Replies to Minipulse Plus

[6666]

GB circuit works! I made it on a protoboard together with a 555 generator to mimic real world timing, and I only skipped trimmers to avoid clutter - fixed values are OK for the proof-of-concept. Anyway, the timing works as it should. The next step is to place the components onto a perfboard and hook it to its proper places.
The attached files are as follows:

1. the corrected schematic using simple NAND CD4011 instead of a slightly unpredictable CD4093, and taking control over Schmitt trigger by means of simple resistors
2. CRO photo of a same thing in jpg format - obviously working as advertised
3. same thing, only as a zipped LTspice folder

Great work Davor my MPP has developed some sort of fault got to debug it, but will try to make your GB project asap.

[Qiaozhi]

Great work Davor my MPP has developed some sort of fault got to debug it, but will try to make your GB project asap.

Please send me photos of your MPP, so that I can include them in the Completed Projects thread.

[6666]

Please send me photos of your MPP, so that I can include them in the Completed Projects thread.

Yes happy to when fully working.

[liudengyuan]

Until now, no one can be better than Delta Pulse Pulse, whether or stability detection range, so for the average DIY, I think the best option is delta pulse

[joop]

Have you compared Delta Pulse to Minipulse Plus? What makes you say it is better?

[liudengyuan]

Incremental pulse best choice

[WM6]

Until now, no one can be better than Delta Pulse Pulse, whether or stability detection range, so for the average DIY, I think the best option is delta pulse

Delta pulse follow brute force logic and you need your own power plant to supply it. This is why I dont like it.

I prefer PI constructions like old Fisher Impulse design, one set of battery last for 100 hours.

If Davor successfully finish all his MPP improvement ideas, this could be one of most complete PI design.

[josewashere]

Great work! Do you have a plain circuit diagram for the GB mod? and were it connects to the existing circuit? In my day we just used spice on the roast chicken lol.

Today I tried a matched set of caps for c13 and c14 470nf Matched both to within 300pf and couldn't really notice any difference. No joy to be had. Measured old ones and they were 451nf and 435nf.

[Qiaozhi]

Today I tried a matched set of caps for c13 and c14 470nf Matched both to within 300pf and couldn't really notice any difference. No joy to be had. Measured old ones and they were 451nf and 435nf.

I'm pleased that someone has tested the matched cap argument in practice. Personally I've never found any "detectable" difference (pun intended).

[Qiaozhi]

Until now, no one can be better than Delta Pulse Pulse, whether or stability detection range, so for the average DIY, I think the best option is delta pulse

Delta Pulse is (as WM6 stated) a brute force approach. It is a good detector for finding huge buried items using large search frames. It can also be used with smaller coils of course, but it is not designed to work with early sampling, and therefore cannot find small low conductivity items. So in your case, where you're searching for larger items at great depth, then Delta Pulse will be better. However, you could modify the MPP to create a larger brute force TX pulse (same as the DP), but remember to add a heatsink to the mosfet. You would also need to disable the SAT, as discussed earlier in this thread. The modifications required are small to make the MPP work like the DP, but if you already have a DP then go with that. You cannot simply say that one is better than the other. It's horses for courses.

[Davor]

Great work! Do you have a plain circuit diagram for the GB mod? and were it connects to the existing circuit? In my day we just used spice on the roast chicken lol.

I already placed labels C and D on the diagram to follow on the MPP logic. Here is the latest, only slightly modified circuit to facilitate using MC14538 sockets for a simple plug-in solution. Border between MPP and a add-on board is a dashed grey line. So the idea is to pull MC14538-s out, and plug the add-on board in. Connections B, C, D, -5V, and GND are taken from the MC14538 sockets, exactly where they are already.

There will be 2 potentiometers, one for time base (same function as "reject"), and another for GB. The MPP "reject" potentiometer loses its function and becomes replaced with time base (sample duration) potentiometer.
"First pulse delay" is a GB potentiometer. Because this delay is set to be relative to the sample duration, the GB solution position on a potentiometer is largely independent from sample duration. Hence you may shift sample duration left, right and sideways, and your GB setting will remain virtually the same. This gives me some nasty ideas on elimination of the hole ... later on.

[josewashere]

Excellent work! The GB mod is going to make this detector really nice.

[Davor]

I certainly hope so. The other PI projects can benefit from this approach as well, but I'll have to see where to put what to make them tick.
In essence there is no difference between any of the simple projects against the much more expensive commercial ones. Except for the preamp noise and the ways of reducing it. MPP is limited with the coil damping resistance to 4nV/sqrt(Hz) or so. A select few of the commercial products take care of input noise in a meaningful way. QED for example. Everything else is just a clever play of marketing wits and front panel presentation.

[liudengyuan]

Who pulse detector for iron-discrimination programs and technology? I think discrimination iron is necessary, because the whole world is garbage, if we may expand the topic of discrimination iron a discussion. We need to progress

[6666]

Drats I found the fault with my MPP a short circuit 78l05 reg, no real reason for it to fail, was working fine.
I will record current readings as I put the machine back together as an aid for construction.

Here is a tip LOAD test your voltage regs before construction.