Arduino Nano VLF Metal Detector Project - Main Discussion

[Qiaozhi]

you are right and that is why pulling up the osc line with a 5k resistor to +v works so do you think it will be fine to run it that way? like you say after looking at the data sheet you are right

The idea of synchronizing the voltage converter to the TX oscillator is to eliminate any switching transients that could potentially affect the receive signal.
However, the detector will still work fine if you don't synchronize. It's probably more important for PI detectors.

[kosacid]

you are right and that is why pulling up the osc line with a 5k resistor to +v works so do you think it will be fine to run it that way? like you say after looking at the data sheet you are right

[Carl-NC]

not the same sellers all different sellers a combo of eBay aliexpress they cant be all fake it works if you use a pullup resistor so the external clocks work but there is no example of you having to do that

I will suggest that, yes, they can all be fakes. It sounds to me like all the LT1054 chips you have are actually ICL7660 chips that have been relabeled. Pin 6 on the ICL is not Vref, it is a bypass pin so it cannot be used for a pull-up voltage. Pin 7 on the ICL also works a little differently, and the data sheet suggests that a pull-up to V+ (12V in this case) may be needed.

I'll bet that if someone with a correctly working circuit were to replace the LT1054's with ICL7660's (preferably ICL7660a) they will see the problem you are having.

[Qiaozhi]

not the same sellers all different sellers a combo of eBay aliexpress they cant be all fake it works if you use a pullup resistor so the external clocks work but there is no example of you having to do that

I don't know why you're having this problem.
Look back at Post #60 where I've shown that it works as advertised.

[GeoMax]

Hello,

I would set up the power supply with your IC chips on a breadboard and check the voltages. If the voltages on the breadboard are OK, the IC chips are most likely OK. Otherwise, you know where the problem might be and need to investigate further.
Have you checked the SYNC signal on the Arduino Nano board? Or have you tried replacing the Arduino Nano?

[kosacid]

not the same sellers all different sellers a combo of eBay aliexpress they cant be all fake it works if you use a pullup resistor so the external clocks work but there is no example of you having to do that

[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.

[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]

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.

[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.

[kosacid]

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

[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]

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

[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

[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.