Moodz' Awesome Gold Pulse Induction Version 3 - MAGPI V3 Project

[van0014]

You are right about the low capacitance input and generally you dont want the TX or the damping mosfet to avalanche. So a 300 volt mosfet is better than a 250 volt ...however with constant current damping the Rds on wants to be in 10s of ohms not 100s as there will be an issue as the flyback voltage decays below the IR ( amps x resistance ) point where amps is the damping current and resistance is the Rds on.
The R12 ( I am not looking at the schem ) mops up the small residual leftover damping in a linear way after the diode to ground off the source of the damping mosfet stops conduction.
There is a way to reconfigure this arrangement very simply to create an "ideal" diode off the source of the damping mosfet .... can you see how to do it ?? This will give make the active damping even faster.

An Ideal diode, well I tried, but went for an AI search. I could put a MUR160 (so I don't have to order a more suitable diode) across the (leftover damping) R12 resistor, with the cathode facing the MOSFET. Though i'm also thinking that 'damping option 2' in your original schematic could be the ideal diode setup. Your circuit is making more sense with these descriptions. I tried to understand it in the same way a standard pi circuit works, and misunderstood how the diodes and R12 behave. This will give me a few options, and I may soon be able to show a mate how comparable your design is to his '6000, but due to my mismatched components he got a 5c piece at about 25cm and I got it only by touching it with the coil. And before I told him more about your design (i'm wanting to show him this forum), he left thinking it wasn't very sensitive. He says the 6000 outperforms the 7000. I want to lend him my copy of ITMD 3, because he currently cannot understand why a detector isn't built that can go an extra foot deeper than the current technology. Though I am convinced it is more of a limitation of physics than it is electronics. So I alluded to the main limitation being coil size, but reading that book will be the best way to form an independent and accurate understanding.

[van0014]

This detector makes a nice sound, and I’d been spending an unusual amount of time just seeing how fast I could swing a (nearly 1 meter) screwdriver past the coil and still get a good signal from it. That’s how fast I should therefore be able to swing the coil, right!
I started swinging it as close as I could get without hitting it, and it makes a nice swishy sound in the air. And the speaker noise gives good feedback too. i’m having a bit of fun with this. And I know it’s not meant to be a toy and i’m in my 30s, but it really was captivating me


I’ve been getting much better results by adjusting the X sample point. Though i’m using the commander coil, setting it to 2.06 has given me really good sensitivity compared to before. I can now pick up a 5c piece at about10cm. Though the scope trace for the flyback (not shown) was still clipping or in avalanche, and I have no idea how this circuit can be operating so well and with such sensitivity if it really is still maxing out.
It’s really fun to use the scope, even if i’m not probing the right spots. Also this circuit is quite enjoyable to work with.

[AhmatAhmatov1959]

This detector makes a nice sound, and I’d been spending an unusual amount of time just seeing how fast I could swing a (nearly 1 meter) screwdriver past the coil and still get a good signal from it. That’s how fast I should therefore be able to swing the coil, right!
I started swinging it as close as I could get without hitting it, and it makes a nice swishy sound in the air. And the speaker noise gives good feedback too. i’m having a bit of fun with this. And I know it’s not meant to be a toy and i’m in my 30s, but it really was captivating me


I’ve been getting much better results by adjusting the X sample point. Though i’m using the commander coil, setting it to 2.06 has given me really good sensitivity compared to before. I can now pick up a 5c piece at about10cm. Though the scope trace for the flyback (not shown) was still clipping or in avalanche, and I have no idea how this circuit can be operating so well and with such sensitivity if it really is still maxing out.
It’s really fun to use the scope, even if i’m not probing the right spots. Also this circuit is quite enjoyable to work with.

What is the reaction to ferrite and gold. On my homemade coil with a screen resistance of 150 ohms per 1 cm, gold weighing 0.3 grams, the distance was 5 cm. I applied 2 more layers of graffite to reduce the effect of ferrite. The screen resistance became 20 ohms per 1 cm. The effect of ferrite did not decrease, and gold is not seen closely. Red brick is not seen.Aluminum foil measuring 15*15 mm is seen behind a red brick at a distance of 15 cm. I went out into the field and there is a reaction to the earth's magnetic field. It is impossible to conduct a search. I started making a basket coil. As soon as I finish, I will report the result.

