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Argus 3 Tearup and Reuse

Continuing from the earlier repair page, this page now looks in more detail at the camera chassis and considers options for repurposing.



The Argus 3 camera used a Raytheon BST core (detector plus 'SECCA' PCB) with a supporting control PCB set and an LCD display. While all the imaging functions were part of the Raytheon BST core, the control PCB added on-screen graphics, image capture, zoom and safeguard controls for fire use, along with some standardisation of core settings. It used the digital data from the Raytheon SECCA PCB. The Argus 3 did not use the core analogue output, but this is accessible.

Block Diagram and walkaround

There are 3 main 'EEV' design PCB's (Detector, Motherboard, Video & Control) in addition to the Raytheon SECCA board, and a further 3 ('Shelf', chopper sensor, Lens Limit) that purely serve connection or mechanical purposes.

Block diagram showing signal flows and main PCB interconenctions
The 'Motherboard' is primarily to connect the two larger PCB's and the front PCB. Actual functions are limited to the 10V LCD supply, on/off switching and control over battery charging.

The detector PCB contains the BST sensor and related decoupling and connections via a rear 'shelf' to the Raytheon SECCA PCB.
It is shown here with the detector and chopper sensor fitted, but the chopper wheel removed.

The PLD controls the lens iris by sampling the digital video stream, while shift logic rephases the chopper wheel detection pulse to match the mechanical arrangement of the Argus3.

The DAC supplies DC control voltages for the SECCA to use as offset and gain values in image processing, as the built-in automated mode was not well suited to typical fire scenes.

All interesting signals (timing, digital data bus, core RS232 control, analogue gain/offset, video out) are named on the PCB legend which makes test and modification much simpler.

There is an override to turn off the Peltier if conditions become too extreme for safe function.
SECCA PCB
This was the Raytheon electronics board. It controlled the sensor and held the calibration for each sensor, as such a sensor and its' SECCA are a matched calibrated pair. Argus3 only used the later 'digital' version recognisable by smaller IC's and no multiturn pots
The video & control PCB has several functions, split between post processing the digital data from the Raytheon SECCA PCB into the colour video image and controlling the camera.
  • Image colourisation logic, by lookup in FPGA
  • On screen graphics
  • Saving images
  • Digital zoom
  • Supervision, mainly to guard against extreme fire use. At very high temperatures to turn of the Peltier in the sensor, to monitor humidity and to alert the user to an iris fault
  • RS232 for both user and factory setup
  • Setting up the BST core operating conditions via the DAC on the detector PCB
  • Sensing interfaces for battery level and spot temperature readings
  • Allow indirect access to the BST core RS232, eg to set PAL-625
Front PCB
Connections for front panel wiring as well as the optional spot temperature module and various video transmitters.
Chopper Wheel
A vital part of the BST sensor function, the wheel rotation makes the pattern follow the readout scan of the sensor creating a change between a clear view and a blurred averaged view of the scene. It is this blurring that gives the BST image a characteristic 'halo'. This is a full height wheel for handheld cameras, most/all of the driver vision cameras had a half height image (320x120) and so a different wheel design.

Chassis Power and Test


The chassis is powered through the 6 way connector from the battery PCB when in the camera case. However by using the 'White' not 'Red' input, the chassis will power up without needing to activate the on/off circuit. This is the same as powering the whole camera through the base contacts.

6 Way power connection. Connector Type: Harwin M20 0.1"
View from rear (wiring end or onto the PCB)

 Connect +ve of supply to 'white' pin to bypass on/off
Connect to 'red' to keep on/off
Connect -ve of supply to 'black' pin and ground


When checking a camera, much can be assessed by monitoring the current consumption as the camera turns on. The added current draw of the peltier can be seen and there is some protection if there is a fault. 9-12V 3A is necesary for the inrush and initial Peltier surge, a 1A limited supply will simply fold over. The boards DO NOT include reverse polarity or spike protection. Protection should be considered if the core is not powered from a clean DC supply. A number of 'DIY' conversions to vehicle use have failed as car alternator spikes will kill the BST core, mainly through poorly specified tantalum capacitors. At startup there is a power surge at 10W until the sensor peltier control has stabilised. In normal running, power draw drops to around 3.5W.

Other Pinouts

15 Way LCD connection from Control PCB
Type Molex 53261-15xx 'Picoblade 1.25mm'
Pin Function
1 Video Out
2 Video Gnd
3 10V
4 0V
5 0V
6 0V
7 LCD Contrast
8 LCD Brightness
9 LCD Colour
10 LCD 5V
11 LCD 0V
12 Left (image) button
13 Right (zoom) Button
14 Centre (power) button
15 0V


16 Way Ribbon for Front PCB
Type 1.0mm pitch FFC Molex 87264-1650
Pin Function
1 Video out for BNC
2 0V
3 Video out for transmitter
4 0V
5 Select Tx channel 1
6 Select Tx channel 2
7 Select Tx channel 3
8 Tx Power
9 0V
10 Ambient T sense
11 Ambient T sense
12 RS232 Tx
13 RS232 Rx
14 5V
15 Spot Temperature signal 10mV/°C
16 0V


Core extraction

   

The Raytheon BST was always intended as a simple core to use, and the Argus3 took this a lot further to produce a rugged colour fire camera with added features. Second hand or partly damaged cameras though can be a cheap source of high quality cores that are a starting point for a more minimalist stand alone camera using just the detector PCB and SECCA as shown above. As such it is still a good quality imager and stands up well against mid and low end bolometers, and the access for reconfiguration is a distinct plus point. The main negative is that it cannot do temperature measurement.
It can run as a simple 4 wire 'volts in-video out' camera or with more control and the possibility to pick out digital data by using the 40 pin interface on the detector PCB


Using the test connection

  

This connector (or the remains of it) are a test connector for the BST core assembly. It was provided to satisfy export controls for the BST core, that it had to be exported as a 'camera' is capable of providing a video output. To export the detector alone was more complicated under the rules at the time. So a 6 way header was fitted to what were originally only meant as handy test points on the board. Three of them then had to be cut off as they shorted to the camera case, unfortunately these are the video pins. A simple replacement with any handy 0.1 inch pitch connector.
It is labelled 'IrisTest' 0 + 0 V on the legend, detailed pinout below. On a full Argus3 chassis this provides direct access tot he core video out.
Pin Function
1 & 2
Iris test		 Shorting these was intended to run an iris test sequence. The PLD code was never finished and all it does is close the iris once
3 = 0V
4 = +ve		 Power in
5-10V good clean DC and 2A capability
Note: voltage requirements for a camera not a core.
5 = 0V
6 = Video		 Core video out. This is the basic mono core video out with very little symbols etc. It is the same as the 10 bit digital data.


More details and the modifications for running the core alone are given in the project here , or for a more blocky core consider Argus2 parts as a base (future project).

Ready to go tested cores are currently available from Fire-Tics for GBP200 (for sale ONLY to UK and EU27 at present). These have been reset to run with RS232 defined fixed brightness / contrast, or custom settings can be requested.
The full 40 way connection is tested and a recalibration performed if needed.
One new 15mm f/1 lens is also supplied, but can be omitted if not required.
If your project does not need the chassis plate, also do not take one as these are in short supply.

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Fire-TICs Argus3 Camera Repair2 page 16 April 2021  All tradename © respective owners