hybridfree/eevblog-posts huggingface dataset:
Is this a resistor - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: June 13, 2019, 01:34:34 am
content: This is markedTF 185 degrees C10ABX X20Is it some kind of heavy duty resistor or fuse?

author: cur8xgo
author_rank: Regular Contributor
timestamp: June 13, 2019, 01:36:19 am
content: Quote from: fixit7 on June 13, 2019, 01:34:34 amTF = "thermal fuse" ?185C = trip temp?10A = max rated currentBX X20 = part number?

author: oPossum
author_rank: Super Contributor
timestamp: June 13, 2019, 01:36:49 am
content: Thermal switch. Probably goes open at 185C.

author: MosherIV
author_rank: Super Contributor
timestamp: June 13, 2019, 06:52:16 am
content: No it is not a resistor.It is a thermal fuse, as others have suggested.

author: Zero999
author_rank: Super Contributor
timestamp: June 13, 2019, 08:38:44 am
content: Quote from: oPossum on June 13, 2019, 01:36:49 amBeing picky but it's not a thermal switch, because that implies it's resettable. A thermal fuse is a one shot device: once it's blown, it'll need replacing. Thermal switches are also often used for thermal protection, but they're normally combined with a thermal fuse, just in case the contacts weld closed.Thermal fuses are normally used for fire protection. Quite often the device will be irreparable before the thermal fuse blows, but not always, so it might be worth replacing. Try temporally replacing it with a wire and if the device works, including the temperature controller (it's very common for a temperature controller to fail with the heater stuck on, causing the thermal fuse to blow), seek a replacement. Obviouslydon't permanently replace it with a wire, because that would result in a huge fire risk.

author: Psi
author_rank: Super Contributor
timestamp: June 13, 2019, 08:49:29 am
content: Soldering/desoldering them can be tricky, they tend to blow if you get to close with the iron.

author: Brumby
author_rank: Unknown
timestamp: June 13, 2019, 11:31:34 am
content: Definitely a thermal fuse.Quote from: Psi on June 13, 2019, 08:49:29 amWhich explains why it looks like it's secured by nut and bolt.

author: fixit7
author_rank: Regular Contributor
timestamp: June 13, 2019, 04:42:36 pm
content: I wonder what the yellow wrapper is?

author: Gyro
author_rank: Super Contributor
timestamp: June 13, 2019, 05:09:36 pm
content: Kapton tape for insulation.

author: fixit7
author_rank: Regular Contributor
timestamp: June 13, 2019, 07:28:17 pm
content: Cool.https://www.bing.com/videos/search?q=kapton+tape&view=detail&mid=406DFDFF8DF50651A6DA406DFDFF8DF50651A6DA&FORM=VIRE
Is this a resistor or a thermal fuse? - Page 1
Forum section: electronics / beginners

author: niemand
author_rank: Contributor
timestamp: September 29, 2022, 04:49:31 pm
content: It's on a bimetal switch of a Black & Decker toaster oven TRO 855 TY8, hidden under an insulating sleeve:

author: Terry Bites
author_rank: Super Contributor
timestamp: September 29, 2022, 05:42:09 pm
content: It looks like a bog standard resistor to me

author: james_s
author_rank: Super Contributor
timestamp: September 29, 2022, 05:44:39 pm
content: It's a resistor, looks like 10k. Can you tell how it's wired? My first thought was a resistor for a neon indicator but 10k is too low for that IIRC.

author: niemand
author_rank: Contributor
timestamp: September 29, 2022, 11:00:58 pm
content: Quote from: james_s on September 29, 2022, 05:44:39 pmThe resistor measures 30kΩ, and it is wired to a small light bulb:

author: Fraser
author_rank: Super Contributor
timestamp: September 29, 2022, 11:04:15 pm
content: Resistor. The “light bulb” is a neon indicator.Fraser

author: james_s
author_rank: Super Contributor
timestamp: September 29, 2022, 11:12:47 pm
content: Oh, yeah that's a small neon lamp, they need a current limiting resistor just like LEDs.
Is this a resistor? - Page 1
Forum section: electronics / beginners

author: CircuitryLab
author_rank: Newbie
timestamp: December 11, 2014, 05:01:25 am
content: If it is a resistor, what type of resistor is this?And how can determine its watt rating?Thank you.

author: c4757p
author_rank: Super Contributor
timestamp: December 11, 2014, 05:11:57 am
content: Yes, that is a resistor. Cement-encased wirewound, likely. Not sure about the power rating - are you sure it isn't marked on the other side?

author: CircuitryLab
author_rank: Newbie
timestamp: December 11, 2014, 05:15:03 am
content: I will take a look at the other side.Thanks c4757p.

author: SeanB
author_rank: Super Contributor
timestamp: December 11, 2014, 06:10:56 pm
content: It is a resistor, likely at around the 25W mark.http://www.ttelectronicsresistors.com/datasheets/1600-1900.pdfThis is an old IRC resistor, made near the end of 1971.
Is this a signal diode or a zener? - Page 1
Forum section: electronics / beginners

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 16, 2021, 04:26:07 pm
content: Could this be a signal diode?Thanks

author: Manul
author_rank: Super Contributor
timestamp: September 16, 2021, 04:35:35 pm
content: It is likely 1N4148, is there also "41" written on the other side?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 16, 2021, 05:01:40 pm
content: Stupidly I put it back before taking photos of the other side... but at an oblique angle...Looks like what I thought were just lines could be a 41!

