hybridfree/eevblog-posts huggingface dataset:
Thermocouple amplifier circuit question - Page 1
Forum section: electronics / beginners

author: ec911
author_rank: Newbie
timestamp: June 01, 2015, 05:07:57 am
content: Hi!I've drawn a schematic of a temperature sensing circuit of an Aoyue hot air station (852A++). I'm not a pro about circuit designing and I'd like to know what you guys think of the circuit and if I could improve it mabye? I find that temperature of the device is inaccurate even after calibrating with the trimmer pot. The display is also slow to react to temperature change and don't know if it's because something's wrong with the T° sensing circuit.Note that the output goes to pin PC4(ADC4) of an Atmega8a AU µC.Also I'm doing this not only to see if I could improve things but also to learn more about electronics..I've been reading on cold-junction compensation when using a thermocouple with ADC, I don't think this circuit have this???

author: charlespax
author_rank: Regular Contributor
timestamp: July 28, 2015, 07:22:30 pm
content: I think R9 might be a thermistor, which is a resistor that changes resistance based on its temperature.R7 is for open circuit detection. When the thermocouple is disconnected R7 will pull that side of the connection toward 5 V. The microcontroller will try to read the thermocouple voltage and see that it is very high and know the thermocouple is not there.
Thermocouple ranges with multimeters, why no small mV ranges? - Page 1
Forum section: electronics / beginners

author: dangerousamateur
author_rank: Contributor
timestamp: December 09, 2019, 07:35:42 pm
content: Hi guys,I've been reading on this site for some time, this seems to be the place to hangout when it comes to electronicsRecently a friend lent me his Fluke 179. Using it with thermocouples I wondered why this and a lot of other cheaper devices are able to measure such small voltages.0,1°C with a K-Type thermometer are some 4µV.OK, not with super accuracy, but the smallest DCmV range has 100 µV resolution (600mV).Just curious do these meters have a seperate circuit for thermocouples?Why isn't there some 60mV range, if the hardware is obviously capable?

author: SeanB
author_rank: Super Contributor
timestamp: December 09, 2019, 07:44:25 pm
content: Mostly noise, the 60mv of the thermocouple is into a lowish impedance, so the noise is lower. If you try to do this with the typical DMM input impedance of 10M or more your input circuitry would be swamped with noise coupled into this high impedance, while with the thermocouple with essentially zero resistance this is not a problem.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 09, 2019, 08:50:25 pm
content: Most of the auto ranging handheld DMM actually have an 10 M resistor in series at the input, when reading voltages and is part of the input protection. This resistor gives quite some noise and also makes it sensitive to leakage currents. So the resolution is limited.The better bench top meter use a different autoranging and protection scheme and thus allow higher resolution. This usually includes a relay aand higher supply and is thus less practical for a battery powered system.Special TC meters can use less protection (you don't expect them to survive some 400 V AC) and do not need automatic range switching. So they can be build lower noise and more stable.

author: dangerousamateur
author_rank: Contributor
timestamp: December 14, 2019, 03:15:40 pm
content: Thank you for your answers.What you wrote makes sense to me.Do you know how they do it in this case , is the input resistance switched?The input selector switch has the same position for mV and TC, you only push the yellow button.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 14, 2019, 04:04:05 pm
content: With a dedicated mechanical switch for a mV range the amplifier can work non inverted. This allows for high impedance (e.g. > 1 Gohms, though not very well defined) and low noise. Modern AZ OPs have no problem resolving down to the µV range, but the input range (e.g. +-2 V, maybe +-15 V) is limited. Higher voltages would need a relay to switch in a divider - so auto-scaling gets more complicated. At the very low noise end it is a compromise between low noise and low input current. So the lowest voltage noise input is no longer suitable for high impedance (e.g. 1 M) sources.TC measurements also needs cold junction compensation. That is an extra thermometer (NTC, PTC or diode) to measure the temperature going from the TC wires to copper.
Thermoelectric Peltier heating/cooling and generation - Page 1
Forum section: electronics / beginners

author: THATguy
author_rank: Regular Contributor
timestamp: October 17, 2016, 09:26:11 am
content: Hi, let me know if you think these are correct, need some improvement, or if I'm misunderstanding peltiers completely.(I know that some of what I discuss is the Seeback effect).Please assume that both insulated areas (if there are two) are connected and at same internal temperature.Also that only the silver parts are exposed, the TEC are well sealed in the walls.My TEC are being exposed to the outside Air.First picture.Some voltage generation.I may need to interrupt the circuit, to prevent the temperature inside from lowering too much?Second picture.Using some voltage to heat inside house.Third picture.Can I generate voltage? Or will I need to apply voltage to get the temperature change?Fourth picture.Voltage generation?
thermografie bridge soffit - Page 1
Forum section: electronics / beginners

author: anastsia
author_rank: Newbie
timestamp: March 26, 2024, 02:52:28 pm
content: I have a question about thermography on bridges. I have a bridge with circular internal cavities. Now, I am examining the underside of the bridge using thermography, and the areas of the cavities appear cooler. I understand that concrete above the cavities cools or heats up more quickly, and that the cavities slow down the heat flow from top to bottom. However, I am unsure how the contrasts of the cavities change throughout the day. What happens when the bridge heats up? How would the contrasts change from morning to afternoon to evening? what happens when sun is directlxý shining on the bridge?Maybe someone can help me.

author: m k
author_rank: Super Contributor
timestamp: March 29, 2024, 02:01:35 pm
content: I think people around here are a bit differently oriented.Is it windy, maybe there are some turbulence.

