Arduino Nano VLF Metal Detector Project - Main Discussion

[kosacid]

i think its the OSC pulse being shared is causing the problems if you lift one of the OSC pins it works this is what i get on the OSC why do you need to sync the OSC anyway ?

[Qiaozhi]

If you don't sync the voltage converters, and allow them to run with the internal oscillator, then any switching noise will be asynchronous.
As you can see from my measurements, there is no problem with sharing the OSC pins.

[kosacid]

same frequency voltage when i test on the breadboard it works fine i put the same chip in the detector i even used the 5v on the Arduino with a 10k pullup attached to the OSC to make sure the clock is fine but still no negative voltage as you can see also i have bought chips of 5 different vendors i just cant work it out

i even tested that chip by exchanging the output capacitor for a resistor so you can see it syncs

[kosacid]

ok i have worked it out the OSC needs a stronger signal to work so pulling it up to 5v is not enough so i used pin 8 +12 and pulled pin 7 OSC up with a 5k resistor

[Qiaozhi]

Now I'm confused.
My build is working perfectly, and it's not the only one. I previously built at least two prototypes without any issues.
The OSC inputs are not being synced with 5V, as the collector of Q1 is pulled up to VREF which is 2.5V.
Have at look at Fig. 12 in the datasheet.
https://www.ti.com/lit/ds/symlink/lt1054.pdf

[kosacid]

Oscillator frequency VCC = 3.5 V to 15 V so 2.5 is not enough i tried with the 5v pullup that wasn't enough it needed just over 5v so i pulled up using the 12v it might be something to do with a 5v pwm 50/50 only gives you 2.5v just at the lower part of the trigger

[turboaleks]

I think C28 and C37 should be 470nF like on the Photo from the Author's PCB and not 47nF like in the BoM on page 134, not sure.

[Qiaozhi]

I think C28 and C37 should be 470nF like on the Photo from the Author's PCB and not 47nF like in the BoM on page 134, not sure.

I think you mean C27 and C38. In which case you are correct, as these capacitors are in fact 470nF.
The BOM is incorrect.
I have added this to the errata.
Thanks.
Arduino Nano VLF Metal Detector Project - Published January 2024

[kosacid]

i just bought another batch of LT1054 same results i even built another to test same results take out u3 u2 will give you a negative voltage

[GeoMax]

Based on the circuit diagram alone, the detector will definitely work. Did you build it step by step, or did you just populate the board and then realize the -5V wasn't working?

[kosacid]

5 diffrent batches all not working unless it's the garret ace sketch

[Qiaozhi]

5 diffrent batches all not working unless it's the garret ace sketch

As GeoMax said, did you build it step-by-step?
It certainly looks like you just populated the whole board before testing the -5V supply.

[GeoMax]

In the left image, there are already too many components installed for my taste. I would first place only the components relevant to the power supply and only continue once the correct voltages are measured. It's possible that your second batch of LT1054s is also fake.

[kosacid]

5 different batches all the same what's the chances ? 2 different boards one fully build one just the sine wave and negative voltage

[GeoMax]

Hello,

If you bought the five different batches from the same seller, I wouldn't be surprised. Perhaps the seller also bought the fake IC chips in China and simply resold them to you. Recently, I've heard from many people that IC chips purchased on eBay or in China are counterfeit.