SNIFFER XR-71

[Max]

uhm...maybe I understand reason for this question...

[ATTACH]5740[/ATTACH]
Is increasing the R3 necessary when increasing the R1 ?

Thanks,
1843

Hi,
there are other parts connected... like inverting input resistor you didn't draw.

In differential configurations you must mantain simmetry of the two halves to get the differentiation on common mode noise: it's a benefit to you.

So, if you change one , you need to change the other as well.

Both, opening or not the switch, you get a polarization voltage at the lower 120K, thus providing the effect of a battery there used to fix an offset, required for proper operations of preamp far from saturation.

In both cases you actually don't need, to simplify, both resistors to be 120K, they could be also different values. But if the scope is mantaining hi immunity to common mode noise... well... it's strongly suggested you keep them same value there.

This way, the simmetry give you always A(V2-V1), V2 is at + lead, V1 is at - lead and A is the voltage gain...(in your case is 120/1=120 times)... that means a common mode noise will have two amplified components in phase opposition and will be virtually eliminated from signal at output.

This is no matter of which signals you put at inputs, if they are compatible with linear behaviour of the amplifier.

So, though not strictly required for signal amplification it's good you keep simmetry to gain the maximum common mode noise reduction.

Without this your preamp will work too, and you'll not notice big differences there... but cause PIs have enormous amplification along the chain you'll get sooner or later that dang noise propagate being amplified and then create big troubles.

Kind regards,
Max

[1843]

To Max


Is increasing the R3 necessary when increasing the R1 ?

Thanks,
1843

dear sinffer xr-71
i need all list schametec and program please I don,t forcet that
my mail
[email protected]
[email protected]
thank you

[amtech2005]

SNIFFER XR-71

Hello Mohi , Remember the file does not contain a Schematic !! Just a bunch of images . Anyway in the circuit there are 2 "pic-chips" 16C71's and I think there is 1 "pic-chip" used per channel . One for Ferrous and one is for Non-Ferrous in an attempt for accurate discrimination !!!!!!! So if you do find a Schematic you will have to write a Basic-Pic-program for each. If your e-mail address is correct I will send this zip-file. Best of luck on this "Detector Project" There are a few other circuits posted on the web, like this one. But you just have to search for it. .....Eugene

dear sniffer xr-71
the pulse star.zip did,t opend please try agin many thank,s for you or sen it to my mail
[email protected]
mohi

[amtech2005]

SNIFFER XR-71

Hello Mohi , The Pulse Star schematics have never been posted here !! . Aban the forum member who built a copy of this has not been on in 2 years, unless he is under another name.I have been on this forum since october 2001. So for a number of reasons we have had some great technician / Members disappear over the years . Sad, But it's a part of life. Anyway here is a zip-file of everything I have , which is already posted over the threads. Do you notice that Pulse-Star 2 has 2 pic Chips ?? The programed "Pics" Are used for "potential" Discrimination. Sorry, these files are all I have for now.............Eugene

hi aban
please send me diagram and shametec of pulse star 2
thanks for you
mohi
e:[email protected]

hi aban
please send me digrame . shametic and list to my e:mail([email protected])
thanks
mohi

[Geo]

Ok i measured the R22. It is 330R. When i will have free time maybe to replace it with a 390R.
Bye

[Geo]

Hi 1853.
Today i will open my XR71p (original pcb) and i will see what is the R22.
After it (if it is 330R) i will change it to 390R and i will do a test
Regards

R22

At the original schematic (XR71p.pdf) the resistor is 330ohm (at xr71 is R22)

Hi Geo,

GTK has said many times that a resistor in the XR71 is wrong, I think it is R22.
Try to change it and see if it becomes improved or...

Best regards,
1843

[Geo]

At the original schematic (XR71p.pdf) the resistor is 330ohm (at xr71 is R22)

[1843]

One of the differences between DP and XR

help me dear max for build lcd for delta pulse one side

Hi
dear Max
Can you help me for buils lcd one side DeltaPulse.
component list , pcb , shema connexion and hex file.
if you know please help me .
thanks alot.

[erolunall]

hello

http://www.electronics-lab.com/projects/test/022/index.html

maybe you can try but ampermeter can measure I dont Know.You can ask forum member Max for this..
if you try please inform us.
regards.
Erol