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1

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Sredni on Today at 02:16:30 pm »

Resistor < Linear resistor U Nonlinear resistor
Nonlinear resistor < incandescent lamps U diodes U ...

So, you can still call it a diode, recognize that it is a nonlinear resistor and, as such, that it belongs to the more general set of resistors.

Does this make any sense to you?

It does not make sense.

All resistors exhibit electrical resistance.
All of those semiconductor devices indeed also exhibit electrical resistance.
However not all devices that exhibit electrical resistance are resistors as they are not components purposely designed to implement a well defined resistance.

Does not matter what you understand as "resistor", the vast majority of forum members you are talking to on here understand it as a device specifically designed to implement a well defined amount of resistance. You don't have the authority to redefine established industry words used by others.

What you are trying to say is that a diode exhibits the effect of "electrical resistance" or "resistivity".

This effect is not particularly special and just describes that the device can consume electrical power and turn it into something else,

The point I make is that this is ALL a diode does.
Huge resistance when reverse biased, small resistance when forward biased. This is not a side effect. It is what it does (if we neglect secondary effects due to parasitics in real devices).
It does not store energy in the electric field.
It does not store energy in the magnetic field.
It does not do whatever sorcery a memristor does.
It just oppose a resistance that takes power out of the circuit.

Yes we all agree on here that at some fixed DC operating point a diode acts like resistance.

The point is that a diode is nothing special at doing this. The laws of physics force all power consuming components to look like resistors in steady state DC. This means that at a fixed DC operating point even a memristor is actually just electrical resistance, much like a diode acts as purely electrical resistance at that DC state.

Like what else do you expect an component to do at DC? It can either act as a power source (like a voltage or current source) or it can resist the flow of current hence resistance. There is nothing else for a component to do at DC.

There is so much to unpack here but let's consider only the last part.
A capacitor at DC can hold a voltage without passing current; try to do that with a resistor.
An inductor at DC can hold a current without a voltage (if ideal, and a small voltage due to small resistive losses if real). Try to do that with a resistor.
You can use these properties to create memory cells. Try to do that with resistors alone.
I am not well versed in memristors to give an eleme tary setting that show their fundamental difference from resistors, but I am pretty confident  you got that part wrong, as well.

Have you looked up the Science Direct link I gave above? I am not redefining industry standard terms: diode have been considered to be nonlinear resistor for decades. You just wasn't aware of it.

2

Buy/Sell/Wanted / Re: FS: Affordable DMM Checkers: AC Reference, DC Reference, OHMS Reference, etc.

« Last post by Majorassburn on Today at 02:15:15 pm »

I design 'em and build 'em and they REALLY work! 
eBay Links:
https://www.ebay.com/itm/285825801852
https://www.ebay.com/itm/285823822244
https://www.ebay.com/itm/285807578003
https://www.ebay.com/itm/285823885283
Thanx for looking! 

Also, about those "0.05% Precision Resistors" do you know the temperature coefficient ? They look like your generic metal film and could be around 200-100 ppm/C. So even, if they were selected, change in ambient temperature could easily move them outside the 0.05% you are mentioning. I don't think calling them "Precision Resistor" is really accurate.

I don't want to be overly negative but all that look a lot like a modern snake oil salesman. Of course your clients are not going to complain, they are not equipped to validate your claims. I'm not even sure you are.

Thank You for your comments. You have a very sharp eye.
For that eBay photo, I actually hand-selected 1% metal film, 100ppm resistors for that prototype and used it for the photo so I could list it quickly.
However, For the actual devices that I'm selling, the resistors are pre-selected 0.1% 25ppm precision resistors.
And, yes, I am equipped to validate my claims and I can select to better than 0.05% with the DMM6500 that I have access to. But, I will change the spec in the ad to 0.1% based on your observation.
Unfortunately, I don't have any snake oil to sell you! Sorry. 

