Recent Posts

1

Buy/Sell/Wanted / Re: Canceled Because Thread All Shit Up by "tggzzz"

« Last post by tggzzz on Today at 08:50:27 pm »

That 3.5 digit meter remark was pretty nasty

That is a misrepresentation.

The actual remark includes an important caveat, highlighted for convenience: 'If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.' https://www.eevblog.com/forum/buysellwanted/fs-affordable-dmm-checkers-ac-reference-dc-reference-ohms-reference-etc/msg5465140/#msg5465140

That gave him the perfect opportunity to point out that his device was better than 3.5digit. He chose not to. Why?

after he had explained that he was using 6.5 meters with fresh calibration. So 5.5 digits would have been a realistic estimate.

I cannot see any 6.5 digit statement of the OP's. Where is it? When was it made?

Note also that after the sale the OP sends documentation that the claims are based on operating in an unrealistic single exact environment "...no-draft ambient of 78F and 60% humidity." https://www.eevblog.com/forum/buysellwanted/fs-affordable-dmm-checkers-ac-reference-dc-reference-ohms-reference-etc/msg5465119/#msg5465119 Ensuring operation in such a precise environment would be very expensive and difficult; it would be cheaper to buy a more expensive well-specified and characterised voltage source.

I think there is a good reason for somebody looking for alternatives instead of paying collectors prices for legacy equipment with unknown history.

I agree - as my statement above demonstrates.

But that was not claimed in the adverts, so I don't think you have a point.

2

Jobs / Re: Contract work

« Last post by Sniper1 on Today at 08:49:37 pm »

this is mostly SW stuff here is my advice:

• get a esp32 dev board + digital microphone breakout + wires
• wire it all up
• write the sw and perfect it , all sub tasks presented are already implemented in libraries
• now you can make the pcb since you know well what is needed + how it works
• make another post if you are stuck/ need advice

3

Test Equipment / Re: Magnova oscilloscope

« Last post by egonotto on Today at 08:43:04 pm »

Hello egonotto,

......

How much memory would you have at 10 ms/div?
80 Mpts surprises me a little.
Would you then have 666,666 Mpts/s sample rate?

If the memory is no longer sufficient for the entire recording time at the highest sampling rate, the next lower rate is used. At 10 ms/div (120 ms/screen) and 4 channels, this would be 500 MSa/s. The memory remains at 60 Mpts per channel.

Best regards,
Andre

Hello,

I don't understand the thing with the 320 Mpts and the 12 divs.
When do you have 80 Mpts with 4 channels?

Best regards
egonotto

4

Test Equipment / Re: New Keithley DMM6500 and now DAQ6510

« Last post by Hydron on Today at 08:41:30 pm »

Great to hear that helped, even if it's not totally fixed

Out of interest, how high is your mains voltage typically?
Mine runs close to 250V which is asking for issues like this even at the 240 setting, but having had a quiet demo unit meant I knew it could be improved by a replacement transformer.

5

General Technical Chat / Re: Does anyone make good SSDs any more?

« Last post by Infraviolet on Today at 08:38:16 pm »

"If your data matters it doesn't reside on a single device - any loss of a device should cost you nothing more than the last few hours"
Yes, I keep many copies of all my important data, but restoring my OS, programs, settings... even with some system images I've made to speed up the process, still costs me two days, and opening up the laptop to physically swap the drive out is unpleasant (it is one without a bottom cover, so you have to take everything apart, and had to remove the laptop's rubber feet to get at the screws when I last changed the HDD.

I've had enough of having to do this procedure multiple times in the last year, I want something that won't fail on me again so soon.

From what I'm reading the MX500's bug is perhaps less serious than the EVO 870's? The EVO 870 has an actual degradation of the physical flash chips I think, whereas the MX500 seems to be solely an issue in firmware. There look to be workarounds to maybe do MX500 firmware updating in Linux, or with bootable images, though I hear they need some tinkering wit before they'll work with keyboard input. So if I went for the MX500 I'd encounter any problems immediately, rather than later down the line?

