Replies to Minipulse Plus

[joop]

I bet it is a temperature effect what you are seeing... VCO drift.

[josewashere]

Yes it could be but it recovers quickly when you remove your finger, maybe too quick to be temp related
Jose

[josewashere]

Qiaozhi. Further investigation into using the TL072 in place of the Ne5532. I hadn't noticed this the other day but if you check at longer sampling delays you will find that the detector ignores metal almost completely. Interesting effect!

Anyone have any ideas why this would be the case?

[KingJL]

Qiaozhi. Further investigation into using the TL072 in place of the Ne5532. I hadn't noticed this the other day but if you check at longer sampling delays you will find that the detector ignores metal almost completely. Interesting effect!

Anyone have any ideas why this would be the case?

GBW (or rather lack of it)!

[KingJL]

GBW (or rather lack of it)!

For an improvement, try the MAX412. I really like the OPA2211, but the available packages make hobby usage extremely difficult. I have used the single opamp version (OPA211) successfully in project detectors (as it is available in SOIC).

[josewashere]

I will give the OPA2211 a try Thanks!

[multieagle]

There are dip adapters, but fairly expensive: http://www.ebay.ca/itm/1PCS-OPA2211A...item3390bb5205

[KingJL]

There are dip adapters, but fairly expensive: http://www.ebay.ca/itm/1PCS-OPA2211A...item3390bb5205

I believe that this one includes a mounted OPA2211... I would suggest you ask the seller to be sure.

[josewashere]

I have a friend who has these small adapter boards so that should not a problem.

[Tinkerer]

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

DIP adapters cheap

[josewashere]

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

[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.

[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.

[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.

[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...