Recent Posts

11

General Technical Chat / Re: Your pet peeve, technical or otherwise.

« Last post by paulca on Today at 01:38:34 pm »

I bought a passive audio channel switch box on Amazon.

After 3 weeks the selector buttons became intermittent and scratchy.

I said that in the review.

"Your review has been rejected because of reasons."

12

Test Equipment / Re: Vevor SDS1104 for first oscilloscope?

« Last post by kripton2035 on Today at 01:36:32 pm »

https://www.aliexpress.com/item/1005005698409712.html

13

Test Equipment / Re: Handheld meter robustness testing

« Last post by joeqsmith on Today at 01:34:45 pm »

Someone has asked about testing the 121GW again, suggesting that the rotary switch and input protection may have improved since the last time I looked at it late in 2019.   

Has anyone bought one in say the last 6 months that would be willing to pull it down and post some photos?  I would like to see the PCB thickness, shim if present, closeup of switch contacts, PCB any other areas of interest. 

14

Test Equipment / Re: Magnova oscilloscope

« Last post by Ranayna on Today at 01:32:54 pm »

You have good points... The integrated handle and convection cooling make rotating the scope awkward at best, and impossible at worst.
It looks a lot like a tablet scope, but it isn't one after all.

Both things would not be impossible to account for, but way too late now for the first revision.

15

Test Equipment / Re: SDS800X HD Actual Use Cases

« Last post by Njk on Today at 01:32:03 pm »

BTW that use case shows that a floating scope can't be always substituted with an isolating transformer.

16

Metrology / Re: ADR1001 - Ovenized Voltage Reference System

« Last post by picburner on Today at 01:31:00 pm »

It says July 3rd to me.... and date approximate an subject to change.....
Will we talk about it again for 2025?

17

Microcontrollers / Re: Attiny1606 burning out when connected to a drv8251

« Last post by pcprogrammer on Today at 01:30:29 pm »

Your Attiny might need better power supply decoupling. In the schematic there is only a 10uF capacitor to decouple the Attiny, and it might be that internal oscillations cause it to overheat. Try adding a 100nF capacitor as close as possible to the Attiny power pin.

Another problem can be when the motor starts to run due to the low capacitance in the device. It depends on the input supply voltage and the startup current drawn by the motor. If the voltage temporarily drops to low it might cause a reset of the Attiny. As long as the input voltage onto the MCP1792 stays above the minimum 4.5V it most likely won't be a problem.

18

Test Equipment / Re: Magnova oscilloscope

« Last post by Njk on Today at 01:30:23 pm »

Rotating the screen would mean removing and reattaching the stand. We don't know if that is supported, and I doubt it. For starters, the handle is integrated in the case and would likely block the procedure. Cooling is passive too, and convection does play a fundamental role, as opposed to forced ventilation. I don't know if putting it upside-down would affect the thermal design, though.

So they're experimenting with unusual exterior forms, where the input connectors are located at the side of the instrument. That disposition can be handy in certain use cases. But it will not be unusual for a user to find that the side is wrong and the other side would be better, and the solution is to rotate the scope by 180 degrees. So obvious. Any provision for that?

19

Microcontrollers / Re: RIP Z80

« Last post by coppice on Today at 01:29:02 pm »

If you try to sell an MCU to many large customers now they show no interest unless it has an ARM core

That however is a reasonable approach.

Nowadays, with a 168MHz core, 99% of applications can be done with 1 or 2 chips e.g. the 32F4xx. These have been around > 10 years, even the chinese do copies, the dev kits are free and well understood by anyone using them, the chips are $5 in quantity, and they are 10x to 100x fast enough for most jobs. I've just done a project with a 32F417 and I am certain I will not need to look at another CPU in the rest of my actuarial life expectancy (20 years). With ETH and USB done and working (not optimally but well enough) and with 21MHz SPI, I can do absolutely anything I have done since 1980 and absolutely anything I can imagine having to do. For highly specialised stuff e.g. a modern DSLR one needs specialised chips, but for nearly all "industrial control" and consumer stuff, more is not needed.

You must have worked on a very narrow range of MCU applications, or perhaps only on small volume products, to have such a view. The vast majority of MCUs produced are quite narrowly tailored to a few applications they suit well. If you don't think the chip is narrowly tailored you probably just don't recognise the applications it was tailored for, You gave no explanation for why an ARM core would be beneficial. Sticking with one maker, and their peripheral set, can be a big speed up in development work. Who cares what the core is, apart from a few special qualities like getting in and out of low power states, where a few designs excel?

20

Test Equipment / Re: Siglent SDL1000X/SDL1000X-E Electronic Load

« Last post by Mortymore on Today at 01:26:56 pm »

The batteries I've been testing are those used in small UPS, Pb (AGM) 12v, 6Ah to 18Ah

As usual, the battery datasheet must be observed, but in general for 12V/7Ah, the settings are, I.discharge = 1.2A and V.stop=10.5v (1.75v/cell). Under this circumstances it is expected a 5h test duration and 6000mAh drawn from the battery, if in good condition.

Multiple test conditions could be adopted, but to my needs a 5h run to test a good battery with a discharge (6Ah) near the stated (7Ah) that would take 20h, is a good compromise.


1) As an example, from the datasheet of the Ultracell UL 7-12 we can extract the test conditions to set (1.2A;10.5v), and what to expect (5h;6Ah)




2) As another example, according to the datasheet of the Ultracell UL18-12, with the discharged settings as I.discharge=3.06A and V.stop=10.5v (1.75V/cell), the test for a good battery should take 5h and the battery should provide about 15.3Ah (see attached datasheet Ultracell_UL18-12.pdf)


3) An example of a test to a Pb battery, 12v/7Ah in end of life



After 10 minutes discharge


After 40 minutes discharge


After 1 hour and 8 minutes discharge


EasySDL has a reported problem of the time axis, with the time stamp being half of the real time.