Recent Posts

1

Test Equipment / Re: Cheap oscilloscope for checking mains power quality? Also logging equipment.

« Last post by adam4521 on Today at 09:41:23 pm »

For low cost power quality logging I've had some success using a commercial-grade electricity meter: Schneider PM5110/PM5111 for example which you can easily find used/surplus. Install into an adaptable box. Lower cost than a power quality analyser, and you can read out voltage, current and harmonic data to a computer via Modbus RS485 interface. But this will be a bit of a do-it-yourself project.

For RCBO/GFCI nuisance tripping, often this will be linked to a switching transition -- something being connected to the system or switched on, that creates a transient unbalanced current in the live and neutral conductors. For LED flicker, it's traditionally associated with unstable timing of 'phase cut' dimming: the lighting driver is interacting with the dimmer. If you really want to see what is going on you will want the oscilloscope, but you will need to convert the current signal you want to observe to a voltage signal. As electrician, you would be confident making up a circuit breakout box with a CT and suitable burden resistor inside? You might make a specific one for measuring residual current -- look for a 'zero sequence CT', which has higher sensitivity.

Multiple times on the forum we discuss safe connection of oscilloscope to mains. The current transformer appropriately terminated will be ok. Differential voltage probes are great (but relatively expensive, unless you land one second-hand). You can use a voltage transformer to keep voltage measurement simple, but won't be super-accurate for observing some of the transient events. Battery powered oscilloscopes from Fluke are purpose-made, but they are really expensive, even for really old ones.

2

Other Equipment & Products / Re: Three most useful tools I got from AliExpress

« Last post by watchmaker on Today at 09:40:16 pm »

Links to the tools please. 

The board holder does look very nice, and do I see you invested in a chip tester? The one Adrian Black (digital basement) used to test al kinds of chips with?

I really like the board holder.    If a board is too long, you can always hold it sideways or buy an Aluminum bar at a metals supplier.

Yes, I am assembling the retrochip tester from 8bit-museum.de.  I found it is much cheaper (but more painful) to order the parts from DigiKey; $120 vs about $250.

Per Request:

https://www.aliexpress.us/item/3256806317632603.html

https://www.aliexpress.us/item/2255800993178532.html

I have to find the ProsKit desolder gun.  But it was about $100; bought it as a "first timer" on another account.  (Yes, I am that cheap!)

3

General Technical Chat / Re: Russia and China to Build a Nuclear Plant on the Moon.

« Last post by tatel on Today at 09:39:59 pm »

It is certainly doable. My previous comment wasn't an endorsement of western safety standards.  In the west we are trending towards finding that a one in a million chance of someone getting a hangnail is unacceptable.  People in the US are currently going crazy over a vacuum thermos that has a lead seal that is not externally accessible, and claiming a billion dollars of emotional damage from being in the airplane that lost a window.

Yeah, after Fukushima all that hype about western secure designs is now clearly understood as BS, one only needs just a functional brain. But, hey, we are winning 3 to 1! Not to mention TMI and those "incidents" while developing the thing because then our advantage would be mostly against de Olympic sport ideals...

4

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by NNNI on Today at 09:30:40 pm »

I was just about to bring up the point about being able to upload code via USB. It is very convenient and fast. However, programming via the SWD pins (using a Raspberry Pi debugger, for example) is another alternative. I am not sure how much SWD programming is dependent on system clock.

I am honestly not sure when I will be getting back to the project. I left it in a rather messy state, so getting everything running and familiarizing myself with the code diminddl and I worked on nearly a year ago will take some time, plus I have to finish testing my own ideas first. The project files are available, so it should be possible to get your own set of boards for experimentation, or replicate the core circuit (it's quite simple) on a breadboard. I understand your eagerness for the results, but all I ask for is a little patience till I can get everything sorted on my side.

5

General Technical Chat / Re: Cable Management

« Last post by watchmaker on Today at 09:28:50 pm »

 

6

Beginners / Re: Quickly Triggering Sensors - need an oscilloscope? what specs? (AU)

« Last post by nate_syd on Today at 09:22:29 pm »

You need Pattern Generator. https://en.wikipedia.org/wiki/Digital_pattern_generator
https://digilent.com/reference/test-and-measurement/guides/waveforms-pattern-generator
Digilent Analog Discovery 3 -  https://digilent.com/reference/test-and-measurement/analog-discovery-3/start

This was REALLY helpful - much appreciated!
Might grab the Disco2, significantly cheaper & good enough for my use case

7

Microcontrollers / STM32F407 - CMSIS DSP - IFFT not working with audio input/output

« Last post by lukegalea16 on Today at 09:22:20 pm »

I'm currently using the stm32f407g-disc1 and reading an audio input through PMOD I2S2. I've carried out some examples and the hardware is working fine (writing data from the rx to the tx buffer) such as the code below.

Code: [Select]

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
txBuf[i] = rxBuf[i];
txBuf[i+1] = rxBuf[i+1];
txBuf[i+2] = 0;
txBuf[i+3] = 0;
}

I now wish to perform the FFT on this incoming buffer, manipulate it (my first aim is to implement a pitch shifting algorithm) and perform the IFFT again. Thus I've tried the following:

Code: [Select]

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
fft_in_buf[fft_in_ptr] = (float) ((int) (rxBuf[i]<<16)|rxBuf[i+1]);
fft_in_ptr++;
}

arm_rfft_fast_f32(&fft_handler, fft_in_buf, fft_out_buf, 0);
arm_rfft_fast_f32(&fft_handler, fft_out_buf, fft_in_buf, 1);

fft_in_ptr = 0;

for (int i=0; i<BUFFER_LENGTH*4; i=i+4) {
        txBuf[i] = (fft_in_buf[fft_in_ptr] >> 16) & 0xFF; // MSB
        txBuf[i + 1] = fft_in_buf[fft_in_ptr] & 0xFF;     // LSB
        txBuf[i + 2] = 0;
        txBuf[i + 3] = 0;

        fft_in_ptr++;
}

In the main initialization I'm also carrying out

Code: [Select]

arm_rfft_fast_init_f32(&fft_handler, BUFFER_LENGTH);

My issue is that I get a very very low output (barely audible) with the above code. I might have a scaling issue as I found in similar issues but I still can't get it to work by scaling fft_in_buf[fft_in_ptr].

8

Beginners / Re: LiPo battery charging problem

« Last post by nate_syd on Today at 09:21:12 pm »

If you want to know more about battery longevity - youtube some Jeff Dahn videos, he goes into depth on why you only 80% charge etc.

9

Projects, Designs, and Technical Stuff / Re: (Yet Another) DIY Multislope ADC

« Last post by Kleinstein on Today at 09:19:45 pm »

To make use of the extra resolution gained from the rundown part one would need additional gain for the residue ADC. Without extra gain there is not much gained.

The comparator noise  should not be an issue - it only increases the range that the residue ADC has to cover a little.
For the aux ADC it is often more the amplifier than the actual ADC noise. With less resolution needed from the aux ADC it would be less than before.
Including the rundown part makes the aux ADC less critical (get some 5 bits from the rundown instead) and even the internal ADC may than be good enough.

Wanting the 12 MHz for an easy code download is a good point.

10

Beginners / Re: Fast PWM IC

« Last post by coppice on Today at 09:19:44 pm »

If you really want a PWM channel running at 100MHz with any kind of reasonable resolution for the pulse width trying looking at things like the TI C2000 MCUs. They have a pulse width resolution far beyond their clock rate, using calibrated delays.