3

Repair / Re: Sony J30 PSU repair

« Last post by Harry_22 on Today at 02:14:07 pm »

If your mains 110VAC this is perfect!

Schottky [B3] is required to cut a back spark on R6 parasitic inductance. Put it back. Just measure it in diode mode. It should be 0.25V in forward direction and "OL" back (means overload).

Please provide me the name of the second controller.

4

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by PlainName on Today at 02:12:59 pm »

For example if the valve is open and you want it to close, it requires a small amount of backflow to make it shut off

Until springs are invented.

Wouldn't that be a closer analog to a diode? The small amount of pressure required to overcome the spring would be similar to Vf of the diode.

5

Projects, Designs, and Technical Stuff / Re: Using Wet SMD component (drop in water)

« Last post by Doctorandus_P on Today at 02:12:14 pm »

In general, electronic parts don't get damaged by water. It's common to wash PCB's with water, some even put old and dirty PCB's in a dishwasher to clean them.

The important thing is to make sure the PCB's are dried completely before power is applied. Water (when dirty) is conductive, and this leads to all kinds of nasty effects when combined with electricity.

The biggest problem I see here is solderability. Water will accelerate corrosion of the tin plating on the pins of the IC's, and this will reduce solderability. In the end it probably comes down to whether the cost of extra rework offsets the cost of buying a new reel of parts.

6

Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's

« Last post by BillyO on Today at 02:05:34 pm »

English is actually very bad language for engineering. As someone that was exposed to both English and, to some extent, German technical literature, German language is much easier to be precise.

I might not go that far.  You can use precise wording in English, but because words take on many meanings and there are so many words with similar meanings it allows people to be lazy.  From my perspective it is easy to be imprecise in English.  Sometimes not only easy, but easier.

To me, when talking about the attributes of an subject, object, process, etc.. the word "feature" has always meant "attribute of special merit or interest in a positive sense".  Kind of an antonym to "quirk" meaning "attribute of special merit or interest in a negative sense"

7

Test Equipment / DMM Input Capacitance

« Last post by mawyatt on Today at 02:03:03 pm »

This was precipitated from a measurement here:

https://www.eevblog.com/forum/testgear/sds800x-hd-actual-use-cases/

Curious what others find when measuring bench DMM +- input terminal capacitance wrt to ground.

Best,

8

Buy/Sell/Wanted / Re: FS: Affordable DMM Checkers: AC Reference, DC Reference, OHMS Reference, etc.

« Last post by Majorassburn on Today at 02:03:00 pm »

I design 'em and build 'em and they REALLY work! 
eBay Links:
https://www.ebay.com/itm/285825801852
https://www.ebay.com/itm/285823822244
https://www.ebay.com/itm/285807578003
https://www.ebay.com/itm/285823885283
Thanx for looking! 

Description states
"LT1236-10 Ultra-Low-Drift 5ppm 10V Reference."
"Final Trim to 10.0000 VDC @ 78F, 50% Humidity"
"NEW, Hand-Crafted in USA to Work PERFECTLY, No Returns."

That's 5ppm per what? Day, month, year, degree C, degree F, supply voltage, RH, shock (since the ICs are socketed)?

Picture below states "Designed to affordably verify the function of Digital Multimeters".
Does that mean it is suitable to verify the function of my Agilent 34410A, Keithley 2015 THD, Solartron 7081?

After reading a mind-sickening slew of your pretentious, bloviating, self-serving and worthlessly hyper-critical replies to almost every thread in the various eevblog forums, I am not surprised that you have, once again, consistent with the nature of your valueless contributions, managed to contextually twist and misconstrue the information contained in my eBay presentations.

