Delta Pulse

[Jose]

Dbanner I tried damping resistors 1k 820R, 735R, 713R, 697R, 682R, 680R, 330R etc in 1/4, 1/2, 3/4 and 1 watts. Its working most silent on 682R 1/2 watts and 697R 3/4watt damping resistor but still not able to keep it silent and stable in end part of T/HOLD pot. The SENS pot keeps making it noisy and unstable while discrimination is working excellent. Unfortunately not much improvement in detection depth. Air testing detects 400ml paint aerosol at around 70-75cm max. I am going to try new LF355 as i believe the one i got earlier died in transit and then move to ground testing. Please suggest how the ghost beeping in the last quarter of T/HOLD can be eliminated. I think whatever depth it has left is in the last bit of noisy unstable T/HOLD pot. My OP42 and TL71 chips are from very reliable source.
Jose thank you for valuable tips. Help me clear the last bit of T/HOLD pot. I am also considering to swap
all mylar caps with polyester.

70, 75 cm for the object you mention is not bad.
I can tell you, what I found.
I use LF357 in the front and TL062 or TL072 in the other integrated ones.
When sensitivity is increased and the threshold is maximized, it tends to be noisy, but must be tolerable.
If the delay is set too low, it can contribute to instability, which is why the damping resistance must be carefully adjusted, in my case, it is about 470 ohms, or less. The coil that I currently use is 400 uH, and its resistance is from 2, to 4 ohms, depending on the size of the coil.
As I said before, the frequency of work if it is incorrect, will increase the noise and instability, if you are testing the DP, in the workshop.

[chuubaba]

Dbanner I tried damping resistors 1k 820R, 735R, 713R, 697R, 682R, 680R, 330R etc in 1/4, 1/2, 3/4 and 1 watts. Its working most silent on 682R 1/2 watts and 697R 3/4watt damping resistor but still not able to keep it silent and stable in end part of T/HOLD pot. The SENS pot keeps making it noisy and unstable while discrimination is working excellent. Unfortunately not much improvement in detection depth. Air testing detects 400ml paint aerosol at around 70-75cm max. I am going to try new LF355 as i believe the one i got earlier died in transit and then move to ground testing. Please suggest how the ghost beeping in the last quarter of T/HOLD can be eliminated. I think whatever depth it has left is in the last bit of noisy unstable T/HOLD pot. My OP42 and TL71 chips are from very reliable source.
Jose thank you for valuable tips. Help me clear the last bit of T/HOLD pot. I am also considering to swap
all mylar caps with polyester.

[chuubaba]

Vadim18 Dear with OP42 the detector is making so much noise despite all pots are on minimum level. Only way i can detect at this minimum level is by a little turn of the DISC pot. If i increase the DEPTH or T/HOLD then it again makes too much pulsating tone. Also low battery starts to blink and sound changes. I think OP42 will work best with this board but how to stop it from making so much noise? The LF355 did not work at all.

[Jose]

I got the "potentiometers" from aliexpress but no info on data. There have been moments when i did suspect some smoke but the pots always read correct values on DMM. I test them as shown in youtube videos.
BTW there are few issues. Firstly it does not detect fast moving target near the limits of detection depth. Also it keeps ringing for some moments after a target has passed the coil. And finally the GEB and SENS pot make it most noisy instead of helping eliminate noise. With TL071 and LF357 the DISC pot does the same so i have to keep these three to minimum position. And finally i am amazed why MOSFET and VD1 don't get hot.

Some tips you can try to improve the performance of your DP.
First, it does not detect the target that moves quickly near the depth limits.
This is normal because the DP was designed to detect large and deep objects.
It also continues to sound for a few moments after a target has passed the coil.
Play with different coils and damping resistance, to improve this effect, even the working frequency.
The GEB and SENS pot make it louder instead of helping to eliminate noise. I am surprised why MOSFET and VD1 do not get hot.
It is possible that you are working with low frequencies and short TX pulse width, so it is normal that these elements do not get hot.
Try to increase the frequency, being careful with the pulse width so as not to heat the mosfet. at a multiple value of the network frequency. This will improve noise and responses to objects.

[dbanner]

Overall, I think your problem is tinkering with the circuit to get the best performance for a given setup.
YOU MUST UNDERSTAND THAT DELTA PULSE IS NOT FOR VACUOUS ELECTRONICS YOUNG PLAYERS.

To your credit, you completed the project successfully. A miracle by any standard.

You should seriously consider a career in electronics engineering. You would need to take formal tuition of course, perhaps even register at a technical institute in your area.

Chuub, you show a penchant for blowing things up, smoking things out regularly, and avoiding catastrophic life ending electrocution.
I'd say you could at least make a First degree in electronics!!!!

Doesn't any neighbour ask themselves what is this guy doing with gloves and holding a long PVC pipe while walking around over some square contraption, with hands aloft holding coca-cola can? I'd be tempted to call the wagon from the funny farm to collect you.

[dbanner]

Thank you for highlighting this. All pots on front panel of my board are "B".
Kindly elaborate more on correct choice for each front panel pot. Thank you again

Yes, you have the correct pots.
Potentiometers with B designation are linear taper, so this is correct for all the front panel pots in the circuit.

[chuubaba]

............One must pay attention to correct type of pots for particular controls........
........

