Minipulse Plus Rev My time has come!

[green]

Thanks green for your reply!
So spacing between the wraps won't reduce capacitance?Did the coil you show work well?

Either coil worked fine for me. Fastest coils I've made. Haven't tried a 3DSS because baun7154 replied magnet wire didn't work good when he tried it. I had a large spool of magnet wire and wanted to use it. Guessing stranded would work fine.

[godigit1]

Hi Mushaba, I have no actual formula to point you to for line spacing. Looking at tesoro coils it looks like one to ne as far as i can see.
As far as a design I was wanting to try a flat DD . The one in figure 7 interests me .
https://patentimages.storage.googlea...17015730A1.pdf
There were more stack example last I was looking but Im not finding them now Ill have to look around more.
Your shop sounds nice, your right i just have to buck up and do it ive been saving a couple older computers with windows 7 on them to dedicate to a mill Just too many projects and work right now.
As far as correct coil your 3d ss looks pretty good or are you looking for the ability to test below 6 us? Recent discussion is DD is the way to go as far as i can tell.
I have Itmd as well but have not been able to give it the lab time It deserves and right after i got it 2 came out so I still have to get it.
Your 3d ss coil should be pretty good for testing or are you looking for something super fast below like 6us?

[mushaba]

Hi guys,i dont know if i should be sad or happy..I still cant understand the hole dumping thing,please forgive me but my knowledge is incomplete in this area.

I've just connected the 3dss i made from 0.64mm ETFE cable.Here are the results:

Sad because i couldnt get the right size at outter diameter of 20cm.



Sad because i couldnt get the right inductance at 300-400 uH



Sad because i couldnt get the right resistance 3-4 Ohms



Happy because the coil works GREAT!!!! I detect and 1966 English gold coin at 25-30cm,i detect my chain with cross at 10cm and generally i detect gold!!!!!The can of soda starts at 65-70cm!!

Although i am happy i would like to learn,why all went wrong and the detection came out right?

Either coil worked fine for me. Fastest coils I've made. Haven't tried a 3DSS because baun7154 replied magnet wire didn't work good when he tried it. I had a large spool of magnet wire and wanted to use it. Guessing stranded would work fine.

Hi green,thanks for your reply...If you had more space between each wire in the spiral should it have less capacitance?How can i calculate the capacitance of my coil??

Hi Mushaba, I have no actual formula to point you to for line spacing. Looking at tesoro coils it looks like one to ne as far as i can see.
As far as a design I was wanting to try a flat DD . The one in figure 7 interests me .
https://patentimages.storage.googlea...17015730A1.pdf
There were more stack example last I was looking but Im not finding them now Ill have to look around more.
Your shop sounds nice, your right i just have to buck up and do it ive been saving a couple older computers with windows 7 on them to dedicate to a mill Just too many projects and work right now.
As far as correct coil your 3d ss looks pretty good or are you looking for the ability to test below 6 us? Recent discussion is DD is the way to go as far as i can tell.
I have Itmd as well but have not been able to give it the lab time It deserves and right after i got it 2 came out so I still have to get it.
Your 3d ss coil should be pretty good for testing or are you looking for something super fast below like 6us?

Hi godigit1,thanks for your reply and the usefull intel..I would answer to your question (are you looking for the ability to test below 6 us) if i could but i dont,what do yoy mean by 6us?



How does this coil seems to you?

[mushaba]

Flat spiral and flat basket I posted awhile back. Coil capacitance less than 1foot of lead wire. Don't seem to need spacing between wire wraps to reduce coil capacitance. Maybe another reason to space wraps?

Inspired by your coils as a Sunday project i made this..All specs in desirable range but detection range little less than 3dss



How can i measure (or calculate) which coil is fast?

[green]

Inspired by your coils as a Sunday project i made this..All specs in desirable range but detection range little less than 3dss

[ATTACH]45987[/ATTACH]

How can i measure (or calculate) which coil is fast?

The way I do it. Been told there are better ways but it's the best way I have. Scope is looking at amplifier out of a operating PI. Set scope gain low maybe 100mv/div. Position test coil near operating PI coil for a reasonable signal on scope. Test coil is a different flat radial coil same as reply#58. 10nf cap is npo ceramic, 100nf cap is polypropolene. Measurements with my multimeter. Measure resonance and calculate either L or C with formula scope screen #2, frequency resonance=1/2pi/(LC)^.5.

[mushaba]

Thanks green i will try that as soon as i can..
Detecting and air tests doing great doth on mono and 3dss (without shielding),still cant understand why i have that big flyback spikes at 600-700 volts,something is wrong and i cant figure what,some help would be nice!!

[godigit1]

Hi Mushaba,

From the Build doc:
"Monitor the signal across the damping resistor using an oscilloscope with x10 probe, where you should see a flyback signal of about 350V or higher."
I dont know if your still on the Hot of the coil or not? But look at the damping resistor at . R4 pl2 side .
Does your signal there still flat top at the end of the spike?
I just got over being sick, and just got two MPP running again so tonight I can check mine at the hot side see if that is there as well. Ive never tested that way but Im always learning.
To me your coil looks slightly over damped. Back things off to 5us and take a shot turn off averageing if you have it on.
What is your final Resistor value?.

[green]

Thanks green i will try that as soon as i can..
Detecting and air tests doing great doth on mono and 3dss (without shielding),still cant understand why i have that big flyback spikes at 600-700 volts,something is wrong and i cant figure what,some help would be nice!!

It depends on the coil inductance and resistance, and the TX pulse width. You should avoid letting the flyback voltage exceed the breakdown voltage of the MOSFET as this will waste energy, make the device get hot, and also slow the decay. The value of 350V is just a guide as what to expect for a typical 300uH coil with a TX pulse rate of 1000pps and a pulse width of 100us.

