PI CHIP

[6666]

mickstv
did you get this project working ?

[mickstv]

mickstv
did you get this project working ?

Hi 6666, Yes I've got the processor section finished and programmed I used PICkit 3 programmer. Now all I have to do is build the front end then start experimenting.






Mick

[6666]

Hi Mick
great job
I will be interested to see which front end you select to make,
moodz said somewhere that the Goldscan Circuit works
but I dont have that schematic, the unisurf looks ok to,
but untested.

[mickstv]

Hi Mick
great job
I will be interested to see which front end you select to make,
moodz said somewhere that the Goldscan Circuit works
but I dont have that schematic, the unisurf looks ok to,
but untested.

This particular back end won't work with the Goldscan because I only have two sample points and the Goldscan needs four. I could use it with HH or SurfPI though. Or I could also try Moodz Diff front end then into a 4066 and comparator and see how this Diff front end works.

What does Moodz think of the last idea ?



Mick

[moodz]

This particular back end won't work with the Goldscan because I only have two sample points and the Goldscan needs four. I could use it with HH or SurfPI though. Or I could also try Moodz Diff front end then into a 4066 and comparator and see how this Diff front end works.

What does Moodz think of the last idea ?



Mick

Already on it ... the dpsic30F4011 code is already built ... just needs testing. This adds more buttons and 4 sample pulses S1 S2 S3 S4. I will post some results.

Give the Diff front end a try in surfpi config as a starter ... I was going to go onto that next but happy to work with everyone .... mostly if you find bugs or need more features tell me and I will try to fix. Also opinion on whether the chip should use crystal oscillator instead of internal clock would be good too.

moodz.

[mickstv]

Already on it ... the dpsic30F4011 code is already built ... just needs testing. This adds more buttons and 4 sample pulses S1 S2 S3 S4. I will post some results.

Give the Diff front end a try in surfpi config as a starter ... I was going to go onto that next but happy to work with everyone .... mostly if you find bugs or need more features tell me and I will try to fix. Also opinion on whether the chip should use crystal oscillator instead of internal clock would be good too.

moodz.

Hi Moodz, I should have a rough front end done over the weekend and will post up some pictures and results.



Mick

[mickstv]

Hi Paul, Just need to do some checking I built up a rough detector similar to the schematic you posted using a NE5534, 4066 and a comparator IC anyway all the timing seems to work and I can see voltage change on the output of the comparator but no change on the output of the pic and no signal change on display. Just won't to check that pin 5 is the ADC input as per the schematic you posted.




Mick

[moodz]

Hi Paul, Just need to do some checking I built up a rough detector similar to the schematic you posted using a NE5534, 4066 and a comparator IC anyway all the timing seems to work and I can see voltage change on the output of the comparator but no change on the output of the pic and no signal change on display. Just won't to check that pin 5 is the ADC input as per the schematic you posted.
Mick

Mick check the button inputs for normal operation these should all be pulled up to +5 volts. Pressing a button should pull low. However all should be high for normal operation

Check the supply and grounds to the analogue pins on the chip ... the logic could be working OK but there could be a power fault on the analogue section ... check ref in pins also for 0 and +5 volts.

If you can dump a screen from the serial uart tool for the Pickit .... 9600 baud.

paul.

[mickstv]

Mick check the button inputs for normal operation these should all be pulled up to +5 volts. Pressing a button should pull low. However all should be high for normal operation

Check the supply and grounds to the analogue pins on the chip ... the logic could be working OK but there could be a power fault on the analogue section ... check ref in pins also for 0 and +5 volts.

If you can dump a screen from the serial uart tool for the Pickit .... 9600 baud.

paul.

Hi Paul, I'll check all the connections again the pull up resistors and post back tomorrow. I Don't think the uart tool works with PicKit 3 but I'll check that also.



Mick

[mickstv]

Hi Paul, found problem number one I made a mistake with two of the 10 k resistors had them going to gnd instead of 5 volts. Then whilst working on the front end I somehow killed the processor chip it only comes up with rubbish on the screen, i erased the chip and reprogrammed but still the same. I had a second IC which I put in and it functioned ok.


Next problem to work out what the problem is with the front end as I only have shallow depth on big objects.



Mick

[moodz]

Hi Paul, found problem number one I made a mistake with two of the 10 k resistors had them going to gnd instead of 5 volts. Then whilst working on the front end I somehow killed the processor chip it only comes up with rubbish on the screen, i erased the chip and reprogrammed but still the same. I had a second IC which I put in and it functioned ok.


Next problem to work out what the problem is with the front end as I only have shallow depth on big objects.



Mick

Hi Mick, the ADC expects to see an increasing voltage for a target .. check polarity of target signals from the diff integrator if that's what you are using. I'll put up the damping code and circuit so you can tweak the coil damping for optimal setting.
Moodz.

[mickstv]

Hi Paul, what I'm actually using is a OP37 into a 4066 and LM358 as the diff integrator. I actually suspect my problem might be timing, after going back through previous posts I missed some info. Which if I read correctly suggests for instance that if I have a 100us TX and I want to sample at 15us then the S1 start sample would have to be at 115us. I hope that is correct.

The coil damping option sounds interesting another good option to test after I get this frontend finished.



Mick

[moodz]

Hi Paul, what I'm actually using is a OP37 into a 4066 and LM358 as the diff integrator. I actually suspect my problem might be timing, after going back through previous posts I missed some info. Which if I read correctly suggests for instance that if I have a 100us TX and I want to sample at 15us then the S1 start sample would have to be at 115us. I hope that is correct.

The coil damping option sounds interesting another good option to test after I get this frontend finished.



Mick

Mick .. you got it ..everything is referenced from Tx ON not OFF .... that would mean you must have ben sampling during TX on.

Moodz

[mickstv]

Hi Paul, I've had no luck getting good range yet so I might wait and see what your schematic is like, then have another go at it.




Mick

[moodz]

Hi Paul, I've had no luck getting good range yet so I might wait and see what your schematic is like, then have another go at it.


Mick

Sorry to hear that Mick ...are you sampling at 15 us ? ...... I am working on the frontend blocking FETs at the moment. Ferrous / non Ferrous descrim is working really well .... I am trying to work out how to encode the descrim AND the target ( yes / no ) in the audio channel.

moodz.