TVSes connected in series to get up to 15 volt, also its only one off ad hoc project.Will these work ?

author: rs20
author_rank: Super Contributor
timestamp: November 03, 2015, 09:31:17 am
content: Yeah, more or less. Your inaccuracies will be tripled, maybe check that it actually does shunt at the absolute max Vgs. Otherwise a nominal 5V TVS which actually trips at 8V * 3V = 24V Vgs and a dead mosfet. But the reason thatBy contrast, things like gas discharge tubes and trisils cannot be used in series, because the V/I curve is discontinuous so you might end up with weird halfway states. But TVSs just have a nice monotonic VI curve; and putting them in series just triples the voltages.

author: BravoV
author_rank: Super Contributor
timestamp: November 04, 2015, 07:48:26 am
content: rs20, thank you !

author: Kjelt
author_rank: Super Contributor
timestamp: November 04, 2015, 12:44:56 pm
content: Interesting, going to test this soon, saves me also an extra component to order
[Assignment] Need to make the most simple circuit possible - Page 1
Forum section: electronics / beginners

author: UberStrike88
author_rank: Regular Contributor
timestamp: March 09, 2015, 05:33:50 pm
content: Hi,Well I got a assignment today from school and the most simple circuit possible and it should be useful with the part you get.Some got a easy chip like the 7805 and some got something harder. Anyway I got this chip:AZ431-Ahttp://www.diodes.com/datasheets/AZ431A.pdfSo yeah it's a three-terminal adjustable shunt regulatorWell I have no idea it should be easy useful and it needs to be with the least parts you can use.Anyone got any idea?(yes we may ask around on forums)Regards,

author: AndyC_772
author_rank: Super Contributor
timestamp: March 09, 2015, 05:37:43 pm
content: What's wrong with the application circuits in the data sheet?

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 09, 2015, 05:38:44 pm
content: Just look to the datasheet and make the first example. It looks perfect to me. To understand it, as well as thefunctional diagram schematic on page 4 is a perfect training for you.

author: UberStrike88
author_rank: Regular Contributor
timestamp: March 09, 2015, 05:42:18 pm
content: Quote from: JacquesBBB on March 09, 2015, 05:38:44 pmOkay will try to make it although they don't specify what rating the resistors need to be

author: AndyC_772
author_rank: Super Contributor
timestamp: March 09, 2015, 06:08:12 pm
content: No, but you can work that out for yourself. You know what the input voltage, output voltage and reference voltage are. Pick sensible currents, and then you can work out the power dissipation in each component from Ohm's law.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: March 09, 2015, 06:13:55 pm
content: As an exercise, you can demonstrate the formula of the first example : Vout = (1+ R1/R2) Vref. You will see that it does not dependson R3 nor on Vin.If you want to get benefit from this simple example, you will have to determine also the minimum and max values for Vin, and as said by Andy, the required specifications of the resistors.

author: Seekonk
author_rank: Super Contributor
timestamp: March 09, 2015, 06:43:24 pm
content: Love the 431, an op amp and a voltage reference. Voltage detectors,relay driver, time delay, even turn it into an audio amplifier.

author: Refrigerator
author_rank: Super Contributor
timestamp: March 09, 2015, 08:14:19 pm
content: Make the first example circuit and add a darlington transistor and you got yourself a little voltage regulator. Simple as that.

author: AG6QR
author_rank: Frequent Contributor
timestamp: March 09, 2015, 11:51:03 pm
content: Another idea: Add a single transistor, use the current source example from the data sheet, and you've got a constant current LED driver. It can drive an LED with 20mA (or whatever you design it for) over a wide range of input voltages.
[Design] How to drive many "high" current relays and LED out of GPIOs (ESP32) - Page 1
Forum section: electronics / beginners

author: crgarcia
author_rank: Regular Contributor
timestamp: May 01, 2023, 04:37:45 pm
content: Hi,I want to build a panel that has:- 8 push buttons (like this one:https://m.media-amazon.com/images/I/51+XvhFq5FL._SL1100_.jpg)- 8 5V LEDs (in the button, but controlled separately)- 8 relaysI want to control all that with an ESP32.The relays are in a modules,triggered on LOW, similar to this one:Relays:I have some 74HV595 shift register, that I thought I could use to control the relays.My concern is that the relays might get triggered while the microcontroller is booting. To solve that, I was planning to add a transistor to a GPIO to control the relays power supply (JD-VCC) (the PN2222A in the schematics bellow)Leds:I was thinking on adding a ULN2003 in series to the 74HV595, that would allow me to handle more current and voltageMy conceptual design:Since I am a self-tough beginner on electronics (pretty dangerous combination)... What do you think on that design?Is there a better way to make sure the relays are all off while the microcontroller is booting?Thank you!

