surf pi 1.2: building my first detector

[vineeee]

I test all components (capatitors and resistors) near U3 and resolder U3, all the same. Detector works but trashold has no effect to circus???


Rechecking again and R18 seems to be problem, when i measure it starts at 17k and slowly grow to 40k. I think is dead.

[Tepco]

Voltage change at pin 7 is good, +5\-5V present, check DC voltage variation at pin 1 U3 , must respond to threshold pot adjustment, if everything is OK at some point you must get continuous audio tone. Also measure pin 2 voltage for slightly less variation, ten's of mV, to see if pot is connected properly. Surf is motion mode detector, pin 1 voltage will just briefly change when metal object is moved near the coil. Check R18,20,21,22 for proper value (misplaced component ) and pot connection. No need to solder upper side PCB traces, holes are metalized.

If R18 behave this way when removed from circuit (disconnect one end) replace it, or temporarily just short it to see if you can get threshold tone.

[migusch]

Hi, kasperfish!
I think original SurfPI is constructed for use with ordinary dynamic loudspeaker (like dynamic headphones) but no piezo-speaker.
Well there is the surfPIpro "clicker"-version which uses a piezo, but thats another thing.
Did you already tried dynamic headphones or simiar dynamic loudspeaker?
I myself had some problems in different metal detector projects when I tried to change dynamic speaker to piezo (which usually resulted in much lower detection range, especially for weak signals)
In your first video i spotted your piezo on the small white breadboard next to the LED.
It looks like you use an active piezo-buzzer (which has an own oscillator-circuit inside). Active piezo buzzer usually have the positive pole marked (+) and are supposed to be used at a certain voltage (like 5V) that is often printed on the case.
In contrary there are bare piezo-membranes like in the back of crystal wrist watches. (which might be a better choice to use in SurfPI)
Surf Pi is generating an audio-signal which is sent to the speaker. When the speaker has its own oscillator inside there can arise some problems (one oscillator drives the other one) .
In my experiments the active piezo-buzzers seemed to be "slower" than bare piezo-membranes or dynamic speakers. They need relatively higher voltage to start oscillating and that might explain the loss of detection range for weak signals. They differ very much in behavior, so you have to have much luck when you buy an active piezo. Some start oscillating at 15 to 20% nominal voltage, some at 80%.
I´m pretty sure the original surfPIpro clicker version doesn´t use active piezo buzzers as well.
Do some experiments with your speaker, it might solve your problems!
migusch

[6blacx]

Surfpi not detect object

hello sir. I ask for help, I am a beginner trying to make 2 Surfpi units but it seems all fail. i am not good in electronics components, i have checked the path and the component makes sure it is in place properly.
The problem that I experienced when I turned on Surfpi was a 1x beep sound.
and when the sensitivity pot is played, it will always make a sound, I mix it by turning offest a silent sound is obtained but cannot detect objects on the coil that I use 320uh. please help, thanks in advance

this image :
back
front
ne5534pin6
tlc555pin2
tlc555pin3
tlc555pin7

[6blacx]

previously i used a buzzer sound audible. then I replaced it with a speaker but there was no sound.
I tried to change the MPSA13 but there was still no sound, I have a multimeter. and mini oscilloscope but I don't understand what to measure using an oscilloscope because I just have it,


on the U4 ic CD4093 I didn't see any waves with the oscilloscope
pin 1 = 4.46v
pin 2 = 4.2 v
pin 3 = 2.5v
pin 4 = 2.5v
pin 5 = 4.41v
pin 6 = 1.52v
pin 7 = 1.14v
pin 8 = 2.27v
pin 9 = 4.42v
pin 10 = 2.15v
pin 11 = 2.21v
pin 12 = 4.43v
pin 13 = 3.32v
pin 14 = 4.46v

U4 pin8

[Carl-NC]

U4-pin14 should be +5v
U4-pin7 should be -5v (give or take)
My first guess is the charge pump (U6) isn't working. Pin5 should be ~ -5v.

[Vadim18]

And also be aware.
I experienced one thing - SurfPI did not work well with traditional coil speakers but work with piezo (not active piezo). This is all due to short output pulses combined with amplitude modulation.

[Qiaozhi]

And also be aware.
I experienced one thing - SurfPI did not work well with traditional coil speakers but work with piezo (not active piezo). This is all due to short output pulses combined with amplitude modulation.

Surf-PI works just fine with coil speakers and headphones, but you need to make sure they are high-impedance. e.g. 50 ohms.

[6blacx]

hi Carl-NC thanks for the reply
i checked u4 is working fine she flatten supply
U4-pin14 + 5v
U4-pin7 -5v
I hope you can help my problem
this is the schema that i use

[6blacx]

Hello, all.
progress now if i set u2 pin 6 = -2.27v detector
and opening a little tune pot, can detect the hammer within 7cm
and the coin is only 2cm
If the pot is turned too much, it will make noise and cannot detect objects.
I have tried to replace U7 and U4 but there is no change in the detection results.
how to fix this problem

[kt315]

combine null o-scope's level to null opamp output's level (free part from the impulse) and give right pic. your pic is nonsence for me.

[6blacx]

combine null o-scope's level to null opamp output's level (free part from the impulse) and give right pic. your pic is nonsence for me.

sorry sir. I'm sorry, I really do not understand what you mean "combine null o-scope's level to null opamp output's level".
I don't have much electronics skills, please tell me which pin to measure. and what should i do


I measured connected to the ground power input and pin 6 on U2 (ne5534)


by turning the offset pot I can adjust the output on pin 6 from -3.5 to 4.1v
like this:

[kt315]

i wrote unright... do offset to nulling like you see on a pic.

[surfdetector]

sorry sir. I'm sorry, I really do not understand what you mean "combine null o-scope's level to null opamp output's level".
I don't have much electronics skills, please tell me which pin to measure. and what should i do

I did a step by step video series on building the Surf PI, you can see them here:
https://youtube.com/playlist?list=PL...UGJdTK59YEC2gE

[6blacx]

i wrote unright... do offset to nulling like you see on a pic.

Thank you for the quick response, sir.
is it true like this