hybridfree/eevblog-posts huggingface dataset:
Yihua 305DA Power supply negative voltage on output and calibration - Page 1
Forum section: electronics / beginners

author: Damian1908
author_rank: Newbie
timestamp: November 29, 2024, 12:18:24 pm
content: Hello everyone i am new here, i am looking for some help with linear power supply Yihua 305DA. I have two problems with it first is calibration does anybody know which potentiometer is coresponding with certain settings. There are six potentiometers described as V1 V2 V3 V4 VR1 VR2 attached picture. Second problem is present of negative voltage -0,7V when output is turned off it is normal behavior? I will be very gratefull for any help, best regards.On my first attempt to calibrate for me it looks like described below but i am not shure it will work like thisVR1 set maximum CURRENT value on displayVR2 set maximum VOLTAGE value on displayV1 set CURRENT on outputV3 set VOLTAGE on outputStill dont know whats it V2 and V4.Now on low voltages and current dislay is fine but on higher is not correct.

author: jwet
author_rank: Frequent Contributor
timestamp: November 29, 2024, 08:00:42 pm
content: Welcome to the group. Your best bet is to get a schematic/service manual from the manufacturer.Here are some educated guesses- you're likely right about the pots that you've found. Watch for interactions between the adjustments- sometimes they aren't completely independent. This is where a test procedure/service manual could help.On the -.7v, when off, this is likely the charge on the output cap clamped by a reverse polarity diode on that little board on the front panel. Load it with a 1k R and see if goes away consistent with value of that Cap - T=RC. A better instrument might have a 10k R across the C to deplete this- in your case, it gets down to .7 and has nowhere to go once the diode stops conducting at .7v.aMy guess for the mystery pots is switchover points that tap the transformer secondary at different voltages. This is common in high current variable linear supplies. At lower output voltages, a lower voltage tap is used to lower the voltage that the pass transistor has to take. If you wanted to make 1v at 5 amp from a 30 volt, basic transformer and rectifier, the pass element would have to dissipate nearly 150W. If you use and 8v tap for these lower voltages, you can limit this case to 35W, much more manageable. Its likely there are three secondaries, a high voltage one- say 30V, a medium one, say 22v and a low around 8V. The output pass element has to dissipate the drop in voltage times the output current.Get a schematic somehow and have fun. I've told vendors that due to being an ISO 9000 shop, all our equipment had to be fully documented. They coughed up schematic from somewhere. Good luck.Good luck.
YIHUA 8858 Upgrade vs 858D for budget rework station ?  - Page 1
Forum section: electronics / beginners

author: DarrenHerondale
author_rank: Newbie
timestamp: April 29, 2018, 09:40:08 pm
content: Hey guys,I did not find any review on the YIHUA 8858 Upgrade heat gun. Does anyone haveexperiencewith it ?Also, which one (the one above or 858D) would be better as abudgetrework station ?858D:https://www.ebay.co.uk/itm/858D-220V-SMD-Soldering-Desoldering-Station-Hot-Air-Rework-Gun-Tool-3-Nozzles/301966004104?epid=581359676&hash=item464e938f88:g:2rwAAOSwSWJXRVdWYIHUA 8858 Upgrade:https://www.banggood.com/YIHUA-8858-Upgrade-LED-ESD-Portable-Constant-Temperature-BGA-Rework-Solder-Station-Hot-Air-Heat-Gun-p-1123609.html?rmmds=search&cur_warehouse=CNThanks

author: Shock
author_rank: Super Contributor
timestamp: April 29, 2018, 10:39:09 pm
content: I'd tend to stick with a "name brand" 858D. The name brand ones are not the highest quality either but better than that selecting one totally unbranded. I've got a Yihua 858D, it's not perfect, the tips are hard to change otherwise it does the job. Replacement handles and heaters are fairly easy to obtain.All in one unit's in my mind are asking for trouble, the backstory is a cheaply made device running at mains potential or a poorly made switch mode power supply that has had no independent testing and sold in a largely unregulated market. Well hopefully you get the idea.The YIHUA 8858 in it's cradle will shoot hot air across the table so not a good idea. The fat part of the handle is right where you need to grip it, and trying to mount it for rework will also affect usability. I also doubt it's performance is superior to the 858D.
Yihua Irons Heat Control - Page 1
Forum section: electronics / beginners

author: trinityracing
author_rank: Newbie
timestamp: July 06, 2020, 02:07:41 am
content: Hi, First post here. I've enjoyed reading many posts on this forum, lots of good info here, however I have a question.I don't do a ton of soldering but have used a WCL-100 for years. Pardon me if I don't use correct terms here but I wanted to buy a station that can regulate the heat better. As in, the iron can double time it when needed to maintain temp when needed instead of one controlled with a dimmer switch which can take time to recover. Among other things, this is #1 reason to switch irons.I don't do enough soldering to justify buying the $100+ Weller or Hakko which I believe can do what I looking for. I figured the Yihua Stations were decent enough copies capable of maintaining heat by sensing actual temp and auto adjust to maintain like the more expensive rigs just maybe not as good of course.I just received the Yihua 939D+ which is probably not much different from other Yihua just that it has 907F handle and has C/F switch. For all I know the temp it shows is close enough (I adjust by feel) but the display appears fake as far as heat up and along with the blinking light when its supposedly heating.My question to anyone who so kind to enlighten me does this 939D+ have any kind of sensor or feedback circuitry to maintain temp or is it simply calibrated display to a given current sent to the iron?If not, is there any Yihua that does have this feature?I don't know what the higher end irons use for feedback whether it be Thermacoupler or what but I'd like to know exactly what I have here and if its even an upgrade from the WCL-100, besides having digital readout and minor stuff.Also, I noticed on a the same popular site I purchased this one, are a few other budget stations that claim to use PID to maintain temperature. The reason I did not try one of those is because of a video I seen showing slow heat up time and it weighs nearly nothing. No heavy Transformer inside.I did spend a substantial time looking up these questions but came up barely short of the finish lineEdit: BTW, my Yihua 939D+ is the black one not the yellow/blue with the 3 preset buttons on the front.Thanks
You can laugh (opamp question) - Page 1
Forum section: electronics / beginners