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 16, 2021, 05:04:28 pm
content: What about this one...Looks like 3V9... so that would be a zener even though it looks similar? The board marking is a bit ambiguous due to the coincidence with the square?

author: Gyro
author_rank: Super Contributor
timestamp: September 16, 2021, 05:29:46 pm
content: Yes, a 1N4148 and a 3V9 400mW zener.
Is this a suitable replacement for a 2N4126 ? - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: November 30, 2012, 01:36:03 pm
content: I have an iffy 2N4126 PNP semiconductor in a frequency counter. the basic spec is at:http://alltransistors.com/transistor.php?transistor=3946I have some BC557B semiconductors, can I use one as a replacement please?The basic spec on the BC557B is at:http://uk.rs-online.com/web/p/bipolar-transistors/5452260/Thanks!

author: amyk
author_rank: Super Contributor
timestamp: November 30, 2012, 01:58:50 pm
content: The BC557B has higher Vce(SAT) 0.64 vs 0.4V and Ice(max) 0.1 vs 0.2V on the 2N4126.It depends if the halved current carrying capacity and higher forward voltage will be critical to your application.

author: Matje
author_rank: Regular Contributor
timestamp: November 30, 2012, 11:37:11 pm
content: Quote from: Chris Wilson on November 30, 2012, 01:36:03 pmAlltransistors has a handy link called "Foo Equivalent Transistors" on each transistors page. Use it, as a starting point at least.It thinks a BC327 is a possible replacement. Whether a BC557 will do you will need to evaluate yourself, as already said. Given that the transit frequency is much lower for a BC557 and you are talking about a frequency counter - it may well be not suitable.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 01, 2012, 04:04:47 pm
content: What is the transistor doing?Sometimes manufacturers use the same transistor in critical & non-critical circuits to save parts inventory.If they have done that on this unit,& the one you need to replace is the critical one,steal one from a non-critical circuit,& replacethatone with a "bodgie" equivalent.

author: Chris Wilson
author_rank: Super Contributor
timestamp: December 01, 2012, 05:15:06 pm
content: I have to be honest and say I am not entirely sure what its function is, all I know is it's iffy and heat sensitive. The counter is deaf on Band 2 until it warms up, and putting a tiny bit of heat into this semiconductor makes it operate correctly. Cooling it with a dash of freeze spray makes it deaf again. Out of circuit its gain varies heavily with temperature. I have found an Ebay seller with the correct devices, so rather than get clever I have ordered the same part number. Here's the circuit, for interests sake. Thanks for the advice.
is this a typical high and low side switching circuit? - Page 1
Forum section: electronics / beginners

author: superwester
author_rank: Contributor
timestamp: February 18, 2018, 04:10:11 am
content: i was struggling thinking that i needed to control two high side switches.but on a second though, as the circuit is powered by a bipolar supply its a good old high and low side half H bridge.am i right?circuit:https://imgur.com/gallery/pmp1Isorry if this requires more info from my part, but im assuming it does not.

author: superwester
author_rank: Contributor
timestamp: February 18, 2018, 04:13:06 am
content: i made the same question a while back and, stupidly enough, i didnt post any circuit and i cant erase it

author: Jwillis
author_rank: Super Contributor
timestamp: February 18, 2018, 04:49:30 am
content: That looks single phase.2 diodes in that configuration is a full wave rectifier.The Fets are switches.

author: superwester
author_rank: Contributor
timestamp: February 18, 2018, 03:15:59 pm
content: im aware of that part, but i dont know if i can consider both fets on the high side of the load or the one controling the positive rail is on the high side and the other controlling the - rail is the low side switch. im guessing its the later

author: PartialDischarge
author_rank: Super Contributor
timestamp: February 18, 2018, 03:32:47 pm
content: For your purpose you can consider it an H bridge.For a moment when I saw the two capacitors in series, this circuit reminded me of an NPC converter.(neutral point clamped)

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 18, 2018, 05:51:23 pm
content: the diodes and caps aredelon bridge voltage doublerbut in this case is to produce dual dc rails. the mosfets (bjts?) are the switching circuit. when top is turned on, it provides current to the windings, after sometime, it will be turned off, and the bottom mosfet will turned on to draw current from the windings. since the bottom mosfet is on the lower rail, so it should be the low side pass element.

author: superwester
author_rank: Contributor
timestamp: February 18, 2018, 06:39:27 pm
content: thanks, all clear now.
Is this a varistor? - Page 1
Forum section: electronics / beginners

author: ElektroQuark
author_rank: Unknown
timestamp: August 14, 2017, 06:45:32 pm
content: 275V?And that 4 stands for...?

author: Gyro
author_rank: Super Contributor
timestamp: August 14, 2017, 08:04:35 pm
content: Itcouldbe... but I'm not sure I'd stake my life on it without seeing exactly where it lives.If itisa 275V VDR then comparing it's physical size against RS, Farnell, etc. offerings would give a reasonable indication of its energy rating.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 14, 2017, 08:20:57 pm
content: Show where it is from.

author: ElektroQuark
author_rank: Unknown
timestamp: August 14, 2017, 08:55:28 pm
content: I don't know. I have found a bunch of them in a drawer.I think they will go to the bin.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 14, 2017, 11:41:56 pm
content: Do you have a capacitance meter? What does it measure?There is nothing printed on the other side?Tim

author: ElektroQuark
author_rank: Unknown
timestamp: August 15, 2017, 04:12:08 am
content: 89pFResistance measures more than 100 MOhm.No, there isn't.

author: Gyro
author_rank: Super Contributor
timestamp: August 15, 2017, 08:46:01 am
content: Those figures do sound consitent with it being a Varistor.There's nothing in the markings that is consistent with a capacitor in the 80-100pF range and it is also a bit too resistive for a capacitor. My other thought was that it might be a useful thermistor but that's gone out of the window too.

