hybridfree/eevblog-posts huggingface dataset:
polyester film capacitors - Page 1
Forum section: electronics / beginners

author: stoica adrian
author_rank: Contributor
timestamp: June 19, 2014, 04:49:55 pm
content: I have a question and I hope someone can help me. Can I replace a condenser which is a type of polyester film with polyester film (box style). This capacitor are from a SMPS , near the driver transistors. Tanks all . Not consider the writing on the two capacitors, these are examples

author: PChi
author_rank: Frequent Contributor
timestamp: June 19, 2014, 08:48:12 pm
content: You can probably replace it. I think that the internal constructions will be similar. Though the capacitor may form part of a snubber circuit where the voltage rise can be very fast and capacitors designed for that purpose have a dv/dt rating (low internal inductance). Alternatively some SMPS circuits pass significant current through the capacitor so the current rating may be important. Did the original capaitor fail?

author: stoica adrian
author_rank: Contributor
timestamp: June 20, 2014, 05:22:17 am
content: Yes, but not only him. transistors, diodes, resistors, PWM driver all fail

author: PChi
author_rank: Frequent Contributor
timestamp: June 20, 2014, 08:03:03 am
content: Sorry to read about the failures. Do you have a schematic? It might be possible to estimate the stress that the capacitor was under and if it's failure caused everything else to fail.

author: stoica adrian
author_rank: Contributor
timestamp: June 20, 2014, 08:09:28 am
content: No, unfortunately I do not have a schematics. You know i can replace 1N5408 with UF5408?

author: PChi
author_rank: Frequent Contributor
timestamp: June 20, 2014, 10:15:15 am
content: Yes I think so. I guess that the 1N5408 is in the input bridge rectifier which only switches at 100 Hz because it is a general purpose rectifier (slow reverse recovery). The UF5408 is a fast reverse recovery rectifier so OK to use on the output probably but is more expensive than required.

author: stoica adrian
author_rank: Contributor
timestamp: June 20, 2014, 10:57:05 am
content: I'm glad they are equivalentm, i already replaced. thanks for help

author: stoica adrian
author_rank: Contributor
timestamp: June 20, 2014, 01:04:01 pm
content: i repair it, thanks

author: PChi
author_rank: Frequent Contributor
timestamp: June 20, 2014, 04:05:16 pm
content: Thanks for the feedback and the good news. One less item ending up in land fill.
Polyfuses and negative voltages - Page 1
Forum section: electronics / beginners

author: seb1982
author_rank: Regular Contributor
timestamp: March 27, 2013, 02:05:37 pm
content: Hi everyone!I'm having a complete brain fart! Obviously, voltage is relative - that's like lesson one!But I'm planning to use a 1.6A polyswitch in series on a positive voltage rail to protect it. There's also a negative voltage rail as well as a ground. Am I right in thinking that the polyswitch will work exactly the same on the negative voltage rail as it does on the positive?I'm sorry for such a basic question, but I've tied my brain in knots by thinking about it too much!

author: c4757p
author_rank: Super Contributor
timestamp: March 27, 2013, 02:12:51 pm
content: Yes.

author: seb1982
author_rank: Regular Contributor
timestamp: March 27, 2013, 09:27:45 pm
content: Clear, concise and to the point!Thanks.

author: c4757p
author_rank: Super Contributor
timestamp: March 27, 2013, 09:35:10 pm
content: A polyswitch is just a special thermistor, which is just a special resistor. And remember that the component doesn't care what ground is, it just cares what it sees applied to it. Applying -20, 0 across a resistor is just like applying 0, 20 across it - it just sees that one side is 20V higher than the other.One thing to keep in mind is that you don't just need to block currents rail-ground, but also rail-rail. Many polyswitches have pretty low voltage ratings and many dual rail systems have pretty high voltages. Make sure it has a good safety margin around the total rail-rail voltage.(Clarification: Ideally, if the fault current is rail-rail,bothpolyswitches will trip and share the blocking voltage. They are resistors, after all, even when tripped. I don't like to count on that, though.)
Polymer capacitors instead of elec. caps - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: June 22, 2023, 11:12:08 pm
content: Hello,a discussion in another forum regarding recapping retro game consoles and equipment sparked the idea of using high quality caps.besides the usual discussion of using Nichicon, Panasonic, and other high end brands or some very good and cheaper brands like Lelon... how about using solid polymer instead?assuming all specs are the same or better like voltage rating... polymer has very low ESR and could enhance the system performance when used in power supply filter circuit right? due to low ESR = less output ripple.also, what about new designs with such choices? do you find yourself using polymer in PSU designs instead?what is your opinion and experience in this regard?

author: thm_w
author_rank: Super Contributor
timestamp: June 22, 2023, 11:28:32 pm
content: https://www.eevblog.com/forum/beginners/can-be-simple-electrolytic-capacitor-replaced-by-polymer-capacitor/https://www.eevblog.com/forum/projects/replace-electrolytic-capacitors-with-ceramic-or-tantalum-capacitors/https://www.eevblog.com/forum/beginners/what-shall-i-replace-this-capacitor-with/https://www.eevblog.com/forum/projects/tantalum-cap-replacement/25/

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 23, 2023, 12:24:58 pm
content: Quote from: VEGETA on June 22, 2023, 11:12:08 pmNew design and recapping are different things. Mostly you may replace 'usual' wet electrolyte caps with solid polymer caps, but I heard about several examples of DC/DC power supplies that definitely don't like solid polymers (because of their too low ESR) and they start to oscillate.For example, typically we may replace output electrolytes in ATX PS with polymers. But once I've seen oscillations after such replacement (it depends on the motherboard to which it is connected too).Another example: I heard Tektronix 246x series oscilloscope power supply doesn't like polymers too.Some low-drop linear regulator IC doesn't like polymer caps at their output too.So, you may consider polymer capacitors as MLCC ceramics - they both have much in similar, like ultra-low ESR (and solid).In new designs, polymer caps tend to replace 'usual' Low-ESR type caps (because they are better in most parameters - much higher ripple current etc).

