Voodoo Main Discussion

[lamoiz]

I assume you're referring to R66? Personally I didn't fit a speaker in the finished detector, but used high-impedance headphones. During testing on the bench I used a 50 ohm speaker. If you're using an 8 ohm speaker, then R66 could potentially get hot, and should be replaced with a higher wattage device. You could also try increasing the resistance to 150 ohms.

yes post 407, r66.
I'll put a 150r to see, or a 33r 2w .. it will be heating for the winter.

[Qiaozhi]

George, the 33r resistance on the hp route, almost gave up soul, due to overheating. My hp is 7.7r (measured), do you think I can replace it with a 100r? Or a 33r 1w? I won't be the only one having this problem, what do you think?

I assume you're referring to R66? Personally I didn't fit a speaker in the finished detector, but used high-impedance headphones. During testing on the bench I used a 50 ohm speaker. If you're using an 8 ohm speaker, then R66 could potentially get hot, and should be replaced with a higher wattage device. You could also try increasing the resistance to 150 ohms.

[MartinB]

hi Godigit, the TX coil is 430uh, and its damping resistance @ 650r. wire 0.8 silicone. The two RX are respectively 5.5 mh or a series total close to 11mh ... wire 0.18; all tuned with a capa 21.6 nf (@ 20 ?) .. the purpose being to have a frequency of 10.5 khz, (10.32, to be precise)

Hi lamoiz
Are you using silver plated copper wire with silicone insulation or plain copper with silicone insulation? Thanks for the information on your coil

[MartinB]

Internal dimensions of the shell are:
Front to back - 293mm
Side to side - 260mm
I have then allowed a further 15mm all round to house the coils

[lamoiz]

Were you able to zero this out?

with the osciloscope I went down to 700mv ..not succeeded in doing better ...

[surfdetector]

R30 tp3 tp1..mini 1.6v .. impossible to zero, there's something I'm doing wrong ..

Were you able to zero this out?

[lamoiz]

nasal detection (without covid of course), is a good fault detection system ....

[lamoiz]

George, the 33r resistance on the hp route, almost gave up soul, due to overheating. My hp is 7.7r (measured), do you think I can replace it with a 100r? Or a 33r 1w? I won't be the only one having this problem, what do you think?

[lamoiz]

r66 hs .. it cooked over a low heat .. I think my 8r hp should not be adapted .. finally I will measure it, because the inscriptions have disappeared, maybe I was wrong.

[lamoiz]

in parallel with this coil construction, i made a large omega with oval center, the tx and rx values are close to this one, but the difference is the use of litz wire for tx.

[lamoiz]

H Lamoiz,

Very clean coil ! Beautiful!

Curious what are the values of your coil?
And what is its speed when you get a chance to scope it?
Thanks

hi Godigit, the TX coil is 430uh, and its damping resistance @ 650r. wire 0.8 silicone. The two RX are respectively 5.5 mh or a series total close to 11mh ... wire 0.18; all tuned with a capa 21.6 nf (@ 20 ?) .. the purpose being to have a frequency of 10.5 khz, (10.32, to be precise)

[godigit1]

you are an observer! this is just for the shape and stiffness. this also affects the inductance, but very little. what are the dimensions of your coil?

H Lamoiz,

Very clean coil ! Beautiful!

Curious what are the values of your coil?
And what is its speed when you get a chance to scope it?
Thanks

[lamoiz]

Hi lamoiz
I am also making this coil when time allows. Interesting to note that you have stepped the TX coil upwards. Is there a particular reason for this?

you are an observer! this is just for the shape and stiffness. this also affects the inductance, but very little. what are the dimensions of your coil?

[MartinB]

Hi lamoiz
I am also making this coil when time allows. Interesting to note that you have stepped the TX coil upwards. Is there a particular reason for this?

[asolone]

can you show some video of this metal detector in operation? I'm very curious