author: ElektroQuark
author_rank: Unknown
timestamp: August 15, 2017, 08:52:42 am
content: Any thoughts about the 4?

author: ElektroQuark
author_rank: Unknown
timestamp: August 15, 2017, 09:04:37 am
content: Found!It's a Harris (now Littlefuse) V275LA4 model varistor.CLICK!Thank you!
Is this adequate in protecting mosfet's Vgs ? - Page 1
Forum section: electronics / beginners

author: BravoV
author_rank: Super Contributor
timestamp: February 02, 2013, 09:33:42 am
content: Just want to be sure, is this enough to protect the mosfet from unexpected high voltage spike at gate pin ?Say for ordinary power mosfet (not logic one) which is usually have max Vgs +/- 20 volt, a 15 volt zener should be fine right ?TIA

author: AndyC_772
author_rank: Super Contributor
timestamp: February 02, 2013, 10:02:20 am
content: Arguably you don't need the resistor at all, it can only allow Vgs to exceed the Zener voltage.I'd personally use a dedicated TVS (transient voltage suppressor) diode, though. They're designed to react very quickly in the event of a spike, and to conduct large currents briefly without damage. The trade-off is that their breakdown voltage is neither very well controlled nor flat over a range of currents, but in this application you don't care.

author: Psi
author_rank: Super Contributor
timestamp: February 02, 2013, 10:50:29 am
content: A TVS is what i'd use too.There can be quite a voltage range between the standoff and clamping specs, so make sure the clamping voltage is less than 20v.Most electronic suppliers will index them by standoff so its easy to get the wrong one.

author: lewis
author_rank: Frequent Contributor
timestamp: February 02, 2013, 08:30:26 pm
content: The resistor in series with the zener in your circuit will render it ineffective. Zener/TVS directly between gate and source will do the trick, but you'll need a gate resistor to limit the current out of whatever you're driving the MOSFET with in the event of a transient. This will slow down the MOSFET switching time, so the resistor value is a compromise between acceptable switching loss and transient 'gate' current.What are you driving the MOSFET with?

author: BravoV
author_rank: Super Contributor
timestamp: February 04, 2013, 03:42:15 am
content: Thanks for the replies, ok, no resistor we go then.About TVS, yes, I'm aware of it, its just a one off simple project and the current available (or at least easy to get) component is just zener.@Lewis,Yes, there will be a gate resistor and it will be driven by pair of transistors npn+pnp in totem-pole configuration.
Is this battery life estimate correct? - Page 1
Forum section: electronics / beginners

author: XOIIO
author_rank: Super Contributor
timestamp: November 14, 2013, 10:37:37 pm
content: Alright so I've never really tried this before and maybe I did something totally wrong, who knows but it seems about right, if I have a circuit that uses 60ma, powered by a 9v battery which I've seen online has a capacity of 500mah, it should run for approximately 8 hours, right?

author: con-f-use
author_rank: Unknown
timestamp: November 14, 2013, 10:44:43 pm
content: That is correct for a first estimate. No black magic to it. Though the voltage will drop before that, causing the circuit to fail. So it depends on what exactly the battery powers. Test your circuit's min. operating voltage. consult the datasheet of your battery. There should be a diagram detailing the voltage drop.

author: XOIIO
author_rank: Super Contributor
timestamp: November 14, 2013, 10:48:22 pm
content: Quote from: con-f-use on November 14, 2013, 10:44:43 pmwell, I don't think there is a datasheet for my cheapo dollar store Panasonic battery lol, but thanks.

author: con-f-use
author_rank: Unknown
timestamp: November 14, 2013, 10:52:21 pm
content: Even cheap batteries use the same chemistry and are standardised. Find a comparable data sheet.

author: IanB
author_rank: Super Contributor
timestamp: November 14, 2013, 11:11:01 pm
content: Take a look at this datasheet for a standard 9 V alkaline battery, for example:http://data.energizer.com/PDFs/522.pdfAccording to the constant current performance chart, you would get about 7 hours life at 60 mA drain down to 6 V.As others have said, the similarities between different brands of alkaline battery are greater than the differences.
Is this buffer sufficient? - Page 1
Forum section: electronics / beginners

author: chipwitch
author_rank: Frequent Contributor
timestamp: March 21, 2016, 02:20:58 am
content: I am connecting an SD card reader to an Arduino MCU proto board. The sketch uses SPI to interface with the SD card. Since the Arduino data pins are 5v and the card reader is 3.3V, I'm using a hex buffer to level shift. All of this is new to me, except for the Arduino part.A trusted source has indicated that these card readers can often draw 100 mA or more when writing data. Okay, so the same trusted source also specifies a couple level shifters for the project. I found some other ones, but when I checked the datasheet, I found that the IOwas only 35 mA per pin! I went back to my the trusted source and checked the datasheets for two of the parts she specified. Their IO's were even less.It would seem that either I'm not reading the datasheet correctly, or my "trusted source" is wrong. The latter of which seems highly unlikely. She is well respected in the Arduino community and a EE if I'm not mistaken.Am I reading the datasheet right? It won't handle the load right? Will I need to throw in some mosfets or something?

author: MK14
author_rank: Super Contributor
timestamp: March 21, 2016, 02:25:50 am
content: Surely the 100 mA or more, is talking about the power supply requirements for the SD card (supply rails). NOT the logic lines. ?Programming flash (SD cards etc), can indeed use lots of current, during writing.

