Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Design of white noise generator for bathroom??

« Last post by MarkF on Today at 12:43:18 pm »

Go old school.
Build an 'out house' in the back yard with a half moon cut in the door.   

2

Beginners / Re: audio amp study

« Last post by Zenith on Today at 12:41:40 pm »

Usually, the maker/designer specifies a quiescent current, which is a trade off between low distortion and low power consumption. You should be able to set it with a multimeter using their instructions.

You might contact the website and ask what they recommend.

Otherwise, in the absence of other test equipment, set it by ear. Try to find the lowest quiescent current that sounds acceptable.

3

Test Equipment / Re: SDS800X HD Wanted Features

« Last post by ebastler on Today at 12:40:49 pm »

Improvement Request: Remember "Navigate by History Frame" mode

Navigation defaults to "by time". Frankly, I have not understood what that mode is needed for at all: I have a dedicated horizontal position knobfor continuous adjustment, or can call up a keypad quickly via the Timebase info box if I want to go to an absolute value.

I would much rather use Navigation -- and the dedicated arrow buttons on the front panel -- to navigate by history frame: Stop an acquisition, and have the buttons ready to step through the history frames right away.

But Navigation keeps falling back into "by time" mode. Even if I change the mode via the Navigation menu, as soon as I restart acquisition it goes back to "by time", and stays like that when the acquisition is stopped again. 

Could this be changed? If I have chosen "Navigate by History frame" mode once, remember that mode, and bring it back when the acquisition is stopped? (Also save this choice and bring it back after a re-boot please.)

4

3D printing / Re: Resize a STL File For Me

« Last post by MarkF on Today at 12:39:22 pm »

I don't know if there is a question there...

FreeCAD 0.16 was released in April 2016.
While it is terribly out of date, you still need to understand how
that version of the program works in order to be productive.
It wouldn't be important to others, but it's worth your time.

Let me pose a modification to the exercise in the video.
How would you rotate the groove pattern around the X-axis instead of the Z-axis?
I haven't tried this.

5

General Technical Chat / Re: Boston Dynamics new Atlas Robot.

« Last post by mawyatt on Today at 12:39:03 pm »

Reminds of the DARPA Wait, What Conference in St Louis way back, where Boston Dynamics had a demo of all their robots. While watching, the Robot Dog came around and sat right in front and scanned me, very spooky!!

BTW think this Robot is done with electro-mechanical methods, the earlier Atlas utilized hydraulics.

Best,

6

Beginners / Re: Amplifier type

« Last post by r6502 on Today at 12:37:43 pm »

Hello elki,

your circuit is a ac coupled standard inverting amplifier with some input filtering. A transimpedance amplifier translates an input current into a voltage at the output, so you need a current source (e. g.  a photo diode) for that.

Guido

7

Beginners / Re: audio amp study

« Last post by mariush on Today at 12:37:27 pm »

Not gonna comment on that 200k resistor, but it would be much easier to just grab a couple TDA2050 amplifier chips, and make a stereo amplifier with them.

They're less than 60 cents on LCSC : https://www.lcsc.com/search?q=tda2050

You have example of single power supply circuit on page 6 in the datasheet : https://www.st.com/resource/en/datasheet/cd00000131.pdf

Or you could use a couple of them in bridge mode like in the TDA2030 example in this datasheet, on page 7 : https://www.lcsc.com/datasheet/lcsc_datasheet_2106070404_HGSEMI-TDA2030_C2683154.pdf

Or you could use 2 or 3 tda2050 amplifier chips, one for bass, one for mids and one for highs like in the tda2030 example on page 9 in the same datasheet above.dk52

8

RF, Microwave, Ham Radio / Re: RF Test Automation

« Last post by vino on Today at 12:32:48 pm »

For now my focus is testing and characterizing RF Power amplifiers. I want to automate the measurement of each parameters.

9

Beginners / Re: good/cheap headphone aplifier/dac?

« Last post by BeBuLamar on Today at 12:31:24 pm »

Although I have never have one I think if I were you I would try the Austrian Audio Hi X25-BT. A bluethooth headphones set has the DAC and amp built in. I had the AKG headphones K240 (ones that made in Austria not China) I liked it a lot. It did go bad after 30 years but I found it's very comfortable to wear. The sound is very neutral and you may not like it because I found Bose sound is no where near neutral.

10

Microcontrollers / Signal filtering - Could this work ?

« Last post by matb on Today at 12:27:51 pm »

Hi,
I am creating a product which will be a weighing loadcell for a client.

The client wants a moving average of the digital signal of around 30 seconds. But the twist is that they also want the ADC frequency to be 400Hz.

A stored value beeing 4 bytes that make for a very big buffer !
4 bytes x 400 = 1600 bytes for 1 second. x30 is 48k bytes !
Maybe I could make this work for 1 signal but I have 3/4 for the prototype software !

So the buffer size won't be doable...

So I was thinking of only adding an average of for example 500ms.
That would be 2 times less values in the moving average buffer !

But is that ok from a signal filtering point of view ? Excel datas from the sensor shows it working but is my idea a red flag.

I am wondering if the ADC beeing 100Hz or 400Hz or 25Hz is going to change anything if we are filtering at such high average ??
And just for the record marketing already that "of course it's possible we'll make it work"