Thank you for highlighting this. All pots on front panel of my board are "B".
Kindly elaborate more on correct choice for each front panel pot. Thank you again

[chuubaba]

By the way, it is important to know the difference between a log pot and a lin pot, they are not interchangeable! Some people just stick any old pot into circuit and expect good results, not so.
One must pay attention to correct type of pots for particular controls. A100K and B100K are not the same pot. This is often overlooked by young players.
Also, some people use trimpots for real pots without realizing there is something known as turn cycles which limits trimpots before failure ocurrs. And it is not complete rotation cycle but it could be just back and forth cycle over a small part of track before failure on that specific portion of the track. I once saw pics of delta pulse home brew PCB with such trimpots used for front panel controls, limited to just 200 cycles according to datasheet.
A recipe for magic smoke on pulse width.

I got the "potentiometers" from aliexpress but no info on data. There have been moments when i did suspect some smoke but the pots always read correct values on DMM. I test them as shown in youtube videos.
BTW there are few issues. Firstly it does not detect fast moving target near the limits of detection depth. Also it keeps ringing for some moments after a target has passed the coil. And finally the GEB and SENS pot make it most noisy instead of helping eliminate noise. With TL071 and LF357 the DISC pot does the same so i have to keep these three to minimum position. And finally i am amazed why MOSFET and VD1 don't get hot.

[chuubaba]

My goodness. hope you remembered to remove your wristwatch and belt that's holding up the pants. And eyeglasses with metal frame,

Chuub, take a break, go into nearby town, look for delicious female to go damping with. I mean't camping with. Oh dear lord.

I had no metal on me except the target (32cmx14cm 1kg iron box). It was not detected beyond 80+- cm when i used plastic gloves or plastic pole to hover it above the coil. I am 5'.11")

[dbanner]

By the way, it is important to know the difference between a log pot and a lin pot, they are not interchangeable! Some people just stick any old pot into circuit and expect good results, not so.
One must pay attention to correct type of pots for particular controls. A100K and B100K are not the same pot. This is often overlooked by young players.
Also, some people use trimpots for real pots without realizing there is something known as turn cycles which limits trimpots before failure ocurrs. And it is not complete rotation cycle but it could be just back and forth cycle over a small part of track before failure on that specific portion of the track. I once saw pics of delta pulse home brew PCB with such trimpots used for front panel controls, limited to just 200 cycles according to datasheet.
A recipe for magic smoke on pulse width.

[dbanner]

It can detect the tons of iron in my roof from 3 meters but what good is it for practicle use?
I have done the tests with 1mx1m coils as seen in many videos for this and similar detectors. As long as i am holding the target with my bare hands and walk over the coil it will be detected as far as my hands can lift in air BUT when i wear gloves or use a plastic pole to hover it above the coil then the same target will be detected at around 80cm.
Yes i lack the knowledge but i have followed instructions. I don't think any equipment is lacking but you may point out whats wanting.

My goodness. hope you remembered to remove your wristwatch and belt that's holding up the pants. And eyeglasses with metal frame,

Chuub, take a break, go into nearby town, look for delicious female to go damping with. I mean't camping with. Oh dear lord.

[kt315]

i totally agree with you George. i only copied bulgarian layout that was checked and tested by me showing nice result.
there was just shielding importance issue that i did not still understand, but later this problem was discovered and resolved.

all the best

[chuubaba]

Chuubaba - numerous people have successfully built the Delta Pulse design, and are happy with the results. When KT315 says that his PCB design is good, you can believe him.

With all due respect, the problems you are having are caused by your lack of electronics experience. Attempting to build a sophisticated metal detector design without some basic skills, and the necessary equipment, is asking for trouble. There is no substitute for knowing what you're doing.

It can detect the tons of iron in my roof from 3 meters but what good is it for practicle use?
I have done the tests with 1mx1m coils as seen in many videos for this and similar detectors. As long as i am holding the target with my bare hands and walk over the coil it will be detected as far as my hands can lift in air BUT when i wear gloves or use a plastic pole to hover it above the coil then the same target will be detected at around 80cm.
Yes i lack the knowledge but i have followed instructions. I don't think any equipment is lacking but you may point out whats wanting.

[chuubaba]

Big coil requires proper gauge wire, connector and cable AND correct damping.
How in the world you're gonna test 1x1 meter big coil in the lab. NO, NO! Take it to the bush!

Dbanner Now I am using 40cm coil 400uH with coax connecting cable. Total resistance of coil and cable is 3 Ohm. Is this ok? R5 is 680 Ohm 1W.

Vadim18 my LM355 and OP42 chips will arrive tomorrow. Lets see how these work with my board.

[Qiaozhi]

Vadim18 I buy all chips and components from china. The detection depth is same for 5kg+ weight pure iron pieces of same size. The 1mx1m coil can detect these 5kg iron pieces at the same distance. This detection depth is trash. Absolute scam. It is very disappointing after spending so much effort and money. Such false claims and fake videos only to sell trash pcb. Now it is very clear why the seller of this design is always playing angry when you ask him questions about the poor performance. He will always attribute the wrong to the customer and if nothing works then will start abusive remarks and language. No wonder he would always advise to get parts from trash. Do not invest much time and money in to this. Its once in life time maybe that you would got search for train burried 15 feet deep.

Chuubaba - numerous people have successfully built the Delta Pulse design, and are happy with the results. When KT315 says that his PCB design is good, you can believe him.

With all due respect, the problems you are having are caused by your lack of electronics experience. Attempting to build a sophisticated metal detector design without some basic skills, and the necessary equipment, is asking for trouble. There is no substitute for knowing what you're doing.