Recent Posts

1

Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by Joel_l on Today at 06:30:55 pm »

Mine is a little different than that, I have 4 more diodes where the signal enters the first switch.

So I think I found two things going on, one really muddied the other. Looks like my attenuator is bad and is causing the high SWR on my TX. This does not explain the initial high SWR with my antenna analyzer, I did not use my attenuator with that.

I went back and looked with my signal generator again. I fed a -20dBm signal in and went through the SA attenuator settings. The reading never changed from -20dBm only the noise floor moved up and down, the SA always measured -20dBm.

Those switches are not very expensive. I think I will just replace those. I hope the programable attenuator at the end is OK, not as easy to find.

2

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

« Last post by Stray Electron on Today at 06:29:44 pm »

I have ordered cables from 6 different places (Germany).
Have you ever checked on the cross section?

   Where were the cables made?   Undersizing of wire and cables made in China has been widely reported on this and other sites.   A lot of the wire is also reported to be made some kind of junk alloy that isn't solderable.  I've learned to not trust the ratings of anything made in China.

  A few years ago my 730 pound Miller welder got dumped unto the ground when the frame of my Chinese made 900 pound rated trailer bend under the load and within 30 seconds of placing the welder on it and before we had moved it even an inch.

3

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

« Last post by Calambres on Today at 06:28:41 pm »

I've got the board holder and the Proskit solder sucker. Both are good and work fine for me.

4

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by OLderDan on Today at 06:27:25 pm »

I was watching a new YouTube dso2d15 unboxing and noticed the icon display for the awg at the bottom of the screen switched between a B and G at different times. I also noticed the screenshots here by Aldo show a B and mine always shows G no matter what settings I have tried,
Any ideas what the different letter B or G signifies?

5

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

« Last post by mariush on Today at 06:27:09 pm »

Do they use the exterior diameter (with insulation), or the inner diameter (as if you stripped)

On stores like Digikey , Newark and others you get a datasheet for the cable where it tells you how many strands of wires are used, and what's the gauge of each strand.

See for example https://www.digikey.com/en/products/filter/single-conductor-cables-hook-up-wire/474  you see there a column with number of strands and thickness of each strand


edit : you seem to be in Germany so TME.eu may work better : https://www.tme.eu/en/katalog/wires-and-cables_112533/

You can see all the parameters at the Stranded cables section : https://www.tme.eu/en/katalog/single-core-cable-strand_100147/

6

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.

7

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 

8

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...

9

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.

10

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).