author: jemarro12
author_rank: Contributor
timestamp: May 11, 2025, 10:50:21 pm
content: I'm just trying to set up variables like opamp_gain and resistor_divider value in a firmware (IronOS project).In other soldering iron these variables are ~ 400 for opamp_gain and ~500 in the divider. Obviously they got the numbers from schematics. Reversing a soldering I'm trying to port this is the opamp config, being vin the T12 tip reading and vout goes directly to ADC. V+ is 3.9v.What kind of opampnconfig are we talking?

author: bostonman
author_rank: Super Contributor
timestamp: May 12, 2025, 01:52:06 am
content: That's a non-inverting gain op-amp config.

author: golden_labels
author_rank: Super Contributor
timestamp: May 12, 2025, 05:57:32 am
content: If you need an introduction to op-amps, Dave made one.(video:1)Mehdi published another one(video:2)recently, if you want a less serious one.Taking your drawing, adding references and marking two separate sections:The upper, yellow part is anon-inverting amplifier. It uses GND (0 V) as reference and provides R2 / R1 = 270 kΩ / 1 kΩ ≈ 270 amplification.The red, bottom part is the input. R4 and the capacitor are likely alow-pass filterto remove noise. R3 may have two functions, both of them at the same time.R3 may act as a pull-up resistor to form a fail-safe mechanism. If the thermocouple connection is broken, the input goes to 3.9 V, which is registered as insanely high temperature and the controller cuts off power to the heating element. Even if it fails to detect the condition, this is still read as signal to reduce temperature, having the same outcome.R3 may also bias the input. Thermocouples produce very low level signals. With single-supply op-amps this means the signal is almost at or even below of what the op-amp may process. Shifting the input value up a bit means later we work with signals that are closer to the middle of the range. The downside is that we lose linearity. But it’s much easier and cheaper to just calibrate the controller, than to design the entire analog circuit so the signal is kept nice and tidy.If R3 was used for biasing, I’d expect to see another resistor in line with the thermocouple. But who knows…(video:1)EEVblog “EEVblog #600 - OpAmps Tutorial - What is an Operational Amplifier?”:(video:2)ElectroBOOM “OpAmp, the Ultimate Component (ElectroBOOM101 – 013)”:
You will appreciate this - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: November 08, 2011, 11:10:22 pm
content: Very Succinct! Good find!

author: FenderBender
author_rank: Super Contributor
timestamp: November 08, 2011, 11:27:59 pm
content: Poor lil amp looks like hes in pain! But yes a good way to think about it!

author: Unknown
author_rank: Unknown
timestamp: November 08, 2011, 11:59:28 pm
content: Thanks alot for this Wartex, is this your own work? I mean, is this protected in any forms?

author: Achilles
author_rank: Regular Contributor
timestamp: November 09, 2011, 12:19:42 am
content: ..I am quite sure that it is protected. Another thing is if anybody would sue you if you use it (which doesn't mean it's ok to copy it)It is funny and brings it to the point. Probably a good starting point for beginner courses in electronics.We were told a water-analogy:A bucket of water is attached with a waterhose.The height above ground of the Bucket is the Voltage, the water-flow through the hose is the current and the diameter is the resistance. Somehow I prefer the cartoon-style

author: Unknown
author_rank: Unknown
timestamp: November 09, 2011, 12:21:29 am
content: Note how all the figures are white male. Nowadays you would have male female, black, yellow, white pffff...

author: Achilles
author_rank: Regular Contributor
timestamp: November 09, 2011, 12:24:08 am
content: Quote from: Alex on November 09, 2011, 12:21:29 amyeah, or a disclaimer stating that all persons are fictional and non-human....blablablaThere seems to be some text printed on the backside of the sketch.....

author: Mint.
author_rank: Frequent Contributor
timestamp: November 09, 2011, 03:14:03 am
content: Excellent!

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: November 09, 2011, 06:50:08 am
content: Why they wear socks instead of shoes? If its a stranded cable they will hurt their feet ?

author: nzo
author_rank: Regular Contributor
timestamp: November 09, 2011, 07:27:21 am
content: This is great and much better for us visual folks.

author: Simon
author_rank: Unknown
timestamp: November 09, 2011, 12:41:56 pm
content: Quote from: Alex on November 09, 2011, 12:21:29 amwell they are not coloured in and I wouldn't know the sex without.... erm.... looking

author: Wartex
author_rank: Frequent Contributor
timestamp: November 09, 2011, 01:30:10 pm
content: Quote from: Alex on November 08, 2011, 11:59:28 pmnot mine. use tineye.com to find the original
Your experience with modbus on Arduino (esp32 S3) - Page 1
Forum section: electronics / beginners

author: Irilia
author_rank: Regular Contributor
timestamp: March 24, 2024, 03:05:20 am
content: Hello I interested by your experience with modbus sensor on Arduino esp32 S3, what difficulty you encounter, or incompatibility.I'm curious in general to know if I can consider modbus for future projects.Best regards Irilia.

author: tooki
author_rank: Super Contributor
timestamp: March 25, 2024, 07:13:06 pm
content: Lots of people do that. The hardware complexity (if you can call it that) is that MODBUS used RS-485 as the physical layer, so you need an RS-485 transceiver to convert to/from the RS-485 voltages.

