Development Of Atemperature Control System Forareal-time PCR Instrument Based On DSP

Polymerase chain reaction (PCR) was first invented by Dr Kary B. Mullis in1983. PCR technology is a revolutionary innovation, which has been playing animportant role in biomedical field. In real time PCR, fluorescent probes are added intothe reaction system, and then the whole PCR process can be monitored by theaccumulated fluorescence signal. Finally, the unknown sample can be analyzedthrough the standard curve. Owing to its high sensitivity and accuracy, real time PCRtechnology has been widely used in biomedical field, such as medical diagnosis, foodsafety, animal quarantine and genetics study.In this paper, we design a temperature control system based on DSP for areal-time PCR instrumentation. The major works include the hardware developmentand the lower computer software development. The hardware includes a DSP mastercontrol circuit, a driver circuit, a thermoelectric cooler (TEC), Kapton heating plateand a temperