TD3X ( pi )

[eclipse]

Do you think there is some room for increasing voltage gain, currently its around ~30db, up to 50-60db (increasing R1/R3 up to 47k - 56k)?
If the device showed stability perhaps this is possible to adjust a little?

[Thomas]

hello all,
again.

regarding the schematic being all on one page..........

as I was using a limited program I suspect that's why it wouldn't let me export
the complete schematic on to JPG.

I ended up doing I the good old fashioned way.......
yup,
separate A4 sheets and a roll of selotape , ( other forms of clear sticky tape are available )
suck it together on the kitchen floor,
hey presto,
schematic all on one big sheet.

Like this?
I have a question,

[DOOLEY]

hello eclipse,

regarding R1 and R3,
gain on the pre-amps is 33 x 33 = x 1089 which is comparable to the "usual" 1k / 1M (x1000)
well,
actually non-inv amp is 33(+1) x 33(+1) = x1156,
or there abouts.........

anyways,
think the pre-amps are doing the usual x,
but I know what you mean,
the whole detector hasn't very much gain, compared to the likes of HH and surf.
and is quite reliant on the "last" opamp being used as a comparator for detection sensitivity.

looking at it,
poss the best place to put another amp would to cut between the 470 ohm and
and TP4 and add an amp in there...........


THOMAS !!!

absolute genius !!!

aww,
thankyou very much !!!

I messed around for ages trying to do that.
got all sections on the same sheet in the program I was using,
but then couldn't lift it off in one piece to a JPG.



ah,
I see the bits you've circled and can guess your question........

"phones -" TP6 ONLY goes to your headphones minus,
"phones +" TP5 goes to headphones plus.

but yes,
audio+in TP3 connects to "to audio" TP6 ONLY.

[eclipse]

looking at it,
poss the best place to put another amp would to cut between the 470 ohm and
and TP4 and add an amp in there...........

HI DOOLEY, you mean something like this?



This should amplify the signal x10 further more, not sure
if this is conservative number and will it work but reading your upper post you mention other schematics use x200... x470 amplification there

[Thomas]

thanks Dooley, you read my mind. The TP6 had me wondering.

[DOOLEY]

hello eclipse,

yes,
just like that would work,
an extra amp in there would increase the overall gain,
and would poss make it more sensitive,
not sure weather or not it would make it better though,
as the final stage is an opamp comparator stage.............


may make it a bit chattery,
not sure.

could always try,
may make targets on the fringe of detection more definite.

hello Thomas,
i'm good at reading between the lines,
I'm a mechanic,
we learn to be able to read minds,
esp when customers are trying to explain whats wrong with their car........

[eclipse]

I have done some simulations to get around the BAT. ALARM & 6.3V section better.

It appears that at 8.1V battery IC2b output is around 8V (in TD3X audio file), D1 (green status LED) is ON.
Slightly lower battery voltage for example 8V forces IC2b into low negative (-1mv) and the LED is OFF.

Testing with higher battery voltage, 12V for example, instead of 8.1V, will result in -8V output voltage instead of the +8V which is very strange (this section cannot operate with higher than 9V because of this).
...

So there is a pretty tight spot where this section must operate: 8.1V - 9V (MAX)
And if it goes lower than 8V the circuit can no longer operate (low battery), higher than 9V will screw up the regulated +8V
Probably a 12V to 8.1V regulator is needed for this part of the circuit ?

[DOOLEY]

hello eclipse,

looking back at the original circuit trying to figure out what's not working right for you.

you mention -8v, the voltage rails are 0v 4v and 8v,
not sure where your getting -8v from...........


I tested the regulator section up to about 15 volts of battery input or so if I remember correctly and all
functioned fine.

oh hang on,
think ive got it now,

the 8v going in to the resistor divider on IC2b is from the regulated 8v rail,
not direct from the battery, which would be anywhere from 8v up to 14v.