author: Irilia
author_rank: Regular Contributor
timestamp: March 26, 2024, 02:18:21 am
content: Rs485 TTL Yes this converter is easy to find

author: Shell Albert
author_rank: Contributor
timestamp: March 27, 2024, 01:15:30 am
content: According to my knowledge, Modbus is a protocol working in application lawyers. As your mentioned before, it does not care about the physical lawyer. Many people using modbus over RS485, CAN, even TCP. It's indeed a good choice for low density data transfer application.
Youtube channel: One Human Lifetime Project - Page 1
Forum section: electronics / beginners

author: ledtester
author_rank: Super Contributor
timestamp: August 07, 2023, 04:15:02 am
content: Just wanted to draw attention to the Youtube channel "Le Vaurien Qui Rit" which is dedicated to EE topics:https://www.youtube.com/@levaurienquirit1053/videosIn particular I found the videos on constructing digital filters to be very informative:One Human Lifetime Project a recipe for designing digital filters-https://youtu.be/Ub0td7ddnGYOne Human Lifetime Project Designing complex digital filters with the bilinear transform 3 Feb 2020-https://youtu.be/o_vL4-qXUcM

author: liaifat85
author_rank: Regular Contributor
timestamp: August 07, 2023, 07:37:20 am
content: Thanks for sharing.
Youtube Video's - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: May 07, 2013, 09:28:14 pm
content: What channel's are really good to watch for information about circuits and components beside Dave's channel

author: EEVblog
author_rank: Unknown
timestamp: May 07, 2013, 10:43:58 pm
content: I have a list on my channel, and on my website.

author: w2aew
author_rank: Super Contributor
timestamp: May 08, 2013, 01:59:26 am
content: I've got a small list of recommended YouTube channel on my channel's page, so you may want to check them out (as well as mine)https://www.youtube.com/w2aew

author: ahnuts72
author_rank: Regular Contributor
timestamp: May 08, 2013, 02:02:45 am
content: Search for humanharddrive on youtube he has some good videos.Sent from my Milestone X using Tapatalk 2
Z97-Pro (Wi-Fi ac) Motherboard - help identifying component - Page 1
Forum section: electronics / beginners

author: kavindajd
author_rank: Newbie
timestamp: February 19, 2021, 05:37:36 pm
content: Hi all,I usually stick to GPU's but managed to get hold of an Asus Z97-Pro motherboard which has difficulties turning on.The POST codes flicker through and dies without pausing at a specific code. Then proceeds to enter an infinite reboot loop.I've found a component that seems to be shorted internally - with the motherboard being on for just 2 seconds it was good enough to burn my skin on touch.As per the title, the marking on the IC is:29 1BL1BAny ideas on where I could source the datasheet? Asus may have rebranded it but am not sure why they would...Thanks for the help!

author: amyk
author_rank: Super Contributor
timestamp: February 20, 2021, 02:47:08 am
content: RT8065ZQW(QFN with xx xx+xxx or xx=xx+xxx is usually Richtek.)

author: kavindajd
author_rank: Newbie
timestamp: February 20, 2021, 11:45:06 am
content: You absolute legend! Thank you!!
ZD-915 problem - Page 1
Forum section: electronics / beginners

author: christos
author_rank: Regular Contributor
timestamp: June 21, 2014, 05:58:24 pm
content: hello..i have a de-soldering station ,the zd-915..it works fine but when i press the button to power up..it shows first a code (U03) and then it works normal...i hear a beep from the soldering iron too...what is it and how can i fix it?thx

author: Cozzmo
author_rank: Regular Contributor
timestamp: June 22, 2014, 07:25:50 am
content: Reporting the firmware version then a short beep ? Doesn't sound like a problem to me... mine does the same.

author: christos
author_rank: Regular Contributor
timestamp: June 22, 2014, 07:56:55 am
content: does it shows a code before starting?

author: GreyWoolfe
author_rank: Unknown
timestamp: June 22, 2014, 12:06:03 pm
content: Mine also does the same thing. In fact, it flashed the code 2 or 3 times before the temp display comes on. It works without problems.

author: christos
author_rank: Regular Contributor
timestamp: June 22, 2014, 06:43:02 pm
content: thx for tee replies.. i was worried cuz i bought it this week...

author: true
author_rank: Frequent Contributor
timestamp: June 22, 2014, 08:09:38 pm
content: I just wish the unit would remember the last temperature, and maybe start a bit faster.Maybe I could look into this if I can ever get all these projects done...
Zener based pre-regulator - Page 1
Forum section: electronics / beginners

author: info
author_rank: Contributor
timestamp: February 12, 2019, 02:41:16 pm
content: Hello there, I was looking around for a simplistic pre-regulator for a project I'm working on and stumbled upon Ian Johnston's power supply project which has (had) a pre-regulator built using a zener.I am pretty much new at simulating in LTspice so I may have done this wrong but here goes (attached image).Is this a viable option for a linear regulator like the LM317 or LT3080? The voltage on the adjust pin is simulating a pot wiper.Regards

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 12, 2019, 03:21:26 pm
content: Discrete pre-regulators have traditionally been used in places where the supply voltage may exceed the main regulator's maximum voltage rating.For instance, in large trucks with a nominal 24 volt bus, the load dump transients may exceed 90 volts (if I remember correctly), so it was customary to use a pre-regulator for the purpose.Another reason was to lower the total power dissipation in the main regulator.

author: info
author_rank: Contributor
timestamp: February 12, 2019, 03:36:16 pm
content: Yes, that is why I was looking into a simple but working pre-regulator so as to reduce the dissipation in the main regulator.

