Posted on Leave a comment

Mini Teardown: Eberspacher 701 BT Controller

It’s well known that there are two versions of the 701 type controller available for Eberspacher heaters, the version with the blue logo is the official un-restricted model, while the version with the white logo is a version built for BT that restricts the heater to 1 hour runtime & has no diagnostics built in.
As these devices are microcontroller driven, I assumed that the hardware would be the same, only the code running in the micro being the bit that Eberspacher changed. This option would certainly have been the lowest cost.

Controller PCB Rear
Controller PCB Rear

Here’s the PCB removed from the plastic housing. There are definitely some differences that I can tell. As the un-restricted version has an extra wire for the diagnostic serial interface, and this board has no unpopulated parts, the PCB is definitely a different version.
In the centre is a Microchip PIC16C622 microcontroller, the OTP version in this case for cost reductions. (I may try reading the binary from this chip in the future, chances are it’s code protected though).
Below the micro is an NXP PCF8577C 32-segment LCD controller, this has an I²C interface to the PIC.
The temperature control function on these heaters is done via applying a resistance to one of the control lines, between 1750Ω-2180Ω, ±80Ω. (Very odd values these, not to mention no standard components can create this range easily, bloody engineers >_<). This is accomplished in hardware with a BU2092F I²C shift register from Rohm, which is connected to a bank of resistors. The microcontroller will switch combinations of these into the circuit to get the range of resistances required.
The rest of the circuit is local power regulation & filtering.

Controller PCB Front
Controller PCB Front

There’s not much on the other side of the PCB, just the LCD itself & the contacts for the buttons.

Posted on Leave a comment

Lethal Chinese Mains Adaptors

With every piece of Chinese electronics I obtain, mainly Baofeng radios, they come with a Europlug-type power adaptor, and a universal plug adaptor for the mains.

The charger units aren’t too bad, there’s a fair amount of isolation between the primary & secondary, and even though they’re very simple & cheap, I can’t see any immediate safety problems with them.

The plug adaptors, however, are a different matter. These things are utterly lethal!

Baofeng PSU
Baofeng PSU

Here’s the inside of the PSU. It’s just a very simple SMPS, giving an output of 10v 500mA. The fuse is actually a fusible resistor.

PCB Reverse
PCB Reverse

Here’s the back of the PCB with the SMPS control IC. I can’t find any English datasheets for this part unfortunately.

Universal Travel Adaptor
Universal Travel Adaptor

Here’s the dangerous adaptor. There’s no safety shield, so the live parts are exposed.

Internals
Internals

Here’s the adaptor split apart. The output contacts are on the left, and rely just on pressure to make contact with the brass screws on the mains input pins to provide power.
This is a very poor way to get a connection, a dirty or worn contact here would create a lot of heat if any significant power is pulled through, and could quite possibly result in a fire.

Not surprisingly, I bin these things as soon as I open the box, and charge all my radios with a 12v charging system.

Posted on Leave a comment

Some Site Changes

After a few years of running with the same look, I’ve decided on some changes.

  • New theme!
    The site now looks much better, and has better support for more eye candy 😉
  • Addition of my QRZ link
  • New QSO logging system
    Accessible from a button in the header, this is my new preferred system for logging my radio contacts. (I was originally using CQRLOG under Linux). If I’ve spoken to you on the radio your callsign will most likely appear immediately. 🙂
    If not, I’m probably working mobile. In that case, drop me a comment or an E-Mail 🙂

Finally there have been some behind the scenes changes to implement some better security on site.
Getting the number of hits I do per day, this site gets attacked by the Internet’s Great Unwashed on a regular basis. No attack has ever been successful but more security never hurts!

73s folks!