Minipulse Plus Rev My time has come!

[mushaba]

...Also, the preamp could be upgraded to have two stages (same as the MPP

George here is a thought:IS it possible to modify the CB with 2 stage pre amp using NE5534 (i have a lot originals from TI and having trouble to order 5532 THT version) ??

Im thinking a small addon "card" ,the I/O of this card will be placed on the U5 (i hane installed an ic socket so i can change the opamp if needed) according to this schematic i made only based on how it is connected on the MPP.Dont know what values of R1 and R2 of this card and if i should change the values of R31-C13 and R25-V47 possibly...It should need 1 extra 0V from pcb.

[Qiaozhi]

Thanks George for your reply,I will have all these advise in mind..I didn't ask for board debugging,just if there is any idea why the same coil dumps at different values in two Pi's running the same pulses with same components As I said above the CB won't go avalanche and damps nearly 560 Ohms so there is must be something faulty on my Mpp build.Nowhaving a second working detector I can spot clearly the difference in all points of pulse production and stages and won't go crazy������...Is there any advice on the sens trimmer and how to set it?

The MPP may be able to use a higher value damping resistor because of the 2-stage preamp and the series diode.
In my experience, I would set the sensitivity preset to mid position.

[mushaba]

Thanks George for your reply,I will have all these advise in mind..I didn't ask for board debugging,just if there is any idea why the same coil dumps at different values in two Pi's running the same pulses with same components As I said above the CB won't go avalanche and damps nearly 560 Ohms so there is must be something faulty on my Mpp build.Nowhaving a second working detector I can spot clearly the difference in all points of pulse production and stages and won't go crazy������...Is there any advice on the sens trimmer and how to set it?

[Qiaozhi]

Couldn't help my self waiting for components so I attached one of my 3dss coil...Just magical!!!Without setting the sensitivity trimmer the soda can is detected near 1m...Interesting though the particular coil that damped at 1.6k with the MPP with the CB it damped very nice and smooth at 560 Ohms with voltage near 440 volts..The preamp out is very clear so I'm thinking I have something faulty with my MPP pcb,I will have to look into the mur the mosfets and the preamp circuitry.I must notice that the CB has way more stable pulsing than the mine MPP..Difficulty is the pcb is both sides soldered and have small traces,take the parts out will need to be very careful,I wish I had another clear board...Never the less the CB seems to work very nice (even with 1 stage preamp)I adjusted the tx pulse at 150us and first sample at 10us(I can go lower).The frequency at 1000pps as advised,I wonder what is the sensitivity trimpot and how we should calibrate it.Also some directions I have at TP3 we calibrate for zero voltage at pr amp out,that done before the hole circuit is soldered,should I calibrate it again with the detector working?

I need your thoughts about damping guys especially George's advice since he is the designer..,what could be wrong with the MPP ...I'm thinking change the mosfets with a new one,the MUR diode and the 7555 pulse generator and the 5532.

The CB is a more complex design than the MPP, and is not considered to be a project for beginners. There are a number of improvements you could do to make it even better, such as swapping out the 7660A for an LT1054, which will allow you to remove the series diode that goes to V+. The diode is only there to protect the 7660A from getting too high an input from the battery pack when it's fully charged. Also, the preamp could be upgraded to have two stages (same as the MPP), and an MUR740 inserted between the MOSFET and the 3R3 series resistor.

It's difficult to know what's wrong with your MPP without probing it personally. Debugging remotely is always a difficult task.

[mushaba]

Couldn't help my self waiting for components so I attached one of my 3dss coil...Just magical!!!Without setting the sensitivity trimmer the soda can is detected near 1m...Interesting though the particular coil that damped at 1.6k with the MPP with the CB it damped very nice and smooth at 560 Ohms with voltage near 440 volts..The preamp out is very clear so I'm thinking I have something faulty with my MPP pcb,I will have to look into the mur the mosfets and the preamp circuitry.I must notice that the CB has way more stable pulsing than the mine MPP..Difficulty is the pcb is both sides soldered and have small traces,take the parts out will need to be very careful,I wish I had another clear board...Never the less the CB seems to work very nice (even with 1 stage preamp)I adjusted the tx pulse at 150us and first sample at 10us(I can go lower).The frequency at 1000pps as advised,I wonder what is the sensitivity trimpot and how we should calibrate it.Also some directions I have at TP3 we calibrate for zero voltage at pr amp out,that done before the hole circuit is soldered,should I calibrate it again with the detector working?

