hybridfree/eevblog-posts huggingface dataset:
HP Power Supplies - Page 1
Forum section: electronics / beginners

author: AustinTxBob
author_rank: Contributor
timestamp: November 06, 2017, 03:53:09 pm
content: I have recently acquired a few HP power supplies and I am trying to decide if I should sell them or keep them. Hp 6284, 6266B and a 6264B. The specs on the last two are in herehttps://accusrc.com/uploads/datasheets/5019_6266B.pdf. Currently I have a BK 1651, GW 3303S and an Elenco XP720 that I imagine I would continue to use. How useful would these new (to me) supplies be? I just don't want to get rid of something I could potentially need.Thanks.Bob
HP power supply for working on multiple projects simultaneously - Page 1
Forum section: electronics / beginners

author: cobbler
author_rank: Unknown
timestamp: November 16, 2015, 12:39:16 am
content: Hello, thanks for the great videos and blog. Have learned so much. I searched the forum and could not find an answer regarding working on multiple completely projects simultaneously.I have built a few ardruino projects and they are going well. I have three projects going in parallel each with their own breadboard and ardruino, Is it possible that a HP power supply with 5v can be used on all three projects simultaneously. I am really interested in this for prototyping. I don't want to keep unplugging the power supply everytime I switch to working on a new project.And I am also considering this for future products where I will need more than 5v or 3.3v.Is that why Dave has 500 PSU's in the background of his videosAlso any other tips for working on multiple projects simultaneously?Thanks in advance for any advice on working multiple things without constant unplugging and replugging as I switch gears.

author: AKADriver
author_rank: Newbie
timestamp: November 16, 2015, 02:02:11 am
content: By "HP power supply" do you mean an old HP bench power supply? Or a PC power supply that's been modified?Both will work for what you want. The PC power supply is almost better since you can't forget you left project A plugged in then twist the knobs for project B, potentially blowing something up; the 5V rail will always be around 5V.

author: cobbler
author_rank: Unknown
timestamp: November 16, 2015, 02:36:29 am
content: ok thanks.... I was talking about a hp bench ps. so even if multiple devices are pulling on the same 5v rail it will not impact the voltage integrity?

author: Macbeth
author_rank: Super Contributor
timestamp: November 16, 2015, 02:53:50 am
content: Providing it does not exceed the current rating or the current limiting you set on the supply then of course it will work perfectlyNow the current limit you set - that is very useful when powering up individual projects for testing or faulty boards - that's when you want the isolation of a dedicated supply and not share it.

author: cobbler
author_rank: Unknown
timestamp: November 16, 2015, 09:16:29 pm
content: Quote from: Macbeth on November 16, 2015, 02:53:50 amOk thanks

author: Ian.M
author_rank: Super Contributor
timestamp: November 16, 2015, 09:26:23 pm
content: So you want to leave powered up projects you are *NOT* working on at the moment scattered across your bench? Bad Move - one stray wire clipping or dropped component or tool later and you havea fair chance of blowing one or more of them up.OTOH if you have a soak test bench or shelf, then powering multiple projects on long term test from the same 5V PSU makes sense, but add an inline fuseholder for each with an appropriately rated fuse.Anyway, what's the big deal with having to plug in two banana plugs when switching projects?+1 for having one supply per project for actual bench testing.
HP3458A measuring error - Page 1
Forum section: electronics / beginners

author: Vivaan
author_rank: Newbie
timestamp: June 24, 2020, 11:38:04 am
content: Hello there,I am trying to measure resistance of a thickfilm substrate using HP3458A multimeter in LS232 laser machine.When i measure it with a hand multimeter, it shows correct value i.e.25kohms, but with HP3458A laser machine multimeter, it always shows a higher value and a different one everytime. I have used APER 0.0005, NRDGS 10000 and 2 point measurement. with OHMF 1000000.It would be really helpful, if anyone can guide me on thisthe figure with multimeter initial measurement is attached

author: Kleinstein
author_rank: Super Contributor
timestamp: June 24, 2020, 12:02:02 pm
content: APER 0.0005 does not sound like a multiple of the mains period. This modes could be sensitive to mains hum.Do other resistance measurements on the 3458 work ? A poor contact / cable could be a problem. So does a short really ready 0 ?

author: Vivaan
author_rank: Newbie
timestamp: June 24, 2020, 12:09:39 pm
content: Yes resistance measurement for other substrate works.
HP438A power meter not detecting sensors - Page 1
Forum section: electronics / beginners

author: geo00
author_rank: Newbie
timestamp: February 15, 2018, 08:05:23 am
content: Just got our HP438A back from cal and it boots up good with no errors other than No CH A error 31. Meaning no sensors hooked up to channel A. But even when I hook up a sensor it does not detect it, not on Ch A or B and I've tried different sensors and cables.Any suggestions?

author: danadak
author_rank: Super Contributor
timestamp: February 15, 2018, 12:17:06 pm
content: Look at the operating theory section of manual for how the sensordetection circuit works to get clues as to what is going on.Regards, Dana.

