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Description: Fingerprint scanners are awesome. Why use a key when you have one right at the tip of your finger? Unfortunately, they’re usually unreliable or difficult to implement. Well not anymore! We’ve found this great fingerprint module from ADH-Tech that communicates over TTL Serial so you can easily embed it into your next project.

The module itself does all of the heavy lifting behind reading and identifying the fingerprints with an on-board optical sensor and 32-bit CPU. All you need to do is send it simple commands. To get started, just register each fingerprint that you want to store by sending the corresponding command and pressing your finger against the reader three times. The fingerprint scanner can store different fingerprints and the database of prints can even be downloaded from the unit and distributed to other modules. As well as the fingerprint “template,” the analyzed version of the print, you can also retrieve the image of a fingerprint and even pull raw images from the optical sensor!

This is the more economical version of the GT-511 which has a decreased memory capacity (compared to the GT-511C3). The module can only store up to 20 different fingerprints but is capable of 360° fingerprint recognition and download and upload templates using serial interface. If you are on a budget and need only a small number of fingerprints stored, this is the perfect option for you!

The module is small and easy to mount using two mounting tabs on the side of the sensor. The on-board JST-SH connector has four signals: Vcc, GND, Tx, Rx. A compatible JST-SH pigtail can be found in the related items below. Demo software for PC is available in the documents below, simply connect the module to your computer using an FTDI Breakout and start the software to read fingerprints!

Note: The module does not come with a cable, check in the Recommended Products section for an appropriate one.

Dimensions: 37 x 17 x 9.5 mm


  • High-Speed, High-Accuracy Fingerprint Identification using the SmackFinger 3.0 Algorithm
  • Download Fingerprint Images from the Device
  • Read and Write Fingerprint Templates and Databases
  • Simple UART protocol (Default 9600 baud)
  • Capable of 1:1 Verification and 1:N Identification
  • 360° Fingerprint Recognition


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Customer Comments

  • What if I have hundreds of people I want to compare to. I am looking for a fingerprint reader that would handle an arbitrary number of users.. If I understand this reader correctly, I’d have to send in each stored template, compare with the freshly captured image, until I found the right stored template. Is there a reader available that will either just do a generic “print to GUID” that would be consistent, so I could store and compare GUIDs on the host side, or maybe a reader which has host based comparison routine that I could do on the host through a SQL server or something?

    • I did a project with one of these a while back where you first put in a PIN and then it would load up that persons template based on that pin. doing this adds an extra level of security and lets you store a lot of prints

      • Yeah.. That’s the “right” thing to do, for sure, but my application was more about convenience than security. I had three organizations come to me for help with this.. One was a sunday school where they wanted the kids to check themselves in and out without having to carry or remember anything, and the others were a karate studio, and a neighborhood pool with similar application.. Device had to be fast, since we didn’t want to cause a line..

  • Error Compiling Arduino Nano Sketch

    FPS_GT511C3\FPS_GT511C3.cpp.o: In function Command_Packet::GetPacketBytes()': C:\Users\eduardo\Desktop\arduino-1.0.1\libraries\FPS_GT511C3/FPS_GT511C3.cpp:17: undefined reference tooperator new‘ FPS_GT511C3\FPS_GT511C3.cpp.o: In function FPS_GT511C3::GetResponse()': C:\Users\eduardo\Desktop\arduino-1.0.1\libraries\FPS_GT511C3/FPS_GT511C3.cpp:735: undefined reference tooperator new

    someone can help to solve this?

  • will the libraries and codes and examples for Gt511c3 and GT511C1 work on GT511C1R? as there are no separate codes and examples available for it (C1R) I am confused whether to use those of GT511C1 or those of GT511C3 also where do I find the 4 pin jumper in India :-(

  • Dear,

    I bought the Finger Print Scanner (GT-511C3) I am developing a project where I need to store the biometrics on a server. Then need to check the biometrics registered in the database. I want to know how to store biometrics in a string to send to the server. I’m doing this with the Arduino Mega 2560

    Thank U

  • hello, please i need serious help here, i bought the sensor and i have no idea how to check if it’s working or not.

    i have EasyPIC V7, how can i use it to connect the sensor to my laptop and run the sensor SDK file ? or can i use a serial to USB adapter ? please help ASAP !!