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 01, 2023, 04:59:37 pm
content: Isn't the ESP32 a 3.3V device? The way you've got Q1 wired means that the relay module would receive less than 2.6V because of Q1's 0.7V Vbe drop...Another way of disabling the relays would be to drive pin 13 (-OE) of U2 high during boot and only shift it low once the data has been clocked into U2 and latched.

author: mishomvp
author_rank: Newbie
timestamp: May 01, 2023, 09:48:39 pm
content: See this schematichttps://kmpelectronics.eu/wp-content/uploads/2019/12/ProDINoESP32-ETHv02-Schematic.pdf

author: Benta
author_rank: Super Contributor
timestamp: May 01, 2023, 10:22:09 pm
content: Place a pull-up resistor on the OE input to the HC595, and a transistor to pull it low when your MCU is ready. Remember a pull-down on the transistor base as well as a series base resistor. A small logic-level MOSFET sould also do the job.
[Dwin Display] Danger: high voltage for ESP32 and others below 5V - Page 1
Forum section: electronics / beginners

author: rtek1000
author_rank: Contributor
timestamp: March 09, 2024, 06:31:50 pm
content: Hello,The DMG80480Y070_02NN display is releasing 5V at output TX2.But Datasheet says: Output Voltage (TXD): 3.2 Typ.I have 2 displays and they are the same.My ESP32 started to stop receiving data from the display.You have to be careful with this equipment without very reliable quality control.If the software has a lot of BUGS, be suspicious of everything.https://github.com/dwinhmi/DWIN_DGUS_HMI/issues/17

author: ozcar
author_rank: Frequent Contributor
timestamp: March 09, 2024, 08:24:01 pm
content: The page of the datasheet you posted there gives no maximum for the TXD high level ("1") output voltage. It also mentions "5V TTL" (or jumper optionally, "RS232", but I don't know why there is then only one set of input and output voltages given).
(entry level) Digital Integrated Circuits Designer - i need your two cents - Page 1
Forum section: electronics / beginners

author: steamedhams
author_rank: Regular Contributor
timestamp: July 14, 2021, 10:30:29 am
content: I am preparing for an interview for a (entry level) Digital Integrated Circuits Designer.The job ad itself was very extensive and i am familiar with the other areas well. However, I am not confident with my knowledge of the areas below.I'd appreciate if people could give their two cents so I can go on a deep dive on these areas based on your inputs. I am worried of any blinds spots before going into the interview.wafer test parametric specificationsI covered Fault models (stuck at, Observability & Controllability..etc) at Uni, but thats about it...CPU architecturesI am aware of x86 and RISCV, are there any other commonly used ones i should know of??DMA managementWhat could this refer to? IP Core to manage memory or something else??

author: rstofer
author_rank: Super Contributor
timestamp: July 14, 2021, 02:48:03 pm
content: Quote from: steamedhams on July 14, 2021, 10:30:29 amThe ARM architecture would be important and knowing how to set up the peripherals to use DMA would be helpful.https://deepbluembedded.com/how-to-receive-uart-serial-data-with-stm32-dma-interrupt-polling/BTW, the STM32xxx ARM chips seems to be very common. These chips are probably a good place to start.https://www.st.com/en/microcontrollers-microprocessors/stm32-32-bit-arm-cortex-mcus.htmlMore fun is the PSOC 6 by Cypress.https://www.cypress.com/products/psoc-6-microcontrollers-32-bit-arm-cortex-m4m0
[Extreme] ESD or EMP? - Page 1
Forum section: electronics / beginners