author: Tony_G
author_rank: Super Contributor
timestamp: February 15, 2018, 04:26:32 pm
content: The input amplifier handles the detection of the sensor - Service Sheet BD3 is the correct starting point for that with Service Sheet 6 being the specific one for the Input Amplifier.Assuming that you have confirmed the that sensors work on another unit, I would open the unit up and first check that the cables are properly seating to A4J2 & A4J3. After that follow the service sheets.Good luck and let us know how it goes.TonyG
HP/Agilent 4195A - Page 1
Forum section: electronics / beginners

author: Roar Malmin
author_rank: Newbie
timestamp: September 15, 2020, 10:50:58 am
content: Hi,I have a 4195A and its Measuring Unit, BUT not the cables that connect bthem. Does anyone have either a service manual or can contribute the wiring on the 50 & 9 pin cables that are supposed to be used?RegardsRMalmin

author: Tomorokoshi
author_rank: Super Contributor
timestamp: September 15, 2020, 02:03:01 pm
content: Starting here at Keysight:https://www.keysight.com/en/pd-334101-pn-4195A/network-spectrum-analyzer?pm=PL&nid=-32775.536883583&cc=US&lc=engDownload all the documents.In the Maintenance Manual 04195-90100 on page 1-8 (21 of 263) there is a diagram with part numbers.Note that the part numbers are all preceded with 4194, the Gain / Phase Analyzer. This is constructed similarly.To double check, I looked at the 4194A manuals. However, I could not find a similar diagram. However, in Service Manual 04194-90100 on page 8-54 (320 of 433) it does reference the 04194-61603 9-pin D-SUB DC power cable.From a previous discussion here regarding the 50-pin Centronics cable:https://www.eevblog.com/forum/repair/hp-4194a-impedance-analyzer-a678-boards/I verified that it is identical to a shielded 50-pin SCSI cable.As the the 9-pin D-SUB cable, it is straight-through, shielded, and perhaps 22 AWG. See the attached image.Both cables are 12 inches or 30 cm long.
HPDL 2416 Display Dimming - Page 1
Forum section: electronics / beginners

author: RobNorthen
author_rank: Contributor
timestamp: October 11, 2016, 08:08:47 pm
content: In the datasheet on page 3-185, they write "Finally, dimming of the display through the blanking input (BL) is not recommended."I was actually thinking of doing this, but as they advice against it, can it be harm full to the display??Datasheet:http://pdf1.alldatasheet.com/datasheet-pdf/view/64706/HP/HPDL2416.htmlBest regardsChristian

author: RobNorthen
author_rank: Contributor
timestamp: November 02, 2016, 11:38:24 am
content: Anyone ??

author: Gyro
author_rank: Super Contributor
timestamp: November 02, 2016, 11:55:20 am
content: It's because the Blanking input resets the internal segment multiplex counter. If you toggle it at high speed you'll get an uneven or unreadable display at a guess. It's only intended for blanking or low speed flashing. It's unusual for it to reset the mux counter though, most displays allow dimming this way.You could always try it. It's unlikely that it will cause damage unless you get one (set of) segment(s) much brighter than the others. They don't seem to specify the internal mux oscillator frequency but you might just find a frequency that is slow enough to work without flicker being too objectionable.

author: RobNorthen
author_rank: Contributor
timestamp: November 03, 2016, 09:12:40 am
content: Thank you Gyro, sounds good, i will try it out then.
HRC Fuses - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 22, 2012, 05:29:27 pm
content: Is there a proper way to check HRC fuses??? I tried doing continuity check which failed ,but I get ohm reading but it's really high...

author: Monkeh
author_rank: Super Contributor
timestamp: December 22, 2012, 05:52:39 pm
content: If it's not a short circuit, it's broken.

author: Unknown
author_rank: Unknown
timestamp: December 23, 2012, 01:48:26 am
content: Quote from: TorqueRanger on December 22, 2012, 05:29:27 pmTry again, this time making sure you are not touching both probes of your multimeter.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 23, 2012, 04:48:19 pm
content: Well bot fuse are gone but seems no damage was done...Where can get both of these and not get rapped on price or shippingI tried ebay but the have a brand name HRC but Only cheap no name brand ceraminc fuses...Cermanic f630ma 250vHRC KTK-15

author: SeanB
author_rank: Super Contributor
timestamp: December 23, 2012, 04:57:36 pm
content: Measure length and diameter and lppk for tat. Note use both metric and imperial dimensions, as they are both common as descriptors in fuses ( some are quoted in a mix as well just to further confuse you).

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 30, 2012, 06:43:44 pm
content: What's is the differenceHRC fuseKTK 15VsKLK 15

author: Unknown
author_rank: Unknown
timestamp: December 30, 2012, 07:54:30 pm
content: That one is made by Littlefuse and the other by Cooper Bussmann? The only difference I see when comparing datasheets side by side is that the KLK series is also rated for 50kA at 500 Vdc, the Bussmann datasheet doesn't mention any DC rating.

author: Wytnucls
author_rank: Super Contributor
timestamp: December 30, 2012, 07:54:54 pm
content: AFAIK, there are the same fuses, one is Bussmann (KTK) and the other, Littlefuse (KLK) designation.
ht132c led driver IC - Page 1
Forum section: electronics / beginners

author: Porto
author_rank: Contributor
timestamp: April 08, 2014, 05:30:14 pm
content: Hello,I've got no experience in LED projects and the driver IC's and have a question about it.I want to build a digital clock using a DS3231 RTC chip.For the display I want to use 8x8 dot matrix panels, 4x horizontal, 2 rows = 8 panels in total.As I don't have much space for one IC per panel, I'm looking for a driver which can drivemultiple panels at once... my guess the HT132C can do this but I'm not sure how manyI need of them... I looked at its datasheet but can't figure this out, again because of my100% inexperience with LED drivers. I can house 2 or 3 driver chips at most.Can someone clarify this for me?Thanks in advance... Porto

author: gregallenwarner
author_rank: Regular Contributor
timestamp: April 08, 2014, 07:45:37 pm
content: Instead of using 8 individual 8x8 panels, I'd recommend using one of these guys:https://www.sparkfun.com/products/12583They can be found on all sorts of vendors sites by searching for 16x32 rgb led panel.They have their own driver IC's built in, and can easily be controlled by a microcontroller through a serial protocol. That Sparkfun link above will link you to an Arduino library for controlling this panel. If you're using a different microcontroller, you can reference that library and port it over to your platform.

