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Thread: OctoWS2811 with WS2815 leds - 12v DC

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    OctoWS2811 with WS2815 leds - 12v DC

    OctoWS2811 is using 74HCT245 logic converter to convert Teensy 3.3v to 5v DC and is works great with all 5v WS281X.
    This is not the case with WS2815 leds. They run on 12v.
    Any idea what will be a good replacement for 74HCT245 chip?
    Paul, any recommendations and suggestions?

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    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by bpenchev View Post
    This is not the case with WS2815 leds. They run on 12v.
    But do they *really* take a 12V data signal?

    So far, every 12V addressable LED product we've seen actually takes a 5V logic signal, not 12V. They use 12V power, but NOT 12V data. These are unlikely to be any different. But if they are, please give us a link to the product page, datasheet or other info about the signal they require.

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    No, i was not able to find this in the spec, so i assumed it will need 12v signaling. I guess best will be to buy some and test it. Thanks Paul.

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    Quote Originally Posted by bpenchev View Post
    No, i was not able to find this in the spec, so i assumed it will need 12v signaling. I guess best will be to buy some and test it. Thanks Paul.
    Or post a link and someone here might be able to help. Or, other forum readers might learn something.

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    I was looking into this spec.
    In electrical and switching characteristics it's mentioned VDD 4.5~5.5, but it is not clear.

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    Senior Member PaulStoffregen's Avatar
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    Maybe try asking the vendor? It is their product, afterall....

    Yeah, I know that's probably fruitless. Even if they do reply, how likely is their answer to be right when the datasheet is filled with obviously contradictory info?

    But it's always interesting to hear what they say, if they even bother to reply. Please let us know?

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    Thanks for the link.

    The question is, "What voltage levels are required on the digital inputs for a logical Low and High?".

    See the section: Electrical Characteristics

    High-level Input: 0.7 x VDD
    Low-level Input: 0.3 x VDD

    For both, the required voltages are relative to VDD. Therefore, if VDD is 12 V, then >= 8.4 V is required for a logical high and <= 3.6 V is required for a logical low.

    @VDD == 12 V
    High-level Input: >= 8.4 V
    Low-level Input: <= 3.6 V

    This is the spec you must meet for the LEDs.

    A next step would be to determine the High-level and Low-Level Output voltages of the level shifters on the OctoWS2811 (74HCT245).

    It would then be known exactly what voltages must be translated from and to.

    [Edit]
    SN74HCT245, IOH, IOL = –20 μA
    High-level Output: >= 4.4 V
    Low-Level Output: <= 0.1 V
    Last edited by markonian; 10-24-2017 at 06:09 PM. Reason: Added SN74HCT245 specs

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    Senior Member PaulStoffregen's Avatar
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    Is that the reply from the vendor? Or is it your reading of the contradictory info in the datasheet?

    Quote Originally Posted by markonian View Post
    A next step would be to determine the High-level and Low-Level Output voltages of the level shifters on the OctoWS2811 (74HCT245).
    This is the part used on the Octo boards PJRC sells. Fairchild's datasheet is very reliable.

    http://www.onsemi.com/PowerSolutions...?id=MM74HCT245

    They have numbers for minimal load, 6mA and 7.2mA, and 3 temperature ranges. For the light load case, the output is within 0.1 volt of GND and VCC, which is connected to VIN-VUSB on Teensy, so nominally 5V but does of course depend on whatever you're using to power Teensy.

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    Here is another China manufacturer products.
    WS2815A is listed as Input Voltage 5V, and when you download the specs it is set as 12V
    Thanks for all response. I will try to order them in US, if i can find them .
    Otherwise will have to wait for them to come from China. I will let you know when i have my hands on them.

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    WS2815 and GS8208 both are 12v addressable led.
    WS2815 led datasheet:http://www.normandled.com/upload/201...0Datasheet.pdf
    GS8208 led datasheet:http://www.normandled.com/upload/201...0Datasheet.pdf

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    I found this thread a while ago because I was wondering the same thing and in the meantime I have already tried it myself and I can confirm:
    The datasheets are confusing. Even though they use Vdd for both logic and power, VDD=4.5~5.5V seems to be for logic and VDD=+9.5~+13.5 for power in case of the WS2815. I was able to use both WS2815 and GS8208 without problems using a 5V logic signal. No idea about the internals though.
    Using the same trick as with 5V LED drivers to supply the first LED with a lower voltage with the help of a voltage divider to use it as a logic lvl shifter has not worked as well/consistently as in case of e.g. WS2812, thus I used a logic-level shifter from 3.3V to 5V to drive it from a 3.3V chip when necessary.
    To sum up, you seem to be able to supply them with 12V and drive them with 5V level logic (e.g. arduino or esp2866 & 3.3V to 5V logic level shifting as with the SN74LVC1T45DBVR).

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    Senior Member PaulStoffregen's Avatar
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    I managed to contact someone from World Semi (on Facebook, of all places...) and they confirmed "VDD=4.5~5.5V" is a mistake in the WS2815 datasheet. They said it will be fixed. No idea of the time frame.

    I'm curious to see if whoever edits the datasheet merely replaces the VDD info with the spec from another page, or if they thoughfully update the voltage levels in that table which are currently expressed as ratios of VDD.

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