IDX-PRO+VDI

[ashefr10]

Hy Edouardo , I notice that on your pcb r26 resistance is 470 ohms, I have used a 47 ohm as mentioned in the partlist. what is the best value among these 2 resistors? thank you

[golfnut]

Hy Edouardo , I notice that on your pcb r26 resistance is 470 ohms, I have used a 47 ohm as mentioned in the partlist. what is the best value among these 2 resistors? thank you

Hi, I think the 47 ohm is what is on my kit. It enables the user to set a lower Threshold to detect.

S

[eduardo1979]

The resistance value depends on the gain of the comparator (LM393). There comparators with little gain and it takes a lower value for the resistance of 470 ohms. I use a 1K trimmer and so you can adjust the desired gain. I have also removed two 1N4148 diodes. Eliminating these diodes, I noticed considerable improvement discrimination. I deleted the 10K trimmer Phase I and replaced by a fixed resistenia 2k2, which is how I work best. I have also resistance 1M substituted by one of 2M2 and thus get something more sensitivity. All this is based on testing and testing.

[reiv]

Hi Eduardo I have done Yours update to PCB idx. But in my case now is worse than before. Masking is really worst, for example rusty nail with 20mm diameter coin before gives me nice strong signal, now is silence. Please check it in Your IDX maybe it is not just my. Ranges are the same, sensistivity I think is stronger, but i don`t know if it`s a bonus beacuse now is unstable, my R25 is about 800Ohm.
Regards

[ashefr10]

hi Edouardo , I leave a video of preliminary small problem I meet the threshold for permanent sound. maybe that is the environment in which I use the detector. can you help me thank you. This pics is Rx signal

[ashefr10]

http://www.youtube.com/watch?v=BH1s4weggVk

[eduardo1979]

hi Edouardo , I leave a video of preliminary small problem I meet the threshold for permanent sound. maybe that is the environment in which I use the detector. can you help me thank you. This pics is Rx signal

For threshold tone discrimination mode, you have to eliminate the resistance of 470 ohms, and connect a 4K7 resistor between pins 6y7 of U4 (LM393). This way you will get a nice tone threshold discrimination mode. The threshold tone level is adjusted with the potentiometer sensitivity. Greetings. Eduardo.

[ashefr10]

ok ,but where is the resistance of 470 ohm? I have a 47 ohm resistor
R25

[golfnut]

R26

[eduardo1979]

ok ,but where is the resistance of 470 ohm? I have a 47 ohm resistor
R25

47 ohms resistor. (R25).

[ashefr10]

R26 is the resistance of 100 ohms on my card and not 470 ohms.

[golfnut]

Hi, your detector is oscillating - this can be from using long wires to the GEB and DISK pots. You may need to get a better NULL, 100mV isnt great.

Check there is no metal beneath test bench.


You may have phasing issue from Tx sig to Rx sig - often the delta betwwen these two is quoted as 20degrees or less.


In PP it can be noisey with the pot turned high.


S

[eduardo1979]

[ATTACH=CONFIG]24036[/ATTACH]R26 is the resistance of 100 ohms on my card and not 470 ohms.

47 ohms resistor. (R25).

[ashefr10]

For values of R24, R25 and R26 I put values on the pcb as in pics

[ashefr10]

What voltage should I have for nulling? 4 mV?