author: CZroe
author_rank: Contributor
timestamp: March 20, 2019, 12:44:55 pm
content: One month ago we took a direct lightning strike to the house. My brother’s car was parked only a few yards away from the obvious point where the lightning found it’s way to ground but it didn’t have a mark on it so we thought it was fine......It wasn’t.Insurance totaled it.He did have two tires in the grass beside the paved driveway. I doubt that mattered much but, well, my car was parked next to his and it was fine. He didn’t have anywhere to go with his car for a couple days, so we were kinda surprised to discover that it wouldn’t start. Everything lights and bings like it should with the key in there except the indicator for selecting PRND12 doesn’t show and nothing happens when you turn the key. It uses an indicator light behind the transmission selection instead of a physically moving needle. If the system doesn’t know it’s in Park or Neutral then the neutral safety switch will not allow it to start, so I was hoping that’s all it was.Fuses and relays all checked fine. Shop said the computer and starter were bad and that those needed to be replaced before they could even start looking for other issues. It seems that the insurance company has dealt with lightning strikes enough to know that other electrical issues are inevitable and they just decided to total out the car at that point.I don’t know much about vehicle electronics but since I see no evidence of a direct hit, wouldn’t the EMP damage likely be less severe than a typical lightning strike? Think they are just treating it as a lightning strike instead of an EMP? What do you think was more likely wrong with it? Looking for info on EMP and cars mostly leads you to speculative doomsday prepper stuff (nothing useful).More:https://imgur.com/a/w44Mxoz
[fluke 17b+] 400ma fuse blown: fuse is replaced but there is no continuity - Page 1
Forum section: electronics / beginners

author: snailevangelist
author_rank: Newbie
timestamp: May 19, 2023, 12:00:39 am
content: ahoy everyone!please bear with me since i am still new to electronics, but i could use some assistance. recently, i did a thing that i now know i definitely shouldn't do— measuring current in parallel with a circuit instead of in series. the fuse on the 400ma port blew, naturally. i ordered some new fuses, which i have tested and are fine, and replaced the old one. interestingly, when i measure continuity between the com port and the 400ma port, there is still no continuity. i've blown the 10a fuse before and replaced it, but i still get continuity between that path and the com port.does anyone have any suggestions, guides, or means of fixing/fault finding this issue? any help or advice would be really appreciated.thank you!!

author: bdunham7
author_rank: Super Contributor
timestamp: May 19, 2023, 12:21:02 am
content: I've attached a schematic excerpt from a 17B, the 17B+ is likely very similar. As you can see, in any position other than mA, you'll have ~1.1k resistance if you measure from the mA/µA terminal to common. In the mA range, this will be about 1.1R, maybe a bit more. This is presuming you dont use an excessively high test current and the voltage is limited to three diode drops. So to test the mA/µA socket, use the resistance range, not continuity. You can also try measuring a small current to verify that the meter works (or doesn't). If it still appears to be broken, you'll need to take it apart and carefully inspect the PCB for damage. Assuming a correct, original fuse was installed, I'd be surprised if anything else was blown up.

author: mwb1100
author_rank: Frequent Contributor
timestamp: May 19, 2023, 02:25:00 am
content: Quote from: snailevangelist on May 19, 2023, 12:00:39 amMeasure resistance, not continuity. Fromthe 17B+ manual:Quote10 kOhm will not set the continuity buzzer.On the other handQuoteWhich will trigger the buzzer.(edited to link/quote the 17B+ manual instead of the 17B manual)

author: snailevangelist
author_rank: Newbie
timestamp: May 20, 2023, 05:06:36 pm
content: thank you so much for the reply! i will certainly test this out, unfortunately i am out of town for the weekend. when i come back i'll follow your instructions and make another reply.

author: snailevangelist
author_rank: Newbie
timestamp: May 22, 2023, 04:43:52 pm
content: i was finally able to test this out yesterday, and my multimeter (affectionally named "grumbo" lol) is chugging along like a champ. in the process of tearing it down, i screwed up reassembling the wheel and the lcd screen and it took me a hot minute to get the whole thing going. i'm glad everything seems to be okay. thanks for your help everyone!
[HELP] parts or circuit to control 5v rail with min loss - Page 1
Forum section: electronics / beginners

