Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by Majorassburn on Today at 02:05:21 pm »

What could be a proved single opamp for a wien oscillator?

Anything with sufficient frequency response, and output voltage swing, and drive capability.

Since you still haven't bothered to tell us those parameters, how do you expect us to help you?

In addition, ponder the second paragraph here.

More thread-choking negativity and useless crap from tggzzz. 
He's a real thread-killer if I ever saw one!

Your question about op amps?  I use T.I. OP07's with excellent results in my low frequency sine wave oscillators.
Data Sheet link: https://www.ti.com/lit/ds/symlink/op07c.pdf?ts=1714331934514&ref_url=https%253A%252F%252Fwww.google.com%252F

Also, check out the numerous TI App Notes for oscillator designs with sample circuitry you might use as starting points. Best Regards.

The context is these threads from MajorAssBurn:
https://www.eevblog.com/forum/buysellwanted/fs-affordable-dmm-checkers-ac-reference-dc-reference-ohms-reference-etc/msg5463700/#msg5463700
https://www.eevblog.com/forum/metrology/affordable-useful-ac-dc-references/msg5438690/#msg5438690
Anybody with too much time on their hands can read those. They will, no doubt, notice that many people have made negative comments about MajorAssBurn's claims in those threads.

BTW, it isn't good practice to read the first couple of posts in a thread and then jump to conclusions without reading the rest of the thread.

I have this mental image of tggzzz sitting in his week-old undies and moth-eaten robe, in the corner of his tiny, gloomy, cold-water flat, in a poverty-stricken slum section of Birmingham, pecking away at his twenty-year-old Pentium computer while desperately searching forums and threads for topics wherein he can spew out his unwelcome drivel and negativity and display his legendary (in his own mind) philosophical and technical superiority as compared to the woefully ignorant and uninformed commoners who participate in these threads looking for useful suggestions from fellow members, as he, the self-ordained master of thread imposition, reflects within himself how utterly failed as a human being he is, as he seeks out these thread-killing opportunities so as to feel somewhat compensated for his lifelong worthlessness and complete failure to achieve anything noteworthy or meaningful.

Now, with those facts in mind, I will ignore all further written diarrhea that tggzzz dumps in various discussions from now on. 

2

General Technical Chat / Re: H5N1 bird flu and how we're risking another global pandemic

« Last post by magic on Today at 02:03:01 pm »

Nice reddit drama thread.

You forgot to add that you don't intend to bash the US because China uses industrial farming too and mention something about chipageddon to make it electronics-related

3

General Technical Chat / Re: H5N1 bird flu and how we're risking another global pandemic

« Last post by Zero999 on Today at 01:59:35 pm »

It's true there will be another pandemic and nothing has been learned from the one just gone, but isn't this a bit too off-topic?

4

Projects, Designs, and Technical Stuff / Re: Control of 2 CAN Open DS402 motors on a single shaft

« Last post by max_torque on Today at 01:57:23 pm »

Ok, i'm gonna ask another "stupid" question: Does the system actually NEED two seperate motors?  It's going to be cheaper, simpler, and more robust to just fit one motor to do the work if you can!

Ie, rather than have to invent some complex control archecture to suit some dynamic load you may never get a chance to properly validate, just simplify the system to one drive node!!

5

Projects, Designs, and Technical Stuff / Re: Build or buy? Multi-level vessel temperature logger

« Last post by max_torque on Today at 01:55:06 pm »

Aside: This ^^ has been done many times!  I use an optical fibre temperature sensing array to measure various temperatures inside a running high voltage permanent magnet machine. Works by firing a lazer down the fibre and measuring the phase shift that is driven by a temperature dependant scintilating end "reflector"



Back with the OP, whats best probably depends on how dynamic the system is going to need to be, ie how quickly temperature changes and how fast it must repond.  For slow systems then a thin pcb with NTC resistors (or serial output temp sensor ICs etc) along it's length could be easily sealed into a length of food grade silicon tube pretty easily.  That silicon covering is going to limit thedegree of isotropic conformity to it's surrounding as compared to a more thermally conductive protection medium (ie stainless steel etc)

Again, you need to consider just how precise, accurate, responsive and complex the measurement device actually needs to be!