author: MK14
author_rank: Super Contributor
timestamp: March 21, 2016, 02:52:59 am
content: Just to confirm. The following official looking (micro) SD spec:http://www.dtt8.com/images/micro-sd%20specification.pdfSeems to say that the POWER CONSUMPTION, can be similar to the 100 mA figure in your OP.But the logic lines, will be a tiny, TINY fraction of that amount. MASSIVELY below the 35 mA or whatever, of your buffers.SD cards, have been designed to use relatively small amounts of electricity, because mobile phones, cameras etc, have relatively small batteries.

author: chipwitch
author_rank: Frequent Contributor
timestamp: March 21, 2016, 02:59:55 am
content: You're right. Thanks to both of you. I went back and checked. She just said over 100 mA. She didn't say it was coming from the data pins. She wasn't specific about it at all. Of course, now it makes sense. Thanks for the link. I couldn't find any datasheets for my module, but your link has some useful info.Cheers
Is this Cap a Tantalum?? - Page 1
Forum section: electronics / beginners

author: K1JOS
author_rank: Regular Contributor
timestamp: August 11, 2015, 03:25:53 am
content: I came upon a stash of MIAL brand axial blue molded caps with a black stripe around one end. At first I thought these were vintage tantalums with the J being the old voltage reference for a tantalum but then I found many were of very low value, e.g, 0.0033 uF at 35v. I don't see any modern tantalums less than 0.1 uF at Mouser or Digikey. Attached is a picture of a typical one. Any advice appreciated.Jerry

author: bills
author_rank: Frequent Contributor
timestamp: August 11, 2015, 03:29:43 am
content: I am not sure but some caps have a stripe indicating the foil end (the lead connected to the foil) old school for rf.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: August 11, 2015, 03:45:24 am
content: Dunno, but if you can sacrifice one, just hook it up to a current limited power supply. If it's tantalum, it should leak like crazy well below it's working voltage if reversed biased. 10mA limit should be plenty. I'd go 5, 10 then 15 if I didn't know the WV.Bonus if it's tantalum, you'll get to know if the stripe indicates the positive terminal or the negative...

author: Psi
author_rank: Super Contributor
timestamp: August 11, 2015, 06:37:52 am
content: If it explodes under full voltage reverse polarity.. It was a tantalum
Is this clock signal ringing normal? - Page 1
Forum section: electronics / beginners

author: danderson
author_rank: Contributor
timestamp: February 12, 2014, 07:22:36 am
content: I'm playing with MCP2515 CAN controllers on a breadboard, hooked up to random ATmegas I had lying around. Unrelated to the CAN functionality, the 2515 provides a clock out signal, so that you can run multiple chips from the 2515's oscillator. Out of curiosity, I looked at the clock output on my scope, with a 16MHz crystal... And I got this signal, with nice clean rises and falls, but lots of ringing in between:http://imgur.com/a/25t9b.The oscillation isn't enough to anger digital chips, but it's still 0.3-0.5V of oscillation, which feels like a lot. This is a breadboard setup, so I'm expecting some noise here and there, but this is rock steady once the scope is triggered, not randomized, which makes me think this is actually a "feature" of the 2515's output signal, rather than something introduced by the breadboard.I'm still very new to peeking at signals with a scope. Is this sort of oscillation on digital signals to be expected? If not, what things should I check to find the source?

author: codeboy2k
author_rank: Super Contributor
timestamp: February 12, 2014, 08:31:24 am
content: That's not ringing. There is a little bit of overshoot on the leading edge, then following that would normally be any ringing, if you had it. But there is little to no ringing there. Ringing would be a initial large amplitude wave then decaying to 0 after a few cycles.What you have there is about 300mV of ripple noise that is showing up on the clock's output.It could be one of two things... Either decoupling, or the voltage regulator bulk capacitance is too low.Start with a decoupling cap on your breadboard near the positive rail pin on the MCP2515. Put about 0.1u there. If that doesn't help, then add bulk 10uF caps and 100uF caps around the breadboard.It's possibly something that is on your power supply to the MCP2515 chip, so check that with a scope and check also that your PSU has enough output bulk capacitance. Maybe you are using a voltage regulator on the breadboard, if so, make sure it has both input and output capacitors.
Is This Compact Fluorescent Bulb And What Do Terms Mean? - Page 1
Forum section: electronics / beginners

author: Boris_yo
author_rank: Frequent Contributor
timestamp: November 24, 2011, 10:31:57 am
content: Hello guys, thanks for answering my previous questions!This bulb (which burned) has some terms i am unfamiliar with on its package, so i photo'ed it:The package:The bulb (just in case):Is this bulb compact fluorescent? What 6400K means and does it reflect on heat emission of bulb? What is 800lm?Thanks you.

author: ejeffrey
author_rank: Super Contributor
timestamp: November 24, 2011, 10:42:13 am
content: Yes, this is a CFL.6400 K is the color temperature. It has to do with the mix of phosphors that make it 'white', and it is basically the temperature of an incandescent lamp that would be the same color. Higher color temperature will be bluer, lower will be redder.15 watt is the power draw. E14 is the socket style -- Edison 14 mm. 800 lumens is the light output: I think that is about equal to a 60 watt incandescent bulb. 130 milliamp is the current rating.

author: Boris_yo
author_rank: Frequent Contributor
timestamp: November 24, 2011, 03:28:07 pm
content: Quote from: ejeffrey on November 24, 2011, 10:42:13 amThanks. So the lower is color temperature, the less heat is emitted? If yes, would it be better for aquarium?

