Schematic of Nexo-Bt, errors and advice - Page 1
Forum section: electronics / beginners

author: Arrow07
author_rank: Newbie
timestamp: July 07, 2025, 07:41:49 pm
content: Hi, Nexo-Bt is a Bluethooth receiver based on an ESP32, with 2 AMS11173.3 and two external dacs with balanced outputs. powered with USB-C, I would like to know if there are errors in the schematic since I am a beginner and I may have made many of them, please don't get angry if I have committed monstrosity. I hope you can give me a hand thanks.

author: PlainName
author_rank: Super Contributor
timestamp: July 07, 2025, 08:08:17 pm
content: QuoteDunno. Too hard to follow what it does - air wires could go anywhere (or nowhere) and don't show flow or anything. The schematic is meant to show the reader what it does, not be a netlist or connection spreadsheet.

author: Arrow07
author_rank: Newbie
timestamp: July 09, 2025, 11:08:34 am
content: Thanks for your advice I removed the netlab and I made the connections clearer clear, I hope it is more understandable

author: PlainName
author_rank: Super Contributor
timestamp: July 09, 2025, 11:25:39 am
content: Much better

author: Arrow07
author_rank: Newbie
timestamp: July 09, 2025, 05:17:52 pm
content: Thank youdo you think that is all correct or do you see any errors?

author: PlainName
author_rank: Super Contributor
timestamp: July 09, 2025, 07:28:34 pm
content: When I said 'much better' itismuch better. But it could still be improved by a lot. For instance, U7.11 looks like it's connected to u7.12 - an example of an untidy line being confusing. There is a lot of that kind of thing. Also, usually ground goes down, never up.However, diagramming aside, I don't want to spend time designing this for you so I'm not getting into whether the design will work or not. What I can do, though, is question why you have two 10k resistors in parallel (R12, R10) for no apparent reason. And think that D1 might not be a good choice because it could drop 0.9V and U5(is it? can't read that properly) and U15 have 1.1V dropout. So 5V - 2V is a little below your required 3.3V.Next, the LEDs U16 and U6 have forward voltage of 2.9V to 3.4V depending on bin code. Let's say 3V to make things plausible and simple. You have a 10k resistor dropping 0.3V (3.3V supply - 3V forward voltage), hence LED current will be 0.3/10,000 (I = V/R), aka 30uA. I'm afraid it's not going to indicate anything useful.Staying on the LEDs, these seem to be intended for things like traffic lights and can take 100mA, but typically are driven at 30mA, which is a good proportion of your regulator output. I think you would benefit by picking high efficiency LEDs which could be driven, and still be bright, at 1mA or so. Depends on how bright you need them, but for simple power-on indicators I would think 'not very'.Edit: The AMS1117 wants minimal load of 5-10mA, so perhaps LEDs sinking 5mA would be good just to keep that in spec since U8/U7 have quiescent current of 2.5mA.Speaking of U7/U8... why does SD_MODE on U7 have a 210.2k(!) pullup whilst U8 doesn't?

author: Arrow07
author_rank: Newbie
timestamp: July 22, 2025, 04:47:11 pm
content: Hello sorry for the reply time thanks for viewing the schematic;The two parallel resistors are definitely a drawing error thanks, I had not noticed.I suspended D1 since looking better the specifications did not be fine with a diode similar like the BAT760-7.For LEDs I still have to check, thanks for the indications.As for the resistance of 210.2k, it is used to select the audio channel that the max98357a must be occupied: 0Ohm per left and that resistance to the rightIn addition, I had to totally change ESP chip because I realized that S3 (very easy to connect) does not have classic bluetooth but only the low energy,As soon as I finish the schematic I will send it