author: VEGETA
author_rank: Super Contributor
timestamp: June 23, 2023, 01:21:30 pm
content: Quote from: Vovk_Z on June 23, 2023, 12:24:58 pmwell, i know high esr elec caps are beneficial in dampening the power supply.in my recent design (which i still didn't manufacture a sample for) i used ceramics everywhere since it is dc-dc buck but i added small 22uf elec. cap in every stage to help dampening. one at switcher input, one in output stage after ceramics, one in 2nd stage filtering stage.I also added just one 330uF solid polymer cap at the end near the connector itself to act as big energy storage for dispatching energy to load and fast enough to reject ripple due to its 9 mOhm ESR.
Polystyrene caps - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: June 17, 2018, 02:36:46 pm
content: I have a low THD 10kHz oscillator PCB board that has populated polystyrene capacitors. It needs to be cleaned very well from flux residue because it is using current feedback OPamps. Any PCB leakage and flux residues usually causing high frequency oscillation. I use medical grade 91% isopropyl alcohol (got it from walgreens). The question is, can submerge the whole board with those polystyrene caps as well? The other parts on the board should be no problem.Thanks.

author: Ian.M
author_rank: Super Contributor
timestamp: June 17, 2018, 02:43:03 pm
content: http://kmac-plastics.net/data/chemical/polystryrene-chemical-resistance.htmIt looks like it should be OK. Don't leave it immersed overnight! Caution: the markings may come off.

author: bd139
author_rank: Super Contributor
timestamp: June 17, 2018, 02:46:00 pm
content: Check the trimpot data sheets as well.

author: exe
author_rank: Unknown
timestamp: June 17, 2018, 02:56:06 pm
content: Is this really needed? How big is feedback current?I don't encourage people leave flux on the pcb, but I prefer using "no clean" fluxes that are non-conductive and non-corrosive (but don't trust package labels, not all no-clean fluxes are really no-clean). That's because cleaning flux from underside of ICs can be a challenge.(of course, for low-leakage applications leaving flux is not an option).

author: Ian.M
author_rank: Super Contributor
timestamp: June 17, 2018, 02:58:21 pm
content: Quote from: bd139 on June 17, 2018, 02:46:00 pmYes. If the pots aren't fully sealed and resistant to IPA you are in for a whole world of grief (or even if you put a hot board into cold IPA so the internal air pressure change overwhelms their seals). If necessary, de-solder them, clean the rest of the board then re-solder them with minimal flux, and spot-clean round them with IPA, brushes and Q-tips.

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2018, 03:35:37 pm
content: Quote from: Ian.M on June 17, 2018, 02:43:03 pmI followed that same chemical resistance data wrt Polystyrene. There was no visible surface damage but I found that contact with IPA increases their leakage currentmassivelyfor a longish period of time (overnight). Granted I was using one in a Picoammeter application but this was a quick surface swab rather than immersion of any significant duration....https://www.eevblog.com/forum/projects/picoammeter-design/msg790190/?topicseen#msg790190

author: IvoS
author_rank: Frequent Contributor
timestamp: June 17, 2018, 04:48:50 pm
content: OK thanks. I will wash it in IPA with brush then rinse with water and dry quickly. Those trim pots are Bourns 3296 series, sealed.
Polyvaricon tuning cap advice needed - Page 1
Forum section: electronics / beginners

author: Quantumplate
author_rank: Regular Contributor
timestamp: August 08, 2023, 11:56:17 am
content: Hi folks, i'm going through an 80s boombox - the Goldstar tsr 800 - repairing its many faults. I have an odd tuning dial indicator that won't move over the lower third of the dial. I've extracted the pcb chassis and can now manually rotate the wheel attached to the varicon. It rotates to the high frequencies (108) and hits the buffers with a definite stop. At around 93Mhz it grinds to a halt in a rather spongy way, like there should be more travel to go. The stringing appears to be fine with no restrictions. The max angle of rotation of the shaft between its current limits is about 120 degrees. I have another varicon lying around, different brand, that rotates 180 deg. So two questions: is 180 standard? And could i expand the rotational limit/capacitance by messing with the trimmer screws?Thanks

author: wasedadoc
author_rank: Super Contributor
timestamp: August 08, 2023, 03:51:40 pm
content: Yes, 180 degress is normal. I've never seen one that is not.No, do not mess with the trimmer screws.Does it have a transparent housing and can you see the insulation sheets between the moving plates?