author: Simon
author_rank: Unknown
timestamp: March 29, 2024, 03:21:09 pm
content: what?

author: m k
author_rank: Super Contributor
timestamp: March 30, 2024, 10:24:16 am
content: Asking from me?World is full of bridges and maybe it's just a small one.If I misunderstood OP will correct me.

author: Simon
author_rank: Unknown
timestamp: March 30, 2024, 10:59:58 am
content: No, I ask what of the original poster. It's so garbled that it was reported as a post by an AI bot.

author: m k
author_rank: Super Contributor
timestamp: March 30, 2024, 11:18:05 am
content: Maybe OP is a seasoned bridge engineer, but new with thermal images and forced to use a translator, for personal reasons.
Thermopile circuit? - Page 1
Forum section: electronics / beginners

author: Teledog
author_rank: Regular Contributor
timestamp: November 17, 2018, 02:15:33 am
content: Hi all!Recently had a gas hot water heater installed - NO electrical hookup to it, whatsoever.The controller (Honeywell) has a status (pilot) LED that pulses every ~3 seconds or so.Did a bit of research & don't believe there is any battery in it at all.I've read that the Honeywell controller uses a "thermopile" to generate ~350mV for the indicator? Not sure of the accuracy.{edit: from what I can gather, the HOT working voltage should be ~658mV, at minimum 350mV}I'd LIKE to make the same sort of passive indicator on our ancient boiler -for a pilot light indicator.I've looked around & haven't found any schematics out there for building such an indicator circuit..Is it a proprietary thing?TIA!{2nd edit: nevermind..discovered the LTC3108 ..groovy stuff}

author: Vtile
author_rank: Super Contributor
timestamp: November 18, 2018, 06:14:49 pm
content: Peltier element can do it. Ie. search for "BioLite".
Thermostat Manufacturer - Page 1
Forum section: electronics / beginners

author: Gp!
author_rank: Contributor
timestamp: June 30, 2021, 05:16:53 pm
content: Hi,a little help, if you have the time.I am trying to find the company that make this thermostat (KSD301-C 250V).It looks like ARV (?). Would you agree ?Are these thermostats standard ?Thanks for any help.

author: TimFox
author_rank: Super Contributor
timestamp: June 30, 2021, 05:44:32 pm
content: What you read as “ARV” is actually the backwards “UR”, meaning “recognized by UL” (Underwriters’ Laboratories), found on components.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 30, 2021, 05:45:32 pm
content: Quote from: Gp! on June 30, 2021, 05:16:53 pmNo.I looks like a delta symbol with a wavey underline - possibly a stylised "e" ? It is followed by a "recognised component" symbol/logo:https://commons.wikimedia.org/wiki/File:Recognized_Component_Mark_logo.svgSorry, can't help futher than that.

author: Twoflower
author_rank: Frequent Contributor
timestamp: June 30, 2021, 06:00:35 pm
content: The first logo looks likeTÜV Rheinland. That's a german Technical Inspection Association. So it looks like the first row shows just the certificates no manufacturer (likehere).
Thevenin equivalent circuit in RC circuit with current and voltage source - Page 1
Forum section: electronics / beginners

author: sean87
author_rank: Regular Contributor
timestamp: July 02, 2012, 10:54:50 pm
content: I have the circuit below and I have to calculate complex current i1using thevenin equivalent circuit method:I tried to follow the rules and open the terminal AB across the resistor:I want to ask if this is a correct way to convert the circuit to thevenin. Also I am not sure is capacitor's reactance -4iis same as -4j or 4, 90 degree ?Then The voltage across AB terminal would be equal to voltage across the capacitor? Is it ok to in this case see the voltage source as a short?Thanks.

author: Neganur
author_rank: Unknown
timestamp: July 03, 2012, 04:06:40 pm
content: If you're asked to use Thevenin's method - shouldn't you end up with just a voltage source and a series impedance?

author: jsoderquist
author_rank: Contributor
timestamp: July 03, 2012, 07:34:27 pm
content: It's been a while, so don't hold me to it - but - I'm pretty sure it will simplify things if you use a combination of Thevenin and Superposition in order to analyze this circuit.1. Open the current source, analyze the circuit.2. Close the current source and short the voltage source, analyze the circuit.3. Your answer should be the algebraic sum of the two.Again, don't hold me to it, but that's what I seem to recall.

author: jimmc
author_rank: Frequent Contributor
timestamp: July 03, 2012, 07:46:09 pm
content: Using Thevenin's theorem only...1. Convert the current sourceand shunt resistorto the equivalent voltage source and series resistor.2. You now have two voltage sources in series, combine them.3. Calculate the current in the circuit (which will of course be the same as the current through the capacitor in the original circuit).4. Combine this current with the current source I1to find the current through the resistor.Jim
Thick terminal pins for PCB mounting - what are they called? - Page 1
Forum section: electronics / beginners

author: synoptica
author_rank: Contributor
timestamp: December 10, 2018, 01:47:58 am
content: Hey all,I remember back in the day, getting a Jaycar voltage regulator kit that came with a bunch of round brass terminal pins. These had a small ridge around them towards one end for limiting PCB insertion.I have tried every description under the sun to find these pins to buy them for a project but the closest I can find are pogo pins which aren't what I'm after.Any help appreciated, thanks in advance!!