author: IanB
author_rank: Super Contributor
timestamp: November 24, 2011, 05:35:27 pm
content: Quote from: Boris_yo on November 24, 2011, 03:28:07 pmNo, it has nothing to do with heat. The color temperature refers to the "color" of the light. Higher color temperatures are more blue, lower color temperatures are more red, but with fluorescent lamps this is only approximate. 6500K as in the picture is going to seem cool and blueish.The amount of heat depends on the wattage of the lamp. So a 15 W lamp as pictured will generate more heat than an 8 W lamp.

author: Zero999
author_rank: Super Contributor
timestamp: November 24, 2011, 05:50:21 pm
content: A higher colour temperature may be more suitable for an aquariam because it will have more blue wavelengths which may be better for the organisms in the tank.

author: Unknown
author_rank: Unknown
timestamp: November 24, 2011, 10:15:06 pm
content: Note that 'color temperature' (better: correlated color temperature) is not a very good measure of a (C)FL spectrum, since you're basically trying to fit the continuous spectrum of a black body radiator to the few peaks produced by the phosphors in the tube. It does give a measure for the amount of blue versus red, though. If you compare the light from an incandescent light (2900K or so) to open shade (maybe 10,000K), the incandescent light will look quite yellow. This is more obvious to a camera since the human eye/brain uses memory colors to correct for light tints. Human skin will appear flesh colored regardless of the light color (within limits).
is this correct way to current sense? - Page 1
Forum section: electronics / beginners

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 21, 2015, 09:36:59 am
content: trying to convert some spare MC33072 into current sense. the residual floating voltage (in simulation) seems to be a problem ...while i think i have got the general idea right, could someone hint if there is a way to remove the residual 3mV?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2015, 09:48:53 am
content: Looks like input offset?SPICE models are often made with a "typical max" amount of offset, so that you are reminded that it's there, even though it's not representative of an average part (which has an expected offset of zero..).Your error due to all the resistor pairs being real resistors will be far in excess, even for very pricey ones.Tim

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 21, 2015, 10:52:21 am
content: what could i do to correct the resistor error? the few mA going thru the divider + op amp feeder?(it reminds me of the video control "pedestal" ... lol adjust the entire setup up/down a few mV)doesnt look like a simple add 1 resistor thingy ... an entire "pedestal" adjustment from another output op amp fix? it looks like i need to add a negative rail if i were to shift "pedestal" wisecome to think of it, it should be fine if im not going for 1mA accuracy. but was wondering ...

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2015, 08:23:36 pm
content: You need three adjustments in total: one to vary the sense/divider ratio, to null CMRR; one to null the DC offset voltage (due to op-amp error and unbalanced leakage currents); and one to adjust overall gain (to calibrate slope).Do your DC sweep thingy in a Monte Carlo simulation, where the resistors all have some specified tolerance. You'll see the problem.Since you have two sets of divider resistors, the CMRR ratio adjustment can be placed in any of them, as long as the adjustable range is give or take the resistor tolerance. You might make one side intentionally "long", then make the other adjustable between normal, long, and twice as long (so, for 1% resistors, make the one side longer by 1%, and give the other an adjustable range of 0-2% longer).Tim
Is this correct/usable (opamp V offset compensation)? - Page 1
Forum section: electronics / beginners

author: firewalker
author_rank: Super Contributor
timestamp: September 06, 2013, 05:09:49 pm
content: Is something like the circuit bellow correct/usable for compensating the offset voltage of a jelly bean opamp?Alexander.

author: Dave
author_rank: Super Contributor
timestamp: September 06, 2013, 05:28:45 pm
content: I don't think so. You are never going to have two completely identical opamps, so the offsets aren't really going to cancel each other out.

author: firewalker
author_rank: Super Contributor
timestamp: September 06, 2013, 05:34:58 pm
content: I was thinking the opamps on a same d?e. I am away fro a bench to test it.Alexander.
Is this course any good? - Page 1
Forum section: electronics / beginners

author: Cujo
author_rank: Regular Contributor
timestamp: October 01, 2019, 11:56:03 am
content: Is this course from TAFE (Technical and Further Education) Queensland, Australia any good if I'm interested in electronics?https://tafeqld.edu.au/courses/18108/advanced-diploma-of-electronics-and-communications-engineering

author: DTJ
author_rank: Super Contributor
timestamp: October 01, 2019, 01:01:02 pm
content: Not so much a comment on the the course content, more the price.$23k for a Diploma sounds steep. A comp sci degree costs less than that at some unis.The course seems to have a lot of fluffy crap in the core subjects. None seem to be engineering focused they are all industrial relations, business and communications units. Some have an engineering flavor to them. They started to add this stuff back int he 80's.All the engineering units seem to be in the electives even those seem light on.In the 80s these courses had a lot more math and electronics theory in them. There may be more practical content these days.Maybe see if you can find a lecturer for the course to chat to. The course adviser guys may not be the best source of info on the usefulness of the course.Good luck.

author: rstofer
author_rank: Super Contributor
timestamp: October 01, 2019, 02:55:23 pm
content: Do a search of the forum for TAFE The subject comes up from time to time including just last week.
Is this inverter logic gate TTL compatible? - Page 1
Forum section: electronics / beginners

author: KJ-90
author_rank: Contributor
timestamp: June 05, 2017, 06:08:26 pm
content: I was wondering if this circuit online athttp://www.nutsvolts.com/magazine/article/understanding_digital_logic_ics_part_1in Figure 2a has a standard TTL compatible input and output. I'm not sure if the circuit will work from a standard TTL power supply of +5V. If the inputs and outputs aren't TTL compatible, what resistor values should I use ( assume I'm driving one TTL load ) and what silicon NPN transistor should I use? I need to have resistor values for both standard and full pull up output. If you are wondering why I'm using this circuit, it is for a vintage technology reproduction project.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 05, 2017, 06:18:12 pm
content: They are compatible with 5V logic but do not have the same input thresholds, output currents, propagation delay's nor slew rates however that doesn't stop you using them in conjunction with 74xx gates.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 06, 2017, 12:02:21 am
content: In practice, probably.It would match up much better with a base-emitter resistor. This is necessary for clean operation of most switching BJT circuits, but is often omitted out of simplicity (or laziness, or ignorance).The problem is that V_IL is around 0.5V, lesser than TTL's 0.8V.Tim