author: Porto
author_rank: Contributor
timestamp: April 08, 2014, 08:43:14 pm
content: Hi,That looks good, I'll consider that, will save me alot of soldering etc.But I'm not into Arduino and programming, just plain electronics!

author: gregallenwarner
author_rank: Regular Contributor
timestamp: April 09, 2014, 02:13:35 pm
content: I believe you can also control these from a PC, using some interconnect hardware. (Parallel port? USB?) I'm afraid I don't know much about this in particular, but I do know some solutions exist to hook these displays up to a PC, so you might have luck with something like that.
HT1621B for Controlling Glass LCD - Page 1
Forum section: electronics / beginners

author: Phaedo
author_rank: Contributor
timestamp: February 16, 2023, 06:18:13 pm
content: Hello ,I did a bit of searching on the threads pertaining to HT1621, but most are reverse engineering existing LCDs without showing the schematics.So I could not get an idea of how the LCD is connected to the HT1621.I am trying to get HT1621 to work with a 3.5 digit glass LCD. I am basically using an arduino code from here :https://www.14core.com/wiring-the-6-digit-7-segment-2-4-inch-ht1621-lcd-display-module-on-microcontrollerI am not too sure about what are the settings for my LCD.a) Selection of 1/2 or 1/3 bias.b) Selection of 1/2 or 1/3 or 1/4 duty LCD.If anyone can give me a bit of guidance or point to some links , would be awesome !!I have attached a schematic of what I have breadboarded FYI.Cheers and TIA

author: Phaedo
author_rank: Contributor
timestamp: February 17, 2023, 03:25:51 pm
content: Solved. Bad connection on breadboard.
HT16k33 and common cathod LED displays - Page 1
Forum section: electronics / beginners

author: Nicals
author_rank: Newbie
timestamp: May 20, 2017, 10:21:57 am
content: Hello,I recently bought someHT16K33chip to drive a bunch of 7 segments display. I have around 122 LEDs to drive, so this chip seemed to be perfect for me.However, I only found some common anode 7-segments and the chip needs common cathode.Anybody have an idea on how I can adapt this HT16K33 chip to work with common anode or if another chip could drive all this LEDs ?I had a really hard time finding all the 7 segments I needed and I am not willing to buy other one with correct configuration.Thanks for the help.
ht4936s protection features - Page 1
Forum section: electronics / beginners

author: shobo
author_rank: Regular Contributor
timestamp: February 06, 2018, 08:26:43 pm
content: Does ht4936s have any protection features for the Li-Ion cells?i ordered one of those 2 cell power bank cases from china for 2 cells that i have laying around and i would sure love that they dont go thermonuclear on me since i'm pretty sure they lack the protection IC.(recovered from a dead laptop battery)An english datasheet would be nice if anyone has one
Huge output ripple from 3 BJT regulator - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 07, 2019, 04:57:21 am
content: Experimenting and making LTspice models, of 3 BJT regulator and SMPSI took a 24.2V internal SMPS from a printer, it's a nice enough looking PCB. It's output ripple on the scope is ~7-8mV, with peaks of about 50mV at the switching frequency of 183kHz. And with it passing 0.24A, the overall ripple is still about 8mA, but the peaks are now up around 85mV.I made a 3 transistor regulator with feedback, that goes from 2.2-22.2V, it only has 1u on input and output.schematic belowIt's no-load ripple is about 50mV. With it at 12.6V @126mA the ripple is like 1.3V. So thats quite the noise amplification.And when I added a 47u output cap, I get 1.9V (volts not mV) ripple, big solid wavy ripple at 183kHz, not spikes.In LTspice I made 2 models, 1 with the large scale T-models , and measured the betas of the 3 BJTs and resistors. And the other uses 2n3904 and 2n3055 in spice.For the input voltage I put a 24V+85mV 183k sine wave. On their output's I get less ripple, only maybe 50uV (micro, not milli like the 80mV on the input). So neither makes the messy thing I made.Tomorrow I'll hook it up to a 36V transformer, see what it does. As a regulator this thing over compensates under load. The SMPS is fine. I haven't done any calculations yet, this is the 1st time in ages I breadboarded something.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 07, 2019, 06:23:39 am
content: Try a series resistor on Q3 collector (say 10k), then an R+C across C-B (say 100k and 100pF?).Do you really need to go out of your way to make a regulator in the first place? What's wrong with a 7812, or zener+follower, or capacitor multiplier? Or just filtering it alone, or just not even bothering because it's not needed?Tim

author: lordvader88
author_rank: Frequent Contributor
timestamp: May 07, 2019, 04:48:02 pm
content: No this is for fun/learning. But I did figure on using that SMPS for >24VI tried it with the transformer and the noise is super low, even at +1A, its under 2mV. Interesting, I'll try it with my 12V SMPS PSU, probably just as bad.All the more reason to stop using these and make a good linear PSU