author: Quantumplate
author_rank: Regular Contributor
timestamp: August 08, 2023, 04:49:50 pm
content: Quote from: wasedadoc on August 08, 2023, 03:51:40 pmMuch thanks to you. Yes, 180 makes sense what with two semicircular vanes meshing.Well it's clear in places. I've just had a really close up look and i think i've found the problem. A great splurge of fawn coloured glue has been laid over many components adjacent to the varicon, and down two of its sides. Incredibly, upon close inspection i can see dozens of fragments of this glue inside the varicon! This is even more interesting to me as i watched a YouTube video demonstrating this boombox once, and it had exactly the same issue with the dial! It even pegged out at the same spot. So it's a factory cock up.Tempting to try a little force and see if i can grind up the fragments maybe, or bite the bullet and go for a difficult extraction and perhaps open the varicon for repair.Note: i meant to call it wax as that's what it is. Maybe i can melt it away...
Pomona banana test leads - Page 1
Forum section: electronics / beginners

author: Jeff5341
author_rank: Newbie
timestamp: March 16, 2017, 08:36:22 pm
content: I was wondering if all Pomona banana plugs have always had their name molded into the plug. A recent eBay purchase advertised Pomona leads, but no name stamped on them.They look to be very similar, but a little cheaper quality to the ones I had.Jeff

author: darrellg
author_rank: Unknown
timestamp: March 16, 2017, 08:44:26 pm
content: Every one I've ever gotten has had the Pomona name on it. It often even specified in the data sheet.http://www.pomonaelectronics.com/index.php?i=prodmain&getDetails=2&parent=TESTKIT

author: Nusa
author_rank: Super Contributor
timestamp: March 16, 2017, 09:03:45 pm
content: If it came from China, and the brand isn't local to China, it's virtually guaranteed not to be actual brand name. That applies to non-Chinese resellers as well. That doesn't stop them from using brand names as descriptors. Dupont-style connectors, Pomona-style connectors....except it's better marketing to leave out the "-style" clarifier, particularly when you aren't subject to US law. Caveat Emptor!

author: jpanhalt
author_rank: Super Contributor
timestamp: March 16, 2017, 10:16:04 pm
content: Post a copy of the eBay listing. There are various tricks to make something look like a Pomona when it is not. ALL of my Pomona jacks have the name and address molded on them.John
Poor frequency response on FT8 data (lower end of spectrum) - Page 1
Forum section: electronics / beginners

author: wcurlew@juno.com
author_rank: Newbie
timestamp: June 27, 2022, 05:03:20 pm
content: I have an FT100D ham radio that I am operating with FT8, and AFSK (data) mode. With FT8 you transmit tones in roughly 50hz bandwidths from about 350hz to 2600hz. I like to hang around the 500-800hz area. Turns out the radio was severely attenuating those tones, anything under about 1k was severely attenuated and very little output power was seen. This is on Upper SideBand (USB).I have confirmed that the input signal is clean and at about 30mv consistant all along the path to the junction of C1304 and r1335 in the attached diagram. Don't see anything at the other side of R1335, but I believe this is expected as the op amp is current driven and no voltages are present.I can't reach the op amp or the mux to see the output of the op amp as they are under another circuit board soldered in over them.Before I start hacking up the circuit board, my question is since the mic input (on the other side of the dual op-amp) is working fine, and the AFSK frequencies above around 1000hz are passed OK, do you concur with me that the most likely culprit is C1455? Possible second culprit might be the FET Q1061, but this is used to control the gain of the AFSK data input, and that function is working OK. I suppose the op amp might be at fault, but since the 1000hz+ tones pass and the gain control function both works I believe it is OK as well.Love to hear thoughts,ThanksBill
Poor load regulation on SEPIC - Page 1
Forum section: electronics / beginners

author: Menxiu
author_rank: Contributor
timestamp: April 25, 2018, 09:58:25 pm
content: Hi,I have build a SEPIC running at 500kHz switching frequency using the LT1370 chip. The prototype was built on a breadboard.(I understand that this is not ideal due to the parasitic capacitance and inductance)Vin=9VVout=1.7V-12VI don't quite understand why it has such poor load regulation at Vout=12V, when the load current is high. I have done the calculations for the components but it seems like the voltage drop is too significant.What could be the reason? Or is it solely because it's running off a breadboard? Is it possible that my compensation design isn't correct?Also, i don't fully understand how the current mode sensing works as shown in the block diagram, i read the operation in the datasheet but it is a bit vague.Thanks in advance.EDIT: I can't seem to add the datasheet and a picture of the prototype. Error keeps occurring stating that file is too large when clearly it's not. I apologize.https://imgur.com/a/Ez9SOB7I have uploaded them on imgur instead.
poor man ovenized buried-zener reference - Page 1
Forum section: electronics / beginners

author: 1001
author_rank: Contributor
timestamp: September 14, 2016, 08:16:00 pm
content: hi everybody! Could be a good idea to ovenize a cerdip MAX6350 buried-zener by a to-220 bjt as heater glued with pt100 or pt1000 RTD onto voltage reference? temp drift and hysteresis could going better?

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 15, 2016, 01:19:51 pm
content: as zener voltage is also a function of current, you also need constant current circuit in there...

author: helius
author_rank: Super Contributor
timestamp: September 15, 2016, 01:29:23 pm
content: I read"poor man ovenized"and thought it must be a Guardian headline.

author: dannyf
author_rank: Super Contributor
timestamp: September 15, 2016, 01:35:58 pm
content: Roasted would be tastier.

author: 1001
author_rank: Contributor
timestamp: September 15, 2016, 05:05:00 pm
content: Quote from: DiligentMinds.com on September 15, 2016, 03:16:11 pmPoor man, ovenized or rosted, maybe doesn't buy tantalum-nitride resistor networks, I am thinking to a5Vdc reference to use with ltc2400 or LTC2410.LTZ1000 is not for poor man, LM399 needs expansive resistor tolower at 5V. Maybe I can use LM399 with LTC1043 to divide by 2 but I don't know if temp drift canraise or not. I can buy MAX6350 in cerdip case, it has a buried zener (like LM399, LT1021, AD586) andlaser wafer trimming of high stability thin-film resistors inside the same ceramic package to lower Vz.It remains the problem of noise, 1.2µVp-p for LTZ1000 vs 3µVp-p for MAX6350.I don't well understand you if I can avoid any hysteresis ovenizing cerdip MAX6350...Temperature hysteresis for LTZ1000 and LM399 are different from Temperature hysteresis of MAX6350?Of course I know it is impossible to reach LTZ1000 standard by a cheap reference.Tnx a lot DiligentMinds.

