Elektor Voltage Current Calibrator Project

[Martin72]

My mouser order arrived today at work, now the DAC is the only thing missed.
And U7 have now the right size...Soldering it and the MAX6350CSA+ in a break, like the tantalum capacitors and the one film cap.
We have also a 3d printer here, so chances are good that I could make the frontplate and the housing for the heater at work.
Next weekend I´ll try to program the display.

[Martin72]

Next weekend I´ll try to program the display.

Couldn´t wait, did it today in the evening..
Success..
Tried several times, several things, at the end it was easy:

- You musn´t open the 4D Workshop main program.
- In windows start, click on the 4D mainfolder and start "Program Loader" (connect the display before via usb adapter to the pc/notebook)
- Choose the right com port.
- Select the Software ->En_cours folder, the executable file will be displayed.
- Click to OK to start programming
- That was it for the cpu part.

SD-Card:

- Must be formatted in FAT16, I´ve bought extra a 4GB card for it and formatted it via windows command line.
- The 4D formatting tool (you can format cards above 4GB with it) won´t work here.
- Copy the files from the USD folder directly to the card

I did this after the programming, before, while the first start of the display, the card was empty and you see only a "+" symbol and a dot on it.

After all I´ll test the display and tap the +/- fields - It works...
So this is finished, next monday I´ll solder the rest on the pcb (loose one 10µF tantalum, must look here at home if I got another).


Martin

[KungFuJosh]

Nice. That's pretty typical regarding the programmer. Programmers and Development environments are often bundled together, but actually separate.

[Martin72]

Oh yes, I´ve studied the manual before, but didn´t find a thing about it.
BTW, another reason why the display is so expensive:
Not only it is "intelligent" (controller for other things), the display itself got the highest selection grade.
Only 0...4 max. dead pixels.

[Martin72]

Finally in stock:

https://www.mouser.de/ProductDetail/Analog-Devices/AD5791BRUZ?qs=NmRFExCfTkEaSRRmY4%2Fg1g%3D%3D

And ordered, should arrive next week - The last one I need for completing the circuit...

[KungFuJosh]

Did you build this yet? I'm curious how it came out.

[Martin72]

Hi,

Unfortunately not yet.
The chip has arrived and is together with the board on the table at work.
I wanted to supply the board with voltage to see if everything is ok before I solder the most expensive part of the circuit.
Too much to do the last few days.
I think, soon it will be so far.

[Martin72]

I wanted to supply the board with voltage to see if everything is ok before I solder the most expensive part of the circuit.

And I already know how, I haven't soldered in the PS1 converter yet, so I can connect two power supplies with current limiting to the +/-15V inputs and carefully boot up....
I am quite sure that I have observed the polarities of all components, but "thanks" to the missing markings on the board, something may still have gone wrong, hence my cautious approach.

[Martin72]

Did it today..
No anormalies....Wait a minute..
Why do I measure 2.5V on the output of the MAX6350
Because it´s a 6250...
Overlooked this, now I´ve ordered the right one - and another part which is wrong:
PS1....
In my "old" BOM its a single 15V, we need a dual 15V...

Mouser-Nr.:490-PEME2-S5-D15-S  is the right one(if you don´t have your BOM updated @Josh)

Martin

[KungFuJosh]

Did it today..
No anormalies....Wait a minute..
Why do I measure 2.5V on the output of the MAX6350
Because it´s a 6250...
Overlooked this, now I´ve ordered the right one - and another part which is wrong:
PS1....
In my "old" BOM its a single 15V, we need a dual 15V...

Mouser-Nr.:490-PEME2-S5-D15-S  is the right one(if you don´t have your BOM updated @Josh)

Martin

You didn't order 700-MAX6350CSA for the 6350? That's what's on the BOM.

If the single output is wrong, then the original downloaded BOM is wrong too. The BOM that comes with the kit says "IH0515SH" - which is single output. Are you sure about that part change? Did you also verify the footprint?