author: soldar
author_rank: Super Contributor
timestamp: May 08, 2019, 10:49:29 pm
content: What's the deal with R14, 15, 16, 17, 18?? why that network? You can just replace with a two resistor voltage divider. Add a pot if you want to make it adjustable in real life.At any rate. What happens if you add a cap between the center of the voltage divider and ground? That should improve ripple (but slow response time).
huh? what device? coolant checker? - Page 1
Forum section: electronics / beginners

author: 3roomlab
author_rank: Frequent Contributor
timestamp: October 17, 2019, 07:53:31 pm
content: in this video @ 1:50the guy uses a coolant checking devicewhich of course didnt ring a google bellanybody out there know what to call this checker? to google?

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: October 17, 2019, 07:59:31 pm
content: It just changes color based on the glycol concentration.https://www.ebay.com/itm/Universal-Refractometer-Glycol-Car-Antifreeze-Tester-Engine-Coolant-Battery-Acid/323860186090?epid=525511105&hash=item4b679243ea:g:mo4AAOSwRG1cgQlzJust search for coolant tester.

author: ConKbot
author_rank: Super Contributor
timestamp: October 18, 2019, 07:35:08 am
content: Refractometer is another name for it, the scale can vary both in range, and units. Brix is a common scale, calibrated for sugar in water for the beverage industry, with conversions, or dedicated units with a scale appropriate for the sample being measured.I.e. The refractometer that a machine coolant vendor sells you will of course read directly for the oil emulsion, but an ebay/amazon one in brix may not.
humidity and parts - Page 1
Forum section: electronics / beginners

author: djacobow
author_rank: Super Contributor
timestamp: June 08, 2014, 01:30:56 am
content: Many parts but not all -- that arrive from Digikey or Mouser arrive in little sealed bags that say that the parts must be reflowed within XX hours of opening. I think it has to do with water absorption through humidity, but don't really know.The parts are obviously going to spend years outside the bad on the board, so it's not like they should fail from being exposed to air. But somehow they do not solder as well?Curious to hear what the real story is.

author: baljemmett
author_rank: Unknown
timestamp: June 08, 2014, 01:39:46 am
content: Quote from: djacobow on June 08, 2014, 01:30:56 amPretty much. I believe the concern is that they absorb water from the atmosphere before soldering - then, when they get hit by the heat of reflow, the water suddenly becomes steam and pops the part off the board or cracks the package.

author: f5r5e5d
author_rank: Frequent Contributor
timestamp: June 08, 2014, 01:52:34 am
content: reflow, wave soldering fast heating profiles, especially with higher lead-free solder temps can cause "popcorning" steam explosions - I've had the orange epoxy dip coating on Panasonic pp film caps tear open on a board run - the assembly house just kept the cap stock on a rack above the oven, >50 C for a day or two before the next run with no problemshttps://www.google.com/#q=popcorning+lead+free

author: djacobow
author_rank: Super Contributor
timestamp: June 08, 2014, 03:22:35 am
content: OK, so then it sounds like this is not of concern to the hobbyist / someone uses an iron and hot air gun. It also sounds like a short bake in a warm dry oven would drive the moisture away, anyway.

author: WarSim
author_rank: Frequent Contributor
timestamp: June 08, 2014, 05:07:18 am
content: Quote from: djacobow on June 08, 2014, 03:22:35 amHand soldering a wetted part with perfect heat control could cause damage. If a hobbyist uses wetted parts it can be changed when there is an after build problem. Because I doubt any hobbyist would go through the time and expense of humidity controlled storage and parts dryers. We just fix the failures when they occur.Humidity control is a larger factor for process reliability? Having sporadic failures on a large manufacturing run is very problematic. This us why the data sheet tells you about the parts absorption rates so the manufacturer can minimize absorption based failures.Sent from my iPad using Tapatalk

author: DJ
author_rank: Unknown
timestamp: June 08, 2014, 05:28:39 am
content: Quote from: djacobow on June 08, 2014, 01:30:56 amThe parts are classified according to MSL, or moisture sensitivity level.Couple of notes explain in detail the levels and how to handle accordinglywww.intersil.com/data/tb/tb363.pdfwww.ti.com/lit/an/snoa550a/snoa550a.pdf
Humidity Spec - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: April 24, 2017, 11:06:26 pm
content: I'm trying to recall how humidity specs are applied. I'm looking at a dewpoint chart, and cannot remember how to interpret it.I think the spec is to indicate a condition where condensation on the circuit results, or something similar. So, if the max non-condensing humidity spec is 95% at 30C, does that mean that 95% at 40C is still OK or would the temp need to be 30C or less?

author: metrologist
author_rank: Super Contributor
timestamp: April 25, 2017, 04:29:59 pm
content: Is this just too painfully obvious or really too tuff for the beginners forum?