6

Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by Joel_l on Today at 01:51:55 pm »

Looking at it, there are a couple I think I can do, though I have always wanted a power meter....

Problem is still the flakey nature of it, might pass this time and not the next.

I will do the ones I can for a baseline. I always thought the noise floor on mine seemed high, so that will be a good one to go through.

Thanks

7

Projects, Designs, and Technical Stuff / Re: a high side load switch made from n channel and p channel mosfet working princip

« Last post by Terry Bites on Today at 01:51:30 pm »

For higher voltages, you can split R2 to keep Vgs to a safe level.

8

Computers / Re: Format a 256GB pendrive with FAT32 using a windows 10 pc

« Last post by magic on Today at 01:49:29 pm »

If you have a similar issue while formatting an SD card and found this topic, there is an official tool from SD card association:

https://www.sdcard.org/downloads/formatter/

This is actually a good idea when formatting SD cards, because they are intended to have a particular alignment of some FAT data structures and user data clusters. This is not guaranteed when using any random format tool. On Linux one has to pass extra flags to mkfs.fat to get it right. And there are cameras which actually complain when it isn't right.

Another matter is that many SD readers can't issue TRIM commands to the card for optimum write performance afterwards.

I would be happy to join the crowd seeing this as yet another artificial scarcity attack. Or at least attribute it to the lack of thinking.

But in this case the explanation is well known and documented, and it is neither of the above. It’s a reasonable decision, which didn’t age well. The person responsible, Dave Plummer, gave the details.

So god complex and over-thinking?

9

Projects, Designs, and Technical Stuff / Re: Control of 2 CAN Open DS402 motors on a single shaft

« Last post by max_torque on Today at 01:46:21 pm »

If you cope with the motors not sharing torque ALL the time, then this (not sharing) may be ok as long as you calibrate the control systems not to fight each other!

Persumably at high loads on the machine, you need both motors to supply enough torque/power to keep the load moving, but you could cal the aggressiveness of the PID so really the second motor only joins in when the load exceeds (or gets close too) the limit of the first motor.  If you use a primarily Proportional control, there has to be a speed error at all times (because the Poutut term = error x Pgain), So the level of speed "sag" is going to massively increase after the first motor controller hits it's torque limit (which you could artificially limit to below it's max rating if you were worried about motor thermals).

So if the absolute speed of the system is not that important, you could effectively calibrate the PIDs to not share, and make one motor do most of the general speed keeping and the other motor add torque when required.  Again this comes back to one in local speed control, one in local Torque control mode in effect. 

Given that you get a feedback of motor torque, you could calibrate the second PID as a much more relaxed (perhaps no I term at all) controller, and then you external controller could actually send it an increasing speed setpoint which would have the effect of increasing it's torque output as it's speed error grows. That speed target could then be calculated by your external master controller based on a long term average motor torque, ie

Say your set point is 1,000rpm (for example)

Send 1,000 rpm target to motor 1, which has I term set to drive machine to 1,000 rpm

Send 1,000rpm target to motor 2, see what amount of torque is is adding as a ratio of the torque being generated by motor 1, and send a higher or lower value to add a relatively slow "balancing" offset. In all cases, both motors are in speed control and so the high speed velocity control is local and in the primary control loop.  You will need to low pass filter and average the two feedback torques from motor 1 and motor 2, and have some form of "Gain table" to calculate a suitable adder to the speed target for motor 2




Of course, if you find it enough to have a single drive in speed control, then that long term average "balancing" value can be calulated and applied in the torque domain, ie you take the feedback torque from motor 1, and send it to motor 2, but have a trim value that lets you balance things out as necessary at a slower rate.

10

Projects, Designs, and Technical Stuff / Re: Homebrew Lock-In Amplifier

« Last post by Terry Bites on Today at 01:41:09 pm »

I agree with Kleinstein, Analog switches are great for low cost mod demod.  The switch method gives the same result as mutiplying the input with a squarewave. Plenty of examples in AD and LT app notes.