MultiGene PCR machine:
This machine consists of a temperature pot which is connected
to a PC. Genetic samples are inserted in the temperature pot and
software
on the PC is used to control the temperature of the samples in the pot.
I did not build the thermal pot itself, I only did the PC controller
card
and software. Below is a picture of the setup. The Multigene
temperature pot is at the
right side of the image.
This machine is used by the Medical Faculty of the University of
Stellenbosch. Genetic samples
are inserted in the thermal pot and software on the PC is used to
control
the temperature of the samples in the pot.
The pot itself was not designed by me, I was only to supply the
software
and interfacing circuitry to control it from a PC. The pot contains two
halogen lamps which are used for heating and a fan which is used for
cooling.
It also contains a temperature sensor.
After looking at user-interfaces for the program I have decided to
rather
design a simple computer language which can be used to control the PCR
machine. Now a program can be written on any text editor, including the
built-in editor of my software. There are basically infinite thermal
cycle
possibilities, and as these machines are used for research, it is very
easy to put the program in an article or thesis. Here is an example of
a program for the PCR machine:
;Test program
temp=30 for 6 seconds ; Hold temperature at 30°C
for 6 seconds
temp=40 for 7 minutes ; Hold temperature at 40°C
for 7 minutes
do profile 0 8 times ; Do profile number 0 8
times
temp=50 for 1 minute ; Hold temperature at
50°C
for 1 minute
do profile 1 30 times ; Do profile number 1 30 times
end
; End of main program
profile
0
; Start of definition of profile 0
temp=60 for 1 minute ; Hold temperature at
60°C
for 1 minute
temp=50 for 2 minutes ; Hold temperature at 50°C
for 2 minutes
end
; End of profile 0
profile
1
; Start of definition of profile 1
temp=92 for 1 minute ; Hold temperature at
92°C
for 1 minute
temp=70 for 1 minute ; Hold temperature at
70°C
for 1 minute
end
; End of profile 1
This example consists of a main part and two profiles (subroutine).
The first line in the main part is a comment. The main part consists of
two setpoints and then an instruction to execute profile 0 8 times.
This
is followed by another setpoint, and then an instruction to execute
profile
1 30 times. The last instruction in the main part is the END
instruction
the tell the compiler that it is the end of the main program. Profile 0
and 1 consists each of two setpoints.
This project consisted of MS-DOS based software and a custom designed
PC expansion card. The software includes an ISR based temperature
control
loop, a program editor and an interpreter. The PC expansion card
contains
an 8-bit A/D convertor as well as 8-bit status and control ports.
Below is a screenshot of the software. The left side contains the
editor
window, while the right side is used for status messages.
The status section is divided into three vertical section, the top
window
is the status for temperature pot 1, while the center window is the
status
of temperature pot 2. The bottom status window is used for error
messages
from the interpreter. Before a program is executed, the dry runs the
program
too make sure that no error will occur during the actual execution.
Below
is a graph of temperature versus time after the program in the above
screenshot
has been completely executed.
Below is a photo of the PC expansion slot card I designed for the
MultiGene:
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