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Test Equipment / Re: POWER DESIGNS PRECISION POWER SUPPLIES
« Last post by rsjsouza on Today at 07:43:08 AM »
T has better regulation than S. I'm shopping for my son's home lab (3rd year EE) and thought a little old school PSU would fit the bill. 50V @ 1.5A should be plenty. No way he is touching my 2020B... no way.  ;D

BTW, is there a Wiki on EEVblog? Seems to be almost no resources out there for PD collectors... which I guess I am now!  :scared:
I have a 5015A and its performance is absolutely amazing - I tested it throughout its range and the ripple was quite low and the voltage was quite stable. The only letdown for me is that it does not work as a current source.

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Test Equipment / Re: Multiple traces after STOP button is pressed
« Last post by rf-loop on Today at 07:42:45 AM »
It depends who you ask, some will say this is the right way to do it.

I come from a history of using Agilent scopes. There the stop button causes it to show a single waveform fro the last trigger so i generally expect stop buttons to work this way. But some scopes have a different idea of the stop button where it freezes the current image on the screen.


Yes. These all what we can see in display after stop is information about signal. Why flush information to garbage as default. I have used this kind of scope and all times it make me angry, why it flush out interesting data and show only last one. It must display to user all possible what it have.
 It can do more clever. Stop, scope show all information what it have (freeze display with tens or hundreds or even thousends of stacked last acquisiotions giving also "third dimension" (Z) about signal.) After then user can touch it and only last acquisition is displayed.  This is idea how example Siglent works or should work.

But after then there is also more. If user is interested about acquisitions before stop he/she can look these. Depending memory and time settings up to 80000 previously trigged acquisitions.  These can find in history fifo. Exept if he have <censored>.  User can play  this history buffer or just select every single acquistion (limiting of course how much it can store)  and do cursor and automatic measurements, use FFT or do window zoom or whole screen zoom because in history buffer all is raw sample data, not imagepixelmap traces.

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Z80 Int pin =  CTC Int pin OR SIO Int pin


Ah yeah, fair point - thanks netdudeuk!  :-+
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Crowd Funded Projects / Re: Preparing EEZ H24005 for crowdfunding
« Last post by steverino on Today at 07:28:46 AM »
Hi Prasimix.  Sorry to post here, I'm not sure how to contact you directly about my H24005 order.  I tried to contact you through the Crowd Supply website, but not sure if you'll receive my inquiry.  Anyway,  I've received my order (thank you, and very well packaged as well).  I've come to discover I had only ordered "Assemblies and Enclosures".  So I have a beautiful enclosure but no electronics.  Is it possible to order the missing parts?  My original order number is 40339.  Thanks in advance.
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Z80 Int pin =  CTC Int pin OR SIO Int pin

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Metrology / Re: DIY Low EMF cable and connectors
« Last post by MisterDiodes on Today at 07:25:49 AM »
Mostly companies working with Gov'ts trying to regulate in safety arc-flash specs and various CAT-level instrument ratings...  Which is certainly OK if you're working in that environment, but not so good for low ppm work.
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I believe that you want an OR gate there.

Really? An OR gate doesn't match the truth table required according to C's previous comments though?

Any low input = Low output.
Using Open collector logic you have a wired OR where any output can create a low.

I know C's stated an OR gate is required but what he says after that matches an AND gate...?
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free_electron

  For the next step up from what you have stated, do you really need  a vision recognition system?

If you have a photo of bare board & a current photo from camera.
Then Position is just overlaying the two photos, Would be like a focus step to get great position. Instead of moving focus ring on camera you would be adjusting the X & Y relation of the the two photos.

Over time, you could have a large number of photos to use.

If you added a step where you placed the fiducial, then the software could handle the problem of PC board position.

I see little things with photo( storing & Using) use helping greatly with with what you propose.
For example you said to
 "machine remembers coordinates for placing"
Just by capturing a photo, you could have optical coordinates for placing. This could allow less precise machine coordinates as need would only be to get in fine tune optical position.


 
 

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Hello all,

And thanks for the positive comments.

About the pdf's:
Probably in the long term I should publish this somewhere else if the design works well for more people. Pdf-merge seems to be a good way to combine them even if I haven´t tried it (I have a complete pdf that took some time to divide   ;)? ) .

About rubidium or OCXO:
I have my rubidium powered all times. Of course we have power interrupts. The longest continuous run without an interrupt has been above 30 million seconds on the internal time counter, that is almost a year!

I was happy to buy two LPRO rubidiums cheap five years ago so I have one spare that I only power up seldom. Now it has been on for a couple of months as I have done a lot of tests and wanted a second opinion from another rubidium. The reason I use the rubidium is that it is by far the most stable oscillator I have in hold mode (free running). For me that want to test other GPSDO´s this is the best choice. My continuously powered rubidium has very low drift. From the 3 hour logs the last 9 months I can see a drift of 700 dac_value units, that is about 1.2E-11 for 270 days so about 4E-14/day. Worse is the temperature coefficient that is about 8E-13/C but in hold mode the temperature is compensated so probably within +-2E-13/C. The worst problem is the air pressure sensitivity of about 7E-14/mbar. I have a pressure sensor BMP180 built in but it doesn´t compensate. The air pressure is mostly a problem for me at long runs that are week long, as the air pressure varies slowly.

For most people I guess an OCXO based GPSDO is best. It will give about 9-11 digits of frequency accuracy. For those that want even lower power of course an VCTCXO based with e.g. DOT050V is a very good choice but only gives 8-9 digits for short times (seconds to minutes).

A lot of people think OCXO based GPSDO's take too long time to start up. If you want the GPSDO to lock in 5 minutes that is just the warm-up time for the OCXO, but remember that even with a retrace of 10ppb after being off for a long time, you will never be off more than 10ppb, as the old DAC value is stored in the EEPROM. So you will have 8 digits and probably better within 5 minutes, but no locked LED. If you set a short time constant say 20 seconds the locked LED will come on within just minutes after warm-up. This will of course give more ripple on the frequency but not worse than other designs that promise short start-up times. If you really want very good frequency accuracy you need to have long time constants mostly depending on the 1PPS stability that limits this. Another thing to remember is that I have used a quite conservative lock time of five time constants to be sure the loop has settled. The frequency probably is stable after half of that time at most start-ups.

Lars
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General Chat / Re: Arduino projects, a little suggestion needed
« Last post by kingoft on Today at 07:19:10 AM »
What subjects or skills are you currently good at? How long did it take you to achieve that level of proficiency?

As with most skills, it takes time and practice to learn more than just the basics. Some learn faster than others or have better methodologies for learning, but there's still a non-trivial amount of time that must be invested.

In this so-called age of instant gratification, worthwhile endeavors still take effort to achieve. So, be patient with yourself, don't give up, and enjoy the journey, not just the destination.

Thanks ! Do appreciate it  :)
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