author: synoptica
author_rank: Contributor
timestamp: December 10, 2018, 02:21:10 am
content: Quote from: blueskull on December 10, 2018, 02:02:01 amOooh, that's some progress, thanks mate! Doesn't look like I can still find anything on AliExpress by that name (interestingly, I've found "PCB dowel pins", but they're stainless which makes me think soldering isn't going to work!)This has been super helpful though, thanks!

author: Brumby
author_rank: Unknown
timestamp: December 10, 2018, 02:31:12 am
content: https://www.jaycar.com.au/0-9mm-pcb-pins-pk-50/p/HP1250

author: JDubU
author_rank: Frequent Contributor
timestamp: December 10, 2018, 02:41:48 am
content: Take a look at this Digikey link:https://www.digikey.com.au/products/en/connectors-interconnects/terminals-pc-pin-single-post-connectors/323/page/1?k=PC%20Pin%2C%20Single%20Post%20Connectors

author: cdev
author_rank: Super Contributor
timestamp: December 10, 2018, 03:20:48 am
content: solder posts?

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 10, 2018, 03:30:07 am
content: Turrets, perhaps?

author: synoptica
author_rank: Contributor
timestamp: December 10, 2018, 04:16:04 am
content: Quote from: Brumby on December 10, 2018, 02:31:12 amThanks mate - I found these after blueskull's post and also some 1mm ones at Altronics. I was hoping for something a bit fatter but these might just suffice!

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 10, 2018, 05:03:03 am
content: Fatter? Again, turrets pins or terminals.

author: lwatts666
author_rank: Unknown
timestamp: December 10, 2018, 11:03:55 am
content: Quote from: synoptica on December 10, 2018, 04:16:04 amRockby (http://www.rockby.com.au) have some 1.2mm diameter. Stock Number 33537. They have several other styles - search "PCB Pins".

author: james_s
author_rank: Super Contributor
timestamp: December 10, 2018, 04:53:17 pm
content: Those pictures remind me of 1980s test gear and medical equipment. I'll have to keep those in mind, they provide a nice clean way to semi permanently attach wires.
Thinkpad 170W power supply has 4 amp fuse and 4 amp rectifier bridge - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: September 26, 2023, 06:44:59 pm
content: If power supply says output is 20 volts and 8.5 amps. and incoming mains fuse is 4 amps and recifier bridge is 4 amps, is that okey?I once had it blow up on me, fuse went and rectifier went. So since I had it replaced with 4 amp 600 volt rectifier and some wire for a fuse. Long long time went by, perhaps since 2017 or 2018. Yesterday I opened it up, bought the correct fuse and stuck in there 10 amp 1000 volt rectifier bridge.

author: Eraldo
author_rank: Regular Contributor
timestamp: September 26, 2023, 07:15:50 pm
content: is that a laptop psu? If yes then its probably a switch mode psu and if the rectifier is in the primary side ( close to the mains cable) then the rating should be fine since the input voltage is 10 times higher so the current passing is 10 times lower ( not even an amp). in your case the rectifier blew and took with it the fuse too.your choice of replacement for the rectifier should be good, but make sure you don't put a higher current rated fuse in the primary and should be 4 A ( 3 A would work too of course but the manufacturer would know best so 4A is recommended) .
ThinkPad dock connector - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: March 23, 2025, 02:12:54 pm
content: I went inside my thinkpad, cleaning it, removing BIOS chip, doing a flash with clean ME. Because I had bad ME and it wouldn't flash from Windows. Then I deflux everything.Turns out dock connector on motherboard is rusted out inside. Individual copper strands on connector are gone. Covered in green crap, and gone after I cleaned the green crap.Anyway to get this connector from somewhere other than a donor mobo?I'm guessing to remove it, I'd need to remove some other connectors from the bottom, or find a bottom preheat and take it through the cycles up to 250C, and then hit it from the top with 150C. I don't have a bottom preheat yet, so will have to take off other plastic connectors on the bottom and just use a heat gun.Attached is a BIOS with clean ME, best working version. Leaving it more for myself in case I'd need it in the future and lose it locally.

author: u666sa
author_rank: Frequent Contributor
timestamp: March 23, 2025, 04:09:20 pm
content: Perhaps inside the housing is another connector. To see it, I'd have to desolder the housing. Which I won't do now. But the idea is that if there is another connector inside, find that thing and replace it.Now taking a look at it, I would be able to desolder the housing using some low melt. Looks easy the 2nd time around looking at it.

author: amyk
author_rank: Super Contributor
timestamp: March 24, 2025, 02:34:18 am
content: Schematic says connector is by JAE, and looking on their site shows that it's likely this series:https://www.jae.com/en/connectors/series/detail/id=64339

author: u666sa
author_rank: Frequent Contributor
timestamp: March 27, 2025, 12:14:25 pm
content: Quote from: amyk on March 24, 2025, 02:34:18 amOn other forums I was told P/N for the connector is JAE-CONN148-6R-1-GP however google search didn't return any hits.Any links to where to find this connector for sale?
ThinkPad X230T digitizer and pen not working anymore! - Page 1
Forum section: electronics / beginners

author: idoit
author_rank: Contributor
timestamp: February 27, 2022, 07:48:49 am
content: Hello everyone,I was working on my ThinkPad X230 Tablet and accidentally cut one of the thin wires. It turns out it was the ground (GND) for digitizer. There are 5 thin wires for digitizer and here is the schematic for it:pindescription23USBP4+24USBP4-25STOP26VCC3BLEDBD27GNDI cut wire number 27. I turned the laptop and neither touch nor pen is working. I tried and soldered wire 27 back together and turned the laptop on. Same, no finger touch or pen.I was wondering what happened? Any way to fix it? Thanks!So, in a nutshell, the laptop was turned on with wires 23-26 all going to digitizer board BUT ground wire not connected (cut).

