Elektor Voltage Current Calibrator Project

[Martin72]

Hi,

The 3d printing parts I´ve ordered now from here(website only in german)

https://www.3ddesign24.de/

Well, let's see if they will also grumble because of the partial thinness, like JLPCB. 

[Martin72]

Hm-Hm...

The battery according to BOM I could not get at Mouser, had not interested me at first.
But now...
Searched and found at Buerklin:
https://www.buerklin.com/de/p/mikroelektronika/akkupacks/mikroe-1120/74S4080/

OK, 2-pin connector, that will be connector J2 on the board.
But then why the multi-pin header J1 on the board with the note "Battery Boost Option" ?
A look at the schematic reveals that something else must be connected to the connector, the battery on J2 alone is not enough.
Especially not the voltage, the 3.7V are not enough for PS1.
So an additional circuit is probably connected to J1, in the schematic it will be called "Step up charger"
But there is nothing to read about it in the documentation...

[Martin72]

Earlier glued the Heater PCB to the designated place on the motherboard, using thermal adhesive.
When it has set, the heater housing is attached.
The two housing parts were also the only thing that was in order from the delivery of the online 3d print provider.
The two front parts I have criticized, my brother with his 200 € printer would have done the same or better.
Now better manufactured come.

[Martin72]

Cured overnight, holds bombproof.
The rest is easy, soldered wires and put the housing on it.
Then switched on again, everything still runs, the area is warm and in the display is also no longer a warning message.
From the wiring diagram, the heater is supplied directly via the usb connection, past the switch.
That is, he heats even if the reference is off, which makes sense.
Next steps are the final installation in the housing and then let age.

[KungFuJosh]

Did you ever finish this? I might actually make one soon.

[Martin72]

Hi Josh,

I'm still struggling a bit with the housing.
The 3D parts that were delivered later and manufactured again are just as badly made as the first ones.
Then I wanted to install 4mm safety sockets, but there is only enough space for the normal 4mm banana sockets, which I don't like.
However, I have planned to simply run the module soon because of aging before calibration(at least for a month).
And in the meantime I might buy another, somewhat more spacious housing.

[KungFuJosh]

I dunno if you looked at my cal chart in the LCR thread, but the two voltage sets are my two different Siglent DMMs. The 3055 is the one that was high, and the X-E was the one that was in spec for the LCR. So I want to get a better reference to see which one is actually closer.

[Martin72]

I understand that and you won't be able to avoid having this reference calibrated externally, just like me.
Because it has deviations which are in the nature of things.
The manufacturer recommends a multimeter with at least 6.5 digits for calibration (I have one), but in order for me to be able to test my multimeter with it, a calibration with at least 7.5 digits would be necessary.
We have seen that the reference from the first start is certainly not as correct as it could be.
And the aging only serves the purpose of being able to take the later calibration "seriously" in the sense of not having too many fluctuations afterwards.
The benefit for you as a later rebuilder will be how accurately the reference can be calibrated.
If it can keep to the recommended 10ppm, you can start rebuilding it, otherwise I would leave it alone.
So look forward to the next few weeks with me.

[KungFuJosh]

Yeah, that's also why I'm torn between this project and purchasing an already (actually) calibrated voltage ref. This project would be the more fun option.

Edit: I just ordered the vref10-001 r9. Significantly less expensive, calibrated, and includes 2 years of free calibration. I'll wait on this project until necessity or boredom bring it on. 😉

[KungFuJosh]

I think my lazy idea to get that 10V ref is crap. I need the versatility this project has, and I still need it calibrated. So I think the first thing I'm going to do is let my 3055 run for a week or two then send that in for calibration and compare my meters. If it's still questionable, then I'll probably build this project. I'd be more inclined if the housing wasn't an issue...though I do have a friend I could bother to make the housing design better.

Right now, my X-E is more stable than the 3055.

[Martin72]

That is the current status.
The 3D parts and the cover for the display do not fit, the bolts are too thick for the openings (well, you could drill them out), overall the housing provided is very tight.
I am looking for a slightly larger housing.

