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I am absolutely new to electrical stuff, and I am just trying to create my first project. I am basically trying to drive a strip of RGB LEDs (in a form of a Christmas tree) using attiny85. I have successfully programmed the attiny and connected it to the Christmas tree on a breadboard, and now I am trying to figure out a way to power it. Everything works fine when connected to 5V and ground pins of Raspberry Pi. But when I try to run everything connected to a small breakout USB-C port, it doesn't work, and I want to figure out why. According to what I read, USB-C without Power Delivery negotiations is capable of delivering up to 500mA of current. If I understand correctly from the attiny's data sheet, running on 1MHz with 5V it requires about 1mA. I am not so sure about the LEDs on the Christmas Tree and not sure how to check it. Are my guesses correct, that my circuit doesn't work because it requires more power than USB allows to supply without a proper negations? If so, what are the alternatives I can use? Would it work better if I used simple micro-USB instead of a USB-C? Thanks.

UPD:

The breakout USB-C board I am using: https://www.pololu.com/product/2585 On the diagram that board seems to already have 5.1k Ohm pull-down resistors on both CC lines of a USB-C connector. Looking at the board it self, I think, I can confirm their existence.

saferif
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  • I may be wrong but I think USB-C has some protocols with it that make sure there is communication before delivering power (Especially if the power bank is PD)? How are you hooking up the USB-C? What is the power source? One thing I would also do is check the wire itself to make sure it is not faulty, and check the power source too. – Jared Cohen Nov 19 '20 at 00:40
  • I just connected VBUS and GND pins of USB-C connector to the VCC and GND pins of attiny. I have a voltmeter at hand, and measuring the voltage between these two pins shows number very close to 5V. So, I am guessing the connector should be fine. Wires are definitely fine too, because when I use same wires to connect the chip to the Raspberry Pi, it works. – saferif Nov 19 '20 at 00:58
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    Your question is already answered here where it is explained that you need a resistor on the CC pin to persuade the other end to source power: [Replacing USB-A with USB-C fails](https://electronics.stackexchange.com/questions/392045/replacing-usb-a-with-usb-c-fails) – Chris Stratton Nov 19 '20 at 04:13
  • @ChrisStratton Thank you for your answer. However, I looked at the diagram of the [connector](https://www.pololu.com/product/2585) I am using, and it seems it include the relevant pull-down 5.1k ohm resistor. Also, I am a bit confused by the fact that when I tried to power a simple LED of that USB-C, LED was on. – saferif Nov 19 '20 at 14:26
  • Looks like that LEDs except the power need some control signal. It could be controlled by I/O pins of MCU but you may try to do it manually with some precaution. Three colors, three pins. May be some program issue. – user263983 Nov 19 '20 at 14:39
  • @user263983 Yes, it needs a control signal, and I have an attiny flashed with a program to control that. This exact controller with the exact Christmas Tree connected work when power is sourced by Raspberry Pi, but I cannot quite make the power over USB-C to work. – saferif Nov 19 '20 at 14:49
  • You may need an adapter from usb-c to another interface . All sources say it needs controller for choosing form of power. Adapter may already have it – user263983 Nov 19 '20 at 15:15

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