Or there's the BX500, the one thing going for it is I don't see many reported errors with it, but would it infact give worse performance than an HDD, due to the lack of DRAM?

6

General Technical Chat / Re: What is this 8-knobbed IBM human interface device in a 1980's Boeing photo?

« Last post by abeyer on Today at 08:37:06 pm »

The king of the digitising tablets, Summagraphics, actually became an early king of actual mice. Sun and other workstation makers used their mice. They required a special pad with matrix of lines that was scanned optically by the mouse. Much cruder than today's correlation based optical mouse, but great for their time.

I'd put a huge asterisk after that "great"... they were pretty advanced technologically, but imho were actually a significantly worse experience to use compared to simpler but well built electromechanical ones.

7

Repair / Re: Trouble identifying 10k? capacitor

« Last post by Wallace Gasiewicz on Today at 08:35:25 pm »

I am with Flooby.   
If you plan on using the unit a lot, consider just putting in an EMI filter.     They contain the Y caps and an X cap and then you have a modern 3 pronged plug, you probably need a new cord anyway.   
Lots more EMI today then when these things were made.

8

Projects, Designs, and Technical Stuff / Re: Distance sensor required with 0.1mm accuracy and upto 4m range

« Last post by Conrad Hoffman on Today at 08:34:38 pm »

Ultrasonic sensors have an accuracy of about 1%, so not good enough. There are LIDAR sensors used on 3D printers that do the resolution, but not the distance. I think you need an interferometric laser sensor, and that's not going to be cheap. Or, maybe a mechanical sensor based on a fine cable and rotary encoder. There was also the Trav-A-Dial used on lathes that essentially tracked a surface with a wheel- http://www.lathes.co.uk/trav-a-dial/#:~:text=An%20ingenious%20device%20%2D%20and%20widely,surfaces%20sliding%20against%20each%20other. What's your budget?

9

Beginners / Re: Can a Powerbank be used to start a car?

« Last post by mobby_6kl on Today at 08:29:38 pm »

Hi All,

Thanks for all the replies and the interesting detours this question created.
My understanding is it will never charge a 12 v lead acid battery due to the output being only 5V.

So  because it is a voltage Mismatch the 12V lead-acid battery requires a charging voltage higher than 12V, typically around 13.2V to 14.4V depending on the charging stage. A 5V supply is too low to charge the battery effectively.

I got hold of some PD fooler ccts just to see if I could get 12-15V but on my initial test I didn't get any readings, either I wired it wrong or aliexpress sent me a dud?

Again thanks to all for the answers it was quite an interesting discussion.

Cheers, LateralNw

I have a 20Ah USB-PD powerbank that can output 15V, in fact I've used it with one of those aliexpress triggers to create a charger for my DJI Mavic Air.  So this part works fine. And yes ~15V is ok for charging a lead-acid battery.

This powerbank has a 74Wh capacity, while a small car battery like I have in my Miata is about 500Wh. So I think it only has a chance of slowly topping it up if it was just a bit low, not completely flat. The maximum output of the powerbank is 30W so it'd take about 2 hours. Then disconnect and try to start. Not great but might be worth a shot if you're stuck in a desert or something.

The other option would be hooking up the lithium cells directly, as they usually have a much higher discharge rate than the electroncis will allow. This is basically like that power tool battery approach that was posted here, and I've seen it done with RC hobby LiPos too. You'd need at least 3 cells thogh and it's questionable if the powerbank cells would like that.

10

Beginners / Re: identifying Ferrite bead value?

« Last post by CaptDon on Today at 08:25:39 pm »

That ferrite bead is so small that the inductance is nearly meaningless for audio frequencies, probably marginally effective at less than 100MHz. I think Fender put it there to suppress radiated emissions. Jump it with a wire and you'll never miss it.