author: idoit
author_rank: Contributor
timestamp: February 27, 2022, 09:48:20 pm
content: I'm just wondering have I fried the digitizer pcb?Anyway to identify which component got damaged? Any pointers are welcome.

author: idoit
author_rank: Contributor
timestamp: February 28, 2022, 02:14:47 pm
content: And here are higher quality photos of the PCBs for pen and touch. Thanks for your input.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 28, 2022, 02:20:35 pm
content: There is also the possibility that the OS has only disabled the touch feature and not automatically activates it again.A point to check if the OS detects the hardware at all. This would also give a clue if the problem is more at the OS to touch HW oder touch HW to actual screen part.

author: idoit
author_rank: Contributor
timestamp: February 28, 2022, 06:24:14 pm
content: Hi, thanks for the reply. In Windows 10 > Settings > About this computer, it reads "no pen or touch support". I also checked under Device Manager, and nothing. I don't have my Linux installation handy, so can't test it under Linux.P.S. With laptop on, I used multimeter and measure 3.3v between the pins labeled as+3.3VaandAGND
Thinnest Fiberscope/Borescope to peek between top & bottom pcb - Page 1
Forum section: electronics / beginners

author: loop123
author_rank: Frequent Contributor
timestamp: February 24, 2024, 12:46:38 am
content: Hi I have a device worth $16500 new and I dont want to open lest it might get damage. It has another pcb on top of the bottom pcb. Im looking for the thinnest but least expensive fiberscope/borescope to peek in between the top and bottom PCBs. Know one? I just want to know what MCU and amplifier it used. See images below. Thanks.
Thinnest gauge for usb charging? - Page 1
Forum section: electronics / beginners

author: Kahenraz
author_rank: Contributor
timestamp: October 28, 2017, 11:02:16 am
content: I want to mod my phone with a wireless charger attached to the USB pins. What is the thinnest gauge that is safe to use for this application?Also, is there any risk of damage if I were to have the USB connected to a computer or power source and it came in contact with a Qi base with this setup?

author: Bootalito
author_rank: Unknown
timestamp: October 28, 2017, 07:08:36 pm
content: A qi charger should charge at about 1 amp. A 24awg wire is about the thinnest Id go for 1amp, especially since they are abundant in Ethernet cables. You could use a 28awg wire but you run the risk of a big voltage drop where the phone may charge slower.The bigger issue is the second thing you mentioned. You would need a diode connected from the qi to the positive usb terminal(and ideally another one from the USB charger to the plug) . Doing that reduces the voltage by about 0.2v.So all in all this isn't a great idea.Besides... Qi charging I'm isn't that great. It's 50pct efficient(vs 90+) so you are wasting electricity. That in efficiency goes right into heating your phone up, right next to the battery. And guess what really hates heat? Lithium batteries. You reduce the lifespan. It's also 50pct slower charging at only 1amp.So you use more electricity, kill your battery faster, and take twice as long to charge, for the benefit of saving 1.5seconds each time you go to charge your phone. Meh..Sent from my VS990 using Tapatalk

author: Twoflower
author_rank: Frequent Contributor
timestamp: October 28, 2017, 08:03:07 pm
content: Without telling the cellphone that you want to charge with high current the phone probably draws close to nothing through this connection. The USB standard allows only 50mA drawn without negotiation (not sure about USB3 and newer). This is done either by pulling down/up the datalines with specific resistors or using a protocol on the datalines. So probably this construction won't work. This is probably the reason why some combinations of device vs. charger work better than other combinations.And if you connect a PC to that construction no one knows what could happen.

author: Zero999
author_rank: Super Contributor
timestamp: October 28, 2017, 10:37:07 pm
content: Sizing cable isn't the easiest of things. It depends on many factors: maximum temperature rating of the insulation, how well thermally insulated it is, the maximum ambient temperature, maximum permittable voltage drop and mechanical robustness.
This amplifier gives incorrect V_OUT for small VIN difference - Page 1
Forum section: electronics / beginners

author: king.oslo
author_rank: Frequent Contributor
timestamp: July 27, 2012, 03:55:53 pm
content: Hello there,I've tried to simulate this with all sorts of precision amplifiers, and now I need some help, because I've failed.I have a small voltage difference between non inverting and inverting input of 1mV. But still I get 40mV from the output. The amplifiers I've used, typically have some uV input offset, and low input bias currents.Attached is my circuit.Thanks.M

author: 6502nop
author_rank: Regular Contributor
timestamp: July 27, 2012, 04:32:14 pm
content: In other words, check your Vref (pin 5 of the LT1991) to make sure it's at the zero point (0V if using a dual supply, 1/2 Vcc if using a single supply). The example shown on page 1 of the datasheet shows it at 2.5V on a single 5V supply. Your schematic shows the end of the 450K @ pin 5 is grounded, but the negative rail is also at that point, so... Vee=Gnd?nop

author: king.oslo
author_rank: Frequent Contributor
timestamp: July 27, 2012, 04:55:19 pm
content: It works if I add a dual supply, but at ref = 1/2VCC, I have no luck. Why not?Thanks.M

author: PA0PBZ
author_rank: Super Contributor
timestamp: July 27, 2012, 05:23:31 pm
content: At 1/2 VCC your output will also be at 1/2 VCC when your inputs are equal.It's not right there because your 1K resistor is too small, change that to 10K and you will see.