author: Cerebus
author_rank: Super Contributor
timestamp: September 16, 2016, 01:00:15 am
content: Quote from: DiligentMinds.com on September 15, 2016, 07:34:52 pmDon't be cruel to him, we have to treat these proto-voltnuts gently and slowly pull them deeper and deeper. It's a lot like getting someone hooked on hard drugs, your first LM399 is free..
Popcorn effect  - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: December 17, 2014, 07:19:51 pm
content: What is popcorn effect ?Components can absorb humidity from airand if we apply big heat on theseparts humidity inside don't have enough time to evaporate and starts to make big pressurethat causes mechanical damage of affected parts. When soldering BGA chips it is a well known problem.What method do you use to avoid the popcorn effect?Thanks for the feedback

author: Falcon69
author_rank: Super Contributor
timestamp: December 17, 2014, 07:22:21 pm
content: it is the reflow process that does it. It heats up the whole chip. If you hand solder the component, it is not a problem it seems.

author: c4757p
author_rank: Super Contributor
timestamp: December 17, 2014, 07:27:46 pm
content: Quote from: Jane on December 17, 2014, 07:19:51 pmBake the chips gently and for some time to dry them first.

author: Jane
author_rank: Frequent Contributor
timestamp: December 17, 2014, 07:35:52 pm
content: QuoteWhat do you mean by gently? How many degrees to use? and how long?

author: c4757p
author_rank: Super Contributor
timestamp: December 17, 2014, 07:43:33 pm
content: I don't know, off the top of my head. That's what the little moisture detection cards that DigiKey includes with such chips say to do if they change color.

author: wraper
author_rank: Unknown
timestamp: December 17, 2014, 07:57:09 pm
content: 24 hour baking at 125oCelsius.

author: Jane
author_rank: Frequent Contributor
timestamp: December 18, 2014, 05:59:52 am
content: @wraper: and what device do you use for baking of BGA chips?

author: miguelvp
author_rank: Super Contributor
timestamp: December 18, 2014, 06:33:54 am
content: Quote from: T3sl4co1l on December 17, 2014, 11:57:42 pmIt's been decades since I've heard that song, it was cool then, now it sounds like crap

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 18, 2014, 07:02:03 am
content: Quote from: Jane on December 17, 2014, 07:19:51 pmIn professional mass production, all SMD parts have to be delivered and stored in dry pack.Parts from an opened dry pack has to be assembled within 24 hours, or so, otherwise the components have to be baked, as described. That means, open the tape, take out all components, heat them and then repack them in a fresh tape - on -reel, and repack in dry pack.These cracks can also happen, if you assemble SMD parts on the wave soldering side of the PCB.There's a quality standard describing this whole SMD dry pack handling, but I have forgotten its designator.I think, for amateurs/hobbyists, BGA assembly is not applicable.Frank

author: RobertoLG
author_rank: Frequent Contributor
timestamp: December 18, 2014, 07:32:21 am
content: Quote from: miguelvp on December 18, 2014, 06:33:54 amlol! me too

author: veryevil
author_rank: Unknown
timestamp: December 18, 2014, 09:28:47 am
content: Parts have a MSL Moisture Sensitivity Level which tell you how long it can be in air.http://en.wikipedia.org/wiki/Moisture_sensitivity_level
Popped EXPENSIVE Bussmann 44/100A 1000V fuse in BM869 DMM - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 02, 2017, 12:50:59 pm
content: I was in mA mode, and connected a 555 timer pin3 to gnd, so I popped the expensive fuse. Also that night, I hooked a 45 Ohm speaker between 555 output pin3 and pin4 ground,I wanted to hear the measured frequency, but the 555 heated way up and even melted some of the bread boardI want to connect 200mA fuse in place of Bussmann 0.44mA fast acting fuse, big, ceramic, 10mmx39mm(or 34.5?mm)Now, I should set up transistor 200mA current, and time these fuses, but I only have a few of them too

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 02, 2017, 01:01:10 pm
content: There's nothing I'm doing that needs over 200mA, so if I put descent 200mA fuses in this BM269, I should be goodI have accidentally zapped my Vici VC99 too many times, her mind is going.....so for now she is relegated to mA current measurements.Wow 44/100mA and more info fuses are EXPENSIVE mistakes

author: Wytnucls
author_rank: Super Contributor
timestamp: March 02, 2017, 01:08:22 pm
content: You blew the HRC 440mA fuse. Just replace with same and be more careful next time. Always select 10A range first. Only use the mA range if you need the extra resolution and you made sure the current draw is well within the mA range limitation.

author: bktemp
author_rank: Super Contributor
timestamp: March 02, 2017, 01:18:15 pm
content: Using a power supply with current limiting avoids such problems.
Portable Headphone Amp Power Supply 18V Design - Page 1
Forum section: electronics / beginners