Thanks,
Josh

[Martin72]

I know now what went wrong...
The MAX I´ve googled instead of using the BOM, the link to mouser brings you to the 6250 - Although in my search I´ve typed 6350...
Thank god the 6350CSA+ is avaible.
(There is also a 6350CSA+T, with 0.5ppm/C° avaible, but with a smaller package.)

Are you sure about that part change? Did you also verify the footprint?

Absolutely.
Look at my post, the pic:
https://www.eevblog.com/forum/testgear/elektor-voltage-current-calibrator-project/msg5094678/#msg5094678

Plus the op-amps on this board are needing a dual-supply(output of the reference is +/-10V)

Martin

[KungFuJosh]

Oh well, the original BOM screwed us again. Well, mostly you since I didn't order shit yet. 😉

[Martin72]

If you wait a little longer to run my reference, we'll have all the bugs worked out.
My loss, your gain.

[tautech]

If you wait a little longer to run my reference, we'll have all the bugs worked out.
My loss, your gain.

Martin the guinea pig. 
Having trouble with that image now......

[Martin72]

 

Someone has to do it...

[KungFuJosh]

If you wait a little longer to run my reference, we'll have all the bugs worked out.
My loss, your gain.

That was always the plan. 😉😉🤣🤣🤣

[Andreas]

Why do I measure 2.5V on the output of the MAX6350
Because it´s a 6250...

Hello,

Shure?

the MAX6250 is also a 5V reference. (with 2 ppm/K)
The 2.5V versions are MAX6325 or MAX6225(A).

I would check the supply voltage of the reference on Pin 2. (Minimum 8V necessary).

with best regards

Andreas

[Martin72]

It works !!

Soldered up the DAC at work today, then took it home and plugged in the display and runs right out of the box.
+10V/-10V, 0-40mA, no problem...Very good.
Quick and dirty set up, took a few pictures.
Soon there will be nicer pictures....
But the main thing is that it works already.
@Andreas:
Yes, that was completely the wrong one, I was wrong, it was a 6225....

[KungFuJosh]

Awesome!

So it seems to be accurate only within 3 digits, or your meters are. I'll assume the meters are more accurate. Are you going to have it calibrated? Does it have full adjustment settings?

[Martin72]

Hi,
I just put it into operation for the first time, without any other actions.
These will follow when the board, heater and display have been moved into the case.
I first wanted to know if it works at all....

[skander36]

Hard to compete with Ian's reference.
On Mouser using BOM from Josh the price is 366.67 E. And this is without hammond box, and pcb (which I have them ordered about two years ago when I try to start building the project but stoped because of the lack of DAC on market).
At about the same price you get a ready calibrated and very stable source with PDVS2 mini.
Also this project need calibration with a metrology grade tool.
Just DIY spirit justify spending so much for this project.

[Martin72]

Just DIY spirit justify spending so much for this project.

Exactly. And I still have fun doing it.
Apropos hammond housing:
I must have got a copy, which is rather too narrow in terms of dimensions, because a few components threaten to collide with the grooves ... I'll have to think of something else.

[skander36]

...
Exactly. And I still have fun doing it.
...

I think this is the spirit

When I ordered I used the code from the project (HAMMOND 1455J1201BK) but is the same situation. I think the problem is from pcb design, the author should've leave a clearance between the metal case and the component zone, 2 more mm would be enough.

[Martin72]

I have taken the information about calibration and the benefits of the heater from the website and put it into a text document.

Edit:

but stoped because of the lack of DAC on market).

The DAC is available again.
It was before, but the "very cheap" version is somewhat "worse" in terms of performance.
The same with the voltage reference, Max6350 is not equal to Max6350.
The CSA+ type is the one with the 1ppm, others are above, one has 0.5PPm (CSA+T).
Then the OP amps, "A" grade is in this case the "worse" variant, I have all in "B" grade.
Then I will soon look for a permanent place for the board and keep it in operation for more than a month...

[KungFuJosh]

Don't believe my old attachment BOM without verifying first. I'll export a new one eventually.

Yes, it's 100% the spirit of DIY that makes this project desirable. My $20 AD584L voltage reference covers my needs in reality.