Recent Posts

1

Projects, Designs, and Technical Stuff / Re: more modern version of tl494?

« Last post by xavier60 on Today at 03:54:54 am »

I have a strong preference for the UC3525.
It is reassuring to see in the internal block diagram, the steering flip-flop being clocked directly by the oscillator and also the latch at the comparator's output.
Not so for the TL598 despite the claims. The extra opamp might seem useful but can be difficult to achieve fast current limiting with it.
With the UC3525, I implement fast pulse-by-pulse limiting by pulling down the soft-start pin.

Great info, I have heard a few people saying their problems went away after switching from the TLxxx to the 3525 series, this could explain it.

From the  UC3525 datasheet
All transitions of the voltage on the shutdown pin should be within the time frame of one clock cycle and not
repeated at a frequency higher than 10 clock cycles.

Does this pose a problem to fast current limiting, or do you hold the voltage low for 10 cycles?

Thanks

I only use the soft-start pin 8. It only acts on the comparator input but still terminates the present half cycle quick enough.
A capacitor is normally placed from pin 8  to ground. I include a series resistor so that the pin can be quickly pulled to ground without completely discharging the capacitor with a small transistor or possibly a comparator's open collector output.
The transistor of comparator will be monitoring the rectified, loaded and lightly filtered output of a current transformer sensing primary current.
My application is forward half-bridge converters.
 It provides short term pulse-by-pulse limiting for each half-cycle until a slower main control loop can take control of output current. A battery charger for example.

2

Test Equipment / Re: Siglent SDS2000X Plus Hack

« Last post by rfindley on Today at 03:54:28 am »

I used to write software for option keys and firmware updates, so it's always interesting to see how other companies implement theirs.  I had read that Siglent changed things recently in newer firmware... or maybe just newer models, I'm not sure... so I was curious if this script could reproduce my legit-purchased logic analyzer key for the SDS3000X HD, and nope... it's different.

I was also curious about the .ads files (that's another interesting thread), and it looks like they're still using some of the same obfuscation techniques (reverse file, xor 0xff pattern), but it does look like it's not exactly the same as it used to be.  It's so easy to AES-encrypt these days, especially if the equipment is running Linux, so I wonder why they spend time doing weird obfuscation.  (Maybe it's an export control issue??).  Not that I'm complaining:  some people like Sudoku;  I like my challenges a little more difficult. 

3

Projects, Designs, and Technical Stuff / Re: more modern version of tl494?

« Last post by 2strokeforever on Today at 03:32:44 am »

I have a strong preference for the UC3525.
It is reassuring to see in the internal block diagram, the steering flip-flop being clocked directly by the oscillator and also the latch at the comparator's output.
Not so for the TL598 despite the claims. The extra opamp might seem useful but can be difficult to achieve fast current limiting with it.
With the UC3525, I implement fast pulse-by-pulse limiting by pulling down the soft-start pin.

Great info, I have heard a few people saying their problems went away after switching from the TLxxx to the 3525 series, this could explain it.

From the  UC3525 datasheet
All transitions of the voltage on the shutdown pin should be within the time frame of one clock cycle and not
repeated at a frequency higher than 10 clock cycles.

Does this pose a problem to fast current limiting, or do you hold the voltage low for 10 cycles?

Thanks

4

Beginners / Re: Automatic golf ball dispenser

« Last post by Maclarkson on Today at 03:30:40 am »

Ok guys, the final prototype.
https://youtube.com/shorts/KOmL9WKCEq0?si=T7d2N874ycgET7hB
It would have been nice in their forum if someone could have suggested ways to achieve this.

5

Beginners / Re: 555 driver and Transformer questions

« Last post by Andy Chee on Today at 03:24:24 am »

I have a few thoughts....

Is your current mechanical vibrator system working adequately at the moment?  Can you connect your oscilloscope to the working vibrator to see what kind of duty cycle it generates?

Another possibility is that the working vibrator can be used to drive the gate of the MOSFET (instead of being driven by the 555 timer), the MOSFET (or transistor or SCR) can handle the heavy current switching of the step-up HT transformer module.  This approach would eliminate heat from vibrator contact arcing, but you would still be susceptible to mechanical failure.

6

Repair / Re: Mig welder wire feeder controller board not working

« Last post by .RC. on Today at 03:21:13 am »

Yeah, basic, non critical MIG welding on mild steel is pretty forgiving. I never really understood why some people end up with no penetration on their bird-poop welds....

I actually found it hard to do a bird poo weld with a mig.   What it is easy to do it do a visually fantastic looking weld that has zero fusion to one side.   I have also found cold mig welds on commercially made stuff. The bead stands proud like your nipples on a cold morning.

Mig welders because they are more complex to get the settings right, with volts and wire feed and gas type or gasless or dual shield has opened a whole new level of crap welds.  At least a stick weld looks crap if it is crap and starting out stick welding I did a lot of crap welds.

The old days your 15a socket melting (yes I melted a few of them) AC transformer stick welder had one knob to adjust (well some were flash and had 2 OCV settings), and everyone was running 6013 rods.  Life was simple.

Of course one quirk for Australia that has gone full short bus on regulations.  Dodgy Darryl at his home with his $150 mig welder and a roll of flux core and ten minutes welding experience can weld up a trailer to tow behind his car and get it registered no problems at all.

7

Test Equipment / Re: new killer scope in town - a true game changer from R&S - RTB2002 & RTB2004

« Last post by Darkover on Today at 03:15:04 am »

> RTB2000 is not 12 bit.

Ups, I invented two more bits. 
However, it is noisefree enought that I enjoy it and I think it is very seldom that
I need the gain of 1x probe, especialy if I had to pay with lower bandwith.

Olaf

8

Buy/Sell/Wanted / FS [US to XX] Tek AFG3252 - Like new, single owner - $3K

« Last post by Zucca on Today at 03:03:20 am »

https://www.tek.com/en/datasheet/afg3000-series



I bought it in 2011 spending an insane amount of money.
It was my baby for several years, always a joy to use.
I can't find any defect on it.

It comes with US power cord, two CDs and the cal certificate form 2011.

Lowest I can find on ebay is eBay auction: #305528284623 for $5.5K.
We all know it is pure madness, I will let mine go for $3K + shipping.

Reason for selling: I always use my Agilent 33522A now, I don't need it anymore.

PS: If you have a Agilent 34972A to trade in, I will make you a discount.

Free shipping in US lower states, others please ask.

Datasheet attached here below.

9

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Mechatrommer on Today at 03:02:17 am »

Meanwhile, there are some features that the Rigol brings to the table that I find attractive, including the slimmer size, possibility of powering from a battery pack, HDMI output, easy addition of wifi capability. VESA mount might also be valuable for my limited workspace.

well you've made you choice congratulation! There's nothing wrong really with rigol to begineer, we hope they will fix bugs as before.. even more so with rival appearance from sds800x.

About probe, there's more catch, such as loading at hi freq.. and technique to avoid gnd loop etc. since you dont really concern, built in probe should be fine, you'll learn as you go. I never have a need for fancy 3rd party hi -z passive probe, if i want hi freq i'll go 50ohm 1x coax, or active probe. either way you have to pay extra money. ymmv.

10

Test Equipment / Re: Siglent SDS2000X HD, 12bit, 2GSa/s high definition oscilloscope serie.

« Last post by temperance on Today at 03:01:23 am »

I have the impression that the SDS2000X HD always has a small downward dent in the left in channel 1 when the input is open in auto-trigger mode.

I've noticed this too and I think it is a software problem because it does not depend on the horizontal position.