Tiny

[Anonymous]

Hello to all: In the site www.pulsdetektor.de here are the Tiny circuit. Somebody has constructed it? they have algun commentary that to do with respect to the circuit?
Thanks.

 

[Anonymous]

Sorry, Carlos, I couldn't find the schematic on the site.
By algun chance are you from Ushuaia?
--Dave J.

 

[Anonymous]

Dave,
I just found it by trial and error!
Click the top left button once
then the second button (projeckt) twice
you will see it change to tiny-menu)
select "Schaltplan button" for circuit
regards Rob.

 

[Anonymous]

Thanks, Rob.
The overall scheme looks pretty straightforward. It's possible this design has been around a few years. Although I didn't peruse the schematic thoroughly, I didn't notice any components that weren't widely available 15 years ago.
I noticed a design error, unfortunately a common one: the battery reversal protection diode, D1, is wired in parallel with the battery, rather than in series. This arrangement is more efficient than the series arrangement, and still provides protection-- for a few milliseconds, until the diode goes up in smoke. If it fuses as a short circuit (or if the specified rectifier is rated for 100 amperes), the main circuit will still be protected, but you'll probably fry the traces on the PC board, blow the switch or other wiring, or the batteries will be destroyed or at least get pretty hot.
So, wire the rectifier in series with the battery. If you're obsessed with efficiency, you'd use a MOSFET instead, but you had that obsession and knew how to do the MOSFET trick, the "Tiny" design is not what you'd be building anyhow since it's inherently inefficient.
Speaking of "tiny", a few years ago I built a fully functional PI metal detector in a housing about the size and shape of an old-time "pocket pager". Battery, speaker, everything but the searchcoil. No surface mount, either. Performance was quite respectable by the standards of that time.
--Dave J.

 

[Anonymous]

Hi,
if you put a FUSE of 1 Ampere in series with before the diode it should be a current path involving only the battery , protection diode and the fuse. The last one will burn in few milliseconds breaking the current flow before damaging anything else.
Also self-recovery fuse devices(miniaturized) can be used , to avoid sostitution of burned ones, but considering that the delay of intervention could be higher (in the 10 ms order).
The schematics is pretty simple and could offer performances comparable with other projects like this (twinloop,sandbanks, etc etc) that are on the geotechnology page. Nothing special but a good starting point to approach pi constrution.
Martin

 

[Anonymous]

Did anyone see that there are some other designs on the site? There are a couple of microcomputer based PI's which use Atmel chips called "Twiggy" and "Digger". There is also reference to a design called "Klondike" but it would not come up when I clicked on it.
The Tiny is a pretty cute little design. My guess is that it will work well unless the ground minerals get too bad. Take a look at how the receive timing monostables are triggered. The receive signal is tapped off and amplified by 100. Transistor Q3 turns on and fires the first monostable.
Also, note the use of an opto isolator U9 which is used to drive the audio VCO. This design is without question better than many that are floating around. The Tiny takes two samples instead of the usual one which will cut down the interference from 50 - 60Hz noise as well as other noise sources and the signal due to the earths magnetic field.
The PCB layout is also provided so I am interested in hearing how well this little "detektor" works if anyone builds it. My guess is that it will be a very useful detector.

 

[Anonymous]

Thanks, Martin. But rather than a fuse, how about a (dynamite) blasting cap? That way the user will know immediately that the battery was installed backwards.
--Dave J.
PS: have someone else test it to make sure it works.

 

[Anonymous]

Hi Dave,
and thanks for the ironic dynamite (exploding foil ? ) blasting cap idea!
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But I saw something similar also in the Corbyn's article that's why I delivered the (blasting cap like) fuse hint!
I now that many important designs still now use the fuse strategy to protect electronics from damages both for reversing the battery caps or for the charger plug in circuitry.
Sorry, you are the designer,
next time I'll use a diode in series as protection
taking all its internal junction drifting effects adering your philosophy.
Thanks,
Martin