author: MladenGavric
author_rank: Newbie
timestamp: August 21, 2020, 04:18:25 pm
content: Hey everyone!Disclaimer: I'm new to EEVblog, diyaudio, amplifiers, power supplies, schematics, PCB design and everything that this forum touches on (read: NOOB), so I urge you to be patient with me - I am eager to learn though.That being said - Hi! My name is MladenAnyway, on to the point: Recently I came across @xrk971 threadHakuin SE Class A HP Ampwhich got me interested into building my own amp (PCB design and everything).But, since X hasn't opened source his power supply schematic I decided to tackle that on my own (without some extras he implemented). Basically what I tried to do is Power Supply portion of the amp: Battery Charger --> Boost Converter --> LDO.Spent last few days reading through data sheets, reference designs, TI's design tools (WEBENCH Power Designer) and this is what I came up with. I would greatly appreciate if you could fact check the schematic and suggest things I should do (things that I've probably missed). What I'm mostly unsure about is Battery Charger schematic and USB-C connection.I plan to use Samsung's EB-BJ710CBE battery (if possible), or something else if you recommend it.Data Sheets:MCP73871,TPS61178,TPS7A470
Portable induction hob - Page 1
Forum section: electronics / beginners

author: KawasakiKen
author_rank: Contributor
timestamp: September 09, 2018, 08:31:47 pm
content: Hi,I posted a request for help with a blown hob a few days ago, received several helpful suggestions, made a further reply /request yesterday, but cannot find any sign of my post now. Have I been blackballed or moderated?? My last request was whether I need to isolate the IGBT to meter it for short-circuit, and how to check it? Also, could the AC bridge rectifier be a suspect for blown fuses and tripped ELCB in the consumer unit, but no apparent board burns?
portable on/off pulse generator? - Page 1
Forum section: electronics / beginners

author: samloi
author_rank: Newbie
timestamp: October 29, 2015, 01:29:11 am
content: Hi guys,does anyone knows of portable on/off pulse generator available in the market?Basically, I have a inductive NPN/PNP sensor that senses the bolts of a rotating machine. A Frequency converter then converts this input into volts for monitoring purposes. It would be handy to be able to calibrate the converter without running the rotation machine. Btw, the system runs on 24Vdc.I would probably use around the 20Hz - 500Hz range

author: nbritton
author_rank: Frequent Contributor
timestamp: October 29, 2015, 02:03:20 am
content: I'm not exactly sure what you're looking for. Isn't an on/off pulse just DC with a switch?The $20 LCR meter project being discussed here on the forums is capable of doing PWM, is that what you want?http://www.banggood.com/DIY-M12864-Graphics-Version-Transistor-Tester-Kit-LCR-ESR-PWM-p-986954.html

author: samloi
author_rank: Newbie
timestamp: October 29, 2015, 02:56:05 am
content: Quote from: nbritton on October 29, 2015, 02:03:20 amThanks for the reply. Dosent seem like something i want though.In short, i want to simulate the switching of a PNP/NPN sensor from 20-500Hz so as to calibrate a frequency converter. The frequency converter works on 24Vdc. So yeah, bascially a non-potential switch that is controllable from 20-500Hz.

author: nbritton
author_rank: Frequent Contributor
timestamp: October 29, 2015, 04:16:30 am
content: I think an arduino would work well for your needs. You can wire up a screen, rotary encoder or buttons, and a transistor to control the 24VDC into a project box and you should be good to go. On the software side I imagine you simply code the digital encoder to adjust the frequency and set one of the I/O pins high to turn on the transistor. Not sure if it would produce a stable jitter free pulse.http://www.instructables.com/id/The-RRRRRRRRRRBA-or-What-They-Dont-Teach-You-in-/
Portable Project cases! - Page 1
Forum section: electronics / beginners

author: Vorisi
author_rank: Newbie
timestamp: November 29, 2020, 12:37:31 am
content: Woah! Nice place ya got here!Alright, the question.I'm working on a project with an ESP8266 based wemos D1 mini. This is something that needs to be portable and usable by not just me.So I'm thinking case with an on/off switch and a 3 AA battery compartment.Problem is this doesn't actually seem to exist as a project box type thing.So question is where could I get something that has a 3xAA battery compartment, a power switch, IDEALLY a reset button but not required, and space for the actual stuff (the board and an RJ11 jack.

author: james_s
author_rank: Super Contributor
timestamp: November 29, 2020, 02:47:05 am
content: Your best bet for enclosures is to browse Digikey, Mouser or other suppliers or search directly for the manufactures and see what they have to offer. I know I've seen off the shelf enclosures with built in battery holders but I don't know whether I've seen 3xAA specifically. You're probably not going to find one that has a power switch or connectors off the shelf, you'll have to drill holes and install that stuff.

author: ledtester
author_rank: Super Contributor
timestamp: November 29, 2020, 06:29:40 am
content: PacTec is a major supplier in the US:https://www.pactecenclosures.com/

author: Lomax
author_rank: Frequent Contributor
timestamp: November 29, 2020, 08:00:58 pm
content: I like looking through the Hammond catalogue for things like this:https://www.hammfg.com/electronics/small-case/plastic#general-purpose
porting code from atmega644 to arduino uno/atmega328p - Page 1
Forum section: electronics / beginners

author: peterthenovice
author_rank: Regular Contributor
timestamp: December 24, 2015, 06:55:57 pm
content: hi,i want to port this code for a thermal printer controller to the uno. It is for a radio shack tp-10 thermal printer. how would i go about doing that?the old printer controller runs at 600 baud and uses rs232. the arduino has a built in usb to serial,rs232 ports are hard to find.http://hackaday.com/2014/09/25/thermal-printer-brain-transplant-is-two-hacks-in-one/https://sites.google.com/site/dannychouinard/Home/tp10upgrade

author: Simon
author_rank: Unknown
timestamp: December 24, 2015, 06:57:50 pm
content: and ?
Position Transducer with Arduino - Page 1
Forum section: electronics / beginners

