Recent Posts

1

FPGA / Re: Analog video output with FPGA ?

« Last post by BrianHG on Today at 06:23:02 pm »

Just for those who want a super small RGB DAC for their FPGA projects, this guy: ($1.81 for 1 piece)

https://www.nxp.com/docs/en/data-sheet/PTN3393.pdf

Runs on 2 lane display-port, so you need to be able to work with that, but only 6 wires between your FPGA and this DAC.  This DAC also has built in  TTL drivers for your VGA plug's HS and VS signals as well as 5v tolerant level translators for the DDC SDA&SCL lines.

2

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by xvr on Today at 06:22:11 pm »

> How do you see thats its limited to only 4A?

It stated in its datasheet. LTSpice do not take in account physical limits of devices which it [LTSpice] simulate.

> Could you please reccomend me a PMOS model i could use?

You should firstly select REAL transistor, by its real parameters. Ids and Rdson firstly.

What maximum voltage drop on MOSFET you can tolerate? 0.1V (0.5% of Supply Voltage for AMP) will be acceptable?
And what budget limit for MOSFET? High power MOSFETs can be expensive 

3

Power/Renewable Energy/EV's / Re: 5 out of 6 vendors are scamming people with wrong crosssection of cables

« Last post by eTobey on Today at 06:20:05 pm »

What kind of cables?  Power or signal?  Were they advertised to conform to a particular industry spec or just a specific size?

I wrote in this section of the forum, because it has the word "power" in it. 

But i also found in one delivery where i ordered a few 0.35mm2 cables, one cable to beeing substantially less.

Seemingly, many people just trust what there is advertised. But you cant trust anything nowadays...

4

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

« Last post by coppercone2 on Today at 06:17:14 pm »

wow I don't like that attachment. I thought the weld wire would have to be clean from oil. I guess its not like TIG were they have you religiously clean it. I suppose that feeder might be oiled too lol.

5

Repair / Re: Laser Level Charger PCB ID

« Last post by globoy on Today at 06:15:11 pm »

No wonder the replacement packs are expensive.  That's a complex battery controller PCB.  It's custom, so you aren't going to find an off-the-shelf replacement.  It uses an off-the-shelf TI BQ24296M charge controller https://www.ti.com/product/BQ24296M, a low-end STM32 ARM micro-controller https://www.st.com/en/microcontrollers-microprocessors/stm32f030f4.html, and some other circuitry, at least some of which appears to be a small buck or boost converter.  Looks like the STM32 controls the LED. 

I'd first take a close look for things like a bad/loose solder joint, bad wiring harness connection or corrosion somewhere that might be causing enough of a short to cause a failure.  Then things you might start with to debug this PCB are:

1. Check VDD on the STM32 (pins 5 for analog power in, 16 for digitial power in).  I guess you should see 2.8V, 3.0V or 3.3V.  Ground is on pin 15.  Failure to see good power would probably implicate one of the parts above the micro.

2. Poke around the BT24296 chip.  While charging pin 4 (STAT) should go low (the designers helpfully pulled it high even though they don't appear to use it using the 3rd resistor above the cap on the lower right of the board).  Pin 3 (PG) should go low if the chip likes the battery voltage (2nd resistor above the cap).

3. Use your scope to probe the SW out signals (BQ24296 pins 19, 20) going to the inductor  at the bottom left to see if it's trying to provide power to the system - or you could measure across the two caps above the inductor (according to the spec sheet this should be 3.5-4.35V).

4. If the charger seems alive and the micro is getting power you could probe the I2C bus between the charger and micro (the 4th and 5th 10k resistors above the cap on the lower right).  This might show code is running on the micro.

If it's the BQ chip then that's an easy replacement.  If it's the micro then you're probably SOL.  It could also be one of the parts above the micro but I didn't really try to figure that circuitry out.  Other parts you could also probably replace although you'd have to do that dance where you figure out what part some small chip is based on the cryptic markings on top...

Would be curious what voltages the battery pack puts out and what communications it supports to the level.  Sure is a complex pack to just house a 3.7V battery (your two cells are wired in parallel).

6

Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by TimFox on Today at 06:12:45 pm »

Depending on your (apparently secret) requirements, another approach for stabilizing amplitude is to use a “quadrature oscillator”, with a sample-hold triggered by the zero-crossing of the “cosine” output to sample the peak magnitude of the “sine” output.
This was used by Krohn-Hite in some of their older generators (I believe).
More recent units, including the 4402 ultra-low distortion generator, used a fancy peak-to-peak detector.

7

Programming / Re: Angle wrapping in code, "easy" problem, need to double check

« Last post by ejeffrey on Today at 06:10:28 pm »

. any tips on angle-wrap-respecting code to determine if a supplied angle is inbetween (on the short side) another two supplied angles

If possible I would avoid this.  Specifically the "on the short side."  Instead, define this in terms of " counterclockwise from the first angle, before reaching the second." This gives a unique representation, allows you to define an arbitrary interval rather than restricting to things less than 180 degrees.  Then "x is within the interval [a, b)" becomes:

(x - a) mod 360 < (x - b) mod 360.

If you still need the behavior you asked for then handle that as an input transformation: if (( b - a) mod 360) > 180) then swap(a, b)

As usual, watch out for the edge cases, I have chosen a convention that includes the first point but not the second.  You might choose differently.

8

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by bd139 on Today at 05:59:23 pm »

"Actually you can..."
There might be a simpler way, Windows locked away inside a VM, with some very strict firewalling of any potential telemetry which was trying to escape the VM performed by a trustworthy Linux host OS. That would be a solution for anyone needing to run a program on Windows which wasn;t Wine compatible (unfortunately not that great a fraction of Windows exe programs are Wine compatible, I'm lucky with the few legacy Windows programs I use).

That is literally what I'm doing. I have an EC2 instance in AWS running windows server. There is a SG configured so it can only service RDP. Software is pushed to it over remote folders.

9

Metrology / Re: ADR1399 reference

« Last post by Andreas on Today at 05:57:24 pm »

Hmm,

so you have around 1 ppm/K temperature drift.
I think that your DMM contributes most of the T.C.

Did you try to thermally isolate the ADR1399?
Did you do the TC-Compensation of the LM334 from datasheet or did you adjust the 2 resistors to minimum T.C.
(according to my experiences with LM334 for a LM399 project the resistor values from datasheet are not perfectly).

with best regards

Andreas

10

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by radiolistener on Today at 05:56:46 pm »

hmm... COM3, sounds like something from the ancient past. I think I had my 2400 baud modem on COM2 and mouse on COM1 in mid-90's.

USB serial interface is very popular these days, it also use COMx name on Windows.

Jokes aside, I'll try some time later. Of course I'm using Linux. Will see if it works with mono.

it should works with mono with no issue. Just add "mono" before command and provide proper name of serial port.