Recent Posts

1

PCB/EDA/CAD / Re: Looking for CADSTAR pcb Uplaod Program

« Last post by hello188 on Today at 01:53:17 am »

Thank you for kind reply.

One of the things that I need to do is extract component placement coordinate from the old .cdo file.

I guess I can generate gerber file.

Do you have any good way i can extract component coordinate from gerber?

Thanks

2

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

« Last post by Sredni on Today at 01:50:01 am »

Notice that they didn't write this:

A non-linear resistor is connected into the feedback circuit. In practice, this can be a resistor, but a resistor connected as a resistor is used since the forward biased transfer function is more accurately exponential. The exponential nature of the forward biased resistor leads to a logarithmic decrease in gain of the circuit as the input signal is increased.

 

I don't know. Maybe they are used to specific names, like calling their wifes Helen and Kate, and not just "woman".
They are in good company, tho. For example Bharathwaj Muthuswamy and Santo Banerjee, in their "Introduction to Nonlinear Circuits and Networks", Springer (2019) say:

In order to be able to use nonlinear resistors effectively in a practical design, it is necessary to understand some basic properties.We will illustrate these properties by considering a prototypical example of a nonlinear resistor, the pn-junction diode (henceforth referred to as diode). Although we model diodes as nonlinear resistors, they are so important in circuit theory that they have their own symbol[...]

But, hey, what could they possibly know about circuits and nonlinear elements? They only wrote a book about them.
How many books have you written for Springer?

3

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

« Last post by Someone on Today at 01:46:01 am »

Oh new words and definitions to play with. How about we take the IEEE dictionary as the authoritative reference:

static resistance (semiconductor rectifier device) (forward or reverse) The quotient of the voltage by the current at a stated point on the static characteristic curve.

Yes, this is the only one I have used. Did you not realize it?

small-signal resistance The resistive part of the quotient of incremental voltage by incremental current under stated operating conditions.

small-signal A signal which when doubled in magnitude does not produce a change in the parameter being measured that is greater than the required accuracy of the measurement.

As I said in my opening statement, you're just playing with small signal analysis a well known and entirely un-novel method. There is nothing interesting here as most anything can be described as a small signal resistor (with bounds on some other dimension). So you're still wrong and trying to twist definitions to your liking while ignoring the consensus and the established science.

No, I have not used small signal analysis. Where did you study small signal analysis? You are mistaken. Please seek tutoring from someone you trust to straighten this out.

You live in a continuous world with no quantisation or noise? Perhaps in your world there is some difference between those. For those of us in the world I inhabit they are the same thing, an exact derivative of infinitely narrow width does not exist physically or in spice (which you chose to introduce). Both static resistance and small-signal analysis are a delta V on delta I.

4

Repair / Keysight U127A faulty MegaOhms mode

« Last post by KamKong on Today at 01:32:55 am »

Hey guys,
Long time lurker 1st time poster.

I recently purchased an Agilent U1272A (pcb Rev 005) from ebay. I didn't carefully read the add, the seller didn't offer returns of the unit and I was away for work when the unit was delivered.
When I started testing I realized there is only 1 (so far) issue with the meter. In Ohms mode it won't read anything on the Megaohms range and it won't auto-range out of the Megaohms range.
At first i thought the ohms mode was faulty but it seems to just be the Megaohms range.
When the meter powers on and I short the probes together the meter displays Overload, but if I manually range the meter to any range besides Megaohms it will correctly displays 0 ohms (or the correct resistance value).

I dissembled the meter and found residue from battery leakage, i cleaned the board with vinegar, isopropyl alcohol.. nothing doing. (attached picture is of battery leakage residue)

The meter works in continuity and smart ohms mode.
I checked the spec sheet and measured the test current for each range of ohms mode and everything seems ok (the current for the Megaohms range is 93 nA, my other meter is a Keysight U1242C and doesn't read that low but it seems to pick up something...).

I traced the signal path on the board and if I short some test points (bypassing the input jacks) I can get the display to flicker to 0hms but it doesn't stay there and doesn't seem to be conclusive.

I don't know if anyone has seen/had a similar issue? Thanks in advance.

I also messed up a solder job on the meter and need to replace C35, I read around and it seems to be a ~10pF, 3 kV, 1808 case size can someone confirm?

5

Microcontrollers / Re: RIP Z80

« Last post by brucehoult on Today at 01:21:56 am »

Even RISC-V is kind of stuck here, CLIC isn't ratified yet either.

Not ratified, true, but frozen and very unlikely to change. It's currently in ARC (Architecture Review Committee) review, after which it needs Committee Chair and CTO sign-off, then a public review period, then the ratification vote. My guess is ratification will be around July.

6

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Mechatrommer on Today at 01:09:16 am »

thats unofficial hack i dont think its proper to bring it up here, ymmv. the fact still stands that GUI developer is an artist, so much wasted space that can be used for technical infomations. but its minor thing for me, i will concentrate on my subject matter ignoring artistic nature of it.

