dinsdag 28 november 2017

Racal Cougar Standalone Programmer - Part 4

Since i posted about the stand alone programmer earlier this year i have been working on the protocol used to fill the crypto keys, a PCB for the programmer and a 3D printed case to house the electronics of the programmer.
Inside the programmer
In this post will try to give some details including the schematic and binary version of the code driving the programmer (the sketch it self will be released later).


This information is supplied "As is" meaning i'm not responsible for any damage to your precious Cougar. Also i don't have the time to support you on your build, feel free to send me an email message with questions but don't expect 24/7 support.


The design is basically made up of all the components described in a previous post, Racal Cougar Standalone Programmer - part 2 with the addition of some additional parts in a single schema used to create a custom PCB.

The programmer code should also work on a default Arduino Nano with a 4x4 keypad, an I2C LCD driver and a 20x04 LCD as long as you keep the pins connecting them to the ATMEGA 328 the same as used in the above schema.

A note on the I2C LCD driver

The I2C LCD driver is based on the NXP PCF8574A I2C 8-bit I/O expander. There are two versions of this IC: the PCF8574 and the PCF8574A which only differ in the usable I2C address range:

PCF8574         0x20 ... 0x27
PCF8574A      0x38 ... 0x3F

(see datasheet)

On the PCB and in the code i used the PCF8574A set to address 0x38.


I had some PCB's made that could be placed on top of the 20x04 LCD. This PCB contains the following parts:

  • DC-Jack and power regulator to generate 5 volt to drive the battery charger
  • Single cell Li-Po/ Li-Ion charger circuit with status leds.
  • 5 volt DC DC converter (without under-voltage protection so use li-po/li-ion's with protection circruit)
  • ATMega 328 micro controller (as used in Arduino Nano).
  • PCF8574A I2C 8-bit I/O expander set to address 0x38 (see datasheet)
  • Racal interface circuit (level shifter, DB9 connector)
The Gerber files for the PCB can be downloaded using this link.


I used a 18650 Li-Ion battery to power the programmer. There is no under voltage or reverse polarity protection so make sure you use a battery containing a protection circuit and when you accidentally connect it the wrong way around it will for sure damage the DC-DC converter IC.

The Sketch

I'm still working on the sketch and will release the code as soon as i think it is ready to be released. In the mean time i will provide a binary version of the sketch which can be downloaded using this link.

More information about how to upload hex files to the Arduino can be found on the Arduino forum using this link for example.

3D printed case

The housing of the programmer is made up of 3 separate parts that are tied together using M3 hex screws and M3 stand-off nuts:
  • Top part containing all the elctronics
  • 18650 battery holder that is placed on top of the keypad using 4 short M3 screws.
  • Bottom part with ventilation slots.
I printed these parts using PLA and PETG with a 0.4 mm nozzle and 0.2 mm layer height and as long as you set the correct speed/ nozzle temperature there is little shrinkage. I haven't tried to print the casing using  ABS.

The STL files for the housing can be downloaded using this link  

zondag 12 november 2017

3D printed Racal Cougar Battery

I have been thinking of 3D printing accu's for the Racal Cougar for a while and this weekend i fired up OpenSCAD and had a go at it.

Like most of the older surplus radio devices there is a shortage of batteries for the Racal Cougar also. You can find them but most of them are dead and need their cells to be replaced. Replacing the cells is a matter of carefully opening the casing using a hobby knife or saw, removing the old cells and replacing them with newer cells.

The problem with this is there is little room in the casing and you need to solder the cells together which is tricky. I did this a couple of times and in some cases i even overheated the cells damaging them.

3D printed accu

Inspired by the MA-4516B from Racal i wanted to have something which i could take apart easily and use regular cells in without have to solder them.

Center, top and bottom parts

I designed the accu so it has 3 sections: a top section containing the locking mechanism and the power connections, a center section containing the cells and a bottom part.

Center part of the accu housing the cells.
Using the dremel i created two pieces of pcb and soldered battery springs coming from a couple of cheap battery clips. These boards connect the batteries together so the accu is made up of 8 serial connected cells.

When the bottom and top parts are connected to the center part using M3 bolts these boards will be sandwiched between it and stay in position.

The center contact is made up of a M3 Hex bolt cut to length and both metal lips on each side are coming from a dead donor accu.

What is next ?

The design is a tight fit, a bit to tight causing some tension on the bottom part. I need to redesign the parts so all parts fit without applying some tension. Also the metal lips currently come from a donor accu and i would like to create the from metal strips also so we have a 100% DIY accu.