I want to thank you for wasting your time to review my eBay ads and I would like to recommend that you NEVER buy anything that I make or offer for sale because, I know from other sellers' experiences in selling to arrogant, self-important, meaninglessly pretentious buyers, that a business-oriented transaction would quickly deteriorate into just one more opportunity for a super-critic like you to clog the supply chain with baseless criticism, irrelevant observations and product misuse, culminating in costly and unjustified returns, refunds and bad feedback. PLEASE DO NOT BUY ANYTHING, EVER, FROM ME! 

Now, as you and a few of your fellow super critics must well know by now after reading my various threads and comments in this fantastically helpful eevblog forum, I am offering my devices to the sub-200-dollar DMM buyer (predominantly handhelds) and not to legitimately engaged, professionally employed, high-end DMM owners and users unless they want one out of curiosity, etc..

Please note that I said "legitimately engaged" as opposed to "couch-dwelling, socially-maladjusted, hyper-critical forum irritators and thread-disruptors" who claim that they may HAPPEN to own some high-end equipment and, therefore, are somehow entitled to shower their scorn and derision upon all who may have been so foolish to have bought a DMM that cost less than $1,000.00 to check their electrical outlets, etc. around the house.

Now, to your asinine questions/criticisms:
If you knew anything at all about selling these types of devices on eBay to somewhat unsophisticated buyers (which you obviously have no feel for), you would understand that choking an ad with globs of technical specifications would quickly cause buyers to skip to the next seller's ad.  Achieving a balance of general, parametrically illustrative specifications along with typical and comprehensible application information is about the best a seller can do in the very limited space-time available to encourage a transaction.

Therefore, in my ads, I try to present a few technical specs as a reference base to validate the usability and quality of the device and also, present enough application information to help the potential buyer to recognize the intrinsic usefulness of the device and to stimulate the desire to buy one. Of course, this has worked for me and the buyers of my devices. If you doubt my claim, you are invited to check my feedback as SQWARREL at eBay.

I have stated many times in this forum and elsewhere, that I do not claim my devices are going to satisfy the perfectionist demands of what they call "volt-nuts" or of those who are silly enough to seek a $20 calibrator that could actually perform well-enough to calibrate a DMM6500 or 34465A, etc.

So, your persistently annoying, continuously harping on that vein of your misunderstanding of what my devices are to be used for clearly demonstrates your arrogant, self-righteous effort to discredit the purpose for which and the essence of need for such low-cost verification devices. Please, give it up and take your meds and spare me and others from your side-swiping commentary.

Of course, if you were to somehow become magically capable of re-framing your commentary in a more constructive manner rather than to present as the preposterous hypothecator that you are, your comments might possibly be welcomed and appreciated by participants like me. But, with your track record, I don't think that type of positive behavioral change will be forthcoming from you. 

TO: coromonadalix
I totally agree with you. If I were to sell reference devices to super-sophisticated, high-end professionals, I would be spec-ing LM399's and LTZ1000's for $500-$1,000 instead of $20-$40 LT1236's. Thanks for your comments.

9

Projects, Designs, and Technical Stuff / Re: Short (1ms) high current (~200A) current pulses - relay rating?

« Last post by max_torque on Today at 02:02:37 pm »

Update: Change of plan! 

Going to use a crowbar relay that is not is series with the output, but in parallel with it. So when the Estop is hit (or power is removed from the device), not only will i de-power the switch mode convertor that generates the 250Vdc, i'll drop a crowbar across the output capacitor to ensure it is discharged and cannot be charged.  As the device will be connected to DUTs that run at up to 33vdc, i'll probably use some big 40V TVs diodes and a low value power resistor to quickly drop the output voltage below 50Vdc (as required by the Low Voltage directive)

This means my output path from the pulse caps is now just across the output control switch which is a semi-conductor switch

10

Beginners / Re: Capturing video from old LCD interface (3.3V RGB parallel bus)

« Last post by JusTideaFIX on Today at 02:01:46 pm »

So I did it and it works. A video conversion board was designed and installed inside.
(TI TFP410 DVI/HDMI transmitter)
Video demonstration:


pixel perfect image: