Super TGSL With H Bridge TX Diff RX Quad Sampling

[Silver Dollar]

Well I fired up the addon board today. Only the Transmitter that was previously tested
and the LM393 for the Disc and Geb were installed. The 393 seems to be oscillating not
sure why? I'll have to recheck my wiring. I did notice the last file 4.1 shows the disc pot
feeds the + input where previously it was the - but that should only affect the Disc and
both outputs look similar...

[Davor]

Not nice. I'm sure you'll find the source of it. The symmetry of the signal is also poor.

[Silver Dollar]

Had another look today. It seems the LM393 is oscillating. I added some decoupling. Changed the pots to fixed resistors.
And tried some small caps to gnd on the input pins and a resistor for hysteresis (not sure if correct value). My PS does
put out a bit of switching noise and I have a coil on the TX who's cable shield is not connected. The resistors have 6"
wires on them. I see some grass on the signal even without the LM393 installed but with the rest of the IC's removed
there's not much that could influence that...

Here's the schematic of what I'm working with. I had a thought, maybe the RX inputs should be tied off, they could be oscillating...

[Davor]

How is the negative voltage like?

[Silver Dollar]

It looks the same as the one called noise. I'm using a tiny switcher (12V) with a linear regulator after it (9V)
I may have to setup a battery supply...

[Davor]

Some of us learn it the harder way...
I had a "classic" power supply with heavy transformer etc., and it was not anywhere near the battery quiet.
Trouble with switchers is that they tend to assume some kind of quasi resonant operation regarding the supplied device, so every imaginable problem may occur.

[hoadlies]

It looks the same as the one called noise. I'm using a tiny switcher (12V) with a linear regulator after it (9V)
I may have to setup a battery supply...

HI ,,S/D ,,Yes those switching P/supplies are not good for some circuits I have found in Audio ,But using the 9v Reg after & filter caps should have fixed that issue..
I wish you Lived near me as I have a ****load of 12v 7amp-hour SLA [gel-Cel] Batteries cost me Nix..you would be welcome to a few..

Best of luck with the Distorsion problem ,i watch this thread with with high hopes for your project..

CHEERS BARRY from a very hot AUSTralia..

[Silver Dollar]

I figured it would be OK with the regulator after it. It seemed fine on the original TGSL pcb.
But I can see 1.7 Mhz oscillation and it seems to be coming from the comparitors. It did help
to put a 0.1 uf cap from the active input to gnd but it changed the output pulse. I don't
know how to redesign the circuit to filter the noise and still get the proper output.

I do have a scooter battery and Miata battery that are not being used right now. A bit of
overkill but will allow further testing.

[Oessi]

there is an error in the chart of strengthener of channel, the resistor of 1MoM is skipped

[Oessi]

I offer the chart of strengthener for ductings X and Y. Think that so it will be better

[Davor]

This could do. I'd set time constants a bit different, I'd throw out C5, and a limiter would be much harder, but this could do.

[Oessi]

permanent time 16 is equal a hertz. here is better repressed signal from earth and the signal of purpose is better selected

[Davor]

Sure, but it is very fast, so you have to wave with your coil very fast even when you are near the target. With high pass filter (low frequency cut-off) at lower frequency, and harder compression, you can approach a target slowly, and still have a decent indication. The only bad side is 1/f noise that becomes more pronounced this way.

[Oessi]

Such permanent time of filters used for example in Teknetics Mark 1

[Silver Dollar]

Well I wired up 4 laptop batteries for a +- 8V power supply and I still have oscillation
on the output of the comparitor. I have 2 chips and believe they are old stock genuine
parts and they both do the same thing. The only things powered on the board are the
transmitter and the lm393. I double checked the wiring, everything seems correct. I may
have to chat with the Engineers at my new job next week, see if they have some idea's...