Recent Posts

1

Microcontrollers / Re: A couple questions about Milk-V Duo boards

« Last post by brucehoult on Today at 01:35:42 am »

Thanks! So, in terms of pure performance, at least from your benchmark, the C906 looks way behind a Cortex-M7 at the same clock freq

Sure. The M7 is a pretty good dual-issue uarch -- better than A7, A9, A53, maybe close to A55. And running from SRAM not DRAM helps too. The C906 is purely single-issue, in order.

Note that the Duo has massively more RAM with 64 MB (and 256 MB and 512 MB models just becoming available for only a few dollars more)

2

Beginners / Re: Help identifying these possibly RF/Microwave components?

« Last post by arlo_g on Today at 01:34:26 am »

That's a nice microscope image, Cincin. It looks like there might be edge contrast in the image: do you have Darkfield or Nomarski/DIC fitted on your microscope? 

As for the TriQuint chip, those spirals look like integrated inductors to me. That wouldn't be a big stretch on TriQuint's traditional GaAs substrates. Based on the number of inductors, and the shortage of clearly single-ended signal pads, my guess would be that this is a tuned RF circuit. Maybe an oscillator, mixer, frequency doubler or reactively matched switch/ switched reactive components?

3

Programming / Re: Linux Dependency Black Hole

« Last post by mag_therm on Today at 01:32:00 am »

I don't take it emotionally. I don't really care what you do to your system. But what bothers me is when people go on the forums and complain that "Linux sux" when they mangled their system by installing random stuff from tar.gz.

Installing into "~" is fine. Installing into "/" is just asking for trouble.

But it also depends on the type of a system. If this is some random RPi that can be re-imaged when necessary, then who cares. If this is your primary system, not destroying it is a good call.

As I wrote earlier, I am staunch linux user of 18 years, having earned my living from it and I like messing about with it now in ham radio.
from my o/p, see, I am not complaining about linux; I am asking questions about the increasing problem of dependencies.

I am retired with a few left over computers .
For risky trial stuff like trying this MCUXpresso I use a standby computer on Fedora 37 now.
On that I don't care if reloading Fedora as I like to keep it up to date

Linux is fairly fault tolerant in my experience, but when clients would ask to fix problems, I would always recommend to just reload the whole thing.
Because it is difficult or impossible to find out what somebody else did especially if they had root.

4

Beginners / Re: LM317 Based Digitally Controlled Power Supply

« Last post by TerrySt on Today at 01:26:33 am »

Hi there,

Actually I was referring to the accuracy of the set point of the voltage that would be controlling the LM317.  If the user wanted to output say 5 volts then they would have to apply about 3.75 volts to the ADJ pin.  If it was just 3.70 volts then the output would be 4.95 volts.  If the design could get that right though (3.75v) I don't think there would be any worry, but that could easily require feedback which brings in the issue of control stability into the picture.  If the designer wants to use feedback then it's going to be their responsibility to get it stable.  That means the uC will have to sample the output and make adjustments, and that means there will be a delay.

As far as regulating once the right voltage is actually applied, that may be ok but I have not looked into that in detail.

Yep.  I hope the OP realizes the issue and has a plan to deal with it.

Terry

5

RF, Microwave, Ham Radio / Re: Detecting very low power motion sensors

« Last post by ejeffrey on Today at 01:23:29 am »

TinySA Ultra can detect motion sensor frequencies around 10 GHz, in these examples

I thought it only went  to 6 but I now see there is a higher frequency version. My understanding is that it has much worse sensitivity above 6 GHz so I would count on it working.

Could ultrasonic sensors work reliably through a wall ?

Is it possible to somehow detect the emissions of ultrasonic sensors placed behind a wall ?

Depends on the wall and the sensor.  Going from wall to air, reflecting, back to the wall and to the sensor is probably a tall order?  It's also possible to hide things by e.g. drilling a hole in the wall, mounting sensors in the hole, skim coating it and painting over.

A microphone with an audio signal analyzer would work as long as the microphone works up to the frequency in use.  I think the things used in parking sensors are like 40 kHz?

6

Test Equipment / Re: Magnova oscilloscope

« Last post by vk6zgo on Today at 01:22:34 am »

Mi concern was more about partialy obstructing the screen view when crossing the probes over. But maybe it isn't a problem.

Why not place the 'scope to the left of the DUT?
That would mean the leads wouldn't obstruct the screen.

The downside is that if you want to use your left hand to adjust the DUT, you will have to swing your head back & forth, or have a swivel chair.
A number of analog 'scopes have the coax sockets on one side, & the controls on all CROs vary, but at least on the more compact ones, area mostly on the left side, & people of both "handedness" used both styles without problems.