author: Ratch
author_rank: Regular Contributor
timestamp: April 25, 2017, 06:47:55 pm
content: Quote from: metrologist on April 25, 2017, 04:29:59 pmYou would do well to read this link.http://www.shorstmeyer.com/wxfaqs/humidity/humidity.htmlRatch

author: metrologist
author_rank: Super Contributor
timestamp: April 25, 2017, 07:57:52 pm
content: The article was getting difficult to read, and I still question if I am understanding the words correctly, or at least understanding them well enough to apply to my situation.Here is from Myth #1, that warmer air holds more water:CORRECT TERMINOLOGY:ON A WARM DAY MORE WATER CAN EVAPORATE BECAUSETHERE IS MORE THERMAL ENERGY AVAILABLE TO DO THE WORK OF EVAPORATION.In order to claim a mil spec, the non-condensing RH has to meet 95% at 30C. The spec I am reading says non-condensing RH is 95% at 40C. To me, that says it does not meet the spec because a higher temperature is needed to prevent the associated problems with condensation that would result from the lower (30C) temperature.The mil spec continues with two footnotes that say:RH 75% above 40CRH 45% above 50CSo now I am not sure if the spec I am reading means it exceeds the mil spec, because at 40C it can handle 95% humidity and the mil spec only limits to 75% at that temp.

author: metrologist
author_rank: Super Contributor
timestamp: April 27, 2017, 03:56:59 pm
content: Someone finally explained it to me in a way I could understand. I kept thinking of water on my circuit and if it would be better to dry that out 30C vs 40C. It seems intuitive that 40C would evaporate more water and dry off the circuit.But the atmosphere at 40C has a greater water density than when at 30C, if RH is 95% in both cases.
Humming in speakers - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: May 10, 2019, 11:31:03 pm
content: A humming started in my speakers.I use a Logitech external speaker system.If I turn it's volume down, the humming volume goes down.If I unplug/plug its power source the humming goes away for a while.

author: Brumby
author_rank: Unknown
timestamp: May 11, 2019, 12:25:52 am
content: What happens if you unplug/plug the signal input jack?

author: fixit7
author_rank: Regular Contributor
timestamp: May 11, 2019, 11:15:08 am
content: I found out that the speaker output plug was not all the way plugged in.

author: Brumby
author_rank: Unknown
timestamp: May 11, 2019, 01:07:50 pm
content: Do you mean the connection between your computer and the speakers?

author: radiolistener
author_rank: Super Contributor
timestamp: May 11, 2019, 01:11:52 pm
content: Probably you're need to replace electrolyte capacitors in your speakers. This is the most weak elements and often this is a root of cause of malfunction due to low quality.

author: Brumby
author_rank: Unknown
timestamp: May 11, 2019, 01:19:02 pm
content: I went for the low tech idea that a plug wasn't inserted properly. Looks like I was right - and if the "speaker output" the op mentions is the socket on the computer they're using, then I was exactly right.An improperly fitted plug is the easiest way to get hum in your audio.Re-capping the amp in the speakers is not a bad idea - but it would appear to be rather unnecessary in this case.

author: fixit7
author_rank: Regular Contributor
timestamp: May 12, 2019, 10:10:19 pm
content: Quote from: Brumby on May 11, 2019, 01:07:50 pmYes.When I pulled it out halfway, the hum came back.

author: Brumby
author_rank: Unknown
timestamp: May 13, 2019, 12:30:00 am
content: Exactly what I thought - and super easy to fix!Sometimes you can get the same problem even when the plug is fully inserted - especially if it has been plugged in for a long time. Contamination build up and/or oxidation/corrosion (which may not even be visible) can interfere with the connections. Just unplug/replug (maybe a few times) to wipe the contacts clean enough for another period of hum free sound.
Hunting down opamp oscillation - Page 1
Forum section: electronics / beginners

author: iampoor
author_rank: Frequent Contributor
timestamp: May 12, 2015, 02:45:11 am
content: HiI am currently working on a basic baxandall eq project. Of course, the circuit is oscillating above 20khzWhat is your usual process for working out oscillation issues? I think the problem is my PCB layout........but I am wondering what your methodology usually looks like when trying to solve issues like this? What do you usually try and in what order?Thanks!

author: LA7SJA
author_rank: Regular Contributor
timestamp: May 12, 2015, 05:20:18 am
content: Too little information fore someone to give a good answer.But you can try reading thishttp://www.linear.com/docs/45597Johan-Fredrik

author: iampoor
author_rank: Frequent Contributor
timestamp: May 13, 2015, 12:31:13 am
content: Quote from: LA7SJA on May 12, 2015, 05:20:18 amMaybe my question isn't clear, Im wondering what people initially check when they notice opamp oscillationThanks for the article link

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2015, 02:04:56 am
content: "Your circuit is bad, and you should feel bad"?Oscillation is either a topological problem (e.g., you put feedback to +in when you meant -in), or a feedback problem (too much junk in the feedback loop and it's phase shifted to hell). Either way, you have to start with the circuit.There isn't anything general that can really be said, aside from recitations of Nyquist stability criterion. As for what's violating the criterion... you'd have to look.Don't forget to inspect everything related. Supply pins don't have infinite PSRR at just any frequency. They are inputs, just not very good ones! They are also quite good outputs, since any current drawn from the output pin is also drawn from +V or -V. For both these reasons, bypass caps are a good idea.Don't ignore the reference voltage. Usually this is GND. Sometimes it's a floating level between -V and +V. Sometimes it's explicit in the circuit. Whatever it is, it needs good bypass too, otherwise all the impedances driving it give a place for AC signals to roam, and you get feedback loops between stages.Tim

