Recent Posts

21

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

« Last post by Fungus on Today at 06:47:30 pm »

It however starts to fail well below Nyquist (which is 156.25 MHz at this sampling rate): the displayed signal begins to have lower frequency noise at about 100 Mhz and it becomes next to useless at ~130 MHz.

sin(x)/x will start to go wrong at sample rate / 2.5

That video shows exactly what the math says it should.

22

Projects, Designs, and Technical Stuff / Re: DIY Digital Caliper

« Last post by MitkoDyakov on Today at 06:40:55 pm »

Hardware - the footprints for the t-scale and sensor and also gerbers and schematics

Thanks for sharing, But it would be nicer if you could share the Kickad files for schematics and PCB, since We can modify it easier.

You can find it in BluePillCaliper/Hardware /Footprints - KICA

23

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

« Last post by shapirus on Today at 06:37:45 pm »

900 switches when all 4 ch on and MSO

I see. Yeah that's kinda expected.
A hacked 800 doesn't do it, it stays on 312.5.

It however starts to fail well below Nyquist (which is 156.25 MHz at this sampling rate): the displayed signal begins to have lower frequency noise at about 100 Mhz and it becomes next to useless at ~130 MHz.

Frequency counter works only up to 142 MHz.

Here's a 30s frequency sweep from 70 MHz to 170 MHz. Nevermind the intermittent glitches and some jitter, they may be a result of the signal gen that I'm using (TinySA Ultra). A 50 Ohm feed-through terminator was used on the scope's BNC input.

Memory length was deliberately set to a maximum to get a minimal waveform update rate to get rid of the display persistence effects, which are not desirable in this case.

(the 156.25 MHz point is at ~00:25)

24

General Technical Chat / Re: Is LinkedIn worth keeping?

« Last post by joeqsmith on Today at 06:28:21 pm »

I just looked it up and sure enough, they are owned by Microsoft.  Like most things I don't care about, I had no idea.   Because I attempt to block all known Microsoft traffic, I thought I would try to go to their main page:

The connection has timed out

An error occurred during a connection to www.linkedin.com.

    The site could be temporarily unavailable or too busy. Try again in a few moments.
    If you are unable to load any pages, check your computer’s network connection.
    If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

25

Beginners / On ground loop while connecting a Logic Analyzer

« Last post by mindentropy on Today at 06:23:03 pm »

Hi,

While reading through safety page of Saleae Logic Analyzer I found the common ways a ground loop can exist in this page:

https://support.saleae.com/user-guide/safety-and-warranty#common-ways-a-ground-loop-can-exist

In there I find the two points:

1.Other USB devices (such as programmers) are connected to the DUT, or the DUT itself is plugged into the USB port on your computer. In addition to the logic analyzer's ground connection, the DUT's ground is also connected to the PC's ground through another USB port.

2. Non-isolated power supplies Most AC power supplies with 3-prong plugs will short the MAINS earth ground pin to the power supply ground output. That includes your PC's ground. If your DUT is powered from a 3-prong wall power supply and your PC is also plugged in, that will form another ground path. Keep in mind that if you're using a laptop that's not plugged in, even an attached external monitor or printer will create a ground loop.

I have a DUT which is connected to my laptop USB port and also my Saleae LA. Does this mean that both of these will be connected to the common ground of the PC? If yes, would this mean that a ground loop is formed? Will my laptop provide an isolation due to the battery connected? If I have connected the DUT to a PC would it have a common ground then?


In the section on Common ways damages can occur here -> https://support.saleae.com/user-guide/safety-and-warranty#common-ways-damage-can-occur

When connecting or disconnecting probes, one of the ground probes from the logic analyzer is accidentally brushed against a power supply pin on the DUT, such as +5V. If there are no other ground paths between the DUT and the PC, nothing will happen. However, if there is a ground path, then current will flow from that voltage supply through the logic analyzer's ground pin, through the USB cable and the host PC, and then through the secondary ground connection—either MAIN earth ground or another USB port, back to the ground on the DUT. Basically, that is the same as shorting out the voltage supply on your DUT, but it uses the logic analyzer and your host PC as the short circuit, which could damage all components in the loop.

