DIY Scanner Card for DAQ6510

[KungFuJosh]

Correct. Schematic attached.

Thanks,
Josh

ETA: Outdated schematic removed.

[voltsandjolts]

I think R2 should go pin7 to VCC, not to GND?

[KungFuJosh]

I think R2 should go pin7 to VCC, not to GND?

C150 + R2 are in parallel as noted. You can see the traces in the photo.

U14p16 goes to VCC.

Thanks,
Josh

[voltsandjolts]

Hmm, OK, thanks.

Looks like your schematic is just about complete, nice!

[KungFuJosh]

I removed some errors (duplicate IDs), and added the missing connections (or lack thereof).

Please let me know if there's anything else needed. I'm going to look at the remaining random stuff (mostly on the back).

Thanks,
Josh

ETA: Outdated schematic removed.

[KungFuJosh]

This might be complete now. I added missing components from both sides of the board. I don't think there's any missing parts now, but, ya know. I have no idea if there are any missing connections. 🤷

Thanks,
Josh

ETA: Outdated schematic removed.

[Kleinstein]

The resistors R62 and R63 don't make that much sense, at least not with the given values. An in circuit measurement could well give a wrong values.
The circuit around the 2 non latching relays also looks odd - there should be supply connected to the pin 12 side, not just via the diodes and Vdriver. So maybe R62/63 go to the other side with a lower value.
The VDD part from the 4094 should be connected to some 5 V. The capacitor values for C3,C9,C11,C14 are likely smaller as they are in parallel for decoupling. Chances are C4 is the same - it looks a lot like the upper end of C4 is connected to something, like a supply.

[voltsandjolts]

I don't think the current measurement relays are wired correctly. See the schema from the manual:
https://www.eevblog.com/forum/projects/diy-scanner-card-for-daq6510/msg5757233/#msg5757233
The idea is the current measurement channel is shorted ( e.g. CH21 Hi to CH21 Lo) by relays until the measurement is being taken, at which point the current is re-routed through the dmm. This has an unfortunate side effect of momentary disconnect as the relays switch over.

[Kleinstein]

Ideally they would use make before breake relays. However these are rare. Another option could be to have additional protection diodes before the relays, at least as an option.

[voltsandjolts]

Ideally they would use make before breake relays.

Hmm, this card has two DPDT relays per current channel. They could perhaps be wired to function as make-before-break?

[Kleinstein]

They seem to use relay contacts in parallel, to get high current carring capability. It may be possible to ogranize the contacts different: not one relay for the low side and the other for the high side, but so that 1 relay alone would work and the 2nd one in parallel. When than one relay is delayed a little, one would get a kind of make before break with only 1 contact active for the short cross over time.
Getting the delay with the latching relays can still be a bit tricky.

Another option would be to have separate relays for shortening the current paths. This would however need also a different control for 2 more relays.

As shown in the last plan, the directs short at the relays is connects between the channels. I don't think this makes sense. This are links between the pins 3 of the relays K24,25,26,27. It would make more sense to have them not connected.

[KungFuJosh]

The resistors R62 and R63 don't make that much sense, at least not with the given values. An in circuit measurement could well give a wrong values.
The circuit around the 2 non latching relays also looks odd - there should be supply connected to the pin 12 side, not just via the diodes and Vdriver. So maybe R62/63 go to the other side with a lower value.
The VDD part from the 4094 should be connected to some 5 V. The capacitor values for C3,C9,C11,C14 are likely smaller as they are in parallel for decoupling. Chances are C4 is the same - it looks a lot like the upper end of C4 is connected to something, like a supply.

R62/R63 are labeled 1370 and measure ~137Ω in circuit, so that's correct. I can't comment beyond that, as you both understand what's going on better than I do. 😉

4094 Vdd (p16) appears to be connected to VCC, nice catch.

I agree, most of the capacitance values are unreliable since they're all measured in circuit. Some of them were standard enough to be believable, but otherwise, not so much. C3, C4, C9, C11, C14 are all parallel, so I would guess closer to 40 or 50µF depending on tolerance. Unless one of my two cards are unrepairable (is there such a thing?), I won't be removing anything to measure out of circuit.

Take a look at the attached photos of the non-latching relays, and let me know if you see a trace that I haven't been able to find. That whole section is confusing, but I mapped it out pretty well...besides reversing the numbers, but that was an easy fix. 😉

ETA: Download the high-res photos in Reply #10 if you'd like a better view of the traces.
ETA2: Now that I think of it, that means C4 is also missing a connection to VCC. I'll update shortly.
ETA3: Schematic updated.

Thanks,
Josh

[Kleinstein]

From the pictures it look like R62/R63 are connected to the other side of the relay. This would also make sense: the resistors would reduce the current in hold state and Vdriver would provide extra current for engaging the relays.

[KungFuJosh]

From the pictures it look like R62/R63 are connected to the other side of the relay. This would also make sense: the resistors would reduce the current in hold state and Vdriver would provide extra current for engaging the relays.

One side of R62/R63 is direct to VCC, and VCC does not connect directly to K22/K23. The other side of R62/R63 connects to p1 as shown in the schematic. p12's lowest Ω value to either R62/R63 is the same as the value between p1 to p12 per each relay.

I still can't see or trace any connections to p12 that aren't noted. If you have another idea to check, please let me know.

Thanks,
Josh

[Kleinstein]

From the photos it looks like:
Pin 1 (up in the pictures) is connected to the diodes (e.g. CR24+CR27) and R62 or R63
Pin 12 (down) is connected to the transistor (e.g. Q50).

So the difference to the shematics is where the transistor and diodes connect.

[KungFuJosh]

Ah, nice catch...again. 😉

Confirmed, and schematic updated. Hopefully that's the last relay error. I'm guessing that mistake predated the relay reverse goof up. lol, actually, that was the only part that wasn't a mistake before it was reversed. 🤣

Thanks,
Josh

[voltsandjolts]

See attached...

Regarding the current relays, the connections circled in red don't make sense (shorting CH21 to CH22). The connections shown in blue would make more sense (shorting CH21 Hi to Lo and CH22 Hi to Lo, when those channels not selected).

[KungFuJosh]

Something is wacky there. I'll trace that section again.

[KungFuJosh]

Yup, nice catch. What's the score now? 😉

Updated schematic attached.

Thanks,
Josh

ETA: Outdated schematic removed.

[KungFuJosh]

Kicad changed U16, C30, and C31's numbers when I copy/pasted it. That's annoying. I'll post an updated schematic later, but not until I'm done reviewing stuff.

[KungFuJosh]

I've (probably maybe) corrected all the annotations. 🤷

I also added the test points and VR1 (unpopulated).

ETA: Corrected terminal connection order/orientation.

Thanks,
Josh

[KungFuJosh]

It looks like they have some interesting design choices here. Like this looks like middle-layer shielding around the terminal connections.

[voltsandjolts]

Rather than shielding, I suspect it's more likely an attempt to create an isothermal area at each channel terminal pair, to help improve thermocouple accuracy. It may also assist keeping the adjacent isothermal area (with the cold junction sensors) closer to the terminal block temperature, while maintaining electrical isolation of course.

[KungFuJosh]

Thermal pads do make more sense. The board has lots of interesting things going on for the thermal junk. 😉