author: iampoor
author_rank: Frequent Contributor
timestamp: May 13, 2015, 11:38:15 pm
content: Quote from: T3sl4co1l on May 13, 2015, 02:04:56 amHey Tim, thanks for the informative post as always!Im fairly positive (hah get it!) that the issue is in the feedback loop. My circuit routing was pretty awful! In fact....its almost embarrassing to post! Phase shift is of particular concern in active equalizer design right?Love the points about the supply pins, I added some decoupling, but they look pretty good on the scope. The ref voltage Is a virtual earth, just two 10k resistors, a 10uf and a .1uf bypass cap. I have noticed oscillation on the reference point before, but it seems pretty clean again. Im thinking my routing is just causing some brutal phase shifting. I need to redo it anyways as the layout was lost in a hard drive crash..
HV Optocouplers - Page 1
Forum section: electronics / beginners

author: bullet308
author_rank: Frequent Contributor
timestamp: February 01, 2012, 09:58:22 pm
content: Hi:Could somebody tell me something about optocouplers? More specifically, are there any optocouplers out there that could trigger on, say a momentary 400-1400v 10uA surge on the input side and survive?

author: ivan747
author_rank: Super Contributor
timestamp: February 01, 2012, 11:26:14 pm
content: I don't think many will survive those conditions if they are reverse biased. Maybe a filter can dissipate the surges and a high breakdown voltage diode could help to protect it. After all, the impedance of the surge is too high to destroy a filter.

author: Psi
author_rank: Super Contributor
timestamp: February 01, 2012, 11:39:51 pm
content: I think you'd have to use a fet/transistor to take the 1400V signal and switch on the optocouplers led.But i'm guessing you want to avoid a powersupply for the input side.

author: bullet308
author_rank: Frequent Contributor
timestamp: February 02, 2012, 12:39:48 am
content: Allow me to add some details (I was in a hurry when I threw the question up earlier).The "surges" in question are not incidental or environmental, but an integral part of the devices function, the device being a Geiger counter.For those that are not familiar with how Geiger counters work, there are essentially two sides to the electronics package: the high voltage side which loads the Geiger-Mueller tube at 400-1400v and a low voltage side that detects when the high voltage side fires upon the tube being penetrated by a ray or particle of ionizing radiation. The low voltage side then counts it, averages it, turns it into a LED blink or a "click" in a speaker, whatever you want it to.Usually, there are some HV diodes and other circuitry involved in keeping the high voltage side from leaking over and blowing up the low voltage side, but a common failure mode in some Geiger counters is for that circuitry to break down, resulting in blown transistors and such,I was beginning to think in terms of using an optocoupler for that purpose as a way of making the HV and LV sides completely isolated from one another. If there is zero electrical interface between the two, that cant happen any more, can it?Anyway, that is what I was thinking. Thanks for the feedback.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 02, 2012, 12:58:11 am
content: I have seen optocouplers with a neon as the emitter used in telecom applications, not sure of they still make them.However I don't see that it should be much of a problem in a geiger application, as the grounds can be the same between the HV and LV, and protecting a low-level signal from HV just needs a high value resistor and zener.However you do need to pay attention to details like the voltage rating of the resistor, so in practice you'd use a few in series.
HVAC Surge Suppressors - Real protection or garbage? - Page 1
Forum section: electronics / beginners

author: SpookyGhost
author_rank: Contributor
timestamp: December 22, 2022, 02:22:11 am
content: I have 3 AC units, a conventional 4 Ton unit, and then 2 Mini Splits. I'm tempted to spend the $75/ea for Intermatic AG3000 surge protectors to add to the disconnects for each ACDo these actually do anything, or is it just marketing garbage?Worth noting that I do have a surge protector on my main panel (Generac ATS) and the panel directly after it

author: Ian.M
author_rank: Super Contributor
timestamp: December 22, 2022, 03:11:44 am
content: What do you think its going to do when you already have two layers of surge protection upstream of it? If it has to clamp a significant surge, odds are everything else electronic in your house has already died, but at least you'll have aircon!It may offer some benefit if fitted locally to the unit and the unit is on a flat roof or in an outbuilding far from the panel feeding it, by reducing the risk of damage due to induced surges caused by nearby lighting strikes - if they are frequent enough to be a significant concern.

author: Teledog
author_rank: Regular Contributor
timestamp: December 22, 2022, 05:25:18 am
content: Perhaps somewhat off topic..but..Inrush current limiters? dirt cheap (ICL on Digi-Key)

author: BlackICE
author_rank: Regular Contributor
timestamp: December 22, 2022, 09:25:21 am
content: https://invertersrus.com/wp-content/uploads/2020/02/EasyStart_Specification_Sheet.pdfI 1st bought one with some doubts, so I tested it with an oscilloscope with current probe. It did work lowering the peak inrush current from something like 150 amps to 90 amps (from failing memory I could look from the saved traces). This allowed me to startup a 5 ton HVAC with a 15KW generator. After my testing I bought 2 more so that all of my HVAC can now run off of only a 15KW generators. Of course not all 3 at the same time. Another benefit is my lights no longer flicker and dim every time a compressor starts up.I bought the PCB version, not the complete units. Cheaper and easier to mount IMO.
HW Help - Modulation depth vs mean output power. - Page 1
Forum section: electronics / beginners

author: mower
author_rank: Contributor
timestamp: October 31, 2022, 03:09:35 am
content: Hello everybody,I am working on a design task for a communications system class. We are to design an amplitude modulator. The message is 0.5cos(2pi*f*t)+0.5cos(4pi*f*t) where f=1MHz. The system should have a mean output power of 15dBM and a modulation depth of +-5dB. My question is, how can i achieve both? the message signal has a maximum of 1, and a minimum of -0.56, and a mean of 0. Therefore, it is my understanding when the message is at 0, the output power should be 15dBM. How can it swing +5 and -5, if the max and min value of the message are not symmetrical about the mean? Also for more context the carrier is to be 10 GHz

author: mikerj
author_rank: Super Contributor
timestamp: October 31, 2022, 10:39:50 am
content: You wouldn't normally specify modulation index as a +-dB value around the carrier power as this will not give symmetrical modulation. It's more usual to specify modulation index as a percentage of the absolute carrier power (W, mW, uW etc) e.g. 100% would be full modulation, doubling the carrier power on the peaks and giving zero power on the nulls.