I need your thoughts about damping guys especially George's advice since he is the designer..,what could be wrong with the MPP ...I'm thinking change the mosfets with a new one,the MUR diode and the 7555 pulse generator and the 5532.

[mushaba]

Allmost finished the CrossBow (waiting for 5-pole connector for coil and the charging connector) and im really excited!!My first plan was to mount the detector as my MPP right down at the handle but i decided to mount on my belt via a belt clip since i dont have a proper mounting,there are lots of out there but they are pricy since a lot of custom fees and duty taxes are inolved,the housing is medium to large but managed to fit all parts in.I have to say its VCO audio is magical,nice and steady ticking adjustable as it has to be,little annoying on headphones because its too "mid-bass" for my hearing taste..A worry i have is the batteries (3x18650) is very close to PCB and somewhere i read something about 18650 and interferance.Also i will have to see the charging circuit because the original CB had NiMH battery pack.The Tx pulse is very steady (both pulse duration and frequency) and precisely adjustable.
I've also posted on area51 to hear from other guys built the CB and asking if there are some points to look after but i think the forum is nearly dead (no replies except Sven for a long time)..

[mushaba]

Ive explained things that way kinda when running a VLF detector.
ITs Like Adding a fog to our vision more minerals become brighter. On a car you turn on the fog lights a different spectrum. On a High Frequency VLF
you turn down the gain sure you loose some depth but you gain the ability to see better.
The crossbow board looks good Im going to have to look at it more . Kinda interested in the TDX3 that DOOLEY deisgned though, I have a geo barra and chance to do but might shoot for a TDx first . Its a good example of less current to the coil and good performance wonedrful audio.
Soo many projects.

Exactly!A VLF should be on our arsenal and truth to be said from the few things I understood discrimination only with VLF.Is TGSL an easy build?Want also to build a PI with mcu,leaning to 2nd chance..After the CB I will try the Delta pulse,I think it's more suitable to the kind of detection I will try but there are no guides about calibrations..Having also a Svens Mirage board I'm gonna try.I need to learn more more about coils,about the part of receiving signal we try to convert to sound and how targets,ferous non ferrous (and other attribuutes of metals) behave on the above signal..

[godigit1]

Made another coil 20cm OD with 0.4mm double enameld coil wire.It damped at 820 ohms but I noticed scope reading on coil hot lead voltage went at 300v,I removed the 5 ohms resistor I had in series at the tx side and the damping changed..also noticed higher frequency have better detection range than lower freqs..Also read somewhere that an exceed Tx pulse could "overload" the ground we try to read from .(I don't know how to express it)..Almost finished my Crossbow,I'm out of 79L05 but I noticed some parts I didn't use from diydetectors kit had other value written than it's real value.Just hope that rev-c got from area51 are working..



[ATTACH]46378[/ATTACH]

Ive explained things that way kinda when running a VLF detector.
ITs Like Adding a fog to our vision more minerals become brighter. On a car you turn on the fog lights a different spectrum. On a High Frequency VLF
you turn down the gain sure you loose some depth but you gain the ability to see better.
The crossbow board looks good Im going to have to look at it more . Kinda interested in the TDX3 that DOOLEY deisgned though, I have a geo barra and chance to do but might shoot for a TDx first . Its a good example of less current to the coil and good performance wonedrful audio.
Soo many projects.

