Elektor Voltage Current Calibrator Project

[mwb1100]

I couldn't tell if you got the programming cable situation straightened out.  If not, 4dsystems has detailed schematics for the uUSB-PA5 which is a small PCB version of the programming cable.

  - https://resources.4dsystems.com.au/datasheets/accessories/uUSB-PA5/

The schematic shows that the RESET pin of the programming cable is controlled by DTR through a transistor.  If DTR is asserted (5V) then the RESET pin is routed to GND.  So I don't think you'll be able to just use an off-the-shelf USB-to-TTL serial cable.  You certainly can't use a serial port that's using RS232 voltage levels.

[Martin72]

Today the digikey order arrived, except the MAX6350 and AD5791 "of course".
But they will be delivered later, if in stock - So I can not forget about them.
I don't have to worry about the two AD8676 anymore, thanks to a very nice user.
So today the missing resistors and capacitors arrived.
C33 is now a foil with 1µF.
The resistors look quite unspectacular, for that they were so expensive.
The 100 Ohm (R10)with 0.02% tolerance and 0.2PPM Tempco has very narrow solder joints, the 1K (R16) in 0805 case and with 0.01% tolerance looks like any other.
And I'll take the board to work again tomorrow, there is one more component after the L1/L2 and USB port that I can't solder at home:
U3... (because of the exposed metal back)
Hopefully it will work tomorrow, I wanted to solder at home this weekend what I already have.

[Andreas]

Today the digikey order arrived, except the MAX6350 and AD5791 "of course".

AD586L or MAX6250A play in the same ball park as MAX6350 (especially if the heater option is populated).
After my experience the AD586 has better long term stability than the MAX references. (at least in DIP8 package).


with best regards

Andreas

[Martin72]

Thanks for the tips and hints, I will keep them in mind.
The current project is well advanced, I have all the components except the reference and the dac IC, I have the board with appropriate layout, I will finish accordingly and see how it performs.

[KungFuJosh]

And I'll take the board to work again tomorrow, there is one more component after the L1/L2 and USB port that I can't solder at home

You don't have hot air or an SMD PCB heater?

[Martin72]

No Sir..
At work we have reflow, infrared, damp heat, etc., so I don´t need cheap solutions at home which could damage the part easily.

[KungFuJosh]

It's not usually the solution that damages the part. 😉

[Martin72]

With the cheap hot air stations or these homemade reflow ovens, it's simply a gamble and not a solution and as long as I have access to proper tools, I'll use that.
The colleague had already soldered the chip today, so I could take the board home again.
Earlier I have first marked the positions, pin 1 of the ICs, anode of the diodes, plus of capacitors ...
Today also the USB to serial converter arrived(a second, the first order was getting "lost"..)
Would have been nice, there would be a small drawing of what exactly you can do with the small switches...

[mwb1100]

Would have been nice, there would be a small drawing of what exactly you can do with the small switches...

I found these diagrams which should get you going:

[Martin72]

Today I wanted to solder all ICs that I already have here, that worked so far well until I opened the bag where U7 is packed inside:

[KungFuJosh]

Today I wanted to solder all ICs that I already have here, that worked so far well until I opened the bag where U7 is packed inside

Hmmm, that sounds familiar... 😉

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.

[JohanH]

Today I wanted to solder all ICs that I already have here, that worked so far well until I opened the bag where U7 is packed inside:

If that's SOIC vs TSSOP you might be able to bodge it in an emergency. If pinout is the same. Bend up corner pins. Solder the center four pins. Then four small wires for the corner pins. I've done something like that once.

[Martin72]

Hi,
I had already thought about that and I will do the same for another project (curvetracer).
But not for this one, especially since the chip is abundant, even in the SOIC housing.
But I am currently collecting something that I can still order, just the IC alone hardly makes any sense.

[DavidKo]

You can modify the PCB to accept both IC packages on another side seems to be place. You only need to order new PCB .

[KungFuJosh]

This appears to be the correct package: https://www.mouser.com/ProductDetail/584-AD8276BRZ

I'm gonna look over those chips and update the BOM. I already updated my project.

[KungFuJosh]

AD5791 BOM says SSOP, all versions in reality say TSSOP.

PZT2222AT1G is the model specified, but mouser says SOT-23-4, and shows SOT-23-3 in the photo (3 pin is correct). 🤷

I updated the BOM again (attached).

One other part number was off, but I don't know if that matters or not. It said 2N7002-T1-E3 instead of 2N7002E-T1-E3.

As I said before, this is still not fully verified. 😉

[Martin72]

Heater pcb finished - And it works.
Initial (and max) current appx 257mA, then falling, rises again when the pcb is getting "colder", so the regulator circuit is ok.

[Martin72]

I have now tried the adapter - With zero success.
Does a RESET signal really have to be present, or have I already destroyed the module before, that is the question.
What is good:
The adapter has the DTR signal out as a pin, so you could put the reset circuit in between.
For this you would have to know what values the RC part has and if the transistor is a PNP or NPN type.
It's a pain in the ass to spend almost 40€ for the original programming adapter, but if I don't get further tomorrow, I will order it.
And if it works then, examine the adapter more exactly and make it public, so that others do not have to spend the money.

[BmaxTom]

I used the Waveshare FT232 TTL module and connected it to the original programming adapter as follows. The green wire is the DTR signal. I set the voltage level to 5V. With this it worked for me.

[BmaxTom]

I've only just found this thread. I built the Elektor Voltage Current Calibrator about half a year ago.

If the original circuit boards are used, the components on one side are too close to the Hammond housing and can cause a short circuit.

[Martin72]

Hi Tom,
Glad to hear that you already did it 
Isolation:
Yepp this is known, I´ll isolate the edges with capton foil when assembling the board into the housing*.

Display:

I made it...
I wondered why the RX/TX leds on the adapter never blinked when the program scanned the port.
So I connected my scope to the channels and lo and behold, nothing...Nothing at all.
Either the adapter is defective or the configuration was not right yet.
It was the latter....the DIP switch must be set as shown in the picture, then it works.
(thanks again to mwb1100 for the diagrams, it must the first configuration.)
So you don't have to buy an expensive adapter from 4D systems...Very good.
Now I have to buy a micro SD card.

*) If everything goes well afterwards, I will probably take another housing.

[Martin72]

Mouser now have the MAX6350CSA on stock again, order it and the U7 in the right package..
So the AD5791 DAC is the only thing missed, will be in stock in september, october.
But like the other ICs from AD, there are at least two types, A-grade and B-grade.
Where B-grade have the "better" specs in some cases.

[Martin72]

Now I have to buy a micro SD card.

Arrived today, I then formatted it to FAT16.
What I then need to figure out is which files need to be saved to the SD card and which (or which) file is intended for programming the diablo processor.
At the moment I think that the content of the USD_files folder belongs on the card...
I will try the days, what belongs to what.

[KungFuJosh]

The Software folder with the En_course subfolder is the software that would get programmed with the WORKSHOP4 4D Systems programmer software.

The USD_files folder is what goes on the microSD card.

[Martin72]

Sounds logical, we'll see.