Elektor Voltage Current Calibrator Project

[KungFuJosh]

Well, I ordered the PCBs. 🤦

[Martin72]

Well, mine arrived today..

[Martin72]

Here's both again. Hopefully it works this time. They both need verification for quantity and part accuracy. As mentioned previously, reference numbers were not all correct in the original BOMs.

Tested it a few minutes ago by importing the main list into my mouser account.
Batteypack won´t be avaible for me(my region), display won´t be avaible (only for OEM)...
This was the first test, tomorrow I´ll check your list completely.
Display I must get from somewhere else, the housing I like to have it in silver.

[KungFuJosh]

Here's both again. Hopefully it works this time. They both need verification for quantity and part accuracy. As mentioned previously, reference numbers were not all correct in the original BOMs.

Tested it a few minutes ago by importing the main list into my mouser account.
Batteypack won´t be avaible for me(my region), display won´t be avaible (only for OEM)...
This was the first test, tomorrow I´ll check your list completely.
Display I must get from somewhere else, the housing I like to have it in silver.

Here's the LCD direct from the manufacturer: https://4dsystems.com.au/products/ulcd-35dt/

For the regular enclosure, just remove the BK color from the model name: https://www.mouser.com/ProductDetail/546-1455J1202

The battery is uncertain based on size anyway. You might be able to get the original battery from the original BOM (wasn't available to me here in the US).

[Martin72]

Damn....I think I´ll order the parts next week....

[KungFuJosh]

Damn....I think I´ll order the parts next week....

Me too. I had to stop myself from ordering them a couple times already lol. But I think I'll have my PCBs on Monday. We'll see how patient I am.

[Martin72]

We'll see how patient I am.

I felt the same way.
First wait, but then the boards were there and now...crap.

[Martin72]

Made the order by mouser.
Without housing (can get it cheaper), display, battery, 4mm jacks, several ICs (not in stock) and one resistor (not in stock).
All in 156€...
Hint : The AD5791 will be avaible soon (August) by Digikey

Edit:
Missing parts:
MCP1501T-33E/CHY (11/23 in stock (Digikey) )
MAX6350CSA+ (CSA: 1ppm tolerance) (09/23 in stock (Digikey)
AD8676 (11/23 in stock (Digikey) )
AD5791 (08/23 in stock (Digikey))
Vishay 100Ohm 0.02% 0.2ppm (in stock by digikey)

[KungFuJosh]

Oh yeah, I forgot to add that $17 resistor. I was planning to find a less expensive but same spec resistor, but I don't think that's gonna happen. 🙄 Oh well. I added Y1625100R000Q9R to the project.

The rest is on the list, but backordered. I have a separate project for the backordered stuff to keep ordering simple. 😉

[Martin72]

So, display, housing and banana  jacks ordered, that´s enough for now and this month.
Forget to order the heater-pcb...Will do it plus ordering the 3D print parts.
Then I´ll have a pause because of the missing semiconductors.
Good..

[KungFuJosh]

Well, mine arrived today...

[Martin72]

Ah, in fancy brown style..

[KungFuJosh]

It's actually black, that's the lighting playing tricks. Now that I've got it, I paid more attention, and I'm not happy about the micro USB jack. I want to do it with USB-C. I know it's just for charging, but I hate paying attention to micro USB cables.

I'll probably see if I can bodge a charging only USB-C port to it. I think I have enough PCBs to experiment. 🤷

Edit: Who am I kidding, I'll just order a new board version with a USB-C charging port for $10 when I order other stuff. 😉

[KungFuJosh]

Forget to order the heater-pcb...Will do it plus ordering the 3D print parts.

If you don't rush, I can send you the gerbers when I'm done changing it to USB-C power jack, and seeing if there's anything else that needs attention. There were a couple warnings when updating the PCB from schematic.

I'm glad I saw that line about 3D printed parts, I totally missed that. Oops.

[Martin72]

Hi,

The housing has already arrived today, looks well made, nice.

BUT:
The board does not fit, it is a tad too wide, maybe 0.8mm ...
This is just to warn you (and others) about reordering the boards.
Sure, you could go ahead and grind one side of the board, but I think that's a bit uncool...

[KungFuJosh]

That's a minor issue. There are some small variances in the posted dimensions between the different colors of those enclosures. I haven't looked closer than that.

I won't change the PCB dimensions right now because the alignment to the screen is more important than the chassis dimensions, and you either need to trim both sides the full variance amount, or figure out where the dimensional change needs to be made to stay consistent with the LCD mounting.

Well, maybe trimming 1mm off both ends of the board is okay. I'll look at it, I'm working on it anyway.

BTW- there are BOM discrepancies between what KiCad exported and what was supplied with the kit. I'm making a PCBA BOM now to see what small stuff I can get out of the way, and if it's worth it or not.

[KungFuJosh]

In the BOM, R16 is 100Ω, but on the PCB R16 is 1kΩ. I read the article page, and the original BOM is wrong, the schematic is correct. Also, the schematic was lazy. They wrote 1k but didn't include that it needs to also be 2ppm/C or better.

[Martin72]

So R16-R20 must have it..OK, thanks for checking this 

[KungFuJosh]

So R16-R20 must have it..OK, thanks for checking this 

Yup. When a set of resistors needs to have a specific temp co, then all of the resistors in that group need to match. Or so I'm told. 😉

[Martin72]

They told you that right.
OK, then I have to get a 1k resistor of the same kind.
https://www.mouser.de/ProductDetail/TE-Connectivity-Holsworthy/RU73X2A1K0LTDF?qs=CXI0wBT1M2iYnqPwpNKfVg%3D%3D

[KungFuJosh]

They told you that right.
OK, then I have to get a 1k resistor of the same kind.
https://www.mouser.de/ProductDetail/TE-Connectivity-Holsworthy/RU73X2A1K0LTDF?qs=CXI0wBT1M2iYnqPwpNKfVg%3D%3D

lol, no, a friend of mine. I'm designing another circuit, and we're using an LTC6090, and he made sure to point that out about the tempco. 😉

I updated and verified my BOM vs. the schematic, and yes, that's the correct resistor. Nothing should be missing, but there might be something extra. 🤷

[Martin72]

Btw, here the evaluation board with LTZ1000 reference:

https://www.digikey.de/de/products/detail/analog-devices-inc/EV-LTZ1000-REFZ/8598410

And here the very interesting User guide :

https://www.analog.com/media/en/technical-documentation/user-guides/eval-ad5791sdz-ug-1152.pdf

It is already quite similar.
But maybe you can hardly do it any other way....

[KungFuJosh]

I updated my Mouser project again. AD8676 was the wrong size. All of them are backordered, so you probably didn't order it yet anyway. 😉

[Martin72]

AD8676 was the wrong size.

I have already fallen for it in 2 other projects, the components arrive - Mehhh...wrong design, does not fit by any stretch of the imagination, reorder again...Annoying.

[KungFuJosh]

AD8676 was the wrong size.

I have already fallen for it in 2 other projects, the components arrive - Mehhh...wrong design, does not fit by any stretch of the imagination, reorder again...Annoying.

I know the feeling. I did warn you about parts needing to be verified though. I have JLC part numbers for almost everything now too. Unfortunately, most of it is only on their extended parts list. I might see about preordering stuff so they can assemble what's available.