I wrote 8.1v on the schematic to indicate to lowest poss battery input voltage before the
regulator drops out.

so in brief :

battery input voltage can be anywhere between 8.1v to 15v

regulator section outputs are 0v, 4v and 8v

all op-amps are powered with 0v (earth) and 8v
( apart from regulator op-amp which is powered from battery voltage and 0v )

all rails indicated by "8v" connect to the regulated 8v rail

the connector marked as BATT ALARM "6.3v" on the regulator connects to the connector
in the audio section marked the same,

the 6.3v is only an indication of the trip voltage that that section turns on the battery alarm.
it actually turns on the alarm around 8v to 8.1v of remaining battery voltage.

in the regulator section,
when the input battery voltage drops below 8.1v
IC 1a can no longer raise the voltage across the voltage divider (R1 VR1 AND R3) to 4v
via Q1 and Q2 and so its output goes "high" ( about 7.3v )
I just used this to trip the battery alarm.
I picked 6.3v as the trip voltage for a safe margin.

hopes this helps clarity.

[eclipse]

Thanks Dooley that helps.

https://www.circuitlab.com/editor/#?id=2v6v42

This is the simulation page I've created.
It gets the low voltage warning right (lowering the voltage less than 8.1V).

Fails to predict right if voltage (8.1V is higher - example 10,11,12..) - the output 8V goes negative, I guess is just imperfection of the simulation.

Since I'll be using my batter pack consisted by 4x3.7V battery (16.8V charged, 11V discharged I needed some adjustments here and there), thus I've made this simo.
The other adjustment was solved with changing the 5.1V zener with 7.5V zener in the low battery section.

Cheers

[ivconic]

I also tried to put all the pieces together.
But i find some comments bit confusing, like "..audio+in TP3 connects to "to audio" TP6 ONLY..." ?
Here is what i did, i would like this to be checked from mistakes.
Most probable mistakes can be at points where schematic pieces should be connected.
I would like to try to make this detector, since i also like what i saw on video.
Yet, until i got 100% properly connected schematic in one piece; i will not want to waste my time on drawing completely wrong pcb.
Dooley if you can catch some spare time; please do check this:

[eclipse]

Pin 8 of IC1 should be connected to V+, this is all I've noticed missing. Also in order to simplify I swapped Hammerhead oscillator cos it has less parts and does the same.

[ivconic]

Schematic is done in ExpressPCB (Schematic part) and can be downloaded from here:
http://www.expresspcb.com/expresssch/
And here is the .lay file too:
TDX3_PI.zip

[ivconic]

Pin 8 of IC1 should be connected to V+, this is all I've noticed missing. Also in order to simplify I swapped Hammerhead oscillator cos it has less parts and does the same.

Correct!
What a shame!
I founded similar mistake at Dolley's original schematic and reported to him... now i done the same!

[DOOLEY]

hello ivconic.

ah yes,
I issued a corrected schematic further down the thread regarding the missing link between pin 4 & 8 on the 1st 555.
was a silly mistake by the program I was using when I moved the component for more space ..........
but,
schematics checked many times and that was the only error.


I used 2 x 555's for the TX pulse to enable the frequency to be altered WITHOUT affecting the TX pulse width,
simplifying the pulse generator down to only 1 x 555 would be inaccurate.........
unless you disable / remove the frequency pot.
which, to be fair would be fine as I never found I had to alter it anyway.

ok,
checking your schematic against my original............

for YOUR D13 I used a flashing blue led, can be any colour,
I used flashing so that the batt alarm would be on / off / on / off bleep bleep.

phew !!!!!

right, been right round your schematic,
was strange seeing it in a different layout,
but by golly I think you've got it !!

one thing I will say though ,

many many times on here,
schematics are posted with mistakes, deliberate or not, who knows...............

but,
whenever I post, I post EXACTLY what is in my box,
100% , straight down the line,

so rest assured ivconic,
when copied it will work as mine does.


oh,
one further note :
the homemade LDR / IRled coupler,
I used a fairly fast LDR there,
needs to be fast responding to alter the pitch as a target passes.

recently I purchased some LDR's of ebay,they were a bargain !!
but,
they are as slow as hell !!!
and could NEVER be used for this purpose.

hopes this helps.

[DOOLEY]

oh,
forgot to say,

regarding the flashing LED and the diode together used for the BATT alarm,
I know it looks quit odd,
but the second diode is essential to stop back feeding as flashing LED's "leak" !!
lol.

some parts of my design look "odd"
but it works.
i'm not some highly qualified electronics engineer ,
far from it,
just 20 years of being a keen hobbyist , learning all the time.
so,
a highly trained person may look at some things I print and think what the hell's he done that for ???

I work along the lines of IDEA, SIMULATE, REAL LIFE TEST, PERFECT USING TRIAL AND ERROR, THEN CLOSE THE BOX, ENJOY.........