Timeline for Possible impedance problem when moving to new power supply
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Jan 1, 2021 at 3:23 | comment | added | jsotola | @ChrisSchmitz the ground is common between the triket and LED strip ... the difference is that the grounds are not connected through the power supply wires .... my thinking is that the power supply wires could introduce a voltage drop, which would raise the ground pin of the LED strip with respect to the ground pin of the trinket | |
| Dec 31, 2020 at 21:12 | comment | added | Gerben | What happens if you replace the brick with your lab-power-supply (without the USB)? Have you measured the voltage coming out the the brick? | |
| Dec 31, 2020 at 21:02 | comment | added | chrisl | For level shifting up you need a transistor, that switches the higher voltage via the lower voltage pin. Try it, then we can go further | |
| Dec 31, 2020 at 21:00 | history | tweeted | twitter.com/StackArduino/status/1344750194018152482 | ||
| Dec 31, 2020 at 18:25 | comment | added | Chris Schmitz | @jsotola, what's the reasoning behind it? Don't the grounds need to be common? | |
| Dec 31, 2020 at 18:19 | comment | added | jsotola | go back to the two power supply setup ... remove the ground connection between the two power supplies ... connect a ground wire directly from the trinket to the LED strip | |
| Dec 31, 2020 at 17:56 | comment | added | Chris Schmitz | @Mat how would i do that level shift? Is this a case where I'd need to add a transistor to provide a higher voltage signal (e.g. pull the 3.3 from the trinket's top right pin) and then control the transistor with my signal pin? Ah wait, I forgot it can't be the 3.3v pin b/c we'd need 3.5, so maybe a voltage divider coming off the 5v power? | |
| Dec 31, 2020 at 17:54 | history | edited | Chris Schmitz | CC BY-SA 4.0 |
added 156 characters in body
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| Dec 31, 2020 at 17:53 | comment | added | Chris Schmitz | Yeah I moved everything to the wall adapter and I double checked the ground connection and it's good, but still have the issue. I'm adding a new pic in of the circuit. | |
| Dec 31, 2020 at 17:50 | comment | added | Mat | WS2811 expected a minimum of 0.7xVdd for a logic high signal, which is 3.5V. You're marginal at best even if everything is grounded properly. You should level-shift that signal. (And indeed that LED isn't a dropping resistor - your Trinket would have blown up long ago if you tried to feed 1.5A through one of its pins.) | |
| Dec 31, 2020 at 17:41 | comment | added | Gerben | The resistor is on a signal line. There should hardly be any current there. I don't thing it's anything to do with that resistor. Have you tried powering the trinket from the same 5V brick, instead of USB? I think it might be a eathing problem. The bench power supply is mains earth referenced, while the brick is probably floating. Are you also really sure the grounds are connected? Maybe there's a loose breadboard connection. | |
| Dec 31, 2020 at 17:18 | history | edited | Chris Schmitz | CC BY-SA 4.0 |
adds simplified circuit
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| Dec 31, 2020 at 17:10 | history | asked | Chris Schmitz | CC BY-SA 4.0 |