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Maplin A24GU Wireless Audio Module Teardown

Transmitter
Transmitter

This is a pair of modules that Maplin was selling some time back, to send stereo audio over a 2.4GHz radio link. The transmitter identifies as a USB sound card, I’ve personally used these units to transmit audio about 60ft. The transmitter, above, has a single button for pairing with the receiver below.

Receiver
Receiver

The receiver unit has a large external antenna, a link status LED & volume buttons, these directly control the volume level on the host PC via the sound card drivers.

Receiver PCB Top
Receiver PCB Top

Popping the case open on the receiver reveals a large PCB, holding the chipset, along with the audio output jacks & Mini-USB power input. The antenna Coax is soldered to the PCB.

Receiver PCB Bottom
Receiver PCB Bottom

The top of the board has the control buttons, and the status LED.

Receiver Chipset
Receiver Chipset

The chipset used here is a Nordic Semiconductor nRF20Z01 2.4GHz Stereo Audio Streamer, there’s a small microcontroller which does all the register magic on the RF transceiver. The RF chain is at the top of the photo, audio outputs on the top left, and the micro USB power input & voltage regulators at bottom left.

Transmitter PCB Top
Transmitter PCB Top

The transmitter PCB has a Sonix USB Audio Codec, to interface with the host PC. This is then fed into another Nordic Semi part on the opposite side of the board:

Transmitter PCB Bottom
Transmitter PCB Bottom

The bottom of the transmitter has the RF section, and another small control microcontroller.

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Tenma DMM Drivers & PC Software

My new DMM I posted about a while back came with PC software & drivers for the RS-232 interface, on a CD. I haven’t used CDs for some time, so I had to dig out my USB drive.

The Tenma website doesn’t list the software for all their models, so to help others I’m posting an archive of all the supplied drivers here. The archive contains software & drivers for the following Tenma models:

Tenma Multimeter Drivers (783 downloads)

Tenma 72-1015
Tenma 72-1016
Tenma 72-1020
Tenma 72-2610
Tenma 72-2620
Tenma 72-7712
Tenma 72-7715
Tenma 72-7730
Tenma 72-7730A
Tenma 72-7732
Tenma 72-7732A
Tenma 72-7735
Tenma 72-7745
Tenma 72-7750
Tenma 72-7755
Tenma 72-7760
Tenma 72-7790
Tenma 72-8400
Tenma 72-8720
Tenma 72-9280
Tenma 72-9380
Tenma 72-9380A
Tenma 72-9405
Tenma 72-9490
Tenma 72-10405
Tenma 72-10410
Tenma 72-10415
Tenma 72-10440
Tenma 72-10445
Tenma 72-10465

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Turnigy Accucell 6 Multi-Chemistry Charger

Accucell 6
Accucell 6

A lot of the electronics I use & projects I construct use batteries, mainly of the lithium variety. As charging this chemistry can be a little explosive if not done correctly, I decided a proper charger was required. This charger is capable of handling packs up to 6 cells for Lithium, and up to 20v for lead-acids.

External Connections
External Connections

The usual DC input barrel jack on the left, with an external temp sensor for fast charging NiCd/NiMH chemistry batteries. The µUSB port registers under Linux as USB HID, probably so drivers aren’t required. Unfortunately the software is Windows only, but it doesn’t provide anything handy like charging graphs or stats. Just a way to alter settings & control charging from a PC. On other versions of this charger there’s a setting to change the temp sensor port into a TTL serial output, which would be much handier.

Output & Balance
Output & Balance

The other side of the charger has the main DC output jacks & the pack balancing connections.

Cover Removed
Cover Removed

Here’s the top cover removed from the charger, showing most of the internals. A standard HD44780 LCD provides the user interface, the CPU & it’s associated logic is hidden under there somewhere.
The PCB has nice heavy tracks to handle the 6A of current this charger is capable of.

Balancing Network
Balancing Network

The output side of the board. Here the resistive pack balancing network can be seen behind the vertical daughter board holding the connectors, along with the output current shunt between the DC output banana jacks & the last tactile button.

Main Logic
Main Logic

Unfortunately the LCD is soldered directly to the board, and my desoldering tool couldn’t quite get all the solder out, so time to get a bit violent. I’ve gently bent the header so I could see the brains of the charger. The main CPU is a Megwin MA84G564AD48, which is an Intel 8081 clone with USB support. Unfortunately I was unable to find a datasheet for this part, and the page on Megwin’s site is Chinese only.

I was hoping it was an ATMega328, as I have seen in other versions of this charger, as there are custom firmwares available to increase the feature set of the charger, but no dice on this one. I do think the µUSB port is unique to this version though, so avoiding models with that port probably would get a hackable version.
There’s some glue logic for controlling the resistor taps on the balancing network, and a few op-amps for voltage & current readings.

Power Switching Devices
Power Switching Devices

All the power diodes & switching FETs for the DC-DC converter are mounted on the bottom of the PCB, and clamped against the aluminium casing when the PCB is screwed down. Not the best way to ensure great contact, but Chinese tech, so m’eh.