[AhmatAhmatov1959]

What is the reaction to ferrite and gold. On my homemade coil with a screen resistance of 150 ohms per 1 cm, gold weighing 0.3 grams, the distance was 5 cm. I applied 2 more layers of graffite to reduce the effect of ferrite. The screen resistance became 20 ohms per 1 cm. The effect of ferrite did not decrease, and gold is not seen closely. Red brick is not seen.Aluminum foil measuring 15*15 mm is seen behind a red brick at a distance of 15 cm. I went out into the field and there is a reaction to the earth's magnetic field. It is impossible to conduct a search. I started making a basket coil. As soon as I finish, I will report the result.

I forgot to ask what chip you have, I have PIK32..150

[van0014]

What is the reaction to ferrite and gold. On my homemade coil with a screen resistance of 150 ohms per 1 cm, gold weighing 0.3 grams, the distance was 5 cm. I applied 2 more layers of graffite to reduce the effect of ferrite. The screen resistance became 20 ohms per 1 cm. The effect of ferrite did not decrease, and gold is not seen closely. Red brick is not seen.Aluminum foil measuring 15*15 mm is seen behind a red brick at a distance of 15 cm. I went out into the field and there is a reaction to the earth's magnetic field. It is impossible to conduct a search. I started making a basket coil. As soon as I finish, I will report the result.

Ferrite torus is found at about 5 - 10cm. I had been disconnecting pin 4 of the INA125P. I think normally this detector tends to cancel out ferrite

The coil resistance should be low, about 0.5 ohms and 300uH. Also it is important to tune the X2S setting to match your coil. The setting should always be set once you find thd timing that gets the best depth. It doesn’t save, but is critical to match it, and preferably use an oscilloscope. Otherwise increase it (or maybe even decrease) until depth reaches maximum

[AhmatAhmatov1959]

Please post some photos of the board top and bottom and we will try to assist.

Hello Moodz I have a PIK32MX150 chip installed. Does it work with the 2004 LCD? I connected 2 pieces and the screen lights up but they don't work.

[moodz]

which version of the firmware are you using

[AhmatAhmatov1959]

which version of the firmware are you using

MAGPI008_2023_01_28_MX150.zip

[AhmatAhmatov1959]

MAGPI008_2023_01_28_MX150.zip

Извините. Ошибся. Использую версию MAGPI008.X.productionV1.2_MX150

[AhmatAhmatov1959]

Извините. Ошибся. Использую версию MAGPI008.X.productionV1.2_MX150

Sorry, I made a mistake. I'm using the version MAGPI008.X.productionV1.2_MX150

[van0014]

I've spent a bit of time on the firmware source, and had really wanted to have a bar graph for showing the balance. And to have the encoder use interrupts. After spending many days using AI and tweaking the code, I've made something I like. Encoder doesn't feel fast, though I once had the code to a point where it did. It's not perfect, but attempts to show all useful variables while also adding a somewhat useful graph-like display.

It took me a bit of tweaking to get full sensitivity, or at least, better than before. The design is very sensitive, when build as intended. I used some slightly different parts in mine and it’s taken me a bit to work out

After spending much of my spare time trying to improve on this detector, and finally having it work nearly as good as it’s supposed to, I can appreciate something that was talked about in the book ITMD 3, where it said something like ‘shoot the engineer’, meaning it’s time to actually use it

[AhmatAhmatov1959]

I've spent a bit of time on the firmware source, and had really wanted to have a bar graph for showing the balance. And to have the encoder use interrupts. After spending many days using AI and tweaking the code, I've made something I like. Encoder doesn't feel fast, though I once had the code to a point where it did. It's not perfect, but attempts to show all useful variables while also adding a somewhat useful graph-like display.

