Replies to Minipulse Plus

[Qiaozhi]

Is there a suitable replacement for the BC214L transistor? It seems to be getting scarce. I did a search on the internet and found references to BC309, 2N5087, 2N3906 and BC559 as potential replacements. Would these make suitable replacements or is there something better? Thanks.

Almost any general purpose BJT will do. You can replace the BC214L with a 2N3906, and the BC184L with a 2N3904.
Please be aware that there's a few mistakes in this back-engineered design that need to be corrected. Once I have a completely working board, I'll document everything and post it here.

So far I have the power supplies and the transmitter working. Hopefully, the rest will be completed before the end of this week.

[eogeo]

Is there a suitable replacement for the BC214L transistor? It seems to be getting scarce. I did a search on the internet and found references to BC309, 2N5087, 2N3906 and BC559 as potential replacements. Would these make suitable replacements or is there something better? Thanks.

[Davor]

OK, so I'll not hold my breath, but I'll surely keep my eye here.

[Qiaozhi]

Just received 3 PCBs today from Siverdog. Once I've got the components together I'll build one unit to check everything is OK, and then write a "build document" to try and prevent the same failures that Surf-PI builders are experiencing.
Be patient though, as this is very much a background task.

[Qiaozhi]

Thanks Qiaozhi for a great project and all the updates you made.

I noticed something in the Minipulse Plus top layer.jpg that looks a bit odd, the trace between Q4 and R28 appears to cross over the trace between U8 pin3 and R29 as though they are connected although the schematic does not have them connecting. The area has been circled in blue in this screenshot.

Looks like cut and past of images does not work. Trying the Insert Image icon, hopefully that works.

[ATTACH]28533[/ATTACH]

It appears that this error was in fact flagged by the DRC report, but I missed it (human error ) as a result of modifying the PCB footprint for the cermet trimmers to add a 4th pin. This extra pin produces a number of clearance errors because of the copper track embedded in the footprint, and the track-to-track error near Q4 was buried in the list.

I'll fix this layout issue later today, but this of course means the first batch of Silverdog boards will need a simple cut and strap operation.

[eogeo]

Looks like cut and past of images does not work. Trying the Insert Image icon, hopefully that works.

[eogeo]

Thanks Qiaozhi for a great project and all the updates you made.

I noticed something in the Minipulse Plus top layer.jpg that looks a bit odd, the trace between Q4 and R28 appears to cross over the trace between U8 pin3 and R29 as though they are connected although the schematic does not have them connecting. The area has been circled in blue in this screenshot.

[sinclairuser]

hi all if you would have mentioned those boards before dave i'd have probably bought them, but further investigations have revealed to me that none of the vlf projects here will beat the vlfs i allready have, idx(original) and whites 3900 pro plus(not a treasure detector).
so i'm only going to build pi in future, i may buy an idx kit for future repairs, as a side note the 3900 pro plus is a cracker for 300 quid brand new a better machine than the coinmasters for that money IMHO, the only cons of that is its 14khz(15kh dont work apparently but i dont tinker untill the warranty is up),and coils are hard to find (love a 6" for it).
i'm looking forward to this project, and will buy a kit in fact even just the board depends whats on offer.

[satdaveuk]

Yes (as you've noticed) the original layout is in the sticky thread. The layout was single-sided, and there are a few links on the top layer. Actually the links are zero ohm resistors. However, there's some odd tracking in the original layout, and a few components fitted that are unused in the model I disassembled. The Minipulse Plus version is more sensitive, the main delay can be adjusted down to 10us, it's much more stable and less susceptible to external EMI, and has a slow SAT. It hardly seems worth messing around with nasty chemicals, when you will be able (in the next weeks) to purchase a high quality double-sided PCB from Siverdog for a reasonable price. I think there will also be a kit available with all necessary components.

Hi George
I think in this instance after listening to your advise its not worth attempting to build the original because of the main delay not been able to drop low enough which is the same problem and disappointment todate I had been experiencing with the mini pulse 3.
Can see you have done your homework with this design and the fact you have got down to the magic 10us (Gold detection) and got the SAT speed lower its telling me its worth at least one build.
Also component count and overall cost is quite cheap and cannot see much problem for up and coming hobbyists/engineers.
Your correct far as PCBs Its not financially worth doing DIY,but in reality neither are these projects on here, If you work out time spent from first initial interest to completion of a fully working detector in money terms its not viable because £ Per hour compared to repairing customers equipment in the same workshop, could at the very least buy me a top of the range Gold mask with a SEF coil.
With this project unless someone here is willing to spend the time doing single sided layfiles will do as you advise and buy ready made PCB.
Still have Two Silverdog ITGSL boards here which were never used if anyone wants to make me a reasonable offer.

[Qiaozhi]

Sorry George just noticed you already put them on the sticky, im tired

Yes (as you've noticed) the original layout is in the sticky thread. The layout was single-sided, and there are a few links on the top layer. Actually the links are zero ohm resistors. However, there's some odd tracking in the original layout, and a few components fitted that are unused in the model I disassembled. The Minipulse Plus version is more sensitive, the main delay can be adjusted down to 10us, it's much more stable and less susceptible to external EMI, and has a slow SAT. It hardly seems worth messing around with nasty chemicals, when you will be able (in the next weeks) to purchase a high quality double-sided PCB from Siverdog for a reasonable price. I think there will also be a kit available with all necessary components.

[satdaveuk]

Sorry George just noticed you already put them on the sticky, im tired

[satdaveuk]

Well enough said
If its anything to do with Eric Foster its a must build job , Eric has proberly forgotten more about PI format than most of us know on here, soon as time permits will join you here, In the meantime shall just observe and see how you all get on.
Just a quick question please, Was Erics version on single or double sided, also really interested to be able to see his original circuit etc first hand if your able and Eric doesnt mind.
Thanks again qiaozhi your a gent.

[Qiaozhi]

Hi
Thanks Qiaozhi
Looks a nice project , when I first seen Mini pulse I thought it was going to be a revised version of the Minipulse 3 I built a couple of years ago which was based round the ATMega 8, but of course its not.

The name Minipulse was originally associated with Eric Foster, as per the detector in this project. Later Minipulse designs have simply purloined the name, but (as far as I'm aware) they have nothing in common with Eric's designs.

Has anyone here thought about making a single sided board layout of this project for those of us who prefer to make are own boards?
Regards

I'll leave that to someone else, as I don't have the time available.

[satdaveuk]

Hi
Thanks Qiaozhi
Looks a nice project , when I first seen Mini pulse I thought it was going to be a revised version of the Minipulse 3 I built a couple of years ago which was based round the ATMega 8, but of course its not.
Has anyone here thought about making a single sided board layout of this project for those of us who prefer to make are own boards?
Regards

[6666]

I was curious about the 555 circuit in the Pulse Technology Minipulse PI Detector, because it was a bit different from the normal 555 circuits we see, anyhow i knocked it up and it works ok.

Video with audio at http://www.youtube.com/watch?v=P-B-5...ature=youtu.be