Recent Posts

1

Power/Renewable Energy/EV's / Re: PCMC+PSFB on STM32 is it possible?

« Last post by mtwieg on Today at 04:35:15 pm »

As ST does not provide any relevant examples for full bridge phase shift designs, I had to use an example from TI (TIDM-02000), where up-down mode is the core of the approach.

Interesting, I don't quite understand why they would use up-down mode for this, I'm guessing it somehow makes implementing their synchronous rectifier control easier.

In up-down you can differentiate the front and end of the pulse explicitly (one relates to UP, another to DOWN direction).

The action qualifier (AQ) submodule in the C2000 ePWM modules do recognize the counter direction in determining actions, but I don't know if HRTIM has equivalent functionality. I also don't see why you'd need to differentiate the edges of the pulse in such a way.

I am not saying that with single-slope you cannot achieve similar operation, but it is definitely more complex as requires special measures.

I doubt it, but it depends on exactly how the underlying PWM logic works.

For example, you said you were struggling to implement blanking. In the C2000 design, this is done using the digital compare (DC) submodule, which is IMO by far the most complicated and confusing aspect of the entire ePWM module (I usually don't make use of any of the digital compare functions, but just configuring it to pass events through is insanely complicated). I highly doubt the HRTIM works in a similar way. You should look at how HRTIM implements blanking and start from there.

TIDM-02000 shows the circuit, and for me it is not quite clear, why they used a full bridge rectifier for current transformer, if it is operated in unipolar mode?

Agreed, that is strange. I wonder how the magnetizing flux is reset properly...

2

Test Equipment / Re: FNIRSI-1013D "100MHz" tablet oscilloscope

« Last post by ECJ on Today at 04:34:23 pm »

Hello everybody! I'm new here and firstly I would like to thank pcprogrammer and Atlan for this open source alternative firmware! I'm an electronics technician and programmer, and one of my hobbies is developing projects with microcontrollers, so i can imagine how much work this was and how much dedication was involved.

For now, i would just like to report that my touchscreen stopped responding during tests in acq long mode (trigger mode auto) of version 0.025o. The only way to get it working again was to go back to version 0.025m.

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Test Equipment / Re: Agilent Keysight 33500B Repair - looking for photos

« Last post by salvagedcircuitry on Today at 04:33:34 pm »

Woah there, how did you find this??? Thanks tremendously! 
I have hopes of getting this waveform gen back up and running properly again. Woot woot.

Thanks a ton 

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Power/Renewable Energy/EV's / Re: Smart Meter Installed

« Last post by Bryn on Today at 04:30:08 pm »

I never bother with smart meters... one engineer from a gas company we were with years ago tried to convince us with one until he had to agree with my mother that it's no point (given that it's only two of us in the house and we don't burn a lot of energy on average).

Now, I have British Gas trying to persuade me with getting one but I hear they're not all that reliable and not many work. Plus, they're too much of a distraction and would make you feel more paranoid of how much energy you're using, just to "save the planet" 🙄

5

Beginners / Re: Beginner to BGA

« Last post by zapta on Today at 04:28:04 pm »

Power the board up. If it works the solder job is properly done. If it fails, well, then I guess you are up shit creek. 

We need transparent PCBs and ICs. ;-)

That's the reason I avoid BGAs. I wonder what those small repair shops that replace BGAs do.

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General Technical Chat / Re: What do you WANT to buy?

« Last post by Bryn on Today at 04:25:39 pm »

I can see that some things on people's wishlist aren't all technical stuff so, here's mine to match...

I'd like to buy chicken salt, just because of this thread 😂 (and plus the fact that I'd like my mother's home-made chips taste a wee bit better as well)

7

Microcontrollers / Re: CH32V003 - SSD1306 Oled library

« Last post by DavidAlfa on Today at 04:25:01 pm »

Maybe something like:

Code: [Select]

#define bf_sz 32

typedef struct{
    uint8_t data;
    uint8_t row;
} row_data_t;

row_data_t oled_cache[bf_sz];  // Stored in priority order

Anytime a new row is accessed, fetch the data from i2c and overwrite the lowest priority block. Whenever a cached row is accessed, increase the priority and sort.
But I think this would only work in very specific cases, like writing to a very small area.

