Sunday, June 14, 2020

Motorcycle cheap Aliexpress clock voltmeter thermometer

Hello, this time I want to rant about this cheap thing I bought for my motorcycle:

Picture stolen from an Aliexpress user

This is actually the second one I buy. The one I bought first cost me double and was a double piece of shit because it was so dim, I couldn't see shit while riding during the day.

The one I bough this time has the looks like the one in the picture, a fake Rizoma. It's funny because looking at the pictures of the users, it seems like each one gets one slightly different. The white letters, the size and the package differs from one user to another.

Anyway, I wanted to share some measurements I made to check how shitty these things are and this is what I found:
Voltage measurement: Resolution is 0.1 V. The measurement seems to be off by -0.1 V consistently across the hole range. 

Opinion: This maybe caused by some diode in series to protect against backwards connections. Considered how easy it is to achieve a proper 0.1 V resolution voltage measurement, this shit is totally unacceptable.  

- Temperature measurement: Resolution is 1 ºC. The measurement error differs but generally it's 1 to 2 degrees off the right value.

Opinion: The temperature is sensed with an NTC. Considered how easy it is to achieve a proper 1 degree resolution voltage measurement, again this is totally unacceptable.  

- Current consumption during operation: approx 30 mA.

Opinion: This really doesn't matter much, 30 mA is the typical power used by a multiplexed LED segment display plus some bits of circuitry more. Nothing new here.

- Current consumption during standby: approx 3.9 mA.

Opinion: This is absolutely huge power for standby. This can empty a full 6 Ah battery in a couple of months. This is not a surprise though... A regulator that can achieve standby consumption in the uA range is expensive, no way this was going to fit it.

The specs of this cheap shit are completely out of the acceptable and the performance is pretty poor. This piece of crap belongs in the bin. 

However did I installed in the bike? Yes. 2 simple reasons:
- This cost under $4 while the original Koso Mini 3 is near $100 or in some places even more! Unfuckingbelievable! 
- There seems to be no better alternative that has the 3 features of this one for a reasonable price of let's say, maybe $15 or $20. So, I think I'll live with one this for now. 

Wednesday, May 13, 2020

Edifier S350DB high pitch noise defect

I bought these speakers for all the good opinions in the internet and it seems like there are many units with a manufacturing defect that involves a high pitch noise. Symptoms are:

- High pitch noise independent of speaker volume
- Only happens in Bluetooth, PC and AUX modes.
- Temperature dependent. As the unit warms up (after 10 min), the noise gets lower but never disappears. The colder the room, the worst.

I captured this picture with a spectrum analyser app:

You can see, it detected a peak around 4.4 kHz. This peak starts with higher frequency and amplitude when the unit is cold. As it warms up, it rolls down until maybe 1 or 2 kHz.

I investigated the problem. The sound amplification electronics are in the subwoofer box. It seemed like there was a problem with a switching power supply that steps down 20V from the main PSU to 5V for other parts of the circuitry. This noisy supply is controlled by a AOZ1210 IC. If one blows or apply heat to this IC, the noise frequency changes very noticeably.

I observed with an oscilloscope the supply output but no noise was being injected. This made me think, the noise wasn't being produced at the output but could be inductively coupled to other part of the PCB.

After this I decided to return the speakers, since, this was a manufacturer problem, not mine.

The replacement

The replacement speakers luckily worked fine. There was no noise at all.

As for the serial numbers, this new unit was manufactured actually before the defective one.

Defective unit SN: 441405044429
New unit SN: 441405042325

I try to visually inspect the PCBs of both units but couldn't notice any differences. The PCB revision was the exact same one, so no layout changes. The codes written in the AOZ1210 package were also the same ones.

The defective:

The new:

(The IC and the supply circuitry are located in the bottom right corner, next to the antenna).

The remote
Just as a remark, in my first unit the remote needed to be pointed exactly to the receiver in the speaker. It was very tricky but now I feel it's better. (BTW, the battery was more than OK).

Bottom line

I couldn't really tell what was the reason of the problem. but if you are in the same situation as I was, return them.

Tuesday, March 31, 2020

Drivers for CSR 4.0 Bluetooth dongle


I bought this cheap dongle from Ebay because the built-in bluetooth device in my laptop is shit and produces high pitch distortion when connected to HiFi bluetooth speakers.

According to all Ebay sellers, this is plug and play but in that case you get the generic drivers from Microsoft. In my computer these drivers where such a piece of shit that the laptop couldn't even establish a connection with the speakers.

After lots of search, I found the proper proprietary drivers from Cambridge Silicon, which seems to be a shut company now.

Here there are for you. I got them running on Windows 8.1. Can't say for sure if this will run on Windows 10. Please, if someone tries, comment the result.


Cheers fuckers.