VDI-RODERICO

[SWL]

Hello roderico! I have a question. I can’t find Pic18f25k22. Can I use Pic18f26k22 instead of 25? I have the opportunity to buy it. Thank you!

[waltr]

Hello roderico! I have a question. I can’t find Pic18f25k22. Can I use Pic18f26k22 instead of 25? I have the opportunity to buy it. Thank you!

I can answer that.
The difference between them is the F26K22 has twice as much memory so yes, the PIC18F26K22 will work. You will need to start with Roderico's Source code and create a project in MPLAB X for the 26K22 then build to produce the Hex file.

[SWL]

Oh my God.. ... it's too hard for me ... Have to study...

[roderico]

yes, the answer is exactly waltr's post. I've been looking for other alternatives to the LM336 and MCP1525 could be a good alternative, for a 3.3V I couldn't find any...

[waltr]

Roderico, Here is the Scope plot with the Furnace running. Also the X-Y plot when furnace is not running.

[waltr]

Oh my God.. ... it's too hard for me ... Have to study...

SWL,
Post which display you are using from Roderico's list and I can build the Hex file and post it for you.

It is mind bending to do this first time but very easy later.

[SWL]

128х64 ks0108.... PCB has already mocked up

[roderico]

Roderico, Here is the Scope plot with the Furnace running. Also the X-Y plot when furnace is not running.

neither was the mains nor was it noise , X and Y have ~ the same amplitude, ~10Hz and are ~90 phase-shifted, so a Lissajous curve (circle for 90) produced by the furnace

[waltr]

128х64 ks0108.... PCB has already mocked up

Ok, here is the Hex. Only code that changed is a few conditionals for 18F26K22 instead of 18F25K22.
Hope this helps.

[SWL]

Wow! Thank you very much,waltr! You saved me ... I will order the details ... Thanks again!

[roderico]

128х64 ks0108.... PCB has already mocked up [ATTACH]49310[/ATTACH]

SWL, if you have not already built your new pcb maybe it would be better to wait for the 2.5V voltage reference tests since it will replace R7 and R8. I don't have yet the MCP1525 or LM336 but maybe someone else could test it sooner...

[SWL]

Yes, of course .. I?ll wait for the results .. ..

[roderico]

I did a quick test with a TL431 as 2.5V voltage reference and it is a little more stable but the resistor divider should be fine, the flickering comes from X and Y, i.e if it does not come directly from the coil then it is generated in the path to the ADC input, e.g. some filtering might be needed, reduce the gain, etc. nevertheless the diode is a better approach IMO than the resistor divider for the Vrange/2 reference.

[waltr]

I did a quick test with a TL431 as 2.5V voltage reference and it is a little more stable but the resistor divider should be fine, the flickering comes from X and Y, i.e if it does not come directly from the coil then it is generated in the path to the ADC input, e.g. some filtering might be needed, reduce the gain, etc. nevertheless the diode is a better approach IMO than the resistor divider for the Vrange/2 reference.

Interesting. Any 'noise' not coming from the coil might be reduced with better Reference of the op-amps and ADC.
Noise coming into the coils is tougher and possibly nothing can be done to reduce it. The two differential amp stages are 'Bandpass' filters centered around 11Hz.

Did get out yesterday and away from AC Mains the ADC center values flicker about 5-6 counts. Maybe better ref, op amps, etc could reduce this but probably not worth the effort since the VDI does work rather well and has been very helpful addition to the TGSL especially in the Iron junk rich farm site.

Something I did play with is looking at the VDI numbers with varying the DISC control. At farm sites I keep the DISC nearly all the down and not DISC out foil whereas in Parks I turn the DISC up to remove foil. This does change the VDI numbers but makes sense when thinking about what the DISC does.
With the VDI one can leave the DISC below foil and note a low VDI number, ~10, is Foil. Or if turning the DISC up to eliminate foil the VDI numbers for other target decrease by about 10. Example is Brass gun shells that VDI around 38-45 drop to 28-35.
Nothing wrong here, just noting how the VDI and the TGSL (IDX would be similar) works.

[roderico]

Interesting. Any 'noise' not coming from the coil might be reduced with better Reference of the op-amps and ADC.
Noise coming into the coils is tougher and possibly nothing can be done to reduce it. The two differential amp stages are 'Bandpass' filters centered around 11Hz.

this can explain why it picked up the furnace (10Hz) and not the mains (50-60Hz), however if I remove the coil then mine picks up the AC mains (see picture)

Did get out yesterday and away from AC Mains the ADC center values flicker about 5-6 counts. Maybe better ref, op amps, etc could reduce this but probably not worth the effort since the VDI does work rather well and has been very helpful addition to the TGSL especially in the Iron junk rich farm site.

If there is a 10mV permanent signal or noise then for 5V range the ADC resolution is 5V/2^10 ~5mV then 1-2 counts for 3.3V the resolution is 3.3V/2^10 ~ 3mV then you need 4 counts. Maybe it has to due with the nulling of the coil since it is of the same order of magnitude (10-20mV)

Something I did play with is looking at the VDI numbers with varying the DISC control. At farm sites I keep the DISC nearly all the down and not DISC out foil whereas in Parks I turn the DISC up to remove foil. This does change the VDI numbers but makes sense when thinking about what the DISC does.
With the VDI one can leave the DISC below foil and note a low VDI number, ~10, is Foil. Or if turning the DISC up to eliminate foil the VDI numbers for other target decrease by about 10. Example is Brass gun shells that VDI around 38-45 drop to 28-35.
Nothing wrong here, just noting how the VDI and the TGSL (IDX would be similar) works.

there might be something wrong here, mine does not change when changing the DISC, maybe is the pot or where it is connected in the TGSL