author: Dado87
author_rank: Newbie
timestamp: June 19, 2015, 11:25:45 pm
content: Hi,I would like wire my position sensor (http://www.novotechnik.de/uploads/tx_extprodfind/T_TS_e.pdf) into Arduino. I would like to connect it with arduino 5V supply and then read analog input values. It is potentiometric sensor and has 3 cables.After looking at datasheet there are many values for current in uA range, like Recommended operating wiper current (<1uA). Can somebody take a look at datasheet and check if I understand it right... If, yes, how to wire it to acheave such a low current with 0-5V proportional output signal. Have somebody experience with such a sensor.I just dont wand to burn it...Regards,Damir

author: retrolefty
author_rank: Super Contributor
timestamp: June 19, 2015, 11:34:00 pm
content: You should be able to wire the wiper terminal directly to a analog input pin as they are very high impedance.
positioning LDR - Page 1
Forum section: electronics / beginners

author: darinsquared
author_rank: Contributor
timestamp: November 21, 2017, 01:48:50 pm
content: I am building a circuit with a Light Dependent Resistor and relay that will turn the lights off in a room when the natural light is sufficient to light the room. How do I position the LDR so that the electric light does not cause the LDR to cycle off and on? If possible, I want to have the LDR in the room. I may also add a PIR sensor and an OR Gate so that if no one is in the room the relay will also turn off.

author: fourtytwo42
author_rank: Super Contributor
timestamp: November 21, 2017, 02:37:37 pm
content: Enclose the LDR in a tube with a blanked and and attach the open end to a window....
Positive (?) feedback in an opamp - Page 1
Forum section: electronics / beginners

author: npelov
author_rank: Frequent Contributor
timestamp: May 08, 2015, 05:08:06 pm
content: Hi,I was looking atLM399 Datasheet, typical applications section on page 6 (portable calibrator). The LT1001 opamp has a resistor from output to (+) input. What is this resistor used for. It doesn't change the voltage on the (+) pin. If you put 8.8k and the 19k+3k in parallel it's about 6k. Is the 5k for canceling the input bias current? If yes, isn't it supposed to go in series with the (+) input? And why it's not 6k?

author: Andy Watson
author_rank: Super Contributor
timestamp: May 08, 2015, 05:18:36 pm
content: Quote from: npelov on May 08, 2015, 05:08:06 pmIgnore the 200k. For a stable voltage from the reference zener it would be advantageous to drive it with a stable, constant current source. Imagine if you had a stable voltage, say 3.05V higher than the zener voltage - 3.05 V / 5 k = 610uA. It appears that you have just such a voltage at the output of the op-amp! (and it should be very stable)The 200k is there to ensure that the circuit starts-up when you first power it.

author: npelov
author_rank: Frequent Contributor
timestamp: May 08, 2015, 07:40:36 pm
content: Ow, so the 200k is not really driving the zener. Stupid me ... It doesn't provide enough current, right? So that's why when I put second multimeter the voltage changes. So the 5k is actually driving the Zener relying on the far better output of the opamp, rather than the power supply. Well, that means that this circuit is no good for low voltage outputs. I thought I can put a divider in the input and have 1 volt instead of 10. Well I can do that, but on the output and I'll need a buffer.Thanks!
Positive input, negative output request - Page 1
Forum section: electronics / beginners

author: Karamel
author_rank: Regular Contributor
timestamp: April 10, 2016, 11:10:30 pm
content: Hi,I have to get -7V from +12v or +24v input. I have searched someting on internet. There are some solutions but I didn't choose anything which is the best solution for me.I will use it for at070tn92 lcd screen and I have just single positive power supply.What should I do to solve this problem?

author: danadak
author_rank: Super Contributor
timestamp: April 11, 2016, 01:43:44 am
content: Some approaches -https://www.dropbox.com/s/k1yn4m7heaixvmg/ADinput%20negative%20inputs.zip?dl=0Regards, Dana.

author: Karamel
author_rank: Regular Contributor
timestamp: April 11, 2016, 08:14:19 pm
content: Thanks for replying and information.I will use it just an experiment for one time so, I think that, Can I use small another external power supply? Like phone charger unit? I can use minus side adjustable regulator which it could be Lm337 and maybe I can get -7V from it? Is it logical solution?

author: danadak
author_rank: Super Contributor
timestamp: April 11, 2016, 08:21:46 pm
content: Hacking apart the walwart could be problematic, maybe potted.Depends how the regulator is designed inside the walwart, could be switchingand changing Vout a little more involved depending on IC regulator used.You can get simple charge pumps, they are dirt cheap.Regards, Dana.

author: Rudane
author_rank: Regular Contributor
timestamp: April 12, 2016, 04:31:38 am
content: How much current do you need from the -7 V rail?

author: jdraughn
author_rank: Regular Contributor
timestamp: April 12, 2016, 10:41:19 am
content: You could possibly use a +12v and +5v supply and make the +12v your ground and the +5v your -7v. The supplies need to be isolated from each other, but those are both very common voltages so it should be easy to find a couple of power bricks.

author: tggzzz
author_rank: Super Contributor
timestamp: April 12, 2016, 10:48:59 am
content: Quote from: jdraughn on April 12, 2016, 10:41:19 amPower bricks often, but not always, have their 0V output connected to mains earth. Been there done that

author: ion
author_rank: Regular Contributor
timestamp: April 12, 2016, 11:16:46 am
content: Quote from: tggzzz on April 12, 2016, 10:48:59 amWould be easier with an adjustable power adapter - set it to 7V and hook the positive to your circuit ground. I haven't come across any that have an earth connection so it should work fine.
Positive voltage of an electronic device touching the outter metallic casing - Page 1
Forum section: electronics / beginners

author: beeboopbeep
author_rank: Contributor
timestamp: June 25, 2020, 03:27:24 pm
content: Hi everyone,I was wondering if there are any safety concerns with the device and any concerns in the environment if the device's +5 V is touching an aluminum casing which will be exposed to the user. Please assume that there is no way for the device ground to somehow touch this +5 V. Also, the internal source resistance of the +5 V source will be large enough so that only max current of ~50 mA can be output when shorted with ground.My assumption is that nothing will happen since the +5 V and its ground will be well insulated and this 'floating' +5 V will have no way to travel to ground or any parts of the device traces unless the user punctures the device accidentally and shorts something.Here is a photo to better illustrate the device structure (https://imgur.com/a/ukCvaS2).Thanks!