author: allenpan
author_rank: Contributor
timestamp: March 21, 2016, 12:55:03 pm
content: parts or circuit to control 5v rail with min losslong story short: I have MCU that use 2.1v for GPIO, and i have a separate 5v circuit, i would like to use the 2.1v logic to switch 5v on an off... (5v will be up to 200mA, typical 100mA)feel free to suggest other parts or circuit..but simple with min part countsi did exploredBJT (2N3904): problem, the Vce has 0.6v drop at 200mAEnhanced n-MOSFET: problem, Vgs threshold = 1.8v-2.1v too close to my logic voltage, and Vds = 0.6 drop as well...any other suggestion? i was thinking get another controllable voltage regulator, but i dont know if that is good idea or put too much load on the 3.3v rail..-Allen

author: ovnr
author_rank: Frequent Contributor
timestamp: March 21, 2016, 01:17:32 pm
content: Use a dedicated PDU IC, like theTPS22929D?Alternatively, just use a BJT to control your FET. Or a cheap gate driver.

author: soligen
author_rank: Contributor
timestamp: March 23, 2016, 03:31:22 pm
content: The AO3400 has a Vgsth under 1.5V.
[Help] Suggest opamp to shift and gain 50x of AC signal to ADC? - Page 1
Forum section: electronics / beginners

author: nhn
author_rank: Newbie
timestamp: September 22, 2019, 02:20:26 pm
content: HiI'm new here. Sorry if my English is not good.I has a simple knowledge about Electric. I try to design my own energy meter using voltage transfomer, current transformer and STM32's ADC. To read AC Voltage I use current type transformer, output swing from -0.033V to 0.033V. I searched and found that I can use differential amplifier with Voltage Ref is 1.65V, below is my schematic. I run simulator and it's working. But I don't know which opamp is good for my case, so I post here looking for any suggestions, dual opamp is better, one for buffer, one for shift and gain. Source voltage is AC 230, 50Hz. SDADC run as 6 MHz, 300ksps.Thank very much

author: rstofer
author_rank: Super Contributor
timestamp: September 22, 2019, 02:42:20 pm
content: Figure 4-7 in "Op Amps For Everyone" - look at curve for TLV2472https://web.mit.edu/6.101/www/reference/op_amps_everyone.pdfThe TLV2472 is a single supply rail-to-rail op amp with output characteristics that get very close to the rails. The TLV2472 is a dual op amp. It is also available as a single and quad. You should still design the circuit to stay away from the rails. Check the datasheet.Rail-to-rail is a marketing term, not an engineering reality. If you look at the output voltage (high and low), you will see that it only comes within 150 mV.http://www.ti.com/lit/ds/symlink/tlv2472.pdf
[Math] Solving circuit analysis problems - Page 1
Forum section: electronics / beginners

author: nForce
author_rank: Frequent Contributor
timestamp: January 04, 2018, 02:14:38 pm
content: Hi,this topic will be a little refresh of math and circuit analysis. The first circuit is here:Here U = Voltage.How do we get U_1? I know that here is used a voltage divider, but I can't see it.More problems to come

author: Andy Watson
author_rank: Super Contributor
timestamp: January 04, 2018, 03:08:22 pm
content: I get the feeling that there is more to the original question that you are telling us.With the given diagram, my first step would be to write-down the impedance for the parallel combination of \$L\$, and \$R + Z_b\$.

author: nForce
author_rank: Frequent Contributor
timestamp: January 04, 2018, 03:27:08 pm
content: I forgot to mention that L and R are inside two-port network. Those circles are contacts. Does this help you?

author: Andy Watson
author_rank: Super Contributor
timestamp: January 04, 2018, 05:33:35 pm
content: Quote from: nForce on January 04, 2018, 03:27:08 pmOnly to confirm my suspicions that there is more to this question than you have shownYou asked "how do we get \$U_1\$. Since an equation for \$U_1\$ is given I assume you want to know how to get that equation?As I said, my first step would be to find the impedance of the parallel combination of \$L\$ and \$R + Z_b\$ using the short-cut \$Z_p = \frac{Z_1 Z_2}{Z_1 + Z_2}\$. If you put \$Z_1 = R + Z_b\$ and \$Z_2 = j \omega L\$, I think we have:$$Z_p = \frac{(R + Z_b) j \omega L}{R + Z_b + j \omega L}$$Now you have your divider of \$Z_g\$ and \$Z_p\$ - plug those into the first equation given and the equation for \$U_1\$ readily drops out.However, the diagram is labelled with \$I_1, I_2\$ and \$U_2\$ which leads me to suspect that the original question also specified a method for the solution (e.g. "using Kirchhoff/Thevenin/nodal analysis, "... or whatever), and now you mention "two port network".