author: mag_therm
author_rank: Frequent Contributor
timestamp: October 31, 2022, 01:05:03 pm
content: I agree, in my day modulation depth was expressed in percent, so -5dB would be 56.2 percent which is OK.The carrier level can then be determined and the base power of the combination.Better to ask your supervisor about the +-dB notation asap.

author: jonpaul
author_rank: Super Contributor
timestamp: November 01, 2022, 07:03:48 am
content: read any classic theory of communication text book.Modulation theory (1953) Modulation theory by Harold S. BlackYou will learn.Jon
.hws files - Page 1
Forum section: electronics / beginners

author: Deboscope
author_rank: Contributor
timestamp: December 07, 2019, 08:52:16 am
content: My Hantek 4202C saves waveforms on a USB Stick in a .hws format.I have tried but can't seem to find a way to make these files to open.Any ideas?

author: dodge bullets
author_rank: Newbie
timestamp: October 12, 2022, 04:41:50 am
content: Did you ever figure it out? I have the same model and I am beating my head against a wall. I don't find anyone or site mentioning this strange format (except this post)

author: austfox
author_rank: Regular Contributor
timestamp: October 12, 2022, 08:13:10 am
content: Could it be that the .hws files are only for displaying on the scope itself, and that you need to save as a CSV file to be able to view it on a computer?
HY1803D power supply schematic confusion - Page 1
Forum section: electronics / beginners

author: MikeK
author_rank: Super Contributor
timestamp: March 31, 2021, 02:14:02 pm
content: Please see the attached schematic. The op-amp on the right controls a relay, but I don't see how the op-amp inputs will ever change. Neither input seems to be referenced to anything that changes. Am I wrong?

author: bd139
author_rank: Super Contributor
timestamp: March 31, 2021, 02:34:03 pm
content: The entire supply's internal ground is referenced to positive output of the supply. The power supply varies the negative rail rather non intuitively (consider voltage drop across the pass transistor). The opamp is a comparator in a schmitt trigger arrangement (to give it some hysteresis otherwise it'll chatter the relay to death) that samples the difference between the internal + reference from the 7812 and the negative rail.Fixed a couple of these and it gave me a headache the first time or two (and now!)Edit: let me guess you're fixing one that has blown up the transistor? This is super common and usually happens because the relay stops working, failing to the highest voltage across the pass transistor (stupid design), followed by it dropping dead.

author: MikeK
author_rank: Super Contributor
timestamp: March 31, 2021, 02:38:39 pm
content: Thanks! Didn't get it yet. I have the chance to pick up a non-working unit and wanted to understand the schematic first.

author: bd139
author_rank: Super Contributor
timestamp: March 31, 2021, 02:51:44 pm
content: If it's non-working it'll probably be easily repairable. They are made of entirely standard bits. Only risk is the transformer being toasted. Good luck with it
HY6264 SRAM - CS1/CS2? - Page 1
Forum section: electronics / beginners

author: gmc
author_rank: Regular Contributor
timestamp: November 08, 2019, 09:28:38 am
content: Busy messing around with an Arduino and some of this old school ram.On the truth table to read/write you put CS1 low and CS2 high.To power down chip CS2 goes low.Just curious why they didn't just use a single CS pin. Why the need for CS1 and CS2?What am I missing?https://datasheetspdf.com/datasheet/HY6264.html

author: capt bullshot
author_rank: Super Contributor
timestamp: November 08, 2019, 09:32:28 am
content: Quote from: gmc on November 08, 2019, 09:28:38 amYou're missing nothing. There's no need for a second pin, they've just used a spare package pin to provide you with a second CS pin for your convenience. Sometimes this was used to easily power down and protect battery backed memory from accidental writes when the CPU powers up or down. Saved a gate back then.

author: gmc
author_rank: Regular Contributor
timestamp: November 08, 2019, 09:34:53 am
content: Thanks for the info. Thought it was odd.
hybrid stepper motor - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: November 04, 2019, 12:41:34 am
content: Hi ,does anyone know if i can drive a hybrid stepper with a drive meant for a unipolar motor?

