Slim Fingerprint Sensor 4750 Short Circuit

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swagginty
 
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Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

Hello,
I ordered the Slim Fingerprint Sensor (4750) and I recently hooked it up with a USB to UART converter to my Rasberry Pi and when I touched the sensor pad it was extremely hot. I unplugged it and tried only directly hooking up power and ground to the Rasberry pi and it still got hot. I think this might be due to a short circuit in the sensor although I'm not sure what could have caused this. What should I do?

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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

Without connecting it to the Pi can you show the wiring you used between the fingerprint sensor and the USB to UART converter?

Which guide were you following for the pins to use?

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swagginty
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

Hi, thanks for your response. Yes, Here is my wiring.
Wiring.png
Wiring.png (957.46 KiB) Viewed 107 times

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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

Those connections look tenuous. Are you only using electrical tape or are they soldered?

Try using these for the pinouts. Don't only go by color, but also by pin number from left to right. Notice how the red is GND and black is RX (not intuitive).

Can you take a picture of the back of your slim connector while it is plugged in so we can verify the wire colors? The product page suggestions these pinouts. I noticed your yellow wire was not connected.

Code: Select all

    Black to GND
    Yellow to Microcontroller TX (data out from microcontroller)
    Green to Microcontroller RX (data in from microcontroller)
    Red to 3.3V VIN
    White to IRQ (can leave disconnected)
    Blue to 3.3V VCC (can leave disconnected)
https://www.adafruit.com/product/4750

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swagginty
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

The connections are soldered under the electrical tape. I switched to the right pinout (according to color) but I think you're right about the pinout number thing. I'm looking at the picture from the website and it looks like the colors are mirrored. Here is a picture of mine.
IMG_5027.png
IMG_5027.png (1013.68 KiB) Viewed 86 times
And a picture from the website.
colors.png
colors.png (858.57 KiB) Viewed 86 times
Do you think this is the issue?

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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

Using the color chart I provided should be the correct layout. On another site it shows the pin ordering from left to right (ignore the colors there).
Screenshot from 2022-12-05 15-56-59.png
Screenshot from 2022-12-05 15-56-59.png (88.99 KiB) Viewed 84 times
https://wiki.dfrobot.com/Capacitive_Fin ... KU_SEN0348

Walk me through your current connections to the FTDI now that you have changed it.

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swagginty
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

Right now I have 1 going nowhere, 2 to nowhere, 3 to power, 4 to UART white, 5 to UART green, and 6 to GND

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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

I think you are reading it in reverse.

pin# | color | connection
1 | black | GND
2 | yellow | Microcontroller TX (fingerprint RX)
3 | green | Microcontroller RX (finger TX)
4 | red | 3v3 Vin
5 | white | disconnected
6 | blue | disconnected

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swagginty
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

Ya, that's how I have it wired right now. At least I have those colors going to those places. But in the diagram it looks like 1 corresponds to where my blue wire is, 2 to white, and so on.

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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

Please post a photo of your current wiring. The earlier photo did not show yellow connected to anything and white was being used (should be disconnected).

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swagginty
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by swagginty »

This is my current wiring.
Attachments
wires_3.png
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mikeysklar
 
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Re: Slim Fingerprint Sensor 4750 Short Circuit

Post by mikeysklar »

Thank you for the photo. That is good quality and I can see everything.

The current wiring you have matches the Adafruit product page and guide instructions. You have the correct wires connected.

Have you plugged it back into your Pi? Does it still get hot? Do you see anything via serial console or dmesg?

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