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

[Gunghouk]

Thanks for that. I suspect the op-amp as the behavior changes with U4 in or out so the mosfet is changing state. I don't have another LM6171 will a NE5534 do temporarily?

[moodz]

Here is the Android APP and the Corresponding Firmware. ( THIS REQUIRES A HC-05 Bluetooth Module ) and the latest Schematic.
You dont need the rotary encoder or LCD.

Note that the Android app is unsigned. If you load it into your phone and it drains your bank account dont blame me.
Use an old phone ( not too old though )

I tested on first generation PIXEL and OPPO ... worked OK.
Android 10 and above ??

This is a work in progress .. your mileage may vary.


MAGPI008_2024_04_23_V1.5_DEVEL.X.production.zip
app-release-unsigned.zip

[moodz]

Hi Moodz I have a query regarding R20. At one point this went to 10Mohm but is now 10k. The reason for my question is that the TX signal at the coil does not have any flyback pulse and looks almost square wave however if I remove U4 the classic signal appears leading me to believe Q2 is permenantly off. Any ideas?
Thanks

If your flyback is missing it means something is blown ... eg Q2 or the input to the opamp U2. Does the opamp feel warm ? This can happen if too much voltage is applied or a probe in the wrong place.

R20 value can vary according to the firmware .... The flyback is proportional to the ( total ) X ie reactive load the collapsing magnetic field sees.
Kind of hard to explain in a few words but basically R20 controls the X or reactive recovery time which changes with reactive loads eg ferrites near the coil etc.

10K is a faster recovery ... 10 meg is a slower recovery.

[Gunghouk]

Hi Moodz I have a query regarding R20. At one point this went to 10Mohm but is now 10k. The reason for my question is that the TX signal at the coil does not have any flyback pulse and looks almost square wave however if I remove U4 the classic signal appears leading me to believe Q2 is permenantly off. Any ideas?
Thanks

[moodz]

GB controls are functional and SAT value added to APP.

[moodz]

Been watching in the background will get back into it when I get out of hospital hopefully the final operation is on the 23rd Cheers.

Regards, Ian.

Get better soon Ian.

[IBGold]

Been watching in the background will get back into it when I get out of hospital hopefully the final operation is on the 23rd Cheers.

Regards, Ian.

[moodz]

[moodz]

Looking good. Can't wait to give it a try

Will the HC-05 run on 3.3v or need 5v?

I have never found a HC05 ( hundreds ) that wont run on 3.3 volts and in this case it obviously works.
However 5 volts is available from the TX regulator if required.

[Gunghouk]

Looking good. Can't wait to give it a try

Will the HC-05 run on 3.3v or need 5v?

[moodz]

[moodz]

... one of the biggest issues with metal detectors is the physical weight. You have to carry it around.

Adding the LCD and rotary encoder just adds more to lug around. A 5 gram bluetooth interface is much cleaner.

Software does not weigh anything so I have reworked the Android app for the MAGPI. Coming soon ...

[moodz]

Hi Moodz is the change to D3 purely due to higher breakdown voltage or some other reason. I have a MUR460 in my box of bits with a 4A, 600v rating so presumably that would do?
Is R12 coil dependant and if so what is the selection criteria/formula?

Thanks

D3 can be almost any fast recovery diode rated for higher than 250 volts reverse and less than 1 volt forward voltage at 400 mA.
MUR160s are cheap and available ... MUR460 should work fine too.

R12 is set to "safe" value of 330 ohms .... the coil should be 300 microhenries +/- 10%.
R12 mops up the residual damping when the diode D2 stops conducting after the damping current stops flowing.

[Gunghouk]

Hi Moodz is the change to D3 purely due to higher breakdown voltage or some other reason. I have a MUR460 in my box of bits with a 4A, 600v rating so presumably that would do?
Is R12 coil dependant and if so what is the selection criteria/formula?

Thanks

[moodz]

doh ... typo on the damping mosfet ... Here is the FINAL FINAL schematic.