It took me a bit of tweaking to get full sensitivity, or at least, better than before. The design is very sensitive, when build as intended. I used some slightly different parts in mine and it’s taken me a bit to work out

After spending much of my spare time trying to improve on this detector, and finally having it work nearly as good as it’s supposed to, I can appreciate something that was talked about in the book ITMD 3, where it said something like ‘shoot the engineer’, meaning it’s time to actually use it

Hello. Could you tell me what the reaction to gold is? I reflashed the 32-150 chip because it wasn't displaying the display, and I connected the coil without turning it off. The 9640 transistor immediately started smoking. I replaced all the components, but the circuit still didn't work. Instead of a TX pulse, I get a constant 2 V. I ordered the 32-250 chip; I'll test your firmware as soon as I receive it.

[van0014]

Hello. Could you tell me what the reaction to gold is? I reflashed the 32-150 chip because it wasn't displaying the display, and I connected the coil without turning it off. The 9640 transistor immediately started smoking. I replaced all the components, but the circuit still didn't work. Instead of a TX pulse, I get a constant 2 V. I ordered the 32-250 chip; I'll test your firmware as soon as I receive it.

I'm not sure what the reaction to gold is like. I had to tune my XSS. But I was also using modified firmware with too large of a Tx pulse. Now my detector seems to finally detect a large silver coin at 10cm. The last time I had gold, it couldn't detect it because my settings were wrong, and I was using modified source code. It was a tiny amount in a small container.

This is an updated version that includes a major change in audio and target response. Sine wave calculation sample array has been increased from 128 to 1024. MAGPI008_v1.4b.zip
Audio tone needs tweaking, but sounds better when increased.
ADC conversions now use interrupts instead of polling. Encoder turning needs tweaking

Auto ground balance tracking is included, as well as a different way of doing the exponential target response. Varying coil swing speeds are somewhat accounted for. The exponential rise gives reasonable responses for slow movements, and isn't quite as responsive on the faster movements. It's impressive how fast you can swing things past the coil and hear the response. The detector design is quite good. I like looking at the schematic and learning about it.

[AhmatAhmatov1959]

I'm not sure what the reaction to gold is like. I had to tune my XSS. But I was also using modified firmware with too large of a Tx pulse. Now my detector seems to finally detect a large silver coin at 10cm. The last time I had gold, it couldn't detect it because my settings were wrong, and I was using modified source code. It was a tiny amount in a small container.

This is an updated version that includes a major change in audio and target response. Sine wave calculation sample array has been increased from 128 to 1024. MAGPI008_v1.4b.zip
Audio tone needs tweaking, but sounds better when increased.
ADC conversions now use interrupts instead of polling. Encoder turning needs tweaking

Auto ground balance tracking is included, as well as a different way of doing the exponential target response. Varying coil swing speeds are somewhat accounted for. The exponential rise gives reasonable responses for slow movements, and isn't quite as responsive on the faster movements. It's impressive how fast you can swing things past the coil and hear the response. The detector design is quite good. I like looking at the schematic and learning about it.

Hello. I was wondering if you've tested the metal detector in the field? Have you found anything? How did it perform?

[IBGold]

I'm not sure what the reaction to gold is like. I had to tune my XSS. But I was also using modified firmware with too large of a Tx pulse. Now my detector seems to finally detect a large silver coin at 10cm. The last time I had gold, it couldn't detect it because my settings were wrong, and I was using modified source code. It was a tiny amount in a small container.

This is an updated version that includes a major change in audio and target response. Sine wave calculation sample array has been increased from 128 to 1024. MAGPI008_v1.4b.zip
Audio tone needs tweaking, but sounds better when increased.
ADC conversions now use interrupts instead of polling. Encoder turning needs tweaking

Auto ground balance tracking is included, as well as a different way of doing the exponential target response. Varying coil swing speeds are somewhat accounted for. The exponential rise gives reasonable responses for slow movements, and isn't quite as responsive on the faster movements. It's impressive how fast you can swing things past the coil and hear the response. The detector design is quite good. I like looking at the schematic and learning about it.

Hi Van0014,

I have not touched the Magpi for about 20 months due to illness but now you have an enabled version I re programmed it today it is one of Pauls so has all the correct components I am off to the specialist tomorrow so on Thursday I will have a play with it and report back if I can not work out the menu and how to drive it I will get back to you.

Regards, Ian.