author: David Hess
author_rank: Super Contributor
timestamp: February 13, 2019, 07:33:18 pm
content: It will work just fine and I have used the same circuit with the LM317 to protect against input voltage spikes. Pick the right depletion mode power MOSFET and no other parts are required.A more comprehensive circuit uses the input voltage to implement fold-back current limiting so that the regulator shuts down if the input voltage remains high for too long protecting the input transistor also.
Zener circuit not working as expected - Page 1
Forum section: electronics / beginners

author: @rt
author_rank: Super Contributor
timestamp: March 05, 2020, 03:12:15 am
content: False alarm.. mods please delete.Transistor was shorted collector to emitter.

author: greenpossum
author_rank: Frequent Contributor
timestamp: March 05, 2020, 04:03:44 am
content: Even so, you need to calculate the series resistor so that you're running the zener on the slope, not where a little leakage current will turn on the transistor if it has enough gain. A zener is not a perfect threshold switch.

author: Zero999
author_rank: Super Contributor
timestamp: March 05, 2020, 10:00:54 am
content: And a zener probably isn't required in this application, just use a higher value base resistor. The relay is also missing the important flyback diode across the coil, to protect the transistor against the back-EMF, when it turns off.

author: JoeyG
author_rank: Regular Contributor
timestamp: March 05, 2020, 10:35:32 am
content: No diode snubber across the coil to protect the transistor???

author: @rt
author_rank: Super Contributor
timestamp: March 05, 2020, 01:11:09 pm
content: No, the transistor was out of a junk box and already no good.My circuit does have the protection diode, caps for the reg, and another diode for reverse polarity protection.
Zener diode adc protection - Page 1
Forum section: electronics / beginners

author: scarrier
author_rank: Contributor
timestamp: March 10, 2013, 05:24:38 pm
content: I saw in a reference design : (http://www.maximintegrated.com/app-notes/index.mvp/id/4663) on Figure 8, They put BAT54 30V zener diode, i don't understand what purpose do they serve. From what understand from the question at the end is that they use the reverse voltage, how do they clamp.

author: Marco
author_rank: Super Contributor
timestamp: March 10, 2013, 06:26:28 pm
content: Quote from: scarrier on March 10, 2013, 05:24:38 pmMaybe it would be more helpful to read the answer rather than the question ..."The reverse 30V breakdown voltage is incidental."So, they use the forward voltage.QuoteA zener diode is still a diode, with a forward voltage it acts just like a diode ... when V-foward is exceeded it rapidly starts conducting more current. With Vf in this case being around 0.3 Volt, so the input voltage on the ADC pins is clamped to -0.3 volt on the low end.

author: c4757p
author_rank: Super Contributor
timestamp: March 10, 2013, 07:37:23 pm
content: BAT54 is Schottky, not Zener.
Zener Diode advice needed (matching near equivalent) - Page 1
Forum section: electronics / beginners

author: prefabpeti
author_rank: Newbie
timestamp: February 06, 2022, 09:46:42 pm
content: Hello all, first time post here.I was hoping to get some advice on zener diodes please. I have been tracking down a problem with a 1989 Pioneer laserdisc player and believe a short has damaged several components (e.g. I have two very hot transistors). This particular laserdisc player appears to be quite bad at shorting due to all the various wiring looms connecting the different boards (and people like me doing unrelated repairs and getting said wires caught). i believe I have corrected the short that caused the original problem. I may replace the transistors after testing, but fortunately these are still in production and relatively inexpensive.I may need to replace two zener diodes nearby (as I can't seem to get any kind of reading off them with a dmm), however it looks like they are now very hard to get hold of (short of ordering a large quantity from Japan).The part in question is:HZS8.2NB2Which is an MHD:400mW power dissipationMin zener voltage: 7.82Max zener voltage: 8.15Full data sheet and info here:https://www.datasheets.com/en/part-details/hzs8-2nb2-renesas-electronics-16393219#overviewThe closest I can find:https://www.digikey.co.uk/en/products/detail/nexperia-usa-inc/BZX79-C8V2-113/763276?fbclid=IwAR2Jd69M303COOam9XWSnOe7HUTdIFgnjwO26_AgimzKu9d3ofp6sHBqO8Uhttps://uk.rs-online.com/web/p/zener-diodes/8185165?fbclid=IwAR2ykt_qdeSs_bL1-1Jxk32CLWZPAGR0Jr98BQTTLO5HdbEnaXIecfhgwZESo my question boils down to - are these close enough to likely do the job?I'd appreciate any advice or alternative suggestions (preferably in shops in the UK, but anywhere so long as there isn't a high minimum order quantity).Many thanks all,

author: TimFox
author_rank: Super Contributor
timestamp: February 06, 2022, 10:13:31 pm
content: The HZS8.2NB2 data sheet shows three bins sorting what would normally be an 8.2 V, +/- 5% production range of normal Zeners.The part in DigiKey is a similar 8.2 V +/- 5% 400 mW Zener, not further sorted. It should be compatible.If you think the tighter voltage spec of the original part is important, you can make a simple test circuit out of a 12 V supply and a 800 ohm resistor to get 5 mA at 8 V and measure the voltage of, say, 10 units on a DMM.(The usual value is 820 ohms--close enough for this purpose.) DMMs are not sufficient to measure the Zener voltage, since their current sources are not compliant up to 8 V.Both datasheets show voltage specs at 5 mA current.