(from reply#37) coil inductance, resistance and pulse width effect peak current at Tx off. Power supply volts,D10 and R3(3R3) effect peak Tx current also. With a fast coil(low capacitance) peak volts at Tx off equals peak Tx current*Rd[(R1*R12)/(R1+R12)]. With R1=470 Rd=320. Would take 2A peak current at Tx off to get 600V. For damping with a fast coil R1 would increase taking less peak current at Tx off to get 600V.

[waltr]

All correct Green.

When I was building my HH2 I experimented with coil current and TX pulse time verse detection distance and circuit stability.
What I found is:
1- best when tx pulse width is at least 3 time coil TC (L/R).
2- best stability is with less coil current.
3- adding 10 Ohms is series with the coil, dropped peak coil current from 1.6 Amp to 0.6 Amp, but did not decrease detection distance. In fact detection distance was increased due to circuit being more stable so Gain in integrator and Sat could be increased.
4- With 10 Ohm in series the fly-back Voltage is greatly reduced.
In the design I also have a 1 Ohm resistor from MOSFET to power which allows easy coil current measuring with a scope.
Also allowed a resistor to be inserted in series with coil to MOSFET to adjust the total coil TC.

Try measuring with O'scope the coil current. Best is when coil current almost level off before turning off the coil. Then try adding some R in series with the coil.

Increasing coil current does not increase detection distance by much. To double distance coil current needs to increase by 8 times.
Increasing distance is better done in the receiving side.

[godigit1]

Also I just got to thinking, you and I have the same inductance meter. I have found mine to be unaccurate by about +-30% down in the uH ranges its good higher.
I found this out when I sent Green some coils for testing a couple years ago and he measured different values than I did.

[mushaba]

Hi Mushaba,
From the Build doc:
"Monitor the signal across the damping resistor using an oscilloscope with x10 probe, where you should see a flyback signal of about 350V or higher."
I dont know if your still on the Hot of the coil or not? But look at the damping resistor at . R4 pl2 side .
Does your signal there still flat top at the end of the spike?

Hi godigit1,Thans for your reply and help.yes



What is that negative voltage,what is happening there?

I just got over being sick, and just got two MPP running again so tonight I can check mine at the hot side see if that is there as well. Ive never tested that way but Im always learning.
To me your coil looks slightly over damped. Back things off to 5us and take a shot turn off averageing if you have it on.
What is your final Resistor value?.

Hope you get well soon!!I must do something wrong at the damping process,i connect a pot instead of R4,i didnt see differences if i connect (the resistor parallel reistor+pot)..When the output (TP3) has the smallest (negative) duration i disconnect the pot measure the resistance and put a resistor to place...The above pictures are with 3300 Ohms R4..

1- best when tx pulse width is at least 3 time coil TC (L/R).

Hello waltr thanks for your reply and help! What TC acronym stands for (embarrassed to ask but i dont know)

2- best stability is with less coil current.
3- adding 10 Ohms is series with the coil, dropped peak coil current from 1.6 Amp to 0.6 Amp, but did not decrease detection distance. In fact detection distance was increased due to circuit being more stable so Gain in integrator and Sat could be increased.
4- With 10 Ohm in series the fly-back Voltage is greatly reduced.
In the design I also have a 1 Ohm resistor from MOSFET to power which allows easy coil current measuring with a scope.
Also allowed a resistor to be inserted in series with coil to MOSFET to adjust the total coil TC.

Try measuring with O'scope the coil current. Best is when coil current almost level off before turning off the coil. Then try adding some R in series with the coil.

I dont have a current probe for my scope...I will connect an 1 Ohm resistor from power to source of irf840..

Increasing coil current does not increase detection distance by much. To double distance coil current needs to increase by 8 times.
Increasing distance is better done in the receiving side.

Thank once again for the understanding and great help!

It depends on the coil inductance and resistance, and the TX pulse width. You should avoid letting the flyback voltage exceed the breakdown voltage of the MOSFET as this will waste energy, make the device get hot, and also slow the decay. The value of 350V is just a guide as what to expect for a typical 300uH coil with a TX pulse rate of 1000pps and a pulse width of 100us.

(from reply#37) coil inductance, resistance and pulse width effect peak current at Tx off. Power supply volts,D10 and R3(3R3) effect peak Tx current also. With a fast coil(low capacitance) peak volts at Tx off equals peak Tx current*Rd[(R1*R12)/(R1+R12)]. With R1=470 Rd=320. Would take 2A peak current at Tx off to get 600V. For damping with a fast coil R1 would increase taking less peak current at Tx off to get 600V.

Hello green thanks for your reply and for the help!Im building the Rev-E "D10 and R3(3R3) effect peak Tx current also"

Also I just got to thinking, you and I have the same inductance meter. I have found mine to be unaccurate by about +-30% down in the uH ranges its good higher.
I found this out when I sent Green some coils for testing a couple years ago and he measured different values than I did.

This inductance meter sucks but its the only thing i have right now...I ordered an LCR meter Atmel based from ebay,i heard they work pretty decent..

[green]

Where do I find a schematic for REV-E?

[mushaba]

Where do I find a schematic for REV-E?

Here sir https://www.geotech1.com/forums/show...475#post241475

[mushaba]

Works smoothly,the sound of the threshold became more stable but very nervous to turn..

[green]

Here sir https://www.geotech1.com/forums/show...475#post241475

Thanks

Have you tried looking at amplifier out on your MPP while positioning either your 3DSS or basket coil near the operating coil to see what resonant frequency the have?