author: SmokedComponent
author_rank: Regular Contributor
timestamp: June 25, 2020, 03:50:31 pm
content: If the device has own isolated supply then it doesn't matter - there is no circuit if the device casing touches some other grounded object.You can declare that internal +5V as external ground and device runs on -5V, as seen from the outside world.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: June 26, 2020, 12:26:07 am
content: Cars used to be positive ground.There is much debate as to why it was changed. My guess is NPN transistors had a good bit to do with it. Low side switching is cheaper.

author: langwadt
author_rank: Super Contributor
timestamp: June 26, 2020, 08:03:31 am
content: Quote from: JustMeHere on June 26, 2020, 12:26:07 amif that was the case we should have stuck with positive ground, that way you only need one low side switched wire to each load. With negative ground you need two wires, positive supply and a switched ground to each load
Positive/Negative voltage trigger controlled switch circuit - Page 1
Forum section: electronics / beginners

author: _Vendetta_
author_rank: Contributor
timestamp: August 10, 2021, 10:01:01 am
content: Hello EEVbloggers,I would like to design an electronic switch circuit whichturns ONwhen you apply apostive trigger pulse voltageandturns offwhen you apply anegative trigger pulse voltage. I exampled out the circuit behavior as depicted by the figure below:I wonder if the circuit is achievable through transistors and some other passives..I would like to have some ideas or maybe some references i can go through !Thank you in advance.

author: Zero999
author_rank: Super Contributor
timestamp: August 10, 2021, 10:35:12 am
content: A Schmitt trigger will do that.C1 and R3 ensure the circuit starts, with its output low. If you need it to start, with the output high, connect the other side of C1 to -V, instead of +V.

author: _Vendetta_
author_rank: Contributor
timestamp: August 10, 2021, 02:07:30 pm
content: Thank you. I always had the idea of using the schmitt trigger for this. Would it be possible to use a single supply OP amp ( V+ connected to 3.8 Battery and V- to the ground) while still keeping the same behavior.

author: Zero999
author_rank: Super Contributor
timestamp: August 10, 2021, 04:03:26 pm
content: Quote from: _Vendetta_ on August 10, 2021, 02:07:30 pmYes, but it's a little more tricky.Note that the thresholds depend on the supply voltage, so you'll need a voltage reference, if you want them to remain fixed, irrespective, of the supply voltage.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2021, 01:38:28 am
content: It is also known as a Schmitt multivibrator which might help finding examples. Below is a two transistor version used by Tektronix in their PG505 high voltage pulse generator. They are often used to transfer DC information across an AC isolation boundary like a transformer.

author: _Vendetta_
author_rank: Contributor
timestamp: August 11, 2021, 07:35:57 am
content: @Zero0999 Yes i see what you have done right there. You gave it a little DC shift bias usign that divider. much appreciated buddy !@David Hess, Yes i know that type of schmitt trigger (called emitter coupled), if that circuit proves good stability and frugal energy consumption, i will go with it. Thanks again.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2021, 07:38:46 pm
content: Quote from: _Vendetta_ on August 11, 2021, 07:35:57 amIt does not have to be emitter coupled. That was just the example I had immediately available.A modern integrated comparator like you used is probably the best way to go unless you have a special requirement.

author: Zero999
author_rank: Super Contributor
timestamp: August 12, 2021, 09:10:30 am
content: An AC coupled solution might not work in this case, because it's triggered by the rate of change of the input, rather than the absolute input voltage. This means the output will go low on every negative edge, irrespective of whether it crosses zero, or not.
positve and negative rails using single dc source - Page 1
Forum section: electronics / beginners

author: techninja80
author_rank: Regular Contributor
timestamp: September 09, 2021, 04:14:51 pm
content: So I am trying to learn about op amps, and found that I need a negative line as well as a positive line. I figured I could use lm79xx, and lm78xx to accomplish this however most seem to say I need two power sources in order to do this. I did find this video, and demonstrated exactly what I was trying to accomplish however upon creating the same circuit I am getting the -5v with ref to the virtual ground, but only 1.56v with reference to the virtual ground from the lm79xx.Attached is the circuit sorry for the long leads, but its all I got, and here is the video I followed.

author: rstofer
author_rank: Super Contributor
timestamp: September 09, 2021, 04:48:42 pm
content: If +-12V will work, these power bricks from Digilent are pretty neat. They take in 5V via USB and create both positive and negative voltages. Of course, you can't hang a heavy load on the outputs. At +-12V, you are limited to +-100mA and that's a lot when working with modern op amps.https://digilent.com/shop/powerbricks-breadboardable-dual-output-usb-power-supplies/You could always change to single supply op amps and reference signals to Vcc/2.

author: rstofer
author_rank: Super Contributor
timestamp: September 09, 2021, 05:33:01 pm
content: This power supply from Jameco is also workable. I have one of these.https://www.jameco.com/z/PD-2515-MEAN-WELL-Power-Supply-Dual-Output-Open-Frame-15V-1A-Negative-15V-1A-24W_2100857.htmlThere are a lot of dual 15V power supply projects on the Internet.

