Arduino Nano VLF Metal Detector Project - Main Discussion

[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,

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?

[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.

[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.

[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

[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.

[Carl-NC]

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?

I would think so but there is a risk. The ICL7660 is rated for 10V and the ICL7660a is rated for 12V. I have seen a 10V part run at 12V but it may become damaged over time if it is running hot.

[Qiaozhi]

I would think so but there is a risk. The ICL7660 is rated for 10V and the ICL7660a is rated for 12V. I have seen a 10V part run at 12V but it may become damaged over time if it is running hot.

I forgot to mention that.
Especially true since any fake ICs are probably sub-standard.

[fitos]

TFT display 2.4 in 320x240 Where are the pins MOSI anf MISO I couldn't find it. Does anyone know where I can get it? Thanks

[Qiaozhi]

TFT display 2.4 in 320x240 Where are the pins MOSI anf MISO I couldn't find it. Does anyone know where I can get it? Thanks

The pin mapping for the TFT is shown in Table 13-3 on page 107 of the book.

[KenS]

I have also had problems with the -12V supplies. They were OK to the point of adding the demodulator, don't know if it was the time it had been powered or the incremental increase in load, but something had failed in U3 (LT1054) causing a low reference voltage, hence low amplitude osc signals on both U2 and U3. Using a new pair of LT1054s with their pin 7(Sync) bent out (i.e. removing the external sync), all ran normally again. Looking at the datasheet for LT1054, is the Sync pulse frequency from the Nano acceptable? Its running at 4.3KHz, which is much slower than the lowest recommended LT1054 frequency of 15KHz. Is this what is causing the problems with LT1054s?

[Qiaozhi]

I have also had problems with the -12V supplies. They were OK to the point of adding the demodulator, don't know if it was the time it had been powered or the incremental increase in load, but something had failed in U3 (LT1054) causing a low reference voltage, hence low amplitude osc signals on both U2 and U3. Using a new pair of LT1054s with their pin 7(Sync) bent out (i.e. removing the external sync), all ran normally again. Looking at the datasheet for LT1054, is the Sync pulse frequency from the Nano acceptable? Its running at 4.3KHz, which is much slower than the lowest recommended LT1054 frequency of 15KHz. Is this what is causing the problems with LT1054s?

Are you sure the LT1054s you're using are genuine parts?
Some people have found that they were re-labelled ICL7660s.
Of the many projects I have built using the LT1054, I have never encountered a problem.

[GeoMax]

Hi KenS,

if you purchased your LT1054 IC chips on eBay, Aliexpress or Alibaba, you can be sure (99%) you bought a fake IC from China. Only buy at trustet companies. Many local reseller buy in China as well and got cheated without knowing it.

[Op04]

ridiculous way would be using 5 watt qi wireless charging pad for watch and 2.5W receiver pad to get 5-+

[KenS]

Hi, my LT1054s came from a fairly reliable UK supplier, cannot be sure they are genuine parts but pin 6 is 2.5V and free running (pin7 OC) they run around 25KHz, so definitely not ICL7660. Running the sync at 4 to 5KHz and feeding both oscillators via the single 20K resistor seems to upset these parts, since this usage is outside those defined on the datasheet its hard to know if the devices are substandard. I wonder if the grade/ESR of the capacitors is a contributing factor in this since I am not using Tantalum caps. I don't think free running at 25KHz will be a bad thing, so I am not going to get hung up on this, happy to leave pin 7 open and carry on. Thankyou.