This is a review, teardown and (improvement) of a Mobile Speaker with LED Flash Light. I bought it for PHP 100 or about ~$2.
It has a nice box with the descriptions:
DKNSH MD-329
Main Technique Parameter
1. Trumpet specification: 50mm*2
2. Load power: 3W*2
3. LED quantity: 6PCS
Power Supply Method
1. The DC5V/500mA
2. The computer USB power supply
3. Built-in lithium battery(1200mA)
4. Charging time: 2~3 hours
Product Enclosure:
The USB power supply inputs line
The descriptions do not make any sense, this product appears to be a Chinese one and something may be lost in translation.
Based on my understanding this product has the following features:
It has 2x 3W Speaker, built-in Lithium Battery Rechargeable (1200mAh?), power supply input can be via 5V DC Jack, and has a LED Flashlight function.
Dimensions of the product: 113 mm x 78 mm
Using the LED flashlight and the speaker at the same time.
It also has a volume control, Line In (3.5mm) input (free cable 680 mm length) and a DC Jack power supply (free USB to DC Jack cable). The cables are very thin, no label about its size or wire diameter.
The speaker produced good sounds but it ran out of juice (battery power) quickly.
Tearing it down and reverse engineering the PCB:
The speaker box has four screws hidden under the soft circle that is used for preventing friction from surfaces.
Inside, there is a battery a lithium ion flat battery that has the label 700mAh, but the packaging says it has a 1200mA! notice the missing h, Chinese can never be trusted in labeling their products correctly.
The wires are thin, the PCB board soldering connections are poor. Maybe they want to save more money! There is only one screw that is holding the PCB but there supposed to be two more!
The PCB does not have any SMD (Surface Mount Devices) but only a single IC that has the label of HT4863M it may be the amplifier? It has 16 pins and I cannot find any english version of the datasheet. The IC is a 2.5W amplifier? (I can only read the numbers but the rest are all in Chinese!), it can be powered from 2V to 6V (absolute maximum rating maybe?).
The HT4863M IC
The other components are all through hole packaging.
Marking on the PCB:
MEIER
KM329-M
09-7-30
I want to know if there is a charging circuit for the lithium battery and a boost converter to convert it to 5V, but I was VERY surprised that there is no charging circuit nor boost converter, the DC 5V jack input is connected directly to the lithium ion battery!!! That means there is 5V accross the battery terminals! IF IT IS USING AN UNPROTECTED CELL, THEN THE BATTERY MAY EXPLODE OR BURST INTO FLAMES!
The included battery has a protection circuit as it shuts down the load, thus preventing the over discharge of the battery.
The IC chip is connected directly to the lithium battery and this means the chip is under powered (3.7 to 4.2V only) from the recommended 5V input!
I have added a hot glue to prevent the wires from being disconnected.
The blue one is the 700mA battery included and the green is my 1600mAh replacement battery.
Computations:
Current consumption: (@ 3.5V 18650 battery)
– If the LED flashlight is ON and speaker is OFF: 0.07 A
– If the Speaker is ON at maximum volume and LED flashlight ON: 0.29 A max
Schematic made with KiCad eeschema:
Possible improvements:
– Add a TP4056 Module with DW-01 Protection circuit, connect it to the DC 5V jack and use the OUTput to power the entire board.
– Add a fuse to the battery.
Except where otherwise noted, this work is licensed under Creative Commons Attribution-ShareAlike 4.0 International License (http://creativecommons.org/licenses/by-sa/4.0/).
I hope that this post is useful to you, if you liked this post you may support me via Patreon or liberapay. Thank you for your support.
