Replies to Minipulse Plus

[josewashere]

That's a great looking coil and looks like it could be shielded if needed by wrapping some spacer material and applying a shield over that.
It could well be ok as it is given that even just twisting two wires together creates a shielding effect.

[Qiaozhi]

Resistor R12 (1k) is in parallel with the damping resistor R1 if monocoil is used, and it is a part of a negative feedback circuit of an op amp. Therefore, when adjusting a damping resistor, one must have U5 (NE5532) running, or otherwise R12 is not going to show its 1k resistance at small amplitudes.

That's correct. You should always make the damping resistor adjustment with the coil connected to the detector, and with the preamp running.

[Davor]

Here's my BasketWeave Coil.

Yours is much better looking than mine

[Davor]

@Qiaozhi, I may suggest a small improvement for a future release of the board. I placed a MUR460 diode in series with R3 resistor (my choice, not a suggestion), but it turned a bit of a struggle, as the diode's pins are very thick. I had to grind one pin so that it may enter a hole. Having larger holes there could be beneficial, as R3 has thick-ish pins as well.

I also have a suggestion to clarify a small detail regarding a damping procedure. Resistor R12 (1k) is in parallel with the damping resistor R1 if monocoil is used, and it is a part of a negative feedback circuit of an op amp. Therefore, when adjusting a damping resistor, one must have U5 (NE5532) running, or otherwise R12 is not going to show its 1k resistance at small amplitudes. Perhaps it would be a good idea to split this resistor in two 510ohm in series to avoid arcing, or at least give it a bit more room, as most obviously many will go for higher voltages and faster coils, and this resistor will be forced to take the most damping load on itself.

[Silver Dollar]

I just ordered a PCB. Here's my BasketWeave Coil. It measures 320uh and 1.5 ohms.
I'm hopeing it shields itself via the outer windings. I just drilled alternating holes approx.
the size of 6 or 8 wires. If you look close I had to add an extra row as the wires take
more space when wound. I don't have a working PI to try it on yet but soon.

[Davor]

Have you tried your woven coil? Been thinking of making one here but they just seem too hard to shield

Not yet. Most probably on Monday. I populated the most of the board, but something else came up.
The idea of a "spider basket" coil is to wind the hot end of a coil inside, and wind around and around towards the cold end and in effect the hot end becomes encapsulated in increasingly "colder" windings. That way the static-prone end becomes shielded in the very coil it is made of. Of course, I have no idea if it really works, and I made mine free-style, which means it is ugly-ish. It will serve its testing purpose.

[Qiaozhi]

Just finished my MMP and found it a pretty straight forward build. Instructions are easy to follow and the quality of the board from Silverdog is good. Its only an experimental board so I am not going to put it all in a case but I think it would definitely benefit from sheilding. In my workshop there is lots of RF interference from fluros, lots of SMPS and various other instruments so there was quite a bit of noise on most of the test points. I am also using an unsheilded, 345uH relatively high capacitance coil and running the board from a 12v 10A power supply which doesnt help. Even so, I am pretty impressed with the air tests. With a small 3mm bolt I get about 10cm.

Even though you're using the MPP as an experimental board, and do not intend to put it in a case, please email me some photos of the completed PCB. It doesn't matter if it looks like a rat's nest. I will then add this info to the Completed Projects thread. I'm certain there are many other completed MPP boards out there, but either everyone is being shy at wanting to display their work, or they think the detector needs to be in a nice shiny box and mounted on a stem. What it looks like is not important.

[CAS]

Just finished my MMP and found it a pretty straight forward build. Instructions are easy to follow and the quality of the board from Silverdog is good. Its only an experimental board so I am not going to put it all in a case but I think it would definitely benefit from sheilding. In my workshop there is lots of RF interference from fluros, lots of SMPS and various other instruments so there was quite a bit of noise on most of the test points. I am also using an unsheilded, 345uH relatively high capacitance coil and running the board from a 12v 10A power supply which doesnt help. Even so, I am pretty impressed with the air tests. With a small 3mm bolt I get about 10cm.

[josewashere]

Have you tried your woven coil? Been thinking of making one here but they just seem too hard to shield

[Silver Dollar]

I took a machine pin socket and used buss wire to connect a SMT
opamp to it then used it in a dip position...

[sinclairuser]

you can build your own chip adapters from perf board and 8 jumper pins, you can also grind out the centre of a dip chip with a dremel, glue in the soic chip in the centre and solder component wire to connect up the pins.

[KingJL]

http://www.ebay.ch/itm/20-PCS-SOP8-S...item2a2cadda99

DIP adapters cheap

These will not work for the OPA2211... The only so-8 package TI has available for the opa2211 is the so-8 PowerPad... it is an so-8 outline with a large thermal pad between the two lines of pads.

[Davor]

I made my first PI coil today. Some kind of self supporting basket weave wound free-style with party straws as supports, and hoping for self-shielding action. 300uH sharp. I made it with little more inductance at first and unwound two turns to make it right. Funny, at the end it took 19m of wire, just as the calculation says. One can always cut a 20m wire and expect that a coil will be somewhat over 300uH.

[josewashere]

Thank you.. Yes I think these are the ones my friend has.

[Tinkerer]

http://www.ebay.ch/itm/20-PCS-SOP8-SO8-SOIC8-TSSOP8-MSOP8-to-DIP8-Adapter-PCB-Conveter-Board-DIY-239A-/181138217625?pt=LH_DefaultDomain_0&hash=item2a2cadda99

DIP adapters cheap