I am not sure why it would not be proper to bring up the hacks that are available? As the OP, that is one of the things I asked about early on in this thread. Obviously, different folks will have different priorities and needs, but the degree to which either of the scopes in question is hackable is definitely of interest to me. Perhaps I am not understanding what is meant by "unofficial" hack - I would have thought that any hack was, by definition, unofficial? I plead for patience, as I am no doubt further reinforcing my newbie status ...

I think he means some hacks are "official" in the sense that you enable things by installing license keys (eg. bandwidth upgrade).

I don't see why other hacks are lesser hacks though.

sorry i sometime mixed up english... first unofficial i meant is its not from official FW in rigol website, and secondly, that specific hack only applies to current FW being hacked/hex edited, once the FW is upgraded, its gone and the original creator of the hack has to "re-edit" the newer FW and redistribute it for others to "re-patch". other type of hack like vendor.bin hack which will still valid on newer FW without you doing anything, FWIW... anyway "unofficial" also can mean, you have to work something after you make a purchase and possibly invalidated the warranty, and some people are not comfortable doing it.

if we can include hackability in decision making, i can vote on rigol DHO800 since upgrading AFG and LA is now possible (at cheap cost), even though with charming 2GSps and faster FFT on siglent SDS800X, i think i can squeeze more functionalities out of DHO800 + downloaded data to PC for analysis. charming measurement in SDS800X such as Trend, i can just eyeball or make some simple rig circuit using arduino or something to get the same functionality, i can also learn in the process, albeit waste more time. but for some, they just want everything to be ready in scope in silver plate to save time or whatever reason, which DHO800 is lacking on few aspects compared to SDS800X... so ymmv.

just as analogy, some people like to buy coat or office dressing and hate jungle trekking dressing, because they work in office for living and afraid if even a little scratch got onto their skin. but for some other people, they swear by jungle or army tactical dressing and will put coat dress in dustbin even if someone give to them for free, because their life is in jungle and have no use to office dressing, so people come here to ask what dress to choose? i question back, what type of person are you? where do you work? if they ask what type oscilloscope to buy? i ask, do you enjoy hacking and tearing your scope apart to do "unofficial" hack? or you are type "i dont want to void warranty sticker" i just want it to work out of the box with plenty of fancy bells and whistles. both situations will give different answer. ymmv cheers.

7

Microcontrollers / Re: RIP Z80

« Last post by nimish on Today at 01:01:53 am »

Today, most embedded stuff (except low end) is done in C and if the clock is fast enough the CPU architecture becomes almost irrelevant.

If you try to sell an MCU to many large customers now they show no interest unless it has an ARM core, or perhaps increasingly a RiSC/V core. You can talk about a totally unsuitable chip for their needs, and they'll listen if is has an ARM core. You can talk about a great fit for their needs, and they are not listening simply because it doesn't have an ARM core. But the core is almost irrelevant, because almost all new MCU code is developed in C. The MCU's value is all about its unique qualities - interesting peripherals, special memory qualities, like error detection/correction or non-volatility, partitioning to meet regulatory requirements, etc.

ARM cores have a far better software development toolkit than one-off proprietary architectures and you aren't forced to buy from a single vendor. Since software development is the most expensive part it pays to reduce those costs. Would you rather use LLVM 18 or some jank vendor gcc? Even RISC-V is kind of stuck here, CLIC isn't ratified yet either.

So I'm not surprised they stop listening when someone proposes the use of a wacky new ISA for no realy good reason.

8

RF, Microwave, Ham Radio / Re: HFH ROHDE & SCHWARZ RECEIVER LOOP antennas

« Last post by coppercone2 on Today at 01:01:36 am »

it might work those antenna are used for some kind of official measurements

9

Projects, Designs, and Technical Stuff / Re: MCP3008 and MCP23017 experiments - first project verification

« Last post by moffy on Today at 12:49:01 am »

Additionally, I've added resistors to drop the supplied voltage to the chips to 3.3V, even though they can function at 5V, which might be unnecessary.
I have included ZIP file containing KiCad project

Just an FYI, not everyone uses or has Kicad, if you want a broader input, if you post your schematics etc as JPEG or PDF no one will need specialist software to view what you post. Secondly resistors make poor voltage drops because their voltage linearly depends on current which can vary. If you want to drop from 5V to near 3.3V, use a couple of series diodes, they'll drop between 1.2V to 1.5V in normal operation, this is not a comment on whether it is desirable or not.

10

Repair / Re: Rivets/eyelets for PCB repair

« Last post by mightyohm on Today at 12:33:27 am »

Rembrandt electronics in the Netherlands is selling copper eyelets on Ebay.  You can get a nice assortment of various sizes for around $22 USD.  They also sell small lots of one size.  Just search for TH eyelets

It looks like the Rembrandt store is down due to family health issues - that doesn't sound good. Does anyone have a good source for inexpensive rivet assortments, or knows where Rembrandt was sourcing their rivets? I could use a handful in the smaller diameters and it looks like the Aliexpress rivets are larger.