Probably fetching the data from i2c isn't that slow, but it requires some smart prefetching to avoid a lot of overhead.
The drawing routines could detect the rows beforehand, and request filling the cache as required.
For example, drawing a line from xy(0,0) to xy(128,0) would need accessing row 0, columns 0-127.
If the buffer size is 32 rows, break the operation in chunks, much faster than single-byte reads.

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Projects, Designs, and Technical Stuff / Re: Hydrochloric Acid small volume (<=1L) NZ (Christchurch) ?

« Last post by Xena E on Today at 04:24:14 pm »

Hydrochloric acid is also used in the boiler trade for descaling industrial boilers... another possible source?

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Manufacturing & Assembly / Re: Tronstol E1 experience

« Last post by lamabrew on Today at 04:22:09 pm »

I haven't noticed anything I would attribute to the drive system.  There's optical gratings on both axes for position measurement and it appears to me (with my limited knowledge of such systems) the resolution and control software works as advertised.

I asked Tronstrol about upgrading, and I'll summarize that: the controller changed so they have to design new driver boards (i.e. mapping the computer connections to the things that run all of the hardware) and as part of that redesign they also changed some of the electromechanical aspects of the machine.  With the need to replace so much purchasing a new one made more sense.  IMHO they should have called the new one the E2 or whatever to make it clear it was different from the E1, though I get that functionally and appearance wise it's pretty much the same machine.

As to other machines: I haven't followed things since making the purchase 2+ years back.  This category of machine is kind of an odd price point: below it you have the hobbyist machines that are totally cost driven at what appeared to me to be expense and ease of use (I know someone with one of those and he rarely uses it because it's such a PITA).

Next step up you get in to the cartridge feed system, which when you take the cost of the machine plus all of the feeders you will need puts the starting price point at about 2X the E1.  If you're a production house that needs some small machines for odd jobs then you probably wouldn't consider the E1 due to the change over times of a pin feed system, as well as you would probably want all your feeders to be of the same type.

My guess is that this leaves the E1 in an odd position in the market between people that make do with the cheapest ones and people that go with machines with cartridge feeders.

For me it's the right balance of features, ease of use, and cost.  I couldn't justify going to feeders, nor did I want to waste time coaxing a low end machine in to being useful.  From the lack of others on this forum it seems like there's not as many people in this category as I would have guessed.

I would not consider a machine that does not include a nozzle changer.  For a short time my nozzle changer was broken and I had to do it manually. Had to sit there and be ready for the change as otherwise throughput got really low.  I would look for something with "the most" feeders; a bit less of an issue for cartridge feeders but I keep wishing there was a way to attach a 3rd bank to the E1...

10

Beginners / Re: Supercapacitors and ESR

« Last post by jwet on Today at 04:21:09 pm »

> Any idea how one may cap the current to 1A w/o simply using a resistor to charge the capacitor as fast as possible? I.e. 1A goes through the capacitor till it's full >and then a sharp decrease to 0A instead of a gradual decrease. (The 1A limit is to avoid damaging the supply.)

The classic current limiter circuit uses a PNP with a shunt resistor (.6 ohms will drop .6v at 1 amp) between its base and emitter.  The input voltage is fed into this  resistor at the base.  There is a 470 ohm? or so pull down on base to ground.  The transistor is on and saturated normally (drops about .15v), if the current gets too high the shunt will develop more than .6 and throttle things down. You need a transistor with good beta and high current.  Xetex (now Diodes Inc) make good parts in the "E Line" parts, something like ZTX751 is a favorite- beta is high at 200, Ic is 2A max and Pd is 1W.  While its limiting current, it will dissipate power- its good for a watt which should be enough.

You can get fancier with current mirrors of towards IC solutions like high side current sense amps, comparators.  IC companies even make specialty super cap chargers- LTC4425 is one of the originals.

Have Fun,
John