author: Audioguru
author_rank: Super Contributor
timestamp: June 06, 2017, 02:30:31 am
content: The text shows that the transistor with resistors is an RTL circuit, not a TTL circuit. Both logic families are very old, Cmos is used today.Why do you want an RTL circuit to work in a TTL circuit? They are both completely different. If you want a TTL inverter then buy an IC that has them.

author: matseng
author_rank: Frequent Contributor
timestamp: June 06, 2017, 03:27:39 am
content: And without a Baker clamp or a well-choosen pulldown resistor at the base you won't have much joy if you're trying to invert a signal at about 100khz or more. Being saturated the transistor will happily stay in conduction for a long time after the input switched to low.

author: Audioguru
author_rank: Super Contributor
timestamp: June 06, 2017, 04:06:39 am
content: How many of us have seen an RTL circuit in operation? I haven't.I used DTL about 50 years ago, then TTL a few years later. I discovered Cmos logic about 40 years ago and have used it ever since.
Is this LED dimmer also a driver? - Page 1
Forum section: electronics / beginners

author: dzarren
author_rank: Contributor
timestamp: April 14, 2020, 02:50:45 pm
content: I have bought a few 10W LEDs to act as my light source for a microscope.I am looking for ways to be able to dim the LEDs. I saw this device, made for my microscope, but it is a bit out of my price range. its about 200 dollars.http://www.s-fernald.com/retrodiode/Ortholuxnew.htmlIt seems to consist of a 10W led on a heatsink, a dimmer module, and a 12V wall wart, and nothing else.My question is, if i bought just the 10W led, a 12v 3A Wall wart, and this dimmer module, would i be able to drive the LED?https://www.banggood.com/DC-12V-8A-Adjustable-Dimmer-Switch-Control-For-Single-Color-LED-Strip-p-945991.html?rmmds=myorder&cur_warehouse=CNDoes the dimmer act as a driver? can i connect 12V directly into the dimmer, and then just have the LED on the output?Or will i still require a driver, such as this one?https://www.ebay.ca/itm/10w-20w-30w-50w-100w-Constant-Current-LED-Driver-DC12V-For-high-power-led/251931422218?ssPageName=STRK%3AMEBIDX%3AIT&var=550807054047&_trksid=p2057872.m2749.l2649Thank you for reading and your time.

author: Zero999
author_rank: Super Contributor
timestamp: April 15, 2020, 05:43:10 pm
content: Quote from: dzarren on April 14, 2020, 02:50:45 pmA bare LED would require a constant current source, but that dimmer module requires a constant voltage source.Another option is to use a dimmable constant current LED driver and a suitable LED. You can get constant current LED drivers which can be dimmed by connecting an external potentiometer.https://uk.rs-online.com/web/p/led-drivers/8377819/

author: madires
author_rank: Super Contributor
timestamp: April 15, 2020, 06:02:26 pm
content: That dimmer is a PWM with a MOSFET switching the output. Since you have a 12V PSU the most simple solution would be to add a power resistor in series with the LED to limit the current.
Is this library compatible with Waveshare 1.5 ssd1327 oled? - Page 1
Forum section: electronics / beginners

author: Rishles69@
author_rank: Regular Contributor
timestamp: January 12, 2024, 02:03:08 am
content: So i brought a ssd1327 oled from waveshare. I found a better library from adafruit. Its called Adafurit ssd1327 in the library manager of arduino but the display can't get to work

author: m k
author_rank: Super Contributor
timestamp: January 14, 2024, 07:25:07 am
content: How you are connecting it?I2C seems to be the current configuration.

author: DavidAlfa
author_rank: Super Contributor
timestamp: January 14, 2024, 08:19:05 am
content: No? BS1 & BS2 are set to "0", that's 4W SPI.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 14, 2024, 07:43:02 pm
content: sometime in the librairies you have to comment or uncomment out some lines and or adapt the wiring definition in the INO filewhile checking in the files, where thay are defined
Is this LIR2032 dead? - Page 1
Forum section: electronics / beginners

author: PeterFW
author_rank: Frequent Contributor
timestamp: February 15, 2015, 02:50:35 pm
content: Hello Folks!A while back i bought a cheap chinese breakout board, the battery on it was dead though. They put in a old cell to make it "look good".Not a problem, i was not even mad since the RTC and EEPROM on the board work just fine and it was dirt cheap.But today i replaced the battery and noticed the old one it is a rechargeable LIR2032.When measured with the scope i get 60mV that drop to 10mV in about 2-3mS.Google told me, these things do not have a protection circuit (not much space in there for one) and they are just tiny Li* cells, i know a good bit about Li* cells...At this voltage the battery is dead and is only good for the trash, am i right?Greetings,Peter
Is this material correct? EMC Radiation - Page 1
Forum section: electronics / beginners

author: Simon
author_rank: Unknown
timestamp: April 08, 2019, 06:38:46 pm
content: So attached is a lesson from my current module. I am confused, pages 9 and 14 talk about electric fields in the short conductor and magnetic fields in the loop conductor.So the first thing that confuses me is that it talks about there fields being "stronger than the plane wave". I thought the plane wave was made up of both so they are saying that the field is stronger than itself?I also think they have got the names back to front or the ratios with which the fields reduce as when the electric field reduce by one over the cube of the distance and the magnetic field reduces by one over the square of the distance they call it an electric field and vice versa when it is the other field that prevails in the near feild range.