author: prefabpeti
author_rank: Newbie
timestamp: February 07, 2022, 08:59:20 am
content: Thank you @TimFox!I'll be honest, I'm not sure how tight the voltage spec is. Though this particular power supply is giving 9v on one of the lines when the service manual and markings on the board indicate it should only be 7v. So I'm hoping I can 'get away with it'.Like I say, I'm hoping I can extract this intact and use a Multi-function tester on it to see and I'll put it back again if it appears OK.
Zener diode between Gate and Source in N-ch MOSFET. Enough to touch freely? - Page 1
Forum section: electronics / beginners

author: analogo
author_rank: Regular Contributor
timestamp: May 23, 2017, 11:10:37 am
content: I would like to use put a diode between gate and source in my MOSFETs to avoid frying them (see alsohttps://www.eevblog.com/forum/beginners/esd-boxes-dissipative-or-conductive-or-both/).Putting a Zener diode between G and S looks like a common technique (among many othershttp://www.diystompboxes.com/smfforum/index.php?topic=100760.0#msg888061,https://electronics.stackexchange.com/questions/187075/mosfet-gate-source-protection-question).But does this technique also work when the chip is out of circuit? Will it protect my poor MOSFETs when I take them out the box and stick them into the breadboards?

author: Cervisia
author_rank: Regular Contributor
timestamp: May 23, 2017, 12:50:51 pm
content: ESD destroys a MOSFET by creating too much voltage between gate and source, which permenently breaks down the gate isolation. The diode prevents this, as long as it is there, so it will work even outside of the circuit.But if the diode is in the circuit, and the MOSFET is not, then it won't be able to repair the damage afterwards.Quite a few MOSFETs have a separate, built-in Zener between gate and source. See the datasheet.(If a through-hole MOSFET doesn't have it, you could short its legs together (with aluminum foil, a non-isolated paper clip, etc.) before handling it.)

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 23, 2017, 12:51:40 pm
content: Where would you put the zener? Soldered across the leads?I don't think I've ever had problems with ESD on the breadboard. Just a matter of touching component and board with your fingers, before touching component to board.Simple riddle. Each conductive object is a capacitor (the board, your body, the component, etc.). Your body shorts things together when you touch them. which ones do you need to short together, to ensure the capacitor(s) don't discharge harmfully through a device?Note that you can hold a component in your hand, and discharge your body with the other hand, and the component feels no ESD (even if your finger did). Holding a component counts as a Faraday cage, shielding it from ESD.Tim
Zener diode characteristic curve - Page 1
Forum section: electronics / beginners

author: Wytnucls
author_rank: Super Contributor
timestamp: March 24, 2014, 04:30:40 pm
content: I've been trying to visualize the characteristic curve of a 5.1V Zener diode on the oscilloscope, using the X-Y mode of a Rigol DS1052E.I probed voltages across the Zener and a 1kOhm resistor in series, hooked up to a function generator producing a 100Hz sine wave at 20Vpp.The best picture I could get, after some tweaking, is shown below.Not entirely happy with the result.I was wondering if anybody has tried this experiment and managed to get a smooth curve using a similar method.

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 04:57:52 pm
content: Why don't you set the FG to a slow ramp that one cycle is the same duration as your screen width and enough dc offset to just get the forward conduction portion. trigger off the FG voltage at the bottom of the ramp and capture one cycle.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 24, 2014, 06:08:26 pm
content: Tried that before without much success. Tried it again with same disappointing result.If you have a screen grab and a set-up diagram, I may be able to replicate it. I must be doing something wrong.Thanks for the suggestion.Setting up the ramp and trigger is fine, but I can't get a proper curve for the zener.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 24, 2014, 06:43:41 pm
content: OK, I think I found my mistake. Not enough resolution on the vertical scale.Here is the result (looks much better than the X-Y mode):Thanks Robrenz!

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 07:02:06 pm
content: Looks good
Zener Diode failure modes and Diode identification - Page 1
Forum section: electronics / beginners

author: Gtx21
author_rank: Contributor
timestamp: September 21, 2018, 07:12:42 pm
content: I am working on repairing a 1995 era audio system that is comprised of all through hole components on a 2 sided pcb. It has somewhere around 80-100 diodes of at least 5-6 different types, almost all of which are in glass packages with no labels save for a single color stripe.The forward breakdown voltages are pretty consistent (650-700mV) but the reverse breakdown voltages are very inconsistent even between diodes that I’m pretty sure are the same type.When Zener diodes fail, do their reverse breakdown voltages ever go higher? Or vise versa, do reverse breakdown voltages of regular diodes ever fail in way that makes them appear to be Zener-like?For instance, I have 2 identical diodes with the same forward voltage (and capacitance) where one has a reverse breakdown of right around 2.6V and the other somewhere >> 15V (max of my current supply). Either one of them has failed or I have 2 diodes that look identical in every way physically but are different.

author: SeanB
author_rank: Super Contributor
timestamp: September 21, 2018, 07:41:53 pm
content: Normally zener diodes fail by going short circuit, open circuit or getting really leaky. Generally is they have a blue band or a green one, they probably are ISS1 diodes, which are pretty much a 1N4148 or 1N914 in most cases. Breakdown at 2V6 in circuit or out, it makes a big difference, but to see if it is a regular diode or a zener you will need to reverse engineer or find a circuit diagram of the amplifier.Out of circuit about the only test aside from using the manufacturers test conditions is to use a curve tracer to show up leakage or noisy diodes.

author: Gtx21
author_rank: Contributor
timestamp: September 22, 2018, 07:59:38 am
content: Quote from: SeanB on September 21, 2018, 07:41:53 pm80% of them have either a single blue or single green band, but no text printing.Is ISS1 a brand, model, or line of diodes? Google seems vague on it.

