The step by step build of the Delta Pulse Rev. 5

[Carl-NC]

No politics please.

[Infamy]

Testing Testing Exploding.

Delta pulse metal detector by Felezyab
Page 20



"In PCB you see these points. but what are they?
They are test points (TP). For example designer say for adjusting that point must has that voltage or that
frequency. For this metal detector must be some values but I couldn't find any reference."



This the only information I have found on the test points.



Stage 1 Test with battery connected





Well VD9 exploded VD8 was dead and I changed VD7 although it checked out OK. C23 was changed for a better value it was out by 10%.
C43 22uf cap SMD on the back was dead it was the one the wrong way round, change all other SMDs even though they had good values.

Tested again, nothing blew up but as for values unable to say if all is working properly as I don't know what values I should have besides approximately 12v values.
LF357 gives reading but what should they be and on which legs?
Will look at the TP list of values today to see if that reveals anything.

Soldering, resoldering on this board is not easy as the holes operate as if they have two doors of solder on either side of the board.
Best method I found for clearing the holes was to use a bread board connection wire that has a strong pin.
Heat solder, press in pin, heat solder on other side then rotate pin through this cleans the hole.

Used a 3.5amp glass fuse in the power supply, that seems to have passed stage one testing.

PS if it were only politics.
Its Survival.

[Infamy]

PI Polones Metal Detector DIY part #1
https://www.youtube.com/watch?v=xFvUDjTjvzk

Stage 1 test at 3 minutes, values on LF357 legs 4 and 7.


Using the PI Polones as I guide I have the following results.

[kt315]

good. on the splitter opamp output you have sure half voltage. but you measure in relation to the output, GND, it is -half and +half.
5.62 + 5,62 = 11,24
11,24 + 0.8 + 0.8 (VD8 VD9 diodes in the circuit) = 12.8V, your battery voltage.
the schematic has full description in every its parts. you have to read.

[Infamy]

https://www.youtube.com/watch?v=ODtvLeWdre0
Delta Pulse PI metal detector. 1 stage. Sound checking. Проверка звука.

This is stage 2 in my build, Sound Test, passed.
I used 3.7k resistor.




PS where do the 0.8 values come from?
Is this diode loss?
If so its more like 0.6

[GeoMax]

Hi Infamy,

what are the dimension of your electronic case? And where can you buy it?

[kt315]

i show on 1N4148, but 1N4001 is same. take a diode and put it in your tester. you see REAL direct voltage on the diode.

A specific diode's V_F depends on what semiconductor material it's made out of. Typically, a silicon diode will have a V_F around 0.6-1V. A germanium-based diode might be lower, around 0.3V. The type of diode also has some importance in defining the forward voltage drop; light-emitting diodes can have a much larger V_F, while Schottky diodes are designed specifically to have a much lower-than-usual forward voltage.

[Infamy]

Hi Infamy,

what are the dimension of your electronic case? And where can you buy it?

220*135*75 I bought 20+ years ago in a second hand shop. No idea where to find this exact box.

[Infamy]

Have completed stage 3, No.2 on schematic Geomax Post 8. Now for testing and setting frequency and pulse width. I have a FY6900 wave form generator and wondered if I could use this as
I'm putting off using the oscilloscope for as long as possible.

FY6900 Series Fully Numerical Control Dual Channel Function/Arbitrary Waveform Generator. Page 28 of manual, measures Frequency and Pulse Width. Input is on the rear for DC.
gotronik.pl › images › FY6900 Series Users Manual V1.0.pdf

Oscilloscope beginners guides

https://beyondmeasure.rigoltech.com/...32/t/page/fm/0
https://download.tek.com/document/55W_17291_6_0.pdf

Other useful beginner places to go

https://forum.allaboutcircuits.com/
https://www.youtube.com/@LearnElectronicsRepair


The testing and setup, I think this all happeneds on legs 5 and 9, outputs of the 14 leg LM556 chip?
https://www.alldatasheet.com/datashe.../TI/LM556.html
And as its an analog IC, earth point DA4?


Mistakes to avoid, mixing up 620 Ω with 620 KΩ
Using IRF840 which I will solder in at the very end of the build.

Soldering in an adjustable resistor setup at R5 with a range of about 100 Ω - 1600 Ω
An example can be found here but I am confuse in this example there appears to be a damping resistor on the coil too, see 5 minutes 21 seconds.
https://www.youtube.com/watch?v=8MvkmhSDfnk

[Infamy]

Something else that's not clear, at what stage do I need to build a coil to set damping resistor?

[kt315]

you do not need to set damping resistor. DP working with big FIRST STROBE DELAY that is 40+us minimal. while really in hunting you will set the pot on 100-120us.
in this range damping resistor value has not importance.

however if you do MPP, Bara, Polonez, White Surfmaster PI, Eric Foster's detectors, etc you have to tune the resistor be cause for gold nuggets, small jewelry, coin etc. you want to seek, with FIRST STROBE DELAY 5...10...15us.

[Carl-NC]

as I'm putting off using the oscilloscope for as long as possible.

Why? It's an instrument that is critical to success. Measuring the frequency and pulse width of a single signal does not tell you how it relates to another signal, you need to look at both of them at the same time. Hook up your sig gen to the oscope and play with both to get a feel for how they work, time well spent.

After you have verified the power supplies all work and the timing is all correct, hook up a coil and a preamp and start looking at analog signals. Work your way down the analog path one stage at a time. This is where you can try different damping resistor values and see how it affects the signal. Take notes, oscope screen photos, drawings, etc.

[Infamy]

Why? It's an instrument that is critical to success. Measuring the frequency and pulse width of a single signal does not tell you how it relates to another signal, you need to look at both of them at the same time. Hook up your sig gen to the oscope and play with both to get a feel for how they work, time well spent.

After you have verified the power supplies all work and the timing is all correct, hook up a coil and a preamp and start looking at analog signals. Work your way down the analog path one stage at a time. This is where you can try different damping resistor values and see how it affects the signal. Take notes, oscope screen photos, drawings, etc.

"Space the final frontier" and time just to reread the manuals and watch a few videos. I'll probably just see how it goes with the wave form generator, and then build the coil some where in the region of 30 - 42 inches diameter. Make some space to set up the oscope and see how the wave form generator faired, then on to the next stage. This is not going to work right, I need to dig out a small coil for testing unless I'm working in an open field. But then again I need to set it up some how. Calculated 36 inches is a large as I can build.

So at what stage can I connect the coil?
Measuring flyback, I have the high voltage leads, do I need IRF840 in place?


This is the video I was looking for on the Oscilloscope, I remember it was the best I could find about six years ago on the basics.
https://www.youtube.com/watch?v=ueOup-XBexU&t=108s

[kt315]

data on coil is on schematic. no another data, not exists. some Russians speak 500-550uH is good for DP. do not know. Bulgarians did not share this info.
you can use a 330uH+ coil.

uH everywhere is MICRO-HENRY.

[Carl-NC]

I need to dig out a small coil for testing

Forget the big coil until the entire circuit is working. For that, use a 6-8 inch coil. When all the timing is verfied correct, then hook up the coil (and IRF840) and look at the flyback. Verify the diode clamps are working, then plug in the preamp.