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A friend of mine gave me a 2in. 4 digit seven segment display. But when I sat down and looked at it, I found it has 7 pins on one side and 5 on the other and no indicators of its pinout on it. The only information I could gleam from it was the (presumably its model number) which said "PARA LIGHT A-5V4G-12-U1 H H0615". I searched online for it but only found ambiguous information that didn't help me. I have a feeling this is a fairly easy question, if so: sorry I am a noob.

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Without an image of the display, I'll have to guess. With 12 pins in total, what you most likely have is: 8 pins for 7 segments and the decimal point, and 4 COMMON anodes or cathodes, a detail you will have to discover yourself. This process requires a power source that can safely light LEDs. A multimeter in diode test mode will do since theres usually about 2 V across the probes and some internal resistance, enough to light up the LEDs in the display, though they wont be very bright. I will try to list the minimum number of steps needed to determine the pinout using this method.

  • Using a multimeter set to diode test mode, place the red probe on any pin (though its good to start at the edges). Now lazily run (i.e. make contact) the black probe through the remaining pins. If the display is a common anode display, you should see the all the segments of a particular digit (not different digits) light up in sequence.

  • Else, keep running the black probe through the pins until any segment at all lights up. Hold the black probe on that pin that caused the segment to turn on. Now run the red probe through the other pins. If all the segments of a particular digit light up in sequence, this indicates a common cathode display.

  • Another possibility is that no segment lights up at all, despite steps 1 & 2. Substitute the red probe, where it is held steady, for the black probe. Run the red probe through the remaining pins. If all the segments of a particular digit light up, then the display is a common cathode display.

  • On the other hand, if no digit's segments light up sequentially while running the red probe through the pins, but at least one segment of any digit lights up, then hold the red probe steady on its current pin, and run the black probe instead through the other pins. If all the segments of a digit light up in sequence, then you have a common anode display.

Take note of the pin that was held constant, in any of the cases above.

Now that you know what kind of display you have, you now need to discover the pinout for the segments and common anodes/cathodes. Get paper and pen so you can label each pin with its function. Create a table with pin numbers in one column (pin 1 - 12) and the pin functions (which you will find out) in the second column.

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  • This image shows the segment labels. During the testing above, one probe (PROBE A) was held steady on one pin while the other (PROBE B) was run through the other pins. This caused all the segments of a digit to turn on. The pin connected steadily to PROBE A is the COMMON pin for the digit whose segments lit up. So in your table, Pin xx = COMMON for Digit yy.
  • To get the COMMON for other digits, move PROBE A to another pin and run PROBE B through the other pins until another digit has all its segments turned on in sequence. The pin connected to PROBE A is the COMMON for that digit. Include this in your table. Repeat until you have identified the COMMON for each digit.
  • Finally to get the segment pins A - G and DP, place PROBE A on any of the COMMONs you have in your table and run PROBE B through the other pins. Each time a segment lights up, the pin connected to PROBE B should be associated with that segment's label in your table. E.g. if segment C lights up when PROBE B is on pin 10, then the table should have something like pin 10 = C. Keep going until you have all the segment pins identified.
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  • An ok answer, +1, except in first bullet you should mention (1) that if no LED lights up then try reversing red and black probes, and/or other pin combinations and (2) the LEDs won't be particularly bright using this method, and it may be necessary to reduce room light slightly Mar 1 '16 at 4:18
  • @jwpat7 ok...editing now... Mar 1 '16 at 10:19
  • Nice step by step how-to. +1
    – JRobert
    Mar 1 '16 at 20:19

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