Replies to Minipulse Plus

[WM6]

By the way, I forgot to mention that I've been using the original Minipulse coil, and this is shielded; which is most likely why the noise level was a lot lower.

To what point is shielding connected?

[joop]

Okay, will do so until the complete detector is ready. It will take about a week or so....

[Qiaozhi]

I can now confirm it is the environment that produces the noise at TP3 in my case. I made a new 8 inch coil and this time added a shield. Noise is about 10 times lower. Also replaced the coil with a 1 Ohm non-inductive resistor, the noise is totally gone.

Thanks for helping out. My build is finished and working. Next I am going to put it in a box and make a complete detector.

Good work! Please email me some photos of the complete build, and any comments you want to make. I will then add them to the completed projects thread. At the moment, other members are either slow in constructing, or too shy to show their results.

By the way, I forgot to mention that I've been using the original Minipulse coil, and this is shielded; which is most likely why the noise level was a lot lower.

[multieagle]

Hi greylourie, if you have heaps of cat5 cable, spend the time and remove the outer insulation and split into the 4 pairs then get one length and undo it so
you have a single strand then wind your coil with it ( I have done this before, but be aware it could take 1/2h or so to do).

Just a thought, no need to remove outer casing, just connect the coloured wires in series to yield two leads.

[Davor]

Hi Davor
so you are going to build your 4017 project, was looking at trying it this weekend but will wait for you to debug.
One thing I dont understand is why the clock goes to the reset.

Don't wait for me - I have a room to paint before my summer shack start producing. I can't say when I'm starting. Off the bat I can tell you that R1 C1 time base is too short with the values presented, and better ones would be 10k in series with a 25k pot, and 3n3 capacitor.
Clock goes to reset to restart counting. 4017 then counts till Q9 goes high, and then the U3/U4 oscillator just stops ... until 555 sends a pulse to reset a counter that turns Q9 low and U3/U4 start oscillation again, and they oscillate till Q9 goes high etc.
A PNP transistor is just a clamp that limits voltage at C1 and thus dictates duration of a first transition. It is a delay till a first sample and thus GB is adjustable. With this setup sample durations are at constant ratio against the delay, so GB once set is valid for a wide variation of sample durations.

[joop]

The original Minipulse coil is 8" diameter. Also, try moving the coil into different orientations and watch if the noise level changes. It may all be external noise.

I can now confirm it is the environment that produces the noise at TP3 in my case. I made a new 8 inch coil and this time added a shield. Noise is about 10 times lower. Also replaced the coil with a 1 Ohm non-inductive resistor, the noise is totally gone.

Thanks for helping out. My build is finished and working. Next I am going to put it in a box and make a complete detector.

[joop]

...

So who is detecting?

[greylourie]

- wolfs' procreation area (only largely without actual wolfs). If that is what you seek - you'll find it here. A stone house with open fire and all commodities 1700's style - no problem. A distant island - no problem at all. Diving? Paradise.

Sounds like paradise.

[6666]

Hi Davor
so you are going to build your 4017 project, was looking at trying it this weekend but will wait for you to debug.
One thing I dont understand is why the clock goes to the reset.

[Davor]

My trouble is that the law in my silly country makes most of my detecting illegal, so unlike most of the people I'm keeping my chastity till fall when all the tourist-related hullabaloo subsides. I'll also have time to actually solder something that I simply can't afford with everything else at hand.

If you've never been to Croatian coast, it is mostly wild and sparsely populated. Tourism is the only thing that really grows there, aside from the prices in the markets. Unlike other places you can still get in touch with nature there and enjoy it, but no detecting.

You may even find places where even tourism is only a foreign expression with no true meaning. We call such places "vukojebina" [woo:koh:yebi:nah] - wolfs' procreation area (only largely without actual wolfs). If that is what you seek - you'll find it here. A stone house with open fire and all commodities 1700's style - no problem. A distant island - no problem at all. Diving? Paradise.

So who is detecting?

[joop]

Hahaha, first time for me that I read about someone that builds a detector while on holiday instead of going beachhunting....

[Davor]

No, but I packed all the parts that I need to make it. I also bought some extra DIL sockets that I'll violate to make FET sockets and facilitate transition. I also bought a few FETs extra of various kinds to cross-compare in the sockets. I couldn't get J113, but I got some other types. Besides, J113 with capacitances that large is perhaps not the best component regarding charge injection.
I don't think I'll be able to do much with minipulse in the next few weeks as I don't have a proper coil yet, but I plan to go for deserted beaches in fall, so no pressure there.
I also packed parts for a modified Nupi pinpointer with automatic settling.
So much to do (finally ) so little time.

[greylourie]

Darn! I couldn't obtain 79L05 so I'll have to cram in a "normal" 7905.
Tomorrow I'll go for a vacation without any chance to get parts that I miss, so 7905 that is. With a view of Adriatic...

Off to the beach ! Have you built the ground balance plugin to take with you ?

[Davor]

Darn! I couldn't obtain 79L05 so I'll have to cram in a "normal" 7905.
Tomorrow I'll go for a vacation without any chance to get parts that I miss, so 7905 that is. With a view of Adriatic...

[greylourie]

Thanks Qiaozhi. Will do.