author: SeanB
author_rank: Super Contributor
timestamp: September 22, 2018, 04:28:02 pm
content: 1990's audio was generally made in the far East, so Japan, Hong Kong, or around there, and often used Japanese made components. Thus the common diode was the ISS1 diode, and yes these are part of a whole range of ISS numbered diodes, including zener and other diodes, all in the same glass package with a band. Thus you will have to reverse engineer the circuit to see what the actual use of the component was, as they can vary greatly while looking identical, and only the reel had the part number on the auto insertion machine that made the equipment in question.What make and model, you can perhaps find a service manual for it online, and this tells you what they used where, often with PCB diagrams as well showing you the location of the component on a grid, that was part of the parts list.
Zener diode numbering conventions BZX**C** questions - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 29, 2013, 01:14:58 pm
content: Trying to see if there's method in the BZX series of Zener diode nomeclature.I have a circuit whose schematic asks for BZX65C51. OK, C51 is the voltage, what is the 65 bit referring to please? I have BZX85C51 here, can I use those instead? I have looked at a few data sheets and not sure what the 65 and 85 refer to. Thanks.

author: c4757p
author_rank: Super Contributor
timestamp: November 29, 2013, 01:17:47 pm
content: It doesn't actually "mean" anything, it's just the series. BZX65 is (was - obsolete now as far as I can tell) a 400mW diode, and BZX85 is a 1W diode. Should be fine.

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 29, 2013, 08:59:05 pm
content: Ah, OK, I was assuming it was some current handling code or something. Thanks, will use what I have. All the best.
Zener diode question - Page 1
Forum section: electronics / beginners

author: Crambone
author_rank: Frequent Contributor
timestamp: December 06, 2022, 11:19:48 pm
content: Can a 1N825 be replaced with a 1N823?

author: TimFox
author_rank: Super Contributor
timestamp: December 06, 2022, 11:42:42 pm
content: The 1N821, 1N823, 1N825, 1N827, and 1N829, along with the A suffix on each, and a few other numbers such as 1N429 and 1N1735 are all specified for 6.2 V +/- 5% at 7.5 mA current.The difference is the specified temperature co-efficient, ranging from 100 ppm/K for the 1N821 down to 5 ppm/K for the 1N829.If you have the equipment, you can obtain zero tempco near your operating temperature by careful adjustment of the current; the manufacturer guarantees these tempcos at 7.5 mA.They are all constructed as a Zener in series with a forward-biased diode to cancel the tempcos at some current.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 07, 2022, 11:35:02 am
content: The 1N821-1N829 are made the same and binned after production. The 1N825 is a better grade with lower specs for the TC than the 1N823. The actual performance may or may not be better than the specs.The TC also depends on the current. In a limited range one can adjust the current to reduce the TC. However the 821 and 823 may not reach the zero TC point with a reasonable current / temperature.So one can give the 1N823 a try, but there is a chance for higher TC. The 1N827 would be a safe bet.
zener diodes - Page 1
Forum section: electronics / beginners

author: glinjik
author_rank: Regular Contributor
timestamp: October 01, 2020, 08:36:38 pm
content: hi folks is it possible to put two 1/2watt Zener diodes in parallel in place of a 1watt zener?

author: chris_leyson
author_rank: Super Contributor
timestamp: October 01, 2020, 08:50:53 pm
content: Unlikely because one would always have a lower threshold voltage and even if they were matched it would be risky. Current sharing resistors might help. Which Zenner diodes are you thinking of using ?

author: glinjik
author_rank: Regular Contributor
timestamp: October 01, 2020, 08:56:09 pm
content: 18v 1 watt its part no 1n4746awas thinking 1/2 watt 18v the voltage is not really important it can be 12-24v

author: glinjik
author_rank: Regular Contributor
timestamp: October 01, 2020, 09:01:22 pm
content: its for this soft start module VD2

author: wraper
author_rank: Unknown
timestamp: October 01, 2020, 09:05:25 pm
content: Quote from: glinjik on October 01, 2020, 09:01:22 pmIf you make it with 400V dropping capacitor (C1) as it's in the circuit, very likely it will fail after some time. X2 ~250V+ safety capacitor or 630V DC rated film cap should be used.

author: glinjik
author_rank: Regular Contributor
timestamp: October 01, 2020, 09:12:05 pm
content: thank you i will change it for an x2 cap

author: glinjik
author_rank: Regular Contributor
timestamp: October 01, 2020, 09:15:27 pm
content: i suppose i could add in a emf filter and mov as an improvement

author: srb1954
author_rank: Super Contributor
timestamp: October 01, 2020, 09:43:40 pm
content: Quote from: glinjik on October 01, 2020, 08:36:38 pmNot really a good idea. Unless the Zeners are closely matched the lower voltage one will take the lion's share of the current and dissipate a greater proportion of the power.A better option is to put two lower voltage Zeners in series. If each Zener is half the desired total voltage them they will share power approximately equally without any need to have them closely matched.