[skander36]

I think my lazy idea to get that 10V ref is crap. I need the versatility this project has, and I still need it calibrated. So I think the first thing I'm going to do is let my 3055 run for a week or two then send that in for calibration and compare my meters. If it's still questionable, then I'll probably build this project. I'd be more inclined if the housing wasn't an issue...though I do have a friend I could bother to make the housing design better.

Right now, my X-E is more stable than the 3055.

With less money than you spend on this project, you can get PDVS2 mini, which is already calibrated and that has stunning stability. 
I was already tried to make this project but I have made the correct choice at the right time and I don't regret.

[Martin72]

I was already tried to make this project but I have made the correct choice at the right time and I don't regret.

We'll know if that wasn't regrettable when I get this reference back from calibration.
But yes, a finished product is of course tempting, especially when it's cheaper.
In addition to the "fun" of building it myself and learning in the process, I also found the possibility of generating a reference current tempting.
Oh, we'll see, of course I hope it was worth all the money.

[Martin72]

The housing has arrived.
Well, blue is not the color of choice, but it's not that terrible.
I got to work and created a new front panel in the front panel designer, I can upload the file to the store and get it in about a week.
I'm currently thinking about aluminum "nature" or blue...

[The Soulman]

Nice, what brand/model enclosure is that?

[Martin72]

https://www.amazon.de/dp/B0CB8GXMSB?psc=1&ref=ppx_yo2ov_dt_b_product_details

You can also get this housing from other suppliers on amazon in different sizes.
For the money, this case is neatly constructed and made mainly of metal.

[KungFuJosh]

I got to work and created a new front panel in the front panel designer, I can upload the file to the store and get it in about a week.

Hmm, that's a good point. I could make my own panels on my laser. 🤔

[KungFuJosh]

Was PEME2-S5-D15-S the part you used for PS1? Did it have 5 pins? I'm assuming that if that's the correct part, then the Mouser pictures are wrong?

Thanks,
Josh

[Martin72]

Hi Josh,

Yepp, it´s the PEME2-S5_D15-S....

Martin

[KungFuJosh]

Thanks. Mouser seriously needs to fix their images.

[KungFuJosh]

You said the Hammond enclosure was too small. In which dimension?

This is the original part number from the original BOM:
1455J1201   1455J1202   L:120   W:78   D:27

If it's too narrow, the 1455K1201/1455K1202 increases depth to 43mm. There are other options for increased dimensions: https://www.hammfg.com/electronics/small-case/extruded/1455

Thanks,
Josh

[Martin72]

Hi Josh,
The inner width of 75mm +/- 0.5mm is a very "precise fit", as the circuit board also measures 75mm.
You have to stretch the housing a little when inserting the circuit board, but of course it holds firmly.
The main problem is part of the positioning on the board, an area is a little under 3mm from the edge of the board - this can lead to collision problems, as the grooves inside the housing protrude approx. 2.5mm.
The component height of the capacitors in the area was also a problem for me, which I could only solve with a lot of "dremeln".
The 27mm depth, on the other hand, is only a problem if, like me, you want to use the larger 4mm safety sockets, otherwise not.


Martin

[KungFuJosh]

So it sounds like for the best options, I should reposition those components with proper clearance from the board edge, and switch to 1455K1201/1455K1202 for the extra depth in case I want safety sockets.

Edit: Actually, looking at my board version. I already reduced the size to 73.5mm, but I could easily shift everything down a couple mm. I think I'll slightly increase it to ~74mm, and shift everything for clearance.

[Martin72]

If the ICs weren't so expensive, I would also put my hand on the design again...
Be that as it may, I have now ordered the front panel in aluminum "natural", the blue was a bit too daring for me in terms of appearance.
The housing isn't huge, but it's big enough to be able to install a stationary power supply - maybe I will.
A little gag on the side:
Not too long ago, I was looking for an electrical load that could provide small currents precisely so that I could compare current clamps in the mA range with it - but I already have a precision current source with deviations in the µA range...LOL.

[KungFuJosh]

I changed the board height to 74mm, and increased the clearance. There's over 4mm clearance from the closest component to the edge. It's hopefully safe now for either enclosure without any "improvements." 😉

If the ICs weren't so expensive, I would also put my hand on the design again...

What else would you change?