Arduino Nano VLF Metal Detector Project - Main Discussion

[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

[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]

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

[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

[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]

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]

ok another batch of LT1054 there is something not right with this build who has actually got this build working ? there is a problem getting the negative voltage

I can assure you that the build works perfectly as advertised.
To prove this, I have taken the attached measurements today.

1) PCB in case
2) Voltage at TP2
3) Voltage at TP3
4) Voltage at TP4
5) SYNC pulse
6) OSC pulse

[kosacid]

ok another batch of LT1054 there is something not right with this build who has actually got this build working ? there is a problem getting the negative voltage

[Qiaozhi]

has anyone built a 3d box for this I'm lazy and need spoon fed, i don't mind building one but if someone has it would save me time lol

The control box is quite large for a 3D printer. It would be much easier to buy an ABS plastic box from RS Components (Stock number: 1920756). The enclosure size is 60mm(H), 136mm(W), and 185.5mm(L).

[kosacid]

has anyone built a 3d box for this I'm lazy and need spoon fed, i don't mind building one but if someone has it would save me time lol

[kosacid]

this is a working internal OSC

[kosacid]

so out of 10 chips i only got 2 working the OSC and Vref are broken or shorted i did further tests they are not fake chips just substandard when i tested them and used a external clock they work as you can see from the diagram, the working ones have saw tooth on the OSC and the Vref a steady half voltage on both them so there internal clock is working

[kosacid]

the descriptions didn't show the first one is the OSC next is Q1 base from the Arduino clock next is the output of the chip

[kosacid]

if you lift pin 7 you get negative voltage just under supply voltage, i breadboarded them but didn't test the OSC all worked fine, i got 2 that worked out of 20 chips

[Ronin0000]

@kosacid have you gotten it to fully work yet? If so what did you fix. Thanks, Ronin