The Crossbow Classic PI

[Carlos]

This is my search coil 45 cm. 13 turns telephone wire 235 uH.

[Carlos]

In my detector i put 1k x 2w and remplaced for the IRF740.
I see in my scope the curve of decay the wave (see my photos)

[kt315]

sandbanks has R7 value 100 Ohm. what did you set?

[Carlos]

http://www.geotech1.com/forums/showthread.php?11921-Site-poland&highlight=Poland

[Carlos]

Yes

[kt315]

R7 in the crossbow schematic ? near the U4 ic?

I build the sandbanks -??? what you meant?

[Carlos]

R7 in the crossbow schematic ? near the U4 ic?

[Qiaozhi]

No. I build the sandbanks modified with the lm318 and I adjust the time of the two monostable with fixed values of resistances. as the operation is the same I want to regulate the times of these monostable. Currently the values of the delay I adjust it in 35 uS and the sample in 25 uS. the frequency at 400 Hz. and the pulse time at 120 uS

The Crossbow has an internal minimum sample delay setting of 25us (or lower if necessary), and can be adjusted by an external control up to 125us. The sample pulse width can be adjusted between 3.3us and 103us. The TX pulse rate is 1000pps with a pulse width of 120us. The EFE sample pulse delay is 400us.

[kt315]

feeling you did not set damping resistor. or something wrong with a coil. do you see R7 on the board?

[Carlos]

here photos

[Carlos]

No. I build the sandbanks modified with the lm318 and I adjust the time of the two monostable with fixed values of resistances. as the operation is the same I want to regulate the times of these monostable. Currently the values of the delay I adjust it in 35 uS and the sample in 25 uS. the frequency at 400 Hz. and the pulse time at 120 uS

[Qiaozhi]

Can someone comment me the times in uS the times in the delay and in the sample are adjusted ?

Are you building a Crossbow clone?

[Carlos]

http://www.geotech1.com/forums/attachment.php?attachmentid=40739&d=1507986237

[Carlos]

Can someone comment me the times in uS the times in the delay and in the sample are adjusted ?

[6666]

W=192mm, or as far as I can see, 7 9/16". The measurements were made with coil cover on so please take the thickness of that into consideration. Thickness of plastic on spare cover is 1mm, so without cover it would be 190mm.

190mm, great, thanks for the info !