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3 Digit LED Display Information

Discussion in 'Datasheets, Manuals and Component Identification' started by Kelsier26241, Jan 12, 2015.

  1. Kelsier26241

    Kelsier26241

    2
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    Jan 12, 2015
    I purchased a 3 digit LED display on EBay from China. It was a really good price but now that I am trying to tinker with it I cant find any information about it at all. I was hoping someone could point me to a datasheet or some additional information.

    The part has the number "F3361BH" printed on the side and has 11 pins. The only information that was on the listing is the following pinout:

    E --- D1
    D --- A
    DP --- F
    C --- D2
    G --- D3
    --- B

    Maybe it s just me, but I cannot seem to make any sense of this and I cannot find any other information at all. I found an item on a translated Chinese page that showed a volt meter that had the part number I listed above in the description. It seemed to be a very simple device and could very well be the same LED display. The information on the volt meter said that it could handle 4V-30V, would it be safe to assume that the LED display I have could as well?

    Any insight/help you could offer would be greatly appreciated.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hi there
    welcome to EP :)

    That part number doesn't come up in google

    link to your ebay purchase so we can see what you have
     
  3. chopnhack

    chopnhack

    1,571
    349
    Apr 28, 2014
    E-Bay
    shows it to be a common anode, red.

    1pcs 0.36" 3 digit led display 7 segment Common anode Red 22.5*14*7.2mm

    PART# F3361BH

    Other than that the pin out as the OP mentioned is not the clearest.
     
    davenn likes this.
  4. ramussons

    ramussons

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    Jun 10, 2014
    How about some photos of the unit? Top, bottom . . . . :)
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    See chopnhack's post before your one :)
     
  6. davenn

    davenn Moderator

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    Sep 5, 2009
    The way the OP wrote the pin ID is confusing, what you really have is.....

    the segment ID's A, B, C, D, E, F, G and DP these 8 lines are all commoned
    then you have the D1, D2, D3, these are for driving the segments in'
    Display 1, Display 2 etc

    here's an almost identical one .....

    3361 display.JPG



    Dave
     
    chopnhack likes this.
  7. chopnhack

    chopnhack

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    Apr 28, 2014
    @davenn - the common anode (BX) shows all like segments tied together - in practice if wired this way, each 'A' segment on each digit would light up, why does the convention show it this way? I assume that pins 12, 9 and 8 are mostly active and can not necessarily be used in switching, except for on/off.
     
  8. Kelsier26241

    Kelsier26241

    2
    0
    Jan 12, 2015
    http://www.ebay.com/itm/1pcs-0-36-3...-COMMON-ANODE-RED-22-5-14-7-2mm-/141473811628


    The pinout I posted is written in the same way I found it. I was unable to find one that made more since.

    Thank you very much though! This was the kind of information I was looking for.
     
  9. davenn

    davenn Moderator

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    Sep 5, 2009
    no each individual segment only lights up when there is a common voltage to the segment line and the D1 or D2 or D3 line

    no probs ... you just mis-interpreted what you were reading
    fortunately, some posts ago, chopnhack found the eBay listing and I was able to see what was going on :)


    googling driving/using 3 digit led display 7 segment Common anode brings in quite a few examples of circuit ideas

    Dave
     
    chopnhack likes this.
  10. chopnhack

    chopnhack

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    Apr 28, 2014
    I think my answer lies in multiplexing and charlieplexing - thanks for getting me started down the correct search path! Pretty cool what you could do with the correct driver - lot fewer wires and answers my question about why all the common segments are tied together. Thanks!
     
  11. Anoxynym

    Anoxynym

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    Mar 1, 2015
    You must scan the display. That is, you apply positive voltage to a digit while you pull down the appropriate segment lines. Then go to the next digit and do the same, then the next digit, etc. "Open collector" drive, NPN transistor, P channel FETs, or, more possibly output pins on a microprocessor configured as open collector are possible candidates for the segment drives.

    Use current limiting resistors on each segment line. Excessive current through the segment LEDs will destroy the display. This could also destroy the device driving the display. You can not put the current limiting resistors on the digit lines because you don't know how many segments will be on.

    Positive drive to the digit lines could be a PNP transistor to +V driven by an open collector pin to its base or a high current output positive voltage output from the scanning microprocessor. A few processors can provide high current positive voltage output, but most can not. I believe I recall that the PIC processors are rated to source or sink 200ma per pin.

    If you use the transistor drive, you turn it on by pulling the base low with open collector configured output of processor. Drive the transistor through an appropriate current limiting resistor to protect the base to emitter junction in the transistor. I would also put a resistor from the digit drive transistor base to V+ to make sure it is off when it should be off, 10k or so for base (or gate, on FET) to V+.

    I would probably use a microprocessor to drive the display. That would be less expensive than a discrete logic solution. I would still likely need high side transistors driving each digit.

    Since you are scanning the digits you should use a timer to control how long you drive each digit so that all the digits get equal ON time.

    Since each digit is driven for only a fraction of the time you need to hit them with more current than you would use if the digits were on continuously. If you need 10ma to light up a segment to a nice readable level and your total display is 9 digits, you would need to drive the segment with 90ma when it is on during its scan time slot. This is why you might want to have segment drive buffer transistors even if your processor has open-collector pin options. However, check the display data sheet. Also, experiment -- you may find that you need very little current to illuminate the segment.

    You can modulate the brightness of the display by changing what fraction of each digit's time slot you drive the digit. This is PWM, pulse width modulation. Many microprocessors provide PWM options which make this easy.

    Hammering the digits with these high power levels while scanning rapidly through the digits also presents the possibility of creating radio frequency interference (RFI). You should keep the digit drive lines close to the segment drive lines and keep these wires are short as you reasonably can. RFI is transmitted from the separation between the wires. One solution is to mount the display controller close to the display. Another reasonable tactic would be bundling the wires together, perhaps even twisting the bundle together. If you end up making a printed circuit, try to route the digit lines close to the segment lines. That way the magnetic and electric fields cancel as seen from a distance. Also, mount the current limiting resistors and any necessary drive transistors close to the micro controller. That keeps the voltages on the wiring to the display as low as possible.
     
    chopnhack likes this.
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