[mushaba]

Made another coil 20cm OD with 0.4mm double enameld coil wire.It damped at 820 ohms but I noticed scope reading on coil hot lead voltage went at 300v,I removed the 5 ohms resistor I had in series at the tx side and the damping changed..also noticed higher frequency have better detection range than lower freqs..Also read somewhere that an exceed Tx pulse could "overload" the ground we try to read from .(I don't know how to express it)..Almost finished my Crossbow,I'm out of 79L05 but I noticed some parts I didn't use from diydetectors kit had other value written than it's real value.Just hope that rev-c got from area51 are working..

[godigit1]

Keep thinking about this form excellent for underwater. Very little air intrapment.

[godigit1]

I have not searched those detecors So Other members would bebetter to answer that.
But I wanted to add a thought on detector usage and a way of discing out small iron without desensitizing your coil. That is to simply raise your coil off the ground. If it is small shallow iron it will dissapear shortly after you raise the coil and large items will remain.
In prospecting we use the method just the opposite to disc out large Iron.

[mushaba]

This is true but require a thicker housing.

My fastest 3dss i potted in a flower pot bawl,it came near to 800 gr too heavy for its size...

Cool I like the vacumm forming and the way you chose to do it by putting the coil in a perminate form Good Idea!!

My best friend is a carpenter (the guy who has the laser cutter and the wood router i build for him for wood engraving and cutting 2.5m x 1.4m) We made a simple table with 5mm holes..We use 2 vacuum cleaner (household) and the forming looks awesome,we dont use extra vacum tank with compressor some other guys on the internet use (its best but we didnt try it) because we use 2mm PE or PP and it comes out real good..We made tank side covers for a Yamaha DT200R we restored!

I wouldnt use wood glue who knows what the dialectric properties really are.

True that it didnt cross my mind..In fact ive just removed the casting from MDF and it has a little better range..

I found a product called super corona dope and just had a idea for coils shielding using you new forming process.
So
1 make your ply form route in your channel.
2 vaccum your housing remove it.
Lay a loose wound bundle into your channel and I mean with no wrapping or even just rool it into the channel using a little peice of foam to lock each loop as you do it.
Then the super corona dope that is very thin would lock the coil into place. now you have primairilly air as your insulator A peice of cloth tape goes over the channel, the whole form is spayed with carbon paint and attached to ground then you just glue it into you final shell.
I know you are past that but just riffing on it a bit.
Best.

Thanks,im feeling i have long way before i will get to the point i will have my coils shielded..

Today arrived my CrossBow pcbs i ordered from jlcpcb,cant wait to build one..Should i try the Delta Pulse build first??

[godigit1]

This is true but require a thicker housing. Cool I like the vacumm forming and the way you chose to do it by putting the coil in a perminate form Good Idea!! I wouldnt use wood glue who knows what the dialectric properties really are.
I found a product called super corona dope and just had a idea for coils shielding using you new forming process.
So
1 make your ply form route in your channel.
2 vaccum your housing remove it.
Lay a loose wound bundle into your channel and I mean with no wrapping or even just rool it into the channel using a little peice of foam to lock each loop as you do it.
Then the super corona dope that is very thin would lock the coil into place. now you have primairilly air as your insulator A peice of cloth tape goes over the channel, the whole form is spayed with carbon paint and attached to ground then you just glue it into you final shell.
I know you are past that but just riffing on it a bit.
Best.

[mushaba]

Forgot to mention that i think 3dss or spider coils are much easier and robust than the simple bundle monos...

[mushaba]

The wedges are actually ply wood, even the more impressive you coould not have done that with a router.
How do you plan on sealing your MDf. If I may I would suggest a liquid thin epoxy Or a wood hardener used for restoring rotted wood.
Pc Petrifier would work and is not that expensive. I have a wood shell and thats what I was going to use and then clear coat but mine is maple ply wood so I was going to make a woody style coil.
This is a way you can do a easy form for that style of coil and that is to use a embrodrary hoop glue on 1/8 ply and you have a form for a laminate router.
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Hello godigit1 i potted it with epoxy hust to keep it steady and test it.If it works as i want i will vacuum form a coil housing..Also i thought a mix of wood glue fine wood dust and some varnish instead of epoxy