Most left or right handed people can quite effectively use the other hand to do things, otherwise, we would all be pretty much disabled.

7

Beginners / Mystery relic Microchip SOT style chip identify please? Looked everywhere

« Last post by TnF on Today at 01:20:47 am »

I've looked everywhere, the package is same "length" as SOT-89 (4.5mm) but width is larger ~3-3.1mm, and has only 3-pins similar to SOT-23 instead of SOT-89 3+tab.

2nd pin (middle) is directly connected to ground.
3rd pin (right one) 1V forward voltage drop to ground and 0.5V in reverse. Looks like it's directly connected to +5V from a regulator.
1st pin (left one) no forward voltage drop across but it's connected in circuit, 0.5V in reverse. Reads +5V in operation.


The whole board is made in Japan in the 90-00's and uses almost exclusively Japanese branded components. Weirdly this one is branded Microchip. I've even went into checking Microchip's acquisitions thinking it might be a rebranded component.

Came across these but haven't yet checked all variations, the package and brands differ but it could be a copied design.

Any ideas? Thank you

8

Beginners / Re: LM317 Based Digitally Controlled Power Supply

« Last post by TerrySt on Today at 01:19:58 am »

I'd just ditch the LM317 and replace it with an emitter follower. I chose the BD437 because it has a high enough h_FE to be driven by the LM358, even with a collector current of 1A.

It's designed so neither op-amp gets driven into saturation, which can take awhile to recover from. D2, R8 & R9 form another feedback loop when it's in current mode. This limits the voltage over-shoot, during recovery.

The peak current due to the speed limitation of the current op-amp is limited by D3 and D4 which clamp the base voltage to around 1.4V above the output.
(Attachment Link)

That looks like a good approach.  Many ways to go about this for sure.  I like the way the voltage control sums with the current control.

I added models for 'real' op amps to my version and tweaked the component values to make it work with a range of output (load) capacitance (up to at least 10,000uF).
I'm posting the latest.  It could still use some fine tuning, but since the OP hasn't been back, probably no reason to carry this further.

Terry

9

Programming / Re: Is ChatGPT any good at writing code?

« Last post by linux-works on Today at 01:18:35 am »

as others have said, in general, I think this is a time bomb that humanity will not recover from.  once it explodes.  and it will.

not in a single bang, but over time, so much will be changed and we cant change (ourselves) fast enough to keep up.

dan dennett (rip) also echoed this caution.

but hey, we're just stupid humans.  we dont really think thru our actions.  so, go right ahead, guys.  I'm an older guy; the youngers ones are who are really going to pay for this.

(btw, all this applies to regular people.  if you are in the controlling elite, this is the best time in the history of mankind for YOU.)

10

Projects, Designs, and Technical Stuff / Re: Vacuum Fluorescent Display Driver

« Last post by bostonman on Today at 01:15:53 am »

After building a voltage divider and setting up for measuring with the logic analyzer, I finally had time earlier, however, I think more questions than answers came out of it.

My logic analyzer is 16-channels, but the chip has seventeen outputs (not including two additional outputs for decimal places). I made the error of accidentally connecting one of my logic analyzer channels to DP2 meaning two of my logic analyzer channels weren't connected to two of the SEG outputs (one accidentally connected to DP2 and unable to connect to the seventeenth data line due to my logic analyzer being sixteen channels).

The logic analyzer results was not what I expected. Attached are four CSV files (they may not be worth assembling to show the logic because it contains many data points). The CSV files are named accordingly and I'll also upload some pictures of the display which will show the display at the time of the logic analyzer capture (give me a few minutes).

The reason the results weren't as expected: if I kept the logic analyzer set to keep polling, the pulses changed. I expected different because when the display showed (as in one file) all 1's and I removed the input so the display remained frozen, the logic analyzer (as I expected) shouldn't show different pulses each time it polled.

If the entire display is twelve digits, and each digit has fourteen (?) segments, and two decimal places, that uses sixteen out of the seventeen data lines (not sure where the seventeenth is used). The G lines are twelve total (for twelve digits?).

Due to the display having 'period', 'frequency', 'ch1', etc... and assuming each G line is for each digit, that leaves the question of how does the other stuff get lit? My guess is that more than one G line is on so the data lights MHz, CH1, etc...

Unfortunately I didn't have time to investigate this. If my assumption is wrong, then I should see the logic analyzer output to have each channel in sequential order (or no two G lines on simultaneously).

Due to the complexity of trying to not damage anything, I'm close to pulling the trigger and just swapping the IC.