Hack The Spy Ear and Learn to Reverse Engineer a Circuit

Step 2 Draw the Schematic

To draw the circuit and simulate it I used Linear Technology's LTspice. It's free and it is great.

LTspice
http://www.linear.com/designtools/software/switchercad.jsp

I make the Spy Ear schematic available for the first time on the web in this instructable.

V1 N001 0 1.5
Q1 N006 N009 0 0 2N3904
Q2 N004 N008 0 0 2N3904
R6 N001 N004 4.7k
Q3 N005 N004 0 0 2N3904
R7 N004 N008 200k
C4 N008 0 5n
R§VR1 N002 N003 5k
R§VR2 N003 N006 5k
R2 N001 N002 220
C§BigC N002 0 10µ
R8 N006 N009 200k
C1 N007 N009 .1µ
R1 N002 N007 3.3k
C2 N003 N008 .1µ
V§Microphone N007 0 SFFM(0 1u 2000 100 100) AC .1u
R§Earphone N001 N005 75
C3 N001 N005 .1µ
.model NPN NPN
.model PNP PNP
.lib C:\Program Files\LTC\SwCADIII\lib\cmp\standard.bjt
.tran 0 100ms 0 1ms
.backanno
.end

Comments

[achraf52]

Do I really need that transistor or use any type .

[Biotele]

yes any transistor will work.

[achraf52]

Great you helped me from having to buy those type as I have so much ones but no one is this type, now I only have to grab capacitors and resistors and put them together .

[Dave54321]

Wow that's great, here is another diagram of the Spy Ear from area 50
it allows you modify the Spy ear by removing a transistor and powering
it by the computer to make a super duper sensitive Condenser Mic
which worked well for me as I wanted a better mic than I could find at
radio shack.

here is the link to several directional Mic's the last one is the Spy Ear
http://www.techlib.com/area_50/PTM/audio.htm#super and also includes
the schematics.

also the .1 uf caps don't appear to be electrolitics so observe the DC potential
in this circuit when using electolitic caps by putting the + to the higher potential
so they don't blow up, which I doubt at that low voltage.

[Biotele]

this is awesome. they also use the photoresistor/led pair from my other instructable as ACG.

[Dave54321]

I think you mean AGC automatic gain control. I don't know how the
photo resistorwould work in that circuit.

What lead me to the spy ear was I wanted to make my computer
mic actually put out some audio to make a series of affermation
statements to play while I sleep under my pillow. The little condenser
mic's that are powered by the computer audio circuit board lack
sensativity so you must speak closely to the mic and you pick
up a lot of unwanted noises made by the mouth that are not normally
heard in conversation.

What is the title of you other Instructable ?

[Vaxinius]

Im trying to open your schematic in LTSpice and all I get is a bunch of text grid locations in a list. Need a bit of help with this. Bit new to this program but im familiar with programs like it. When i download the file it saves as a .tmp? Should that happen?

[Biotele]

just rename them with their proper names "spyear.asc" and "spyear.net", then open them with ltspice.

[Vaxinius]

nope even when i rename the file i still get a spice error message that says theres "multiple instances of [symattr]"

then it lists a whole bunch of text of wire locations etc. same thing as before.

your help is appreciated as im a training electronics technician in the canadian forces and getting the edge on software like this can only do me good.

[Biotele]

rename the extensions of both the files as ".asc" and try to opening them. I think the files are mixed up.

If that does not work Google "multiple instances of [symattr]". You might find the problem. keep me posted, thanks.

[Vaxinius]

Aha.

Turns out my problem was i didn't know how to properly rename an extension. Kept renaming the file the whole time. ...to the sandbox!

[Vaxinius]

Aha.

Turns out my problem was i didn't know how to properly rename an extension. Kept renaming the file the whole time. ...to the sandbox!