author: king.oslo
author_rank: Frequent Contributor
timestamp: July 27, 2012, 08:31:35 pm
content: Thanks. That worked fineM
This AoE circuit I cannot make sense of - Page 1
Forum section: electronics / beginners

author: Moriambar
author_rank: Unknown
timestamp: June 05, 2021, 03:16:15 pm
content: Hi, while reading tAoE 3rd edition (fig 4.66, page 259).This "T" network should make the feedback resistor seen by the op amp as large as 10M (as advertised). But to me it's just 100k + (100k//1.2k). Where am I wrong? Also, why does the noninverting input have a 53k resistor to GND?Boy sometimes tAoE is frustrating…Thanks

author: langwadt
author_rank: Super Contributor
timestamp: June 05, 2021, 03:30:26 pm
content: it sets the gain as if the feedback resistor was 10Mthe 51K is there so that the resistance to ground for both inverting and non-inverting input is similar, the reduces offset due to bias currents

author: TimFox
author_rank: Super Contributor
timestamp: June 05, 2021, 03:51:26 pm
content: These TEE networks are common when the large required resistance is not practicable.A simple way to consider it is that the 100 k resistor (at op amp output) and 1.02 k resistor feed about 1/100 of the amplifier output voltage to the other 100 k resistor at the input, making the current through that resistor to the "virtual ground" 100 times smaller than that through a 100 k resistor from the output. Therefore, the feedback current equals the current through a large resistor (100 x 100 k = 10 megohm).This has other problems, though, including that the "noise gain" (voltage gain for the amplifier input noise and offset voltages) is increased from unity to x100. Also, the thermal (Johnson) noise current in the circuit is that of the 100 k resistor, not the equivalent 10 megohm resistor, so the noise increases (when driven from a high-impedance source such as a photosensor).This is an example of the general "Y-Delta" transformation, which is very powerful for circuit analysis:https://en.wikipedia.org/wiki/Y-%CE%94_transform

author: Moriambar
author_rank: Unknown
timestamp: June 05, 2021, 05:21:37 pm
content: Quote from: TimFox on June 05, 2021, 03:51:26 pmCool! Thanks by your message and a bit of thinking I exactly got how to deal with this kind of circuit/feedback. Y-Delta analysis has always escaped me, but that's another topic for another day
This has me Confused - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: October 13, 2013, 05:40:56 pm
content: Hi all, I have a very simple circuit here from the Make Electronics book. Basically it's the introduction to transistors. I understand that applying a small voltage to base is allowing the current to flow from the collector o the emitter, but why the two very different voltage drops? If I take a voltage drop between the collector, and the emitter I would think it would be somewhat close to taking the reading from the collector to the negative end of the LED, but it's not even close. The first reading is like .65mV, and the second is like 9.98V.I would think they should very close to the 9.98. Why is it not close seeing how the voltage is flowing between the collector, and emitter either way right?

author: awallin
author_rank: Frequent Contributor
timestamp: October 13, 2013, 05:43:34 pm
content: we probably need a circuit diagram with the voltages you talk about indicated. photos aren't that great for displaying circuits - that's why we like schematics!

author: mariush
author_rank: Super Contributor
timestamp: October 13, 2013, 05:56:53 pm
content: If I remember my transistor stuff correctly, it's normal to have about 0.2v drop between collector and emitter, and about 0.4-0.6v at the base. But do get back to us with schematic.

author: tony3d
author_rank: Frequent Contributor
timestamp: October 13, 2013, 11:10:57 pm
content: Trouble is I was getting like 65mV between the the collector end of the 180ohm resistor. That should have read 12v. Found out I had the other end of the resistor plugged into the wrong rail so I wasn't picking up the plus side of the power. It's all good now. I guess that's how you learn.

author: geraldjhg
author_rank: Regular Contributor
timestamp: October 14, 2013, 01:08:13 pm
content: hitransistors are turned on with CURRENT it is irrelevant to mesurethe base voltage, it is alwways arounf .6 v (silicon)so measure the voltage drop in the base resistor and by ohms lawfind the currentplay around with 1 ma to start withnow for the collectorif you inject 1 ma into the base and the transistor that has a beta of 100the collecyor is capable of sinking 100 ma and the collector voltageshould be around .2 volt (if not it will get HOT and be working in linear mode)so limit this collector current to some safe value and play alongdisregard small variation in voltage, the just appeared with DMMand are so dependant on gain and gain depends on temperature etc etcsaludos
This is going to be built next weekend that's for sure - Page 1
Forum section: electronics / beginners

author: w2aew
author_rank: Super Contributor
timestamp: February 02, 2013, 09:46:21 pm
content: Here are a couple of additional options for RF Samplers:...and here's one that requires no construction at all...

author: M0BSW
author_rank: Frequent Contributor
timestamp: February 05, 2013, 04:55:41 pm
content: Again brilliant video's Alan
This power supply is dangerous right ? - Page 1
Forum section: electronics / beginners

author: eevfan007
author_rank: Contributor
timestamp: December 01, 2014, 07:39:09 pm
content: I pulled this power supply (220V AC) from a cheap shaver i bought. I suspected that is was quite poorly made, had that cheap plastic feel to it.I don't see any isolation slots, and it seems quite dangerous for a shaver. This is after all something you have close to your face. Notice the N and L markings. The wire was incredibly thinIt runs a small motor at a couple of volts DC it seems, and also charges a 500mAh 1,2V Ni-MH battary too.Would you trust this ?