author: ledtester
author_rank: Super Contributor
timestamp: October 02, 2020, 03:55:56 am
content: I recognize that circuit from a Kasyan TV video.Here's a variation... pretty much same idea but they add a resistor in front of the zener and a bleeder on the dropper cap:https://www.eeweb.com/inrush-current-limiter-soft-starter-for-ac-dc-loads/
Zener Effect & Avalanche Breakdown Noise - Page 1
Forum section: electronics / beginners

author: hgg
author_rank: Frequent Contributor
timestamp: April 01, 2014, 08:30:59 pm
content: Hello,I am trying to build a precision voltage reference in which I will use a zener diode with a lowbattery LED indicator circuit. I am using the MAXIM MAX6325 IC which has a very low noisevalue of 1.5uVp-p but I cannot find any actual data for the noise figure of zener diodes.(I am using the 7.5V 1N4737A zener diode)While it is a well known fact that zeners are noisy and they have been used to create whitenoise circuits, I cannot find any actual numbers indicating how noisy they are, at specific voltagesor currents. Nothing listed in the datasheets as well...Is the noise in the order of some uV, or more?Will that noise have an effect on the 2.5V precision output of the MAX6325 or only on the power rails?Thank you.George.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 01, 2014, 10:41:58 pm
content: They are neither rated for it, nor are they controlled/selected based on noise. Possibly some old types were specified for that type of duty, I don't know.If you want low noise, get a proper low noise reference. The cheap bandgap references aren't particularly clean (TL431 around 20uV I think), but LT/AD have some wonderfully low noise and low bias devices.Tim

author: hgg
author_rank: Frequent Contributor
timestamp: April 02, 2014, 06:37:07 am
content: Quote from: T3sl4co1l on April 01, 2014, 10:41:58 pmHello Tim,I am already using a low noise reference. TheMAX6325with1.5 uVp-p noise.Also using a separate 7.5V zener in a small circuit to detect a low voltage condition.This is the zener I am worried about injecting noise in the power rails.Has anybody actually tried to quantify/measure zener noise ?Thanks.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 02, 2014, 12:34:09 pm
content: Noise coupled back into the supply? How weedy of a supply is it??I don't know what the noise is, but even if it's mV, how is that going to disturb a proper power supply rail through the series resistor?Why not use a voltage divider and comparator against the low noise ref? Assuming it's operating in that low voltage condition.Tim

author: hgg
author_rank: Frequent Contributor
timestamp: April 02, 2014, 12:49:16 pm
content: As a last resort I will use a comparator, but if the noise of the zener does not affect therest of the circuit, I prefer the zener.
Is a zener in parallel with the LED required? - Page 1
Forum section: electronics / beginners

author: fabiodl
author_rank: Frequent Contributor
timestamp: January 28, 2022, 10:11:28 am
content: Reading thisdatasheet for the VLMU1610-365-135uv LED, I stumbled upon the wiring diagram on page 4. Why is there a zener diode in parallel with the led? Should I really place a protection (?) diode in parallel with each LED? isn't a curent limiting resistor sufficient?

author: Zero999
author_rank: Super Contributor
timestamp: January 28, 2022, 11:14:40 am
content: The LED already has a built-in diode, so there's no need to add one. It's there to provide protection against reverse polarity, which can easily damage InGaN LEDs, especially the more exotic UV types, which are more delicate. A series resistor will suffice.I don't know why it's a zener, rather than an ordinary diode, since the LED is bound to turn on first. Perhaps it's faster than the LED, so will absorb high current ESD, before it gets to the LED?

author: rpiloverbd
author_rank: Regular Contributor
timestamp: January 28, 2022, 12:39:36 pm
content: I think they suggested adding the Zener diode for reverse polarity protection.

author: Zero999
author_rank: Super Contributor
timestamp: January 28, 2022, 01:41:26 pm
content: Quote from: rpiloverbd on January 28, 2022, 12:39:36 pmWhere does it say that? I couldn't find anything about adding an external zener diode.The internal schematic shows a zener diode is built-inReverse voltage(1)IR= 10 μA VR1.2 V(1)Reverse current is applied for reverse voltage test only (function test of Zener diode). The device is not designed for reverse operation.Operating the LED under reverse current condition for long time might result in damage or failure of the componentAlso refer to figure 7.

author: nigeltron
author_rank: Newbie
timestamp: January 29, 2022, 06:13:59 pm
content: A zener may be placed in parallel to pass current to other leds that it may be in series with if the led fails.Also, it has some use in esd protection.Also, there are "led protectors" that you can buy to do the same thing as the zener...onsemi make them...here is one...https://uk.rs-online.com/web/p/tvs-diodes/7737891p?cm_mmc=UK-PLA-DS3A-_-google-_-CSS_UK_EN_Semiconductors_Whoop-_-TVS+Diodes_Whoop-_-7737891P&matchtype=&pla-806308433405&gclid=EAIaIQobChMI74nRu8jX9QIVSuztCh29_gA3EAQYAiABEgJopfD_BwE&gclsrc=aw.dsNUD4700SNT1G

author: Zero999
author_rank: Super Contributor
timestamp: January 29, 2022, 06:34:05 pm
content: Quote from: nigeltron on January 29, 2022, 06:13:59 pmThat's a good idea, but it's not a zener diode. It's a crowbar circuit, consisting of an SCR and most likely a zener diode in series with the gate. It has a high impedance, as the voltage across is is increased up to around 5.5V to 7.5V, then the impedance drastically falls to the point, when there's roughly 1V across it, irrespective of the current. The idea is so a string of LEDs will not all turn off, just because one of them fails open circuit.
Zener-protected Power MOSFET Benchtest: Good? - Page 1
Forum section: electronics / beginners

author: OpenCircuit
author_rank: Regular Contributor
timestamp: March 24, 2017, 09:31:05 pm
content: f3nk80z:https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&sqi=2&ved=0ahUKEwjezuHdh_DSAhWh3oMKHR3ODhMQFggaMAA&url=http%3A%2F%2Fwww.st.com%2Fresource%2Fen%2Fdatasheet%2Fstf3nk80z.pdf&usg=AFQjCNEaI3qG2ReJG8W6BrdJMS0PV1gQAw&sig2=nKHdcn20BdDQCsgyQEDH3Q&bvm=bv.150729734,d.amc&cad=rjaPin 1 GatePin 2 DrainPin 3 SourceDoes this test indicate proper function? When I remove the +5v supply from the gate the fan stops running (when i put 4k resistor across 1 and 3)?

