Recent Posts

1

Other Equipment & Products / Re: PCB Ultrasonic Cleaner Recommendation?

« Last post by EEVblog on Today at 06:08:08 am »

Old thread, but no point making a new one.
I trust Chemtools here in Sydney, but anything else worth considering?
https://www.chemtools.com.au/product/electrical-electronics/cleaners-flux-removers/pcb-flux-remover/

I've ordered 5L of this stuff, that at least gives me one option for PCB's.
Can you re-use it? I assume maybe yes depending on conditions?

2

Projects, Designs, and Technical Stuff / Re: I made a 50 ohm load with BNC connector, Is this correct?

« Last post by TERRA Operative on Today at 06:07:25 am »

I test the RF signal.
I made a 50 ohm BNC interface resistor,I used 2 100 ohm chip package resistors in parallel.and mount them inside a BNC connector.
Can this be used?
Is it different from a standard 50 ohm load resistor?

You can make it perform better by placing one of the 100 ohm resistors on the other side, so the two resistors are 180 degrees apart, on symmetrically opposite sides of the BNC center contact.

So I disassembled it,The resistance accuracy was found to be 5%，Looks like a resistor with inductance, Would a non-inductive resistor be more effective?

If you mean this one, it doesn't look inductive (wire wound) to me. Looks like a regular film resistor which would be OK.

At higher frequencies, the spiral cut in the resistive film used in through-hole metal and carbon film resistors will cause parasitic capacitance (between the spirals) and parasitic inductance (from the spiral itself) to have an effect on performance.

3

General Technical Chat / Re: Future of computing & ai

« Last post by pcprogrammer on Today at 06:02:42 am »

I think converting water to wine is a much neater trick. Do that instead.

If you believe in it, Jesus already did that. 



  Does not even cut it, for what is dribbling out of this one. 

4

Projects, Designs, and Technical Stuff / Re: I made a 50 ohm load with BNC connector, Is this correct?

« Last post by jonpaul on Today at 06:02:06 am »

dont bother.

Mini Circuits sells fine 50  or 75 Ohm BNC/SMA terms good to 3 GHz.

SM-BM50+

EU/$10

j

5

Projects, Designs, and Technical Stuff / Re: I made a 50 ohm load with BNC connector, Is this correct?

« Last post by Vovk_Z on Today at 05:55:00 am »

How can I test it?

With a VNA. You may want to consiider required frequency range.

6

Projects, Designs, and Technical Stuff / Re: Emergency stop for runaway large DC motor

« Last post by pcprogrammer on Today at 05:54:31 am »

Thanks , folks , for the valuable input, so detection system is the microprocessor measuring rotor speed and then breaking relay/resistor. 
Is there any solution to detect a MOSFET failure ? When it is getting shortened and full power applied to the motor?  I am thinking about PWN "watchdog" that is reseting timer inside microprocessor,   when  it is continuous DC applied to the motor instead of, say, 10 PWM cycles - microprocessor will shut down main power.  is that viable solution ?

Depends on the PWM frequency. But sure there are ways to detect if it is continuously on, only it might be that at times you have 100% power during normal functionality. So your micro needs to take action based on both speed and 100% power and decide what is needed to do. When speed is to high cut both power and short the motor. When speed is still ok, but power is 100% while your setting is below, just cut the power. This can be done on the mains side (AC) with another relay or a solid state relay.

7

General Technical Chat / Also a 3dfx Voodoo2 Card

« Last post by Vertamps on Today at 05:51:26 am »

Also snagged an untested 3dfx V2 for $15. Iv actually sold a few of these for $185-200 on ebay recently. Will recap and test it. I have A Pentium 2 450Mhz system already setup with drivers. 

8

General Technical Chat / Re: Future of computing & ai

« Last post by Doc_white on Today at 05:50:35 am »

With the post I made before you made the purchase I pointed you to I said I was making an offer on i can travel back to that exact moment abd before it with other postd and het it bought before you

https://www.ebay.com/itm/226111666395?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ny_a6mids-e&sssrc=4429486&ssuid=yqy1ot06swe&var=&widget_ver=artemis&media=COPY

Everyone needs this thing to be happy again until it's stolen away by a greedy person. It's stepping up back from the state of despair where transustor testing machine looks ugly but is helavilysly usable to test capacitance of various materials and the current and voltage that runs through a banana peel where the base is a peel outer shell and anode the potassium or vice versa and see what emits from the field

9

Embedded Computing / Re: Graphical Calculators running basic

« Last post by simon christo on Today at 05:50:02 am »

Ill, check it out,
Thanks Simon.

10

Projects, Designs, and Technical Stuff / Re: Digital weigh balance - DIY

« Last post by CatalinaWOW on Today at 05:50:01 am »

 There are all sorts of cheap scales that you could use for this.  The luggage scales that I am familiar with saturate under the weight but that has an easy solution, just hang the four corners of the keg platform from separate scales and add their reports.

All of these should be more stable than the elastomeric feet you propose, and as you say you can recalibrate if necessary.

The hard part is automating the readout.  Video camera to OCR?   Possible but complex.  Tapping into the LCD drive and deciding?  Not easy.   

Do a search for robotic load cells.  I have found these reasonably priced (~$10 the last time I bought).  Or salvage those out of a bathroom scale.  And inexpensive A to D, a micro and some code and you'll be done.

It would even be easy to check for a tap left open by some careless party goer.