Hi, I have an Arduino Uno rev4. This is my first project and I have managed to get further than I thought but have stumbled across my understanding of PULLUP. I have a single line with around 6v coming from an external device that I need to pulse to 0v so that the external device can count how many pulses. I thought the 6v was a little too much for the Arduino so I have used 2x10K resistors to bring this down to 3. I have attached this line to D2 and end of the loop to GND just after D13. The issue I have is that I can't seem to pull the voltage low enough to get the external device to register the count. Any help would be appreciated as I have spent the last 6 hours trying different ways :slight_smile:

Remove the 22k and 10K resistors from the collector pin. Connect the collector pin directly to the device pin. The function of the transistor is to protect the Arduino from the higher voltage present on the device pin. The transistor can withstand up to 60 V on the collector pin. [Capture]

Read the posting at the top of the forum on "how to"....then... post a drawing of your (complete) circuit (no fritzing) Then post whatever code ( in code brackets)

Hi, I can't locate the "how to"! I have searched this forum and google for answers. I don't have a diagram and don't know what fritzing is. I think my post explains what I'm trying to achieve and that I just need some guidance on the possibility. Any code I have tried doesn't work so I have started again. I used this forum once before and had comments about using it correctly. I think I have selected the correct area and give most of the information I know.

[image] amateurkev: I don't have a diagram Then make it! Words are not the way to tell how the circuits are wired. [image] amateurkev: end of the loop to GND just after D13. ?????

Thanks for posting the link. I feel like I selected the right category and also give enough information to answer my question. I don't have a schematic but I did outline the board in use and what pins I was using as well as the resistors that were in play. I think I need to source a beginners forum. Thanks.

[image] amateurkev: I have a single line with around 6v coming from an external device that I need to pulse to 0v Use a bipolar NPN transistor switch to do this, with a 330 (for the R4, use 1K) Ohm resistor to the base, emitter to GND and collector to the line. A HIGH written to the pin turns on the transistor and connects the line to GND. [Capture]

end of the loop just meant after the 2x10k resistors. 6v - 10k - wire to D2 -10k - wire to ground

Much appreciated. I will look to order one. Many thanks.

[image] amateurkev: I feel ...... give enough information to answer my question Maybe, but You gave it in the wrong way. Don't expect helpers to compile poetry and make schematics. [image] amateurkev: end of the loop just meant Words, words and words. That's not the way to get any ware. Use the words and draw the diagram showing it. Please read and use this advice: How to get the best out of this forum - Using Arduino / IDE 1.x - Arduino Forum

Use a bipolar NPN I'm going to "me too" this because I'm in the middle of assembling a dozen circuits like this to bring a +12V signal into a bunch of arduinos :slight_smile:

Pin Voltage Pullup

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Railroader August 24, 2023, 11:17pm 4

Here it is: How to get the best out of this forum - Using Arduino / IDE 1.x - Arduino Forum

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Pin Voltage Pullup

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