Why nothing happens "If there are no other ground paths between the DUT and the PC"? Is it because there is no return path from the DUT power supply to the LA connected to the PC and finally to the ground of another PC?

26

Projects, Designs, and Technical Stuff / How is a motor run capacitor sized?

« Last post by aroby on Today at 06:18:39 pm »

I am trying to understand the sizing of a run capacitor for the 2 motors in a valve actuator for a swimming pool valve.  Only one motor is active at a time, and the simple supply circuit (24VAC) is delivered by a separate control board sending power to the appropriate motor.  A Richey 35uF 150V NP capacitor sits across the motor.  I assume it is a run capacitor that delivers a smooth flow of power to the motor, which has some pretty decent torque.   

I need to replace the small board in the actuator and would like to replace the capacitor at the same time.  But these capacitors are very difficult to find and seem to cost USD30 or more.  So, I'm looking for alternatives, however I am not clear why this is 35uF and why it is 150V.  Can someone help me understand how these values are determined?

Thanks!

27

FPGA / Re: USB BLASTER (FTDI245 vs ch552x) Quartus “No Hardware”

« Last post by Wiljan on Today at 06:16:31 pm »

I read somewhere that the clones does not have the same logic level as the original. That can give problems depending on the actually fpga  board connected.
I would suggest to use a scope to see happens on the jtag.

28

Power/Renewable Energy/EV's / Re: Aussie Fast Charger Company Tritium Goes Bust

« Last post by Faringdon on Today at 06:13:38 pm »

...Sorry to hear it.....though there will be very many following them down...across the western world. Fact: EVs are a gonna in the west...the only way the west can afford it is if the West buys the cheap Chinese EVs. The Chinese are also withholding/keeping in short supply  some of the chemicals needed to make EV batteries (as below link).
EVs are a gonna in the west...maybe just a small percent will have them. ICE cars are going to be majority for next 100 years at least in the west.
Fact: Soon to come is even more eye opening. In short time virtually all Power electronics products from China will be Banned from western markets.

https://www.gbnews.com/lifestyle/cars/richard-hammond-electric-vehicles-petrol-2050

29

Test Equipment / Re: FNIRSI-1013D "100MHz" tablet oscilloscope

« Last post by csuhi17 on Today at 06:11:40 pm »

V0.024V
The device is in original condition, with a charged battery, old edition.
Power source Fnirsi SG-004A, monitored with an Owon multimeter. 7.5V
1x , 2.5V/div.   5Msa/s 20us/div.

old
CH1
Avg=7.20V Vmin=7.05V Vmax=7.40V Vpp= 350mV
Auto
Avg=7.40V Vmin=7.30V Vmax=7.65V Vpp= 350mV

CH2
Avg=7.30V Vmin=7.30V Vmax=7.50V Vpp= 150mV
Auto
Avg=7.50V Vmin=7.40V Vmax=7.65V Vpp= 250mV
 
new
CH1
Avg=7.05V Vmin=6.75V Vmax=7.05V Vpp= 250mV
Auto
Avg=6.95V Vmin=6.85V Vmax=7.10V Vpp= 250mV

CH2
Avg=7.30V Vmin=7.20V Vmax=7.65V Vpp= 400mV
Auto
Avg=7.50V Vmin=7.40V Vmax=7.85V Vpp= 400mV

Before measuring, I fully charged it and went through the entire calibration.

30

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

« Last post by Mechatrommer on Today at 06:10:30 pm »

With the DHO900 (non 'S' model) can you still do automated Bode plots with an external Sig. Gen.?

offically? no. but unofficially, other than hacking it to S model in vendor.bin, you can make PC SW to control both and plot in PC, its possible.