author: Ian.M
author_rank: Super Contributor
timestamp: September 09, 2021, 05:58:22 pm
content: The circuit from the YouTube video (attached below) is no good. If the load on the negative rail is even 1mA less than that on the positive rail, the negative side will loose regulation as the lower LM7812 providing the 0V cant sink current.If you need to split a single floating supply, what you need is arail splitter. If you are only expecting a small imbalance, theTLE2426can do the job. Its good for +/-20mA of current imbalance subject to its dissipation limits. For higher imbalances, consider a resistor divider e.g. 2x 10K, with a 100nF decoupling cap (or two, one across each resistor if you want to avoid power-up imbalance), into a unity gain power OPAMP buffer. That can either be an ordinary OPAMP driving an external power stage or a specialized power OPAMP typically in a TO220-5 package.
Possibilty of operator error - Page 1
Forum section: electronics / beginners

author: AardvarkM31
author_rank: Contributor
timestamp: November 26, 2021, 03:17:07 am
content: Hello,I have recently begun exploring electronics in more depth. I have had an Amprobe AM-530 meter which is seems perfectly functional for all the uses I've had for it previously. Just beginning checking capacitance and the meter seems far off. Unless I am doing something incorrectly. I am testing various type of .047 uF caps and an air gap variable for a crystal radio I intend to build.The meter shows around 60.3 nF on the .047 uF. It doesn't change values when I am varying the air gap. I borrowed my old Radio Shack meter back from my Grandson and it measures correct values on the .047 uF capacitors that I've tested.Downloaded the manual and it shows the probes across the caps leads and the selector on the capacitance position. Then on the side it has a vertical column of 5 boxes, the top shows pressing down on an unidentied button, the second shows the Hold Button and > 2 Seconds, the third box shows the REL Delta button insignia, the fourth Select Button and the fifth shows the Flashlight button insignia. Something is wrong and I can not decipher this capacitance measuring section.Help please if I am doing it wrong because I haven't pushed all those buttons or is my meter giving inaccurate readings on capacitance. Been thick before so any assistance is appreciated

author: CaptDon
author_rank: Super Contributor
timestamp: November 26, 2021, 02:40:11 pm
content: Your air gap capacitor is probably no more than 100 picofarads, maybe 360-400 if broadcast band. That is WAY off from .047uf!!!! Doubt you meter accurately reads picofarads. .063 for a .047 is in the ballpark for tolerance. They used to be something like +50%/-20% years ago new out of the box.

author: AardvarkM31
author_rank: Contributor
timestamp: November 26, 2021, 03:45:11 pm
content: Good day CaptDon,Thanks for your response. Yes the air gap is a 365 pF. Did not get to test it on the old Radio Shack meter before returning it. The error margin must be large on my Amprobe as the Radio shack indicated the value accurately. Go figure!!!
Possible disadvantages of splitting the GND thermal pad of LTC3633 - Page 1
Forum section: electronics / beginners

author: bmxsesh
author_rank: Regular Contributor
timestamp: December 17, 2024, 11:18:11 am
content: Hello, I wanted to ask from electrical standpoint, what are the possible drawbacks of splitting the GND pour at the thermal pad of LTC3633 DC-DC converter to route a signal to the opposite side of the chip?Thank you,-bmxsesh

author: jwet
author_rank: Frequent Contributor
timestamp: December 17, 2024, 03:20:50 pm
content: I don't think its a great idea and would look for alternatives first. One thing that you could do is to reduce your trace widths on low current pins- they all seem rather large. This could give you some layout room to squeeze traces to make that connection.A via on each side and a trace under the iC would be preferable. Though usually that thermal pad is via'd to both sides I don't know what those pins are w/o schematic but do they require a short run?The IC die is bonded to to that slug on the inside, probably mostly in the center, its a pretty small die. By having that gap, you have a thermal gradient across with hot and cold spots.Are you operating the parts at its maxes as far as power goes, etc.The other issue is that you're really depending on solder mask quality next to tinned area to make it work, not completely planar and probably not a 100% yield kind of deal.Also, those under IC thermal pads are supposed to be full of Vias to aid thermal conduction to the other side, etc.The data sheet has some reasonable looking layouts included.My 2 cents

author: bmxsesh
author_rank: Regular Contributor
timestamp: December 17, 2024, 03:43:15 pm
content: I realized that it's just the break in the GND plane (board wise) which is not a good practiceI tried going without internal GND layer and route it on the bottom to make sure every DC-DC converter has its own GND return pathI should probably stick to the datasheet and have an internal power ground

author: jwet
author_rank: Frequent Contributor
timestamp: December 18, 2024, 07:24:45 pm
content: You don't have to go 4 layer I wouldn't think unless there are other places that it might help...
Possible pin damage during ESD? - Page 1
Forum section: electronics / beginners

author: lilmantis
author_rank: Contributor
timestamp: October 22, 2012, 08:46:44 am
content: Hello, I am designing a microcontroller circuit and on the ADC pins I coud get about 9 volts during a ESD discharge. The max. votage for the pin is VCC(5V)+0.3V according to the datasheet. The signal comes from a voltage devider through a 100k resistor with a max. current of 0.6 miliamperes. The pin also has a parasitic diode to VCC and GND.Do you belive it could damage the pin/create SCR-latchup?

author: Rerouter
author_rank: Super Contributor
timestamp: October 22, 2012, 08:51:20 am
content: if it has a parasitic diode, why would you expect 9V? it should be clipped by the diodes,if you are concerned, use some schottkeys to clamp it externally to the rails, but at 600uA the parasitics should be more than capable,