Yet Another Progress Report Mk4 #3

[Tom Droege <droege@wwa.com>]

Lots of progress since the last report on 13 April.  Just about 
everything is working that it takes to make a picture.  The camera 
head parts will soon be here.  I can then assemble a head and take a 
picture.  

I have now run a signal all the way through the system.  There are no 
obvious problems.  I am digitizing to 12 bits or so.  About right for 
a 16 bit system with it's guts spread all over the work bench.  

Here is a summary of the parts of a Mark IV system:

Electronics:

Camera Board:

I have assembled one of the camera boards, and tricked it into 
generating a CCD like signal with a pot.  I can thus simulate a signal 
coming out of the head and test everything else. 

Power Supply:

We are testing using the designed for power supplies.  No problems.  

Stamp Board:

The Stamp Board contains a stamp computer and it's connection to a PC.  
Everything is running and working as planned. 

Scanner Board:

The stamp board contains the horizontal and vertical scan engines.  
These interract with each other to produce the pulse sequence required 
for read out of the CCD. 

Checked Out.  Everything seems to work as designed.  I realize now 
that because of the double integration that the horizontal channel 
needs a crystal oscillator.  This will be added when we revise the PC 
for all the errors. 

ADC Board:

The ADC board contains four 16 bit ADC channels.  Each channel 
performs dual slope integration of the double correlated sample of the 
CCD signal.  

One channel has been tested and works as planned.  A few minor layout 
errors to be fixed.  The other three channels are printed circuit 
copies of the first, so there should be no problems to get the other 
channels working.  

Motor Board:

The motor board contains nine stepping motor drivers and eight model 
airplane servo drivers.  It also contains connectors for 14 position 
sense channels.  It contains registers to drive external devices.  One 
of these is the power control card that can switch 4 channels of 115 
Volt AC power.  

Available for test.  Most parts are here.  One known layout error.  I
forgot the inverters needed by the Model Airplane Servos.  

Memory Board:

This board holds up to 64 Mbytes.  It is loaded from the ADC board and 
read out from the PC. 

One (the old one) memory board is working.  The new one sort of works, 
but seems to have a weak chip.  Since we have enough parts to have a 
working system we will repair this module at our leisure.  

TEC Board:

This board contains four feedback controlled power amplifiers to drive 
four thermoelectric coolers.  The board receives temperature commands 
from DACs on the Stamp board, and closed loop controls the TEC to hold 
the desired temperature.  

Avaliable for test.  Most parts are here.

Misc Board:

This is a collection of many small PC boards.  Some are used to mount 
limit switches.  Others mount SCR switches to control AC power.  
Others are just convenient connectors to allow devices with short 
leads, like the model airplane servos, to be extended. 

Available for test.  Most parts are here.  

Mechanics:

Mount:

Yet again I have scrapped the design.  We now have gone to a dual 
German equatorial mount.  I now also have a better idea of how to 
build a house with built in flat fielding.  At least today I like this 
design.  

Head:

Ten sets of parts are at the anodizers.  We should have them the 
middle of next week.