author: Zero999
author_rank: Super Contributor
timestamp: December 01, 2014, 10:50:07 pm
content: It's quite possible perfectly safe, as long as all of the electrical connections, including those to the motor and batteries are well insulated.

author: Paul Price
author_rank: Super Contributor
timestamp: December 01, 2014, 11:17:17 pm
content: It seems you have not been killed using it so I don't think you were really facing a close shave with death.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: December 02, 2014, 10:52:52 am
content: i saw worst, a shaver with only a diode a capacitor and a resistor , and the DC motor obviously, nothing more. but it shouldn't be dangerous since all metallic part of the shaver are isolated form the circuit.
This Russian push pull tube amp output is really confusing me. - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: January 22, 2020, 06:26:17 pm
content: I just can't even start to understand where the speaker connects, how it even works and it's just weird.Also the 2 power transformers are just weird x 1000.https://www.gstube.com/schemes/pics/Us/001.gif

author: glinjik
author_rank: Regular Contributor
timestamp: January 22, 2020, 06:38:56 pm
content: what i can tell you is the components are soviet era so diodesд7ж =https://eandc.ru/catalog/detail.php?ID=5758i don't know what part of the world your in but i suspect it would be v difficult to get those parts equivalent parts would need to be compared carefully of course here i can buy those parts easyI've given you a link to that diode maybe you use Google Translate or something?

author: Gyro
author_rank: Super Contributor
timestamp: January 22, 2020, 06:43:56 pm
content: It looks like output stage cathode feedback, but using an AC coupled centre tapped inductor rather than (the more usual) dedicated cathode windings on the output transformer. Look up the QUAD II22for an example of normal opt cathode feedback.

author: hermitengineer
author_rank: Regular Contributor
timestamp: January 22, 2020, 07:34:52 pm
content: Hmmm... if you keep a screen at a lower potential than the cathode, could it become a parasitic draw rather than a control? Because they seem to be expecting that, and using it as a feature. I'm assuming that the speaker connects to the leftmost terminals?Never mind. The leftmost terminals must be the input, and the transformer labeled Amp1 must be where the speaker(s) connect.

author: Yansi
author_rank: Super Contributor
timestamp: January 22, 2020, 07:36:34 pm
content: That is a "circlotron" amplifier topology.See more for example here:http://circlotron.tripod.com/

author: Bud
author_rank: Super Contributor
timestamp: January 29, 2020, 03:09:13 am
content: This is funny but I came across the complete article for this amplifier while googling for something else. A diagram on page 2 explains how to use a 4 Ohm or 16 Ohm speaker. The article is from a 1960 magazine.

author: Calvin
author_rank: Regular Contributor
timestamp: January 29, 2020, 03:54:23 am
content: Hi,yes, its a circlotron.The load is connected between the two cathodes of the output tubes.As such the output impedance is lowish, allowing for transformer-less drive of a attached load, though it seems to be preferable to galvanically isolate the load with an output transformer.Circlotrons also seem to cope quite well with electrostatic speakers as load.Besides the requirement for two floating power supplies the driver stages need to be beefier than with conventional amplifier designs since they need to provide for the full voltage stroke.regardsCalvin
This title may be click bait, but... - Page 1
Forum section: electronics / beginners

author: @rt
author_rank: Super Contributor
timestamp: September 23, 2017, 06:42:52 pm
content: What's the difference between 7403 & 7401?Answer: 2But really, the only difference I see is the pinout.Was it really necessary to design two chips in 7400 series for that?Cheers, Brek.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 23, 2017, 08:09:23 pm
content: Open collector outputs.Tim

author: Benta
author_rank: Super Contributor
timestamp: September 23, 2017, 09:03:04 pm
content: Both are open collector. No difference except pinout.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 24, 2017, 01:36:24 am
content: What is interesting is that the 54/7401 had different layouts trough the various series and packages, while for the '03 they seem to be all similar.(from TI The_TTL_Data_Book_For_Design_Engineers_2ed_1981)

author: @rt
author_rank: Super Contributor
timestamp: September 24, 2017, 04:49:51 am
content: I guess I was lucky I used, and already wired HD74LS01, and it was as expected (top left).Quote from: Neomys Sapiens on September 24, 2017, 01:36:24 am

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2017, 10:59:03 am
content: W and T packages are the ceramic flatpack versions, which were also available in many of the original TTL family as an option. As well the 03 has high voltage capable outputs, which can withstand up to 30V on the open collector, used for interfacing to things like reed relays at 24V and such things, and also used as interface to NMOS logic as well.

author: Benta
author_rank: Super Contributor
timestamp: September 24, 2017, 11:41:56 am
content: QuoteBoth the 7401 and the 7403 are rated at 7 V maximum output off voltage. Source:www.ti.comdatasheets.

