EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: redgear on September 13, 2020, 10:07:40 am
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The TM1637 (https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_TM1637.pdf) sinks 50mA current. My 7 segments maximum IF is 20mA. The reverse voltage is 5v and forward voltage is 3v. Can I safely power it from the TM1637? Here is the 7 segment datasheet (https://datasheet.lcsc.com/szlcsc/SUNLIGHT-SLR0394DBA5BD_C225903.pdf)(it's in chinese)
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The TM1637 (https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_TM1637.pdf) sinks 50mA current.
That may be the max but that's not my experience. In practice it actually sinks about 10 mA through the segment so after multiplexing, it works out to a more reasonable 2.5 mA effective. Then there's PWM control. What I found odd working with the TM1637 is that it didn't seem to matter what the voltage drop of the LED was, even with a display that had two LEDs in series per segment, the brightness didn't seem to be affected. You will also notice there is no limiting resistor in the reference design. You will also notice there are several types of modules on sale using different colour LEDs, and hence different voltage drops, but still no current limiting resistor. I suspect the chip has a constant current sink for each segment. They don't tell you everything in those data sheets. So just go ahead and breadboard it and check that the brightness suits you.
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The TM1637 (https://www.mcielectronics.cl/website_MCI/static/documents/Datasheet_TM1637.pdf) sinks 50mA current.
That may be the max but that's not my experience. In practice it actually sinks about 10 mA through the segment so after multiplexing, it works out to a more reasonable 2.5 mA effective. Then there's PWM control. What I found odd working with the TM1637 is that it didn't seem to matter what the voltage drop of the LED was, even with a display that had two LEDs in series per segment, the brightness didn't seem to be affected. You will also notice there is no limiting resistor in the reference design. You will also notice there are several types of modules on sale using different colour LEDs, and hence different voltage drops, but still no current limiting resistor. I suspect the chip has a constant current sink for each segment. They don't tell you everything in those data sheets. So just go ahead and breadboard it and check that the brightness suits you.
Thanks.
I was scared that it could damage the display. Anyways, I will try it on a breadboard.