Replies to Minipulse Plus

[Wahyu]

I know this is an old post but did you solve this problem?
Mine is doing the same and, so far, I haven't found a solution

Maybe this solution http://www.geotech1.com/forums/showt...amp#post219381

[kt315]

sorry but MPP is simple design for beginners for getting new experience and starting the new hobby (for you).
you have to start to do new project, maybe hammerhead, with GB tuning advantage. do not worry, you went successfully through the first stage and are ready
overcome next frontier. you are on right way amigo. we all go through the stages in our life. (ontime i did have AT286 and it was very good PC. then
i bought 386SX33 and it was better. then i bought 486DX66 and it was still better, etc. and we notice - on every stage we just wasted our money)
the most valuable for you is the experience, not gold you are trying seeking by MPP on the beaches. so Eric Foster also doing MPP at time it was good start for him and ascent in career and the ascent to understanding of the meaning of pulse induction.
then he did other detectors and went to modern ones we know. we do not have more modern his schematics to give you right now (i hope they will go).
you must understand every schematic is huge job - to buy the detector, to desolder the board, to draw the diagram, to write detailed report how-to-do
etcetera etcetera. that you repeat MPP is just your appreciation of this job.

[Goaty]

Anyone having Earth Field beeps in their MPP rev. D?

I've tried swinging the coil up in the air and it beeps. It does even at maximum delay. When swung slowly the beep goes away, so I thought it might not be cancelling EF properly.

Does anyone's MPP behave the same way?

I know this is an old post but did you solve this problem?
Mine is doing the same and, so far, I haven't found a solution

[Teleno]

Anyone having Earth Field beeps in their MPP rev. D?

I've tried swinging the coil up in the air and it beeps. It does even at maximum delay. When swung slowly the beep goes away, so I thought it might not be cancelling EF properly.

Does anyone's MPP behave the same way?

[bernte_one]

helloe perzo,

can you upload pcd file (is it sprint layout?) as zipped file as Attachement here in this thread thx

[Qiaozhi]

Hello timekiller.... Like you, this is also my first post to the forum. Thank you to all who share their knowledge and experience here !!

I recently purchased a MPP kit from Silverdog. I took my time and followed the instructions and what do you know ??? It works !!

I'm now waiting for the bits and pieces to arrive so I can attempt KRinAz's modifications. I hunt in the same types of ground....

Thank you for a well thought out project !!

Luke

Well done! You are now living proof that following the instructions actually works.

If you post some pictures and a short description of your experience, I will add you to the Completed Projects thread.

[LukeJ]

Hello timekiller.... Like you, this is also my first post to the forum. Thank you to all who share their knowledge and experience here !!

I recently purchased a MPP kit from Silverdog. I took my time and followed the instructions and what do you know ??? It works !!

I'm now waiting for the bits and pieces to arrive so I can attempt KRinAz's modifications. I hunt in the same types of ground....

Thank you for a well thought out project !!

Luke

[timekiller]

Hello This is my first post in this forum.
I have 2 surf pi working machines made by me on a breadboard pcb board. All work great, and now I made my mini pulse. On the same custom board. Use modified astable oscillator and 7660 supplied 14 volts in 7809. Power in lm350 and 4 lipo batery .I have no oscilloscope, but everything went right. About 25 cm piece 1e stable recording and about 30 cm maximum .Coil turns 18 AWG 22 - 25 cm . Minipulse rev D is an excellent machine, but what is the potential ? What would improve in my case dd or balance coil ?

[perzo]

آHi All this good pcb Dedicated to all friend

[satdaveuk]

Way behiind with this project

Its got to page 26 now,and can see you all have been busy bees, Have my PCB sorted since around page 7 and thats far as I got due to business and family time.
When time permits will ponder through from the beginning and work my way back here and get involved like the old days.
Happy new year to you all and god bless.
Regards
satdaveuk

[Sean_Goddard]

Change the 330K in the snubber to a 86K and lose the series resistor, then re run the sim

[Davor]

When you need to fine tune a 10us delay, 0.6us is simply not good enough. So the first sample is not a place to try with varying delays. A GB sample delay takes longer, and therefore a much better place to play with delay variation.

[scrungy_doolittle]

I can't convince a pic, or any other micro for that matter, to provide a continuously variable delay in a 10us range. I gave already a slightly different solution for this problem using a micro that varies a different delay which is not this tight. So far I'm not that much interested in micros.

Been a while since I was on, so exactly what kind of delay do you want? Given 16 mhz clock, a delay can be pretty simple if you just want to delay a signal. One pin in, one pin out. lets say you wanted a .6 usec delay. There are a number of ways todo this. One is to read the input pin, and or it with the msbit of a byte that you shift left first. Byte starts with all zeros, and implements an 8 bit shift register Basically it looks like this

depending on the clock speed and what the compiler generates, this is one way to do it. If it take 200 ns for the code to execuit, you would have a 1.6 used delay It can be
even less is you use a smaller number of bits. This is based on an 8 bit byte
do
{
if input pin is 1
delay_line=delay_line >> 1 | 0x80;
else
delay_line=delay_line >>1 & 0x7F;
ouput=delay_line & 1;
}while(1);

If you wanted 4 bits of delay, your output would be changed to this
output=delay_line & 0x10; // When a 1 appears in bit 4, it appears in the output. This can be extended to 16 bits, and a any bit delay you want there.

Another way is to have a timer running at a high clock rate, say 1 mhz.
You could

do
{
i=input;
TIMR=0xFF-4;
while(TIMR!=0) // OR you can use the overflow bit in the timer while(timer.overflow is false)
out=input;
This works by setting the counter time out for the timer. Assuming it is running at 1 mhz, and you want 5 cycle delay, and it counts up, subtracting 4 from ff will give the timer 5 ticks before it goes to 0

This technique can give you really fine delays if you are running the clock at a higher rate. Most timers can be set to the clockfrequency / 2, 4, 8 or 15. At an 16mhz oscillator and a divider of 2, you are ticking at 8 mhz 125 nanoseconds (24mhz is 41.6 ns) so at 8 mhz you have 124 nsec steps. There are other ways of doing it also. If you want a true binary counter, and you have 18 I/O's you can simply treat two 8 bit ports as a 16 bit counter and increment it each sample time.

[Qiaozhi]

Hi Qiaozhi

Do you find that if you are useing 12 volts and 300uH coil , that if you go much above the 58 - 60uS TX pulse width then the 740 starts to break down / avalanche ?

The avalanche breakdown voltage for the IRF740 is 400V. Since the flyback is currently around 350V, then I wouldn't be surprised if that's true.

[6666]

Hi Qiaozhi

Do you find that if you are useing 12 volts and 300uH coil , that if you go much above the 58 - 60uS TX pulse width then the 740 starts to break down / avalanche ?