author: SeanB
author_rank: Super Contributor
timestamp: September 25, 2017, 06:41:53 pm
content: Quote from: Benta on September 24, 2017, 11:41:56 amSorry, my bad, went to look at the paper copy of the TI datasheet, and yes, they are 7V rated, I was thinking of the 06 and 07, which were 30V rated for the outputs.Funny thing is the rest of the chip is still only rated for 7V, though you will find that many will work at 10V with nothing other than running pretty hot. Got a wall ornament board where that hapenned, the power supply decided to apply unregulated 14V to the TTL, and the only IC to fail was a SFC5406PM3 30V capable open collector gate, which was easy to find, as it had unsoldered the can of the flatpack lid.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 25, 2017, 09:25:47 pm
content: Quote from: SeanB on September 25, 2017, 06:41:53 pmHow high did you fly that thing?
thoughts about component tester built into Heath scope aka Octopus curve tracer - Page 1
Forum section: electronics / beginners

author: festus
author_rank: Contributor
timestamp: January 16, 2019, 05:24:51 pm
content: Hi guys,I've been recently inspired by watching Mr Carlson's videos and his signature tracer.Hopefully some knowledgeable experts here could comment about the safety-against-damaging-components aspect of the built-in component tester in my Heath SO-4552 Oscilloscope.The RMS voltage and current is significantly higher than that of the typical Octopus circuits.Here are the specs, so please let me know if this risks damaging components:Test Voltage: maximum 6V rms (open circuit)Test current: max 11ma (shorted)Test freq: line freq (aka 60hz)So basically I am wondering whether the 6v rms and 11ma are risky. The manual suggests that it can be, saying:"transistors used in high-gain low noise applications may be permanently degraded when subjected to a B-E reverse voltage that exceeds breakdown rating. The component test open-circuit test voltage can be as high as 9V peak. This voltage can be reduced by resistive loading or zener clamping diode to permit safe transistor testing."Any thoughts? I'd like to use this, since I already have it, and it's built-in. The scope is rather cheap specs, though, only having a vertical down to 5mv, but otherwise suffices for my basic needs.

author: Paul Rose
author_rank: Regular Contributor
timestamp: January 17, 2019, 02:12:01 pm
content: If you haven't already, check out these older threads:https://www.eevblog.com/forum/testgear/inexpensive-curve-tracer/https://www.eevblog.com/forum/beginners/installing-npn-transistor-backwards/9V will exceed the reverse B-Eratingfor many (most) transistors. Whether it will actually do anything is harder to say.However, you already have the tester, and jellybean transistors are cheap. Play with some and see how frequently you actually see B-E current in the reverse direction. You will gain some confidence.You could use a simple diode across the B-E connected opposite polarity from the natural B-E diode for protection. But it means being aware of what you are testing and how it is connected.
Thoughts on my first scope? BK Precision $51 - Page 1
Forum section: electronics / beginners

author: Sypher
author_rank: Contributor
timestamp: October 08, 2012, 02:46:13 pm
content: Just bought my first oscilloscope:http://www.ebay.com/itm/BK-Precision-2160-60-MHz-Dual-Trace-Oscilloscope-Test-Working-/190733363982?ssPageName=ADME:B:EOIBSA:US:3160Thought it was a good deal $50 but forgot that shipping would be another 20 lol. Think it was woth the $70? Think its a good first scope? Any coments?

author: Tube_Dude
author_rank: Regular Contributor
timestamp: October 08, 2012, 02:55:38 pm
content: It looks OK to me, you even get a component tester for free...Ahh... and I love analogue scopes.

author: ModemHead
author_rank: Frequent Contributor
timestamp: October 08, 2012, 03:21:26 pm
content: Looks like a decent deal. I have a BK 2125 of the same vintage that I bought new in the late 80s. Very similar but only 20MHz bandwidth. It has worked well and still works today. Had to perform minor repairs twice I think. Speaking of which, you may have a little work to do, the sweep length looks a bit short in the photo.

author: Tube_Dude
author_rank: Regular Contributor
timestamp: October 08, 2012, 03:28:26 pm
content: Quote from: ModemHead on October 08, 2012, 03:21:26 pmMaybe is in the component tester position. In that position the sweep length become shorter.

author: ModemHead
author_rank: Frequent Contributor
timestamp: October 08, 2012, 03:32:00 pm
content: Quote from: Tube_Dude on October 08, 2012, 03:28:26 pmI think you're right. The comp test button looks to be pushed in. I stand corrected, hopefully it will be in perfect working order!

author: ciikucli
author_rank: Contributor
timestamp: October 12, 2012, 10:22:35 pm
content: I got the exact same scope for 30 a couple months ago. It seems to be a reliable, functional scope.
Thread and Zwave protocol - Page 1
Forum section: electronics / beginners

author: druser
author_rank: Newbie
timestamp: August 02, 2017, 06:45:54 am
content: HiWe are trying to implement Thread and Z-Wave protocol for avr-atmega256rfr2MCU and have a custom build module.For that module, we need to build a stack for these protocols.Already it supports ZigBee and 6lowpan, for that the open stack was available.Likewise, do we have any open stack for Thread and Zwave protocol? Will these can be run in avr-atmega256rfr2

author: ataradov
author_rank: Super Contributor
timestamp: August 02, 2017, 06:59:18 am
content: Thread is 6LowPAN with some some restrictions and additions on top.Z-Wave is impossible, totally different radios, totally closed and proprietary protocols.

author: Zero999
author_rank: Super Contributor
timestamp: August 02, 2017, 05:55:41 pm
content: https://www.eevblog.com/forum/beginners/z-wave-protocol/msg1266480/#msg1266480

author: WastelandTek
author_rank: Frequent Contributor
timestamp: August 02, 2017, 06:04:00 pm
content: again?

author: hermit
author_rank: Frequent Contributor
timestamp: August 02, 2017, 11:32:10 pm
content: Let me offer the same advice I offered in that thread. Use the forum listed on the 'open' site.
Threaded alligator clips for insulation tester probes - Page 1
Forum section: electronics / beginners