  • My fingerprint scanner did not come with a cable. It’s unusable without one. For a >$30 sensor, I expect better. I suggest you ship a cable with these in the future. What cable do I need to order?

  • I am having trouble getting this to work with a Basic Atom Pro. I am able to communicate with it and make the LED turn on but only with the TX pin disconnected. If it is connected, the Atom doesn’t receive any data. I have tried a level translator for 3.3/5V and using that, nothing works. Has anyone gotten this to work with an Atom Pro? Any input would be greatly appreciated.

  • The datasheet specifies USB v1.1 as a communication protocol. Does it mean that this module can be hooked up by USB directly? If so, anyone knows how? I got it running with UART but I find that downloading the fingerprint image is quite slow, even at 115200 (takes about 5 seconds)

  • can it be connected to a raspberry pi……. ??

  • EDIT: Fixed. Due to the misleading diagram, I had the pins wired backwards.

    Keep in mind that the list is from left to right when the fingerprint scanner is face up and on the top edge of the board.

    The list is of pins is on the final page of the Datasheet and the order is as follows:

    Pin 1: TX (black wire)

    Pin 2: RX (first white wire)

    Pin 3: Ground (second white wire)

    Pin 4: 5V (third white wire)

    Remember that TX = transmitter and RX = receiver. So you wire the transmitter of the breakout board to the receiver of the fingerprint scanner and vice versa.

    Here are some additional instructions for newbies like myself. To wire it to the FTDI, the order is as follows

    Scanner TX (black wire) to FTDI RX (RX1)

    Scanner RX to FTDI TX (TX0)

    Scanner Ground to FTDI Ground (GND)

    Scanner 5V to FTDI 5V

    ORIGINAL POST: OK, I’ve tried a number of different things on two different scanners, and the demo still doesn’t work. Initially I tried wiring the scanner directly to the breakout board as shown in the demo video. When that didn’t work, I used a breadboard both with and without a 1.5k Ohm resistor.

    What’s confusing is that I can consistently see that the fingerprint scanner is getting power, and I know that I have the right serial port selected. The best I’ve been able to get so far is a blinking of the TX light on the breakout board when selecting “open” in the demo, so I know the command is going at least through there.

    Could there be something wrong with the JST SH jumper? I’ve also noticed that the bottom of the fingerprint scanners becomes hot enough to burn, has anyone else had this happen?

    • Not sure if you still had an issue, but i believe I have figured it out. They recommend the 5V FTDI breakout board, and I experienced the exact same issue as you when using it. I ordered a 3.3V version and it immediately started working.

    • Hello, I’ve had the same original problem as you with this device and would only get the power button to light up and the TX light of the breakout board to flash when open is clicked. After consulting your advice I still can’t get it to work? Can you give any other advice if possible please? Thanks :)

  • My fingerprint scanner did not come with a cable. It’s unusable without one. For a >$30 sensor, I expect better. I suggest you ship a cable with these in the future. What cable do I need to order?

    • Sorry about the confusion on that! I’ll see if we can get the note more clear in the description regarding purchasing the compatible JST-SH cable.

      • I suggest just include the cable, and up the price of the scanner $1.50 It’s not like it can be used without it.

        • It’s a hard balance. Since we don’t repackage these from the manufacturer, kitting it up with the cable ups the price more than just the cost of the cable. That adds a lot of labor time for our kitting department, which then customers don’t want to pay for either.

          Hopefully you are all set though now with the cable. If you have any other questions, let us know!

          • The S&H costs more than the cable. Will have to wait for next order.

            • OK, cable arrived, but reading the sample sketches, it appears a 1k Ohm resistor is needed because this fingerprint unit is 3v logic. I feel that this should be prominently mentioned in the part description!