author: MrAl
author_rank: Super Contributor
timestamp: January 04, 2018, 06:53:28 pm
content: Hi,I agree with Andy, if you want to see how this works you would first collapse the right side of the network into one impedance Zx, then use that in the voltage divider formula:U1=Ug*Zx/(Zx+Zg)Now you are also in a position to calculate the output U2 using a second application of the voltage divider formula:U2=U1*Zb/(Zb+R)You dont have to do it that way though. That's a "reverse collapse". You can go forward (left to right) by using Thevenin and Norton source transformations.
(Most) Simple "Regen" AM receiver - confused about the feedback circuit - Page 1
Forum section: electronics / beginners

author: AxelGreen
author_rank: Newbie
timestamp: February 26, 2019, 09:40:50 pm
content: Hi everyone !I'm sorry to soil this forum with such a question ! I'm majoring in math (first year at Uni in France), but happened to love electronicsI can't fathom why (in many regen receivers and particularly this one, see attachment) the signal reenters the LC filter through the middle of the coil. I intuitively understand that it cannot but increase the quality factor but I'm a bit at loss on how to handle the analysis of this circuit.Couldn't this parallel LC filter be replaced with a series LC filter, filtering directly the signal from the emitter of T1 ?Is there any induction from one part of the coil to another ? (this is one single coil, the wire from T1 being placed at the fifth turn from the gnd). Or is it just an electrical way to get the signal back into the filter ?Thanks a lot and sorry for my terrible English !

author: Paul Rose
author_rank: Regular Contributor
timestamp: February 27, 2019, 12:29:51 am
content: Your English is good, and regen radios are fun.It would help if you posted a link to (or copy of) an example schematic.You are right that taking the feedback from a tap is about keeping the Q of the overall tank circuit high ( loading it less ).There are other schemes ( often seen in older vacuum tube designs ) where they get the feedback from a separate coil with fewer windings, but wound on the same form.Yes, there is mutual coupling.You can model either case ( tapped coil or separate coild ) in something like LtSpice. Place two inductors with appropriate inductance. To model a tapped coil, connect the "dotted" end of one to the plain end of the other. You may have to enable something in the inductor's properties to show phase dots. Then set the coupling factor between the inductors to something high ( like 1.0 ). Use a spice "K" directive to set the coupling ( example "K La Lb 1" ).You might get more responses in the "RF, Microwave, Ham Radio" section of this forum.

author: Paul Rose
author_rank: Regular Contributor
timestamp: February 27, 2019, 04:42:39 am
content: OK, found this schematic, which is reasonably easy to understand.The collector-emitter voltage drives the top half of the coil. Note that the emitter is AC coupled to the center tap.The feedback into the base of the transistor is taken from the bottom half of the coil.When the top of coil swings positive with respect to the center tap, the bottom of the coil swings negative ( again with respect to the center tap ). This is due to the coupling between the top half and bottom half of the coil.But the collector-emitter voltage swings opposite to the base drive ( more base current = more collector current, so the collector-emitter voltage is lower ).So the net effect is positive feedback. The circuit "wants" to oscillate.But you cut the gain by adjusting R2 so that it doesn't quite oscillate.
(possible or not)Read data from SPI flash memory using a USB SD card reader? - Page 1
Forum section: electronics / beginners

author: zinoviy
author_rank: Newbie
timestamp: February 25, 2017, 09:27:15 pm
content: Hi thats my first post here!, and im happy to be here. im a beginner please be patient with me.let me explain my question,I have seen that we can use µ-controllers and arduino to read/write data using SPI with SD-CARDs.So,would it be possible to read a SPI flash memory (like Winbond) using a conventional USB SD card reader?Please, if it's possible tell me how(that would be fun), and if it isn't tell me whythanks for your attention.

author: ataradov
author_rank: Super Contributor
timestamp: February 26, 2017, 12:30:41 am
content: It is impossible, because SPI is just a fallback mode for SD card, and it uses protocol different from typical SPI flash ICs.SD Card readers use SD mode, not SPI.

author: amyk
author_rank: Super Contributor
timestamp: February 26, 2017, 03:35:23 am
content: You could, however, make an SD card controller and connect it to an SPI flash to effectively use it as an SD card...