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: September 14, 2019, 09:06:10 pm
content: HiI bought recently some uni-t probes with screwable M4 in order to add on threaded allligator clips to serve as spare probes for insulation tester . However i couldn't find properly identical to the original one which is also uni-t .Both have no markings of the model.The best aproach i've got was this "based" fluke AC175:https://ebay.us/CGG1HKBut either i found the same model on other sellers as snap-on only or threaded snap on.The uni-t model for the threaded one is UT-C05A (M4) but didn't find a good price or a local distributor.https://www.uni-trend.com/html/product/qita/ut-c_alligator_clips/UT-C05A.htmlAre there better alternatives to this threaded alligator clips which are compliant for insulation tester up to 1000V? Insulation Tester Model is uni-t ut 501A.
Three phase rectifier: source inductance and conduction angle - Page 1
Forum section: electronics / beginners

author: omglol
author_rank: Regular Contributor
timestamp: November 21, 2017, 08:59:48 pm
content: Hi!I while ago I was asking for help with LTSpice model of three-phase MOSFET rectifier and I got a lot of great help (https://www.eevblog.com/forum/beginners/ltspice-mosfet-triggering-help/). Especially Jay_Diddy_B's model really helped me a lot, and I am attaching it here because my question is based on it.Let's suppose we have ideal three phase source with no inductace with basic diodes ar rectifiers, as shown here (ignore SCR, let's say we have diodes):In this case, diodes are conducting at following angles:30° to 90° D1 and D690° to 150° D1 and D2150° to 210° D2 and D3210° to 270° D3 and D4270° to 330° D4 and D5330° to 360° and 0° to 30° D5 and D6This means that diode D1 is conducting from 30° to 150°, that is exactly 120°.This is how stuff looks like without source inductance:However, after we add some inductance, we see that conduction of diodes starts overlapping - each of the diodes conducts MORE than 120°:Here is my question - does angle extension effect "both sides"? For example, if we say that each diode now conducts 140° (under certain circumstances), does this mean diode D1 is now conducting from 20° to 160° (so: +10° at beginning and +10° at the end)?Let's take a look at this waveform. The source is running at 400Hz, MOSFETs are set to conduct 120°, we are looking at voltage across MOSFET M6 ("diode D1" in previous case). If we pretend we are looking at the exact start of the simulation, does this mean that ORANGE arrow is exactly at 30°, while GREEN arrow is pointing at somewhere <30°? And RED and YELLOW encircled areas should be pretty much the same length in terms of relative degrees (or time)?Many thanks!

author: omglol
author_rank: Regular Contributor
timestamp: November 22, 2017, 04:52:35 pm
content: Can anyone shed some light please?
Three terminal capacitor  - Page 1
Forum section: electronics / beginners

author: powersupply
author_rank: Contributor
timestamp: August 12, 2025, 11:09:23 pm
content: Hello fellow geeks,I am refurbishing a Agilent 6643a PSU, adding front binding posts and the poor things two knobs that were so loose they needed some tightening of the four metal clips that held the rotors encoder together.. The lcd was falling down. Very creative effort was used to get it tightly affixed in proper position. But anyway while I was fixing some PCB paths pulled up by someone while they were probably soldering in a new axial leaded fuse. (The real issue)While doing this I noticed on the HPIB board a large Nichicon capacitor with 3 terminals. 2 went to plus and ground the third went to ground and was in the nine o’clock position with the two others at noon and six. I ask googles and chant and received generic vague answers.Can someone provide a real explanation of the third terminal purpose?Thank youPower [ Specified attachment is not available ]supply

author: Psi
author_rank: Super Contributor
timestamp: August 12, 2025, 11:20:52 pm
content: Regarding large caps with 3 pins.- Sometimes it's just for extra mechanical mounting. If you only have 2 it can vibrate back/forward and eventually snap off. So 3 makes a tripod and is more secure.- They also make large caps that are two caps in one package with a common, hence 3 terminals. Common in old vacuum tube stuff, it's probably not this type.- You also find some where the metal can around the cap is one of the pins and nothing to do with the cap itself. I can't recall if that's done for shielding or just mechanical mounting.Which one you have i don't know. You'd have to read the label and look it up, or measure terminals with meter.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 12, 2025, 11:26:05 pm
content: Typically the third lead is just for mechanical support.Why not look it up in the service manual and figure it out?

author: powersupply
author_rank: Contributor
timestamp: August 12, 2025, 11:32:45 pm
content: Excellent, I never thought of mechanical support Grok is great, but he didn’t mention that. Thank you for taking time to answer.

author: powersupply
author_rank: Contributor
timestamp: August 12, 2025, 11:35:27 pm
content: Now I’m inspired to pull the cover off and check it out for just what is this third terminal doing. The mechanical support never occurred to me. Thank you for your time.

author: golden_labels
author_rank: Super Contributor
timestamp: August 13, 2025, 03:39:30 am
content: It would be much better to post a photo of the capacitor we’re being asked about.In some older equipment you can find multi-section capacitors. They usually have a shared cathode, often explicitly(1)attached to the case. SeeC10 capacitor on page 20 of “Beitman's Most Often Needed Radio Diagrams and Servicing Information”.To reduce inductance, some capacitors have a doubled lead for one of the ends. Seethis postfor a photo.(1)As opposed to capacitors, where this is an unintended effect.