              • OK, so even though the sketch says a 1k Ohm resistor should be added (and mixes up rx and tx), the data sheet says this unit is 5v friendly. I have both the enroll and the ID sample sketches operating fine, with no resistor. Pin 1 on the fingerprint scanner (black wire) is TX and connects to RX on the Arduino (Pin 4 in sample sketch), and Pin 2 (RX) on the fingerprint scanner connects to pin 5 (TX) on the Arduino. Pin 3 on the Finger print scanner connects to Arduino Gnd, and Pin 4 to 3.3v or 5v. I’m using 5v on the UNO.


  • Hello, I’m new to this world of biometrics and I was curious if it needs to be run at 3.3 or 5v because in the data sheet it says 3.3-6.

  • (solved) The data sheet is misleading, as explained by other members the pin1 is with arrow

    Hi All, Is there a problem wiring directly to FTDI 5v directly? I seem to get my FPS burned by connecting TX-TX & RX-RX by an accident :-( Any opinion ?

  • The Datasheet does not specify which pin on J2 is pin1.(Should I assume the pin the arrow is pointing at in the datasheet is pin1?) . On the PCB, is pin1 the one on which J2 is printed (closest to the edge) or the one on which a triangle sign is printed? There is a J1 on the other side of the pcb - maybe the square means pin1 ? Help.

    • Thanks to another member , I think I have my answer. See :

  • What about security? If the finger matches, will the device send some secret 128-bit value that was configured when the finger was learned? (Or allow decrypting using the secret.) If not, then this scanner must be stored in an armored box.

    • As with ANY garage door opener, you should not bring the opener contacts out of the garage UNLESS you have an arnored and properly secured mountng box for it. For a unit like this, you should bring out the Vcc, GND, Tx and Rx, leaving the control (Arduino for example) inside the garage. You also need to make sure that shorting any of the 4 wires will not cause the door to open.

      • Well, it’s not necessarily the opener contacts that public would have access to, it’s the TX and RX. I’m also currently busy with a home automation project that involves the use of this device to provide access to certain parts of the house. Consider using this device; anyone with access to the transmission line (RX/TX) would be able to re-enroll and give themselves access to whatever it was programmed to do. For my project I’ll be using an additional MCU as a translator to provide the added layer of security - Similar to what +Rusty14 mentioned.

  • I have the GT-511C3 ( its great. Its easy to use once you follow the tutorials and get the concepts. Its recognition seems pretty sharp, I haven’t tried anything else, but it is recognising quite effectively. I use the windows app to load my “fingers” into it, then flick a switch in my project to connect it back to the bare bones Arduino chip to do it’s main job. As far as wiring it up, I use a voltage divider to drop the input to RX line as it is a 3.3V device. Works fine. The linked manufacturers datasheet is helpful - Theres really not alot to it as it is self contained. Just follow the guides, use the supplied Arduino library if thats your microcontroller of choice and off you go. No special fingerprint identification skills required!

  • Does this one need to have the lines (tx and rx) reduced to 3.3V like the older one? (Or is it just rx?) Are the back pads the same configuration? What I got for the old one is from left to right- shield (optional) , GND (black) , rx (green), tx (white) and 5V square (red) next to the J1 sign…

    I still can’t get my (GT-511C1) to work, do I have the wires right? Thanks!

  • From the description it looks like the main difference is that this cheaper model “… can only store up to 20 different fingerprints …” . I haven’t used this product yet, but planning on doing so .

  • I have the previous model (GT-511C1), what is the difference to this update?

    • This guy got a firmware update that allows for 360° Fingerprint Recognition instead of just 30°. Also it can now download and upload templates using the serial interface.

Customer Reviews

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3 of 3 found this helpful:

Cool Scanner, but...

… why not include the somewhat difficult to find JST SH Jumper 4 Wire cable with the unit? It is out of stock at SparkFun and twice as expensive elsewhere, not to mention the seperate shipping costs incurred! Otherwise the unit does exactly what it is advertised to do which is a great way for my robot to know which of my children it is speaking to! :-)