This is also what was observed on the scope. While I full and well understand how this circuit works, I'm just a tad worried that the base current to the driven transistor doesn't have anything to limit it and am just wondering if this is OK since it sees a "pulsed" duty cycle. NEW Library to make fading leds a piece of cake https: Media New media New comments Search media.

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The LED lights up constantly, even when I apply the input signal on the coupler manually. The brown wire goes directly to pin 7 and the other two are 5V and ground. Is this really even worth a discussion? Posted 5 Oct Did you find the addition of the 1k - 4k7 resistor to GND made a discernable difference and did you discover this option from your own experimentation.

PC-900 vs. 6N138

I am currently not in a position where I can test that circuit, but since I'm trying to learn about electronics. In which case, you need a pull-up resistor.

What I don't understand is the fact that in this configuration the phototransistor has the 1K limiting its "emitter-base" current, but the driven transistor doesn't appear to have anything limiting its base current. Maybe i just missed it somehow. Okay thanks Cmiyc, I will do that next time. That's not really my question. Hope this helps VC. Articles Top Articles Search resources. Use fricking code tags!!!! Would it be an inconvenience to explain why you used 1K resistors instead of what I did?

Does MIDI output an open collector signal? Some have used values as high as 22K here. This is translated to a voltage by your pull-up resistor R6.

IR Started by transforman2 14 minutes ago Replies: The 6N isn't digital at all. I'm not trying to use a PC, I'm trying to replace one with a 6N and I'm wanting confirmation that this circuit will work as a replacement. Even in the example they also used two Ohm resistors in series.

You need to be a member in order to leave a comment. Articles Top Articles Search resources. MIDI runs at This is because I already had trouble connecting it to the Rx pin before and I wanted to troubleshoot. It can be 1K or higher.

6N Optoisolator Question | Electronics Forum (Circuits, Projects and Microcontrollers)

I hope this is an okay place to ask this. As the input current decreases, the output will snap back at a lower level - so you won't get jittering at a critical level. Which makes total sense why they'd use that resistor there for MIDI applications.

With nothing connected to the input, you seem to suggest that pin 6 going into the Arduino gives a low reading, and disconnected gives a high reading.

PS- I realize your question is about switching to the circuit, so yes to me the re-mapping of the pins looks right, as do the resistor values judging by this core schematic. Jon Wilder Active Member Mar 9, By continuing to use this site, you are consenting to our use of cookies.

Jon Wilder 6b138 Member Mar 8,

2 thoughts on “6n138

  1. Mikalrajas

    Unfortunately, I can help nothing, but it is assured, that you will find the correct decision.


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