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 04, 2019, 01:08:20 am
content: Quote from: m3vuv on November 04, 2019, 12:41:34 amWhat did you find during your research?

author: m3vuv
author_rank: Super Contributor
timestamp: November 04, 2019, 01:26:51 am
content: HI ,to be honest no definitive answers,my steppers are 6 wire nema 23 hybrids,running with bipolar drivers,the sketch and driver schematic i have is for what i can tell 8 wire unipolar motors,i realy want to use what i have to hand,see attached schematic,cheers m3vuv.
Hydraulic Power Pack - Page 1
Forum section: electronics / beginners

author: Remark
author_rank: Contributor
timestamp: November 12, 2022, 09:44:45 pm
content: Hello everyone.There was a need to control a 12V 1.6kW hydraulic station. I want to mention that I have little experience working with hydraulic systems. So, I would like to ask what power supplies are used for these stations? According to the required power of the hydraulic station, I cannot find such a power source... With it, I want to control a hydraulic cylinder with limit switches, and that's it.I also want to ask if a general purpose microcontroller is fine for the station control or should I use one of the PLC controllers?Thanks for the answers.

author: vu2nan
author_rank: Contributor
timestamp: November 13, 2022, 06:10:07 am
content: Such 12 V DC low duty-cycle equipment are generally operated with 12 V high-capacity lead acid batteries.Here's the write-up for a similar piece of equipment.Nandu.
Hypothetical: 10 LEDs VS 1 @ same current? - Page 1
Forum section: electronics / beginners

author: kalel
author_rank: Frequent Contributor
timestamp: January 16, 2018, 06:24:26 am
content: Let's imagine some run of the mill white 5mm LEDs. It could be anything from the cheap Chinese ones to high quality ones (I understand that the choice of LEDs might impact the result).The question is whether or not connecting 10 LEDs in parallel and running them at low current (say 1mA) would yield a human-noticable higher light output than running a single LED at 10mA.I also don't have any specific implementation in mind, I'm just curious if at least in theory, in low power consumption scenarios using more LEDs and running them at very low currents would make sense.

author: Circlotron
author_rank: Super Contributor
timestamp: January 16, 2018, 06:27:52 am
content: The LED manufacturer should provide a graph of luminous intensity vs current on the datasheet. That should provide enough information to answer your question.

author: danadak
author_rank: Super Contributor
timestamp: January 16, 2018, 10:39:33 am
content: The light response relatively linear with current -Problem is LED to LED variation, paralleling them without using series Rs, ballasting, one in series witheach LED, could result in some LEDs with little or no current , others with high current.Then there are optical issues, luminance on an area, size of area, shape......Regards, Dana.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: January 16, 2018, 11:33:57 am
content: Quote from: danadak on January 16, 2018, 10:39:33 amLooking at this chart, it seems five leds driven @0.2 would be ~ 50% better than one driven @1.0, no?

author: Zero999
author_rank: Super Contributor
timestamp: January 16, 2018, 11:37:17 am
content: LEDs are generally more efficient, when run at lower current, assuming an SMPS is used. The light output is proportional to the current, but the forward voltage falls, as the current is reduced, therefore the LED consumes less power and is more efficient. If you're using a resistor or linear PSU, then the extra voltage drop is burnt as heat, but if it's a switched mode, then there will be some gains in efficiency.

author: xibalban
author_rank: Regular Contributor
timestamp: January 16, 2018, 12:11:48 pm
content: Quote from: Circlotron on January 16, 2018, 06:27:52 amHe/she (quoted above) is right.Depends on the LED type as you rightly mentioned in your first post. It all boils down to the efficiency of the LED that you choose to use. 10mA is drawn in both cases, and if there are equal amount of losses (heat loss mostly) in both the cases, the output (or brightness) should be the same.
Hysteresis for low-voltage cutoff circuit - Page 1
Forum section: electronics / beginners

author: Aeternam
author_rank: Unknown
timestamp: September 21, 2016, 08:01:46 am
content: Hey gang,I want to add hysteresis to a low-voltage cutoff circuit (see attachment.)I am designing a dew heater for telescopes. Since these things are used in the field I plan on powering it with a lead-acid battery (already present to provide power to telescope mount etc.) We all know that discharging these below a certain point is inadvisable, hence the low-voltage cutoff.Problem with my current design is, once the cutoff kicks in the load on the battery disappears and voltage rises again. The circuit sees enough voltage and turns the heater back on. Hysteresis to the rescue: cut off the load once voltage drops below 11.5V and do not turn back on until it's above say 11.8V.Problem is, I have NO idea on how to implement something like that. Is that even doable with the attached subcircuit?Sorry for the sucky scan btw. The 10k thing on the opamp's positive input is a 10k pot, VIN is connected to the battery, the rest of the circuit continues to the right of the relay. The opamp compares VIN to a zener reference voltage. As long as VIN is above the zener voltage the transistor is keeping the relay open which in turn powers the rest of the circuit.I'd be happy if someone could point me in the right direction.Cheers!

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 21, 2016, 08:10:46 am
content: 1) add a resistor (say, 1K) in series with the base of Q7 . As drawn, you are relying upon the short-circuit protection of the opamp, not a good thing.2) connect a resistor between the output of the opamp and the non-inverting input, say 470K . The value would define the hysteresis width.CheersAlex

author: Aeternam
author_rank: Unknown
timestamp: September 21, 2016, 08:20:44 am
content: 1) oops2) brilliant, thank you

author: Whales
author_rank: Super Contributor
timestamp: September 21, 2016, 08:28:37 am
content: Just be wary that this hysteresis resistor will change your trigger point. You'll need to re-adjust your pot after you install it.

author: Alex Nikitin
author_rank: Super Contributor
timestamp: September 21, 2016, 08:33:09 am
content: Yes, and one more thing - add a diode (something like 1N4004 is usually sufficient) across the relay coil (cathode/bar to the + supply, obviously) to protect the transistor from overvoltage by back EMF from the coil.CheersAlex