IDX-PRO+VDI

[golfnut]

that was another thing I was going to mention for oscillation, which could be called chatter at a defined rate... The builds using the Lmc6484 (from my experience) are a little more prone to chatter. The builds using the LF347 seem more stable. S

[ampirate]

_____Arduino VDI Experiments SCH Instructions_p47.pdf

I think this all confused v4 v5 is not
small error above-

Pin A0 - > All metal (U3 PIN 1)
Pin A1 - > All metal (U3 Pin 14)
Ground - >Ground
+5v power source.

read number 6

http://www.geotech1.com/forums/showt...108#post147108

I am using the above Pdf attached file.
U3 p1 -> U4 p5
U3 p14 -> U4 p3
Same pins - whats the point ?

I only read about 0.1V change from these pins on the Oscilliscope - with Targets.

[onuba]

Another question :

Why does the VDI PIC Board Design use Mcp602 setup like the Lmc6484 on the IDX Pro Board ?
What is different ? Why not just use the U5 p3 and p5 as Signals to the ADC directly ?

- Why doesnt this work ? Why do these 2 signals (U4 p3 and p5) only vary less than 0.1V ?

My signals only reported :
sensorValueX = 319-320
sensorValueR = 320-324
- with and without Targets from Coins to Can.

I think this all confused v4 v5 is not
small error above-

Pin A0 - > All metal (U3 PIN 1)
Pin A1 - > All metal (U3 Pin 14)
Ground - >Ground
+5v power source.

read number 6

http://www.geotech1.com/forums/showthread.php?18958-Arduino-based-VDI!&p=147108#post147108

[ampirate]

Another question :

Why does the VDI PIC Board Design use Mcp602 setup like the Lmc6484 on the IDX Pro Board ?
What is different ? Why not just use the U5 p3 and p5 as Signals to the ADC directly ?

- Why doesnt this work ? Why do these 2 signals (U4 p3 and p5) only vary less than 0.1V ?

My signals only reported :
sensorValueX = 319-320
sensorValueR = 320-324
- with and without Targets from Coins to Can.

[ampirate]

I tried the Arduino VDI from Arduino_VDI_Experiments.pdf .

But, the U4 p3 and p5 only vary in range of about 0.1V .
So, it always reported nothing or Quarter.

It needs an OpAmp MCP602 or TL072

Also, I think the Pdf is unclear or has typo.
It states to tie the Arduino GND to IDX Pro GND - and shows this as BatV-
But this would boost the X and R to 4V as base value.

I think it should say to use OpAmps GND of 4V ,
else use a Voltaege Divider and subtract Base Value in Program as:
sensorValueX=sensorValueX-320
sensorValueR=sensorValueR-324

[ampirate]

I had to remove the Shield, when adding Coil Windings.

I did find a solution on the Internet ,
- of placing a loose Loop of Wire (like 6inch Diam) across the Coil as a Fine Tuner.
This helps a lot.

[Koala]

For the time, I will stick with 10KHz with the 16V p2p.

I have tweaked the RX cap to 27pf which gives me a 8-10inch range.

But it has horrible stability - often chirps continuously without a Target for periods
- maybe slightly swaying wires with breeze of hand or feet on floor causing slight table shake.
For example, dropping the targets on the table next to it - sometimes sets it off chirping continuously - even if I remove the Target.

Anything I should aim for - measuring the RX with the Oscilliscope ?

Possibly you are talking about chatter if you have not shielded your coil yet. I can get chatter on a un shielded coil just by blowing across the top

try for the lowest peak to peak to start with. Make sure your probes are not affecting the result measure at the detector end a easy mistake that I made once


what measurement are you getting

[golfnut]

27nF !



try ferrite reject, also take a peak at the preAMP output, make sure its not too big.



If you can reject ferrite somewhere on the geb pot travel its not ffar off. If it wont, reduce the Rx cap in 2nF steps - the aim is a bit more sens, ferrite reject.

As for stability, I have had this on a build, it got better with twisted pot, supply, speaker wires,
I have currently got thin coax on the geb pot,..

do you have un sheilded coils?

[ampirate]

For the time, I will stick with 10KHz with the 16V p2p.

I have tweaked the RX cap to 27pf which gives me a 8-10inch range.

But it has horrible stability - often chirps continuously without a Target for periods
- maybe slightly swaying wires with breeze of hand or feet on floor causing slight table shake.
For example, dropping the targets on the table next to it - sometimes sets it off chirping continuously - even if I remove the Target.

Anything I should aim for - measuring the RX with the Oscilliscope ?

[golfnut]

Easy mistake, we all have done that one.

If you have a solid 16Vpp 10kHz.

You need to make a descision now...

Stick on 10Khz machine or go for original Desgin?

[ampirate]

ok, forget tweAKING the Rx cct for now -your main issue is you TX is crap.

Your Tx supply is 8V ? should be.

Your scope is reading correct AC voltages - your probes scale 1:1 and not 10:1 take a look at the writing on your probes.

You are right ! - the darn Probe 10:1 switch was set.
The Reading is about 16V P2P.

[golfnut]

ok, forget tweAKING the Rx cct for now -your main issue is you TX is crap.

Your Tx supply is 8V ? should be.

Your scope is reading correct AC voltages - your probes scale 1:1 and not 10:1 take a look at the writing on your probes.

[ampirate]

If you got a solid Tx volts of 15vpp

No, I am reading 1V-1.5V P2P

Are you talking about the External 33nf Cap ? Yes
Small difference in capacitor value here can make a big difference to distance.

So, what range am I adjusting around the 33nF ?
What is expected as possible values for the Cap ?

[Koala]

Are you talking about the External 33nf Cap ?

Yes

Small difference in capacitor value here can make a big difference to distance.

[golfnut]

try ferrite, when you can tune it out with geb control - your phasing has to be correct.