Serbian "Most Wanted"

[salih]

Where is the problem

in my SMW I have problem There is an inverse relationship between sensitivity and volume key . When the sound is low Detecting coin in the air 40cm . When the sound is high Detecting coin in the air 29cm. I use BC517 Instead of MPSA13. help.

[walkman]

But bd 180 wrong. Turn to 180 degree

[mst]

.

smw

[emoxristov]

Thank you all for your help.

[Davor]

BF245B ... it has almost exact Ugso range and it is made symmetrical (drain and source are interchangeable)

[kt315]

.....

[emoxristov]

Help me to analogues of the transistor TIS75

[mst]

nice

[Davor]

Looks good.

[walkman]

add video

http://www.dailymotion.com/video/xzt8zk_cezar-12x16dd-bobin_tech

[Davor]

These are just all the specifications put together, a 555 audio version, Tx running with 470n at 7.2kHz and producing 8.6Vac, Rx tuned to 8.2kHz with 1nF capacitor (which is the part I don't quite understand).

[walkman]

My SMW 555 TX-470nf - 7.7Khz- 8.6 Vac/ RX- 1nf - 8.2 Khz

I can't understand
you smw 555 tx balance 470nf rx balance 1nf is that so?

also amplitude 7,7khz

but 8,6vac and 8,2 khz

how and where to set?

[emoxristov]

By increasing the frequency is not possible to make a primer and becomes unstable with false tone.7-8 Khz works best . amplitude is greater than 10 volts is not stable.

[Davor]

This version of oscillator is way better than the typical oscillators in popular VLF builds, but there is also a catch... you can't use it with any coil. The coil for this Tx must float, so it must not have any of the ends connected to a shield.

In case you build your own coil it is not a problem at all. The op amp takes care that the conduction is precisely 50:50 so the 2nd harmonic will be greatly suppressed, and purity of signal will depend mostly on how the supply voltage is pure.

The same job would be performed even better with a real balanced oscillator, as you have to have a Tx coil floating anyway. The advantage of a balanced mode operation is that a net E-field of such coil in operation is zero, so capacitive feedback from Tx to Rx coils is off the table and better balance is achieved. With single ended operation a net E-field of a coil is half the voltage across the Tx coil, and capacitive feedback limits the depth of achievable balance.

[emoxristov]

My SMW 555 TX-470nf - 7.7Khz- 8.6 Vac/ RX- 1nf - 8.2 Khz