author: Zero999
author_rank: Super Contributor
timestamp: April 08, 2019, 08:05:05 pm
content: I can't remember the exact maths, but in he near field region, whether the electric or magnetic field is stronger, depends on whether it's a rod or loop.In the far field region, both the magnetic fields decay at the same rate, in accordance with inverse square law, so 1/d2makes sense.https://en.wikipedia.org/wiki/Inverse-square_lawIn the near field region, the stronger field, whether it be magnetic, or electric, decays at a faster rate of 1/d3and the weaker one decays at 1/d2.

author: Simon
author_rank: Unknown
timestamp: April 08, 2019, 08:11:20 pm
content: In the far field it's the inverse square law for the power. Individual fields are inversley proportional so their multiplied result that gives the power will decay to the square.
Is this module a buck converter? - Page 1
Forum section: electronics / beginners

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: April 03, 2021, 11:21:26 pm
content: Is the linked module a buck converter? It doesn't directly say so but it has a coil/inductor?Obviously I'm no expert.https://www.universal-solder.ca/product/dc-dc-switching-voltage-regulator-5v-1a-7805-replacement/ThanksEdit: probably it's not a buck converter. Buck converters are more efficient? This one is:https://www.universal-solder.ca/product/dc-dc-converter-5a-75w-adjustable-led-voltage-display/

author: james_s
author_rank: Super Contributor
timestamp: April 03, 2021, 11:29:55 pm
content: Yes, if it's a regulator with an inductor and the output voltage is lower than the input voltage then it's almost always a buck converter.

author: Algoma
author_rank: Frequent Contributor
timestamp: April 04, 2021, 12:53:54 am
content: It's a small buck converter, a low cost model from China you can order for 1/10 that price on AliExpress or Banggood.Similarly, I've been using these from MPS, lots of safety features and effency for the price.Over current protection OCP,Over temperature protection OTP,Over voltage protection OVP,Short Circuit protection SCP,Etc..https://www.digikey.ca/en/product-highlight/m/mps/mez-dc-dc-plug-and-play-power-module-solutions

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 04, 2021, 01:22:49 am
content: QuoteME3116
Is this Mosfet good for my peripherals? - Page 1
Forum section: electronics / beginners

author: shai
author_rank: Contributor
timestamp: January 21, 2019, 05:11:32 am
content: Mosfets are confusing to me, but after doing extensive research, I found this one:https://www.digikey.com/product-detail/en/diodes-incorporated/DMN3404L-7/DMN3404LDICT-ND/2052805However, I am still unsure if it fits my application or is the best one for me. I should note, I am trying to go with a SOT-23 package. Here it is:https://www.digikey.com/product-detail/en/diodes-incorporated/DMN3404L-7/DMN3404LDICT-ND/2052805One person pointed out to me that 28mOhm at 10V gate for this Mosfet could mean that it will get too hot. Except, I have no idea how to calculate or figure out if this will be an issue for my case? I plan to use this on solenoids, LED ring and to turn on 5V vibrating motor for my OpenPNP build. Here are the specs:Solenoid #1: 5V 1.1ASolenoid #2: 5V 0.22ALED ring (plan to use 6 of these) :https://www.digikey.com/product-detail/en/luminus-devices-inc/MP-3030-210H-40-95/1214-1604-2-ND/9593577Vibrating motor: Not sure yet, but probably a 3V one like here:https://www.aliexpress.com/item/Best-Price-10x-4x8mm-DC-1-5-3V-Micro-Cell-Phone-Coreless-Vibration-Motor-Vibrator-For/32694004681.html?spm=a2g0s.9042311.0.0.27424c4d65RqfRWill this Mosfet work for these peripherals/loads? If not, please provide a detailed explanation why so I can learn.

author: shai
author_rank: Contributor
timestamp: January 21, 2019, 05:25:03 am
content: So based on that calculation, I should be ok using this Mosfet without issues?

author: rstofer
author_rank: Super Contributor
timestamp: January 21, 2019, 08:22:33 pm
content: How do you plan to drive the gate? Vgs is EVERYTHING. Until this number is nailed down, everything else is a guess.At 3V on the gate, the device is only good for 2Amps - Maximum Rating, Page 2 - so somewhere less than that.Look at Page 2 of the datasheet and pay attention to Note 7 for vias at the mounting pads. 2 Oz copper, etc.

author: Kasper
author_rank: Frequent Contributor
timestamp: January 21, 2019, 08:49:12 pm
content: blueskull beat me to it, but it is worth repeating:Include protection diodes.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 23, 2019, 01:27:05 am
content: May I recommend to get some different fet's (and BJT's) in TO092 housing from Ali / Ebay / China?These fit easily in a breadboard and are also handy for prototyping. Always handy to have some lying around.I find it hard to imagine that price can be an arguing point for 80ct for a bag of 20.Also:I agree with BlueSkull & Kasper.Remember a story about an EE practicum where the Students were given MOSfet's in TO220 for experiments.Lot's of them got damaged untill they decided to solder (SMD) TVS diodes directly to the legs of the MOSfets before giving them to the students.
Is this my house grounding rod? - Page 1
Forum section: electronics / beginners

author: matthuszagh
author_rank: Frequent Contributor
timestamp: January 08, 2025, 05:12:58 pm
content: I'm attempting to locate the earth ground rod for my house so that I can properly ground rooftop GNSS antennas. I believe the attached pictures show the metal wire to the grounding rod, though confirmation would be appreciated. If it's unclear, is there any way to determine this for sure? I'm happy to take more pictures too, if that's helpful.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 08, 2025, 07:39:42 pm
content: Looks like it. I would investigate more by digging a bit in those weeds/plants. I would expect a clamp connection from the wire to the rod.

