TD3X ( pi )

[DOOLEY]

hello DBANNER,

on the original ( strip board version )
it's not a 16 pin ic you see,

it's 2 x 8 pin sockets / chips that happen to be placed together,
they are the TL062's for earth field and 1 volt ref source.

but does look like a single 16 pin when a wire passes directly over where the 2 chips meet.

[dbanner]

Of course! Was not expecting that. Never seen two chips that close on any board. Very nice work. Since I don't have a layout for pcb, I'll have to use your stripboard layout as a guide for building.
Very nice work indeed!

[dbanner]

Has anyone got a layout?

[reiv]

Hello, maybe someone helps to simulate the audio section, can`t fire it up in LTspice

audio.rar
Regards

[eclipse]

Quick video of my second attempt to build this thing. Main changes are PIC microcontroller instead of the 2xTS555, 4093.
Low level 4066 switches (directly controlled by the MCU), 1V reference diode instead of the op amp, commercial optocoupler (pretty fast response - no noticeable lag at all).
Voltages +5V for mosfet, +10V for op amps. With this coil I'm getting 200V flyback on 50uS and 330V on 100uS TX.
Only one 555 timer (for the audio) and it's not TS555 (but regular NE555), I will try to get one.
Still fooling around with it, it's not finished yet.

[DOOLEY]

tidy assembly you have there eclipse,

and nice audio also.

[6666]

Which Low level 4066 switches did you use ?

[eclipse]

I used MAX4066 which can work directly with 5V as High state. Regular switches won't work, I guess even 74HC4066 also wouldn't work.
There is much wider choice of 16 pin (different pinout) low level 4xSPST (ex: ADG411 series).

[eclipse]

I've tested different op amps today for the preamp.
I think we have a winner. OPA2134 blasted away the TL072, NE5532, etc... so it's a keeper. Sound at the edge of detection is now more crisp.
I was currious to test the 4.7uF cap in the sound stage, so I've tested different value (100uF) - sheesh don't do that! Sounds like an alarm.
Also tried different op amps (even a LT1018 comparator) for the final TL062. Better op amps perform worse (flattens the "wobble" sound effect) so this one stays that way.
Other op amps (TL062s) are AD712. Closed the enclosure.

[6666]

I used MAX4066 which can work directly with 5V as High state. Regular switches won't work, I guess even 74HC4066 also wouldn't work.
There is much wider choice of 16 pin (different pinout) low level 4xSPST (ex: ADG411 series).

Thanks, I was going to try 74hc4066, but maybe they will not work.

[6666]

Hi Eclipse, when Dooley designed this project he stated that he did not notice much difference between using 4 volts on the coil and using 12 volts on the coil, did you notice the same thing when you used 5 volts on the coil ?

[eclipse]

I haven't got much time to test it but I did take it on the field with 1x1 coil (650uH) with Delta Pulse, which we know runs on 12V and needs heatsinking, timings (250Hz, 500us pulse width) and performance was in same ballpark - aka 1.7-1.8 meters in air for large object.
Reduced heat on mosfet was noticed, also flyback voltage stays very low (on the small 38cm coil on the video with 500us barely reaches 520V on a 600V and 950V limit mosfets).

I went for the 5V/10V config because I used 4x18650 (16.8V to about 11V) battery pack so there was enough room also there are 5V/10V fixed regs (used LDO 10V just to be safe).

One thing I did noticed, and haven't figured out why...

but seems that the trimmer on the preamp don't go well with the integrator. I mean there are adjustments where the signal on the preamp looks well but there is no signal out of the integrator (completely silenced).
This leaves narrow window for adjustment and probably can cause reduced sensitivity.

On the original schematic it says 3V(?) on the preamp out, but with 5V/10V this point maybe other?

Tried swapping 1V reference point with Trimmer that goes 10V/GND but didn't get much success with that.
I will need to look deeper into that. This integrator does seems less noisy.

[eclipse]

I haven't tried other higher voltages on TD3X for the mosfet, the second board design will not allow that (5V for mosfet and the same 5V for CPU..)

Seems that on my issue above increasing frequency to 500Hz allows the integrator to work better. So advice on this is don't go low on frequency... Preamp voltage out set to 1.8V seems to be best choice depth/stability with Ad712 which is slightly noisy but otherwise works okay.

[Wahyu]

hello Dooley, Ivonic, Eclipse and All

how to connect ground shield coil, at +4V or 0V ?

Wahyu.

[Sean_Goddard]

thank you George .


I welcome the positive response from yourself.

was a bit dubious posting one of my projects,
always that self doubt and all.

My Grandfather was from Derbyshire and he always answered the phone to me with "How Doo Lad". Seeing that in your post reminded me of him, thanks! You have NOTHING to doubt regarding this project, it's BRILLIANT. VERY WELL DONE Sir. The best strip board layout I've ever seen too!