author: strawberry
author_rank: Super Contributor
timestamp: March 24, 2017, 09:54:44 pm
content: Gate capacitance(485pF in this case) keeps MOSFET open for a while(if not pulled down). With higher Drain current, Gate will discharge faster by it self and under Gate treshold voltage (of 3.75V in this case) will turn MOSFET off.STD3NK80Z in datasheet Fig7 show Transfer characteristics show that your Gate voltage(5V) is too low for your setup And MOSFET wont deliver sufficient current to load.
Zener voltage clamping - Page 1
Forum section: electronics / beginners

author: tester43
author_rank: Regular Contributor
timestamp: July 02, 2018, 09:42:01 pm
content: Hi again,So ... here I am adding zener diode 1n4728 as overvoltage protection.Voltage is AC rectified unfiltered.To my terrror and shock I found that near zero zener stops at very special value around 0,7-0,8V. I was expecting 0.Looks like typical p-n diode voltage.It's very typical circuit: AC transformer output + load (8ohm).From one end of load goes 680ohm resistor + zener and to GND on rectifier.Probe is between resistor 680 and zener.High end is as expected around 3V.But why low is not ground?Is it because of minimal required current?But here is my "poor man scope" picture attached.

author: tester43
author_rank: Regular Contributor
timestamp: July 02, 2018, 09:51:04 pm
content: I will reply to myself because I am stupid.Once voltage drops below 3,3 it's not this diode any more.It's coming form totally different place.Please feel free to ignore my message.
Zero cross using optocoupler 220vac - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: June 14, 2016, 09:52:08 am
content: 1. I have to detect zero cross using optocoupler of 185Vac-265Vac & 50Hz. Attached is the circuit. Have to feed the signal to MCU pin.Will make MCU pin to give interrupt on both rising & falling edge.2. Is circuit ok. What should be best value for R1 & R3.I have put 4.7K each.But consider max voltage = 265vac,then Vp= 374.76Vaccurrent flow = around 39ma. (via R1, led, & R3 consider led drop zero)Each resistor watt = 7WValue comes out to be very high?If I increase the value of resistor, zero cross distorts.

author: Gyro
author_rank: Super Contributor
timestamp: June 14, 2016, 09:59:59 am
content: The circuit, as drawn will expose the Optocoupler LED to full mains voltage in the reverse direction on alternate half cycles, this will immediately kill it. You at least need to put a diode across the LED with reverse polarity to prevent this.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 14, 2016, 10:09:37 am
content: Quote from: Gyro on June 14, 2016, 09:59:59 amYes. I would also put a diode in series - one that can withstand the peak reverse voltage - this would half the (not inconsiderable) power dissipation in the resistors.

author: bktemp
author_rank: Super Contributor
timestamp: June 14, 2016, 10:15:18 am
content: This circuit needs more parts, but is more accurate and consumes much less power:http://www.dextrel.net/diyzerocrosser.htm
Zero Crossing Detector: AoE 3rd Edition Exercise - Page 1
Forum section: electronics / beginners

author: fatalelieberi
author_rank: Contributor
timestamp: September 30, 2020, 01:23:59 pm
content: Hi,I stumbled upon this exercise in Art of Electronics 3rd Ed in which I have to design a zero crossing detector using several comparators to make sure it triggers exactly at 0V. It's Exercise 4.25:Assuming the solution circuit is based on an example in the book as shown here:I designed this circuit to achieve the goal from the exercise:The concept for this design is when the R4 is connected, the circuit will trigger when the input rising to 0V. But, if R4 is unconnected, it will trigger when the input is falling to 0V. So, based on this behavior, I put a PNP switch to connect and disconnect R4 from the circuit. The PNP is driven by another comparator that turns it on when the input is rising to 50mV and turns it off when the input is falling to -50mV. In my opinion, it actually works as intended with about 10mV miss from the target of 0V. However, I have to remove the capacitors to achieve the goal. Also, there are some redundant components which I think can be reduced more but I don't know how to do it.What do you guys think? Is there a better solution for it?
zero Ohm Resistor - Page 1
Forum section: electronics / beginners

author: Dragon-foot
author_rank: Newbie
timestamp: April 15, 2019, 08:10:53 pm
content: Hello,I have run into what I think is a zero ohm resistor, It looks like a half watt with one black strip. A pic is attached.Please let me know if I'm on the right track.Thanks

author: Mr.B
author_rank: Unknown
timestamp: April 15, 2019, 08:12:54 pm
content: Yes, it looks like a zero ohm resistor to me.Yes, zero ohm resistors are a real thing.

author: golden_labels
author_rank: Super Contributor
timestamp: April 15, 2019, 08:43:37 pm
content: Dragon-foot: yes, you are right. They also exist in SMD version. 0Ω are used as jumpers. They are easier to use in automated environments: the same machine, that places resistors, may be used to make links. A minor advantage is that they do not require a separate footprint in PCB design software.

author: Brumby
author_rank: Unknown
timestamp: April 15, 2019, 11:07:33 pm
content: As stated above, yes you are right. It is a zero ohm resistor - for all practical purposes. We can get all technical and say it isn't exactly zero because it's not a superconductor, but it's as close to zero as a piece of wire.As well as jumpers, they can be used for configuration setting on a board or sometimes you might have a circuit that can have (something like) a current sense resistor in place for testing, but will work better with zero ohms in a production run.For SMD boards, a zero ohm resistor can be positioned with a pick and place machine just like any other SMD component.

author: Dragon-foot
author_rank: Newbie
timestamp: April 15, 2019, 11:43:29 pm
content: Thanks all