author: TimFox
author_rank: Super Contributor
timestamp: January 08, 2025, 08:12:30 pm
content: US electrical codes normally require a grounding rod at least 8 feet = 2.54 meters long: how much of the rod can you see without totally excavating it?

author: matthuszagh
author_rank: Frequent Contributor
timestamp: January 09, 2025, 12:56:52 am
content: Ok, I dug a bit and it does seem to be the grounding rod. There's a clamp attaching the wire to a rod. I've attached a picture. The metal piece with a bolt looks like a clamp to me, and it's a little hard to see it in the photo, but there's a metal rod beneath it.As for how long it is, I'm not sure, I didn't dig too far.Thanks for all the help!

author: Analog Kid
author_rank: Super Contributor
timestamp: January 09, 2025, 01:08:08 am
content: Quote from: matthuszagh on January 09, 2025, 12:56:52 amProbly OK to assume the ground rod is long enough. Unlikely an electrician would skimp on driving in the rod, unless your soil was unusually hard or rocky.

author: themadhippy
author_rank: Super Contributor
timestamp: January 09, 2025, 01:42:23 am
content: QuoteOver here at least they come in 4 ft lengthsQuotesds drills make light work of banging a rod in,you can even get proper adapters these days instead of bodging something up

author: TimFox
author_rank: Super Contributor
timestamp: January 09, 2025, 02:17:50 am
content: Quote from: matthuszagh on January 09, 2025, 12:56:52 amYes, the clamp proves the answer.
Is this opamp being used as a comparator? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: April 23, 2014, 11:55:34 pm
content: Is U1a in this circuit simply being used as a comparator?There's no feedback or anything, just DC a voltage into the inverting input and a square wave into the non-inverting.

author: Hideki
author_rank: Frequent Contributor
timestamp: April 24, 2014, 12:02:19 am
content: Yes.

author: Rudane
author_rank: Regular Contributor
timestamp: April 24, 2014, 12:14:49 am
content: The key hint there, is the feedback loop is not closed. In most cases that I can think of, if that feedback loop isn't closed, the op-amp is being used as a comparator.

author: dentaku
author_rank: Frequent Contributor
timestamp: April 24, 2014, 01:27:49 am
content: Good.Now I just need to build the thing for real
Is this part of the PCB safe to remove - Page 1
Forum section: electronics / beginners

author: CyTheGuy
author_rank: Newbie
timestamp: January 08, 2025, 06:52:30 am
content: I'm working on a project to add bluetooth to my iPod, and was suggested the transmitter linked below. Unfortunately, I also want to add a TinyPico running OpenHayStack for tracking capabilities, and it's just barely too big to fit in the space I have (19mmx44mm). I considered placing them on top of each other but that would make the soldering a pain, and when I looked back at the design of the bluetooth transmitter noticed there seemed to be a large portion of chip with no traces running to it. Both boards have a u.Fl out, and I'm planning on integrating an antenna into the iPod regardless, so my question is,can I cut off this 'extra' bit of PCB?(circled in red). Thanks!https://www.amazon.com/dp/B09BYHBVSJ?ref=ppx_yo2ov_dt_b_fed_asin_titlehttps://www.tinypico.com/

author: squadchannel
author_rank: Frequent Contributor
timestamp: January 08, 2025, 07:02:33 am
content: I think those holes are mouse bites, and for the break into two pieces.

author: BennoG
author_rank: Frequent Contributor
timestamp: January 08, 2025, 07:04:39 am
content: You will lose the integrated antenna for the board.If you plan putting an external antenna on the BT board that is no problem. I doubt it would be as good as the internal antenna.Benno

author: Psi
author_rank: Super Contributor
timestamp: January 08, 2025, 07:11:00 am
content: yeah, it looks like it is intended to be snapped off if you don't want the on board antenna.That should snap off with your fingers with very little force, but you might want to do it with cutters just because some of those passives are pretty close to the holes.
Is this PCB scratch going to be a big deal? - Page 1
Forum section: electronics / beginners

author: Mighty Burger
author_rank: Regular Contributor
timestamp: August 26, 2020, 03:08:26 am
content: Looks like it just exposed some soldermask. You can see the copper trace still so the copper trace width is unaffected. It’s a tiny scratch too anyways.Another potential problem is shorts. But the only thing I could feasibly see shorting out on that trace is with the nearby heatsink, but from the looks of it the heatsink is already connected to the trace! Meaning shorting them out will do absolutely nothing.Unless you have uber sensitive RF components that operate on black magic nearby, which I really really doubt, I don’t think this scratch is going to have any affect whatsoever on this circuit.There’s nothing to worry about.

author: Dokroma
author_rank: Contributor
timestamp: August 26, 2020, 03:38:11 am
content: Quote from: Mighty Burger on August 26, 2020, 03:08:26 amThe heatsink is actually raised off the board slightly by spacers/studs.

author: RoadRunner
author_rank: Frequent Contributor
timestamp: August 26, 2020, 08:07:06 am
content: If you are really concerned about this scratch then you can buy a tube of UV curable solder mask and patch this spot.I had similar issue one of my instrument on very thin trace than yours. I was more worried about corrosion eating exposed traces away.