So, we decided to create a skimmer that transmits sound and pins over the radio channel.
The scheme of work for us will be as follows:
The sound is removed from the magnetic head and transmitted over the FM range to any receiver (for example, an mp3 player that can write a radio or a car receiver for many hours in a row). The signal from the pin-pad will be transmitted in the same way, only instead of the head there will be a tone dialing generator.
As a result, we will get two records - the first will have sound with dumps that can be sent for decode to some service, and the second will have beeps (do-re-mi-fa-sol-la-si), where each note will be match a specific figure. And any musician will guess the pin code from four notes)))) Well, or in the sound editor, open it and see what kind of number is under this or that tone. More on this below.
We will need:
+ Two radio transmitters (we do it in the first step).
+ Tone generator (do on the second).
+ Two radios with signal recording function (buy a player for 1000r and don't worry).
First. We make transmitters.
For the gear you will need:
+ Coil - made independently. We take a PEV0.5 wire (just a copper wire 0.5 mm in cross-sectional diameter), wind it on a cylindrical object with a diameter of 5 mm. 5 turns. Then we take out the object, and fill the coil with hot melt glue.
+ Antenna - remnants of a wire of 5-10 centimeters of arbitrary shape.
+ Battery tablet (1.5 v)
+
Power button (big red XD) + Transistor KT3102 (in radio parts they know what it is, it costs a penny)
+ Resistors for 3.3k, 10k, 1k (also pennies are in the same place)
+ Conder for 12n, 100n, 5p, 10p, 28p (I think you don’t need to explain where to get it and how much it costs)
+ The wiring diagram itself (either print the finished one (link), or solder on the workpiece, scratching the tracks with a clerical knife, it costs 100r maximum )
+ Head for reading sound from an audio track.
Now we solder all this to the circuit.
The microphone in the diagram indicates the magnetic head itself (in another article, read how to strengthen it on the knees, but we hardly need it).
When assembling the second transmitter, the tone generator will act as the microphone.
So the guts for the dump transmitter are ready! In the third paragraph, we will configure them, but you can already mount them in the face!
Second. Putting together a tone dial generator.
We will need (all in the same radio parts, we don't buy pies in the school canteen for a couple of days and save up for details):
+ 10 buttons
+ 1.5 V tablet battery (although it's easier to use the same battery as the transmitter uses)
+ 10 resistors for 20, 40 , 60, 80, 100, 120, 140, 160, 180 and 200 k
+ Transistors KT315 and KT361
+ Conder on 50n
+ The wiring diagram will have to be done already on the pin-pad, because the buttons are scattered over the face.
So we solder! We put an opening key and one of 10 resistors under each pin-pad button.
The red triangle marks the radio transmitter. By the way, you can power on from the transmitter (boldly connect to the same battery in parallel), all the same, our pin-pad from one battery will work for two months in the summer))) But if the transmitter is crooked, then it will slightly change the transmission frequency for each button, so that on the diagram I added a separate battery for the tone generator.
Guts in the pin-pad now lie too, let's go yeah!
Step three. Customization.
If your hands are straight, just turn on the transmitter and on the autosearch of frequencies you will catch your transmitter immediately. It did not work out - we heat it up a little with a lighter with hot melt glue and change the distance between the turns of the coil. And if the hands are also golden and it turns out to tune both transmitters to the same frequency, then only one receiver will be needed and you will not have to synchronize in time from two audio tracks and we will get a pin just between the input and output of the card.
Be sure to listen and memorize the notes that correspond to each pin-pad digit. Well, or write it down in the editor, if the department "k" came to the ear in childhood)))
That's all! You are great!
You can now safely put the skimmer for field tests in the conditions of the far north or harsh Africa, in order to have guarantees that the frequency will not go astray on the transmitter due to the thermal deformation of the copper coil! The maximum operating time of the skimmer has never been established. There is a possibility that he feeds on the holy spirit of Eve)))
Pros:
| + working time - up to two weeks guaranteed, but months (years?) - check it yourself. + security - in case of removing the skim dump from you. + small dimensions - you can wrap everything into an in-slatted rail to pack) + cheap manufacturing - the guts will pay off on average in 0.01 seconds of device operation))). |
Minuses:
| - when changing the temperature regime, the slightest deformation of the coil knocks down the frequency. You have to periodically adjust the receiver. For example in the morning and evening. Or just make thermal insulation, but still, from room temperature to street temperature, the temperature will slowly fall or rise)) - the radio transmission distance is up to 150 meters, but a high-quality signal in line-of-sight conditions is 30-50 meters, indirect - from 5 to 15 meters. You can sniff the receiver with a dictaphone behind the cornice next to it or stick it somewhere. Be smart, not all I think for you! - The frequency of the radio transmission will also drop as the battery is discharged, but in the field at a temperature of 20 degrees (and we all remember that in the cold, the battery capacity drops significantly) within two weeks the voltage from the battery did not drop so much that the transmission frequency would drop. |
(c) Eve
