Recent Posts

1

General Technical Chat / Re: SPICE Generates nonsense with near-zero resistor values.

« Last post by iMo on Today at 05:47:54 am »

..I couldn't be bothered to draw a symbol or find the one I have saved somewhere, so I used the nearest looking one to a potentiometer in the default LTSpice install and added an arrow to make it look more like a potentiometer..

Me too.. Therefore I install Bordodynov's library pack, you will get megatons of stuff which you might find be useful..

2

General Technical Chat / Re: SPICE Generates nonsense with near-zero resistor values.

« Last post by Siwastaja on Today at 05:41:48 am »

It's a good example of low-level details leaking to end-user. And the key finding is that this is unavoidable. It leaks anyway, they can just choose how:

1) They can choose higher precision numbers, and loss of performance. Nearly 100% of users would be pissed and complain, or,
2) They can choose performance over numerical correctness in rare corner cases. But in some cases users accidentally (or purposely) create those conditions and are pissed.

It's a lose-lose situation.

They could also choose to dynamically increase precision from hardware FP to software arbitrary-precision when they detect it's necessary, like some programming languages do, but that's even more complexity.

Yeah, that crossed my mind and in a case like this it might not be even difficult to do, like just loop through all values to find min and max (regardless of units) and decide accuracy (float/double/bignum lib) based on ratio between largest and smallest number. But then again someone would find another corner case where the detection would not work correctly.

3

Repair / Re: strange low frequency switching noice from diy sg3525 smps

« Last post by Herschel on Today at 05:38:49 am »

I would be inclined to suspect EMI.  Try permutations of 'Y' capacitors. In particular, the one to bridge '-' is probably wrong, but one from there to output may be helpful.  Additional filtering (another CMC?), shielding (stuff everything into a box and filter all wires that pass through it) and testing are likely to prove fruitful.

Tim

I tried using the Y capacitors, and it did improved the noise under one "condition":

I was testing my smps with a 400 watt class D amplifier board, which is locally assembled one, I found out that the noise is created by that class D amplifier when I connect it to my smps. Does class D amplifers oscillates to create noise?, but after replacing that with a class AB amplifier, which I made, the noise just vanished! (still audiable when I hold my ears really close, covering the tweeters which I'm happy with)

So the *condition, only applies for the class ABs not Ds. And yes, the Y caps helped a lot

Is it a good idea to use a CMC with .1uf mylar filter caps only for the classD amp does it improves the performance and reduce noise?

4

Test Equipment / Re: NEW Fluke 87-VI Multimeter

« Last post by Fungus on Today at 05:36:28 am »

I think its about time that Fluke makes something new that will lead industry for next 20 years as 87V did.

Fluke customers don't want change, they want the 87V.

They have training courses, written procedures, etc., all based around it.

Fluke bosses don't want it either, the 87V is a cash cow.

I expect they'll still be making it 1000 years from now.

5

Buy/Sell/Wanted / Re: FS Pick and Place system with tons of feeders

« Last post by rx8pilot on Today at 05:29:19 am »

I remember your adventures getting set up...
https://www.eevblog.com/forum/reviews/finally-have-a-pick-and-place-on-the-way-quad-ivc/?all

Yes!! It was a really run project getting this thing up to speed. Since then, a lot of additions.

6

Test Equipment / Re: Siglent SDS1104X-E and SDS1204X-E: Bode plot with a non-Siglent AWG

« Last post by bateau020 on Today at 05:25:54 am »

PM sent.

7

PCB/EDA/CAD / Re: Four ground layers stitched together under an Artix-7 FPGA is a bad idea?

« Last post by bmxsesh on Today at 05:24:37 am »

You're right that you can't get three traces through (at least at 75µm trace/space), I was off by one (should never have learned how to do software! never!) but the rest is all true, see the attached.

You'll need slightly smaller pads than the usually recommended 0.6mm, but with NSMD pads slightly smaller is often good anyway, and I doubt you're going to HVM with this thing so it should be fine. Yes, some of those things need 75µm trace/space (which manufacturers will usually do for you if you keep it constrained to a BGA fanout zone), VIPPO (via-in-pad-plated-over; this is rapidly getting common and has been common in HVM for ages), or even laser drills (still less common for LVM but, again, everywhere in HVM) but... you can do it. Laser microvias may be the hardest thing to achieve here and they are only needed if you must have vias outside of the usual "checkerboard offset" BGA pattern.

Your pad shape looks wrong which is no doubt part of your problems. I don't know why you would want asymmetrical pads like that. Your manufacturer is kind of strange, do they not have an x-ray inspection system or something? You probably don't want them doing prototypes of a 676-ball BGA without x-ray inspection. What are the actual pad dimensions you are using/they are asking for?

This is what I got now: three different footprints for a BGA pad
Now the smallest one at the minimum spec does allow to carefully lay a wire that is conforming to 0.075 mm clearance + 0.075 mm wire width + 0.075 mm clearance
In my initial layout I sticked with NOM. dimensions of the datasheet from a previous post but this now is pretty much the MIN. that is allowed
Last screenshot is how much space I had originally
Only I don't know if this change will help with manufacturing but laying out does become slightly easier

8

Beginners / Re: I have an LED DRIVER on several Aquarium lights...looking for info on the LED dr

« Last post by BennoG on Today at 05:22:56 am »

Usually they do constant current output, so the number of leds does not matter.
When measured with a unloaded output the voltage can be high 70V is no exception.

You need to measure the output when the circuit is loaded and the leds are working.

Benno

9

Repair / Re: DC power supply doesn't work with DC motor

« Last post by ledtester on Today at 05:16:38 am »

I wouldn't use a breadboard for a high-current application like this one. Besides, as you have noticed, the leads of the high-current diodes don't fit.

The diode leads are likely going to be too large even for prototyping boards that have copper pads.

Since this circuit only has a few components a quick and easy way to test it out is to solder the leads of the components together -- perhaps with help of thick solid wire -- creating a "free air" circuit without a supporting board. Once you get it working you can turn your attention to making a more permanent version of it.

10

Buy/Sell/Wanted / Re: FS Pick and Place system with tons of feeders

« Last post by Smokey on Today at 05:14:33 am »

I remember your adventures getting set up...
https://www.eevblog.com/forum/reviews/finally-have-a-pick-and-place-on-the-way-quad-ivc/?all