BARACUDA-Legend-1

[Deghbar613]

Hi Deghbar613,

If you want to use a CD4066, you'll also have to change the timing circuit. This can have further effects on the entire circuit. It's really not worth it. I would use the original FETs, as we know they work perfectly. If you want to improve the circuit, I would use a good coil. There's a guide for a fast coil in the Geotech forum. Take a look at it. That's probably a better way to improve the detector than replacing the switches.

Thank you GeoMax for the advice, I will follow it
I am grateful for your help

[GeoMax]

Hi Deghbar613,

If you want to use a CD4066, you'll also have to change the timing circuit. This can have further effects on the entire circuit. It's really not worth it. I would use the original FETs, as we know they work perfectly. If you want to improve the circuit, I would use a good coil. There's a guide for a fast coil in the Geotech forum. Take a look at it. That's probably a better way to improve the detector than replacing the switches.

[Deghbar613]

Hello Deghbar613,

check the data sheet of the CD4066. The control voltage has a big range but it is always positive. The control voltage from the CD40106 how it is connected in the circuit is negative.

you are right
so i forget to use 4066 or there is other way to use it

[GeoMax]

Hello Deghbar613,

check the data sheet of the CD4066. The control voltage has a big range but it is always positive. The control voltage from the CD40106 how it is connected in the circuit is negative.

[Deghbar613]

Hello,

Run your tests, but they won't be successful because your circuit has a design problem. When Detectorist#1 and I discussed another topic, we spoke about your Baracuda problem as well, since it was related. He highlighted that you can't simply replace the FETs with a CD4066 because the FETs require different control than a CD4066 to switch. Your problem is mostlikely that your CD4066 isn't being driven correctly by the timing circuit.

HELLO GeoMax
my cause of changing FETs is what Carl write in his book (Inside the Metal Detector)
he said

[GeoMax]

thank you so much Carl for you usefull help
i will try some tests

Hello,

Run your tests, but they won't be successful because your circuit has a design problem. When Detectorist#1 and I discussed another topic, we spoke about your Baracuda problem as well, since it was related. He highlighted that you can't simply replace the FETs with a CD4066 because the FETs require different control than a CD4066 to switch. Your problem is mostlikely that your CD4066 isn't being driven correctly by the timing circuit.

[Deghbar613]

I would have expected a little less target depth but it sounds like the circuit is working.

thank you so much Carl for you usefull help
i will try some tests

[Carl-NC]

what do you think about my test result ?

I would have expected a little less target depth but it sounds like the circuit is working.

[Deghbar613]

The schematic in post 1661 has U8 at the bottom, CD4066.

yes you have right
it's my fault i changed it for that i didnt find it in new one

what do you think about my test result ?

[Carl-NC]

i did what you told me and the result is i get a minimal response the coin before i catch it at 30cm on the air but now is 12cm and no response on ceramic magnet other thing main sample and EFE is 11.8us

It sounds like things are working as they should. Originally, did you try adjusting R21 to cancel EFE?

[Carl-NC]

you said : If you are getting a good response then either U8 is faulty
U8? there is no U8

The schematic in post 1661 has U8 at the bottom, CD4066.

[Deghbar613]

The preamp output looks good, the sampling pulses look good assuming the pulse widths are matched. That's what R21 is for, to trim the EFE pulse width to match the main sample width. You should adjust this while waving the ceramic magnet until EFE is canceled.

If you cannot get an EFE null by adjusting R21, then here is something else to try: remove C13 and short U4-pin13 to U4-pin11. This will cause both sampling switches to sample at exactly the same time with exactly the same width, and should cause any target -- even a large piece of metal -- to have a very minimal response, or none at all. If you are getting a good response then either U8 is faulty of there is a problem with the components around U6. If you do get a minimal response then R21 is not correctly adjusted or it is not EFE.

i did what you told me and the result is i get a minimal response the coin before i catch it at 30cm on the air but now is 12cm and no response on ceramic magnet other thing main sample and EFE is 11.8us

[Deghbar613]

take Quaoshi-George's layout, it's free. this your board is a trash... desolder it.
right trassing is HUGE SCIENCE chapter in electronics, no so you draw like you want.
i give you example of WHITE'S COMPANY pcb layout.

THX kt315 for the advice
I'm determined to learn the hard way. I have a lot of trash here, and it's what gives me experience

[Deghbar613]

The preamp output looks good, the sampling pulses look good assuming the pulse widths are matched. That's what R21 is for, to trim the EFE pulse width to match the main sample width. You should adjust this while waving the ceramic magnet until EFE is canceled.

If you cannot get an EFE null by adjusting R21, then here is something else to try: remove C13 and short U4-pin13 to U4-pin11. This will cause both sampling switches to sample at exactly the same time with exactly the same width, and should cause any target -- even a large piece of metal -- to have a very minimal response, or none at all. If you are getting a good response then either U8 is faulty of there is a problem with the components around U6. If you do get a minimal response then R21 is not correctly adjusted or it is not EFE.

you said : If you are getting a good response then either U8 is faulty
U8? there is no U8

[kt315]

take Quaoshi-George's layout, it's free. this your board is a trash... desolder it.
right trassing is HUGE SCIENCE chapter in electronics, no so you draw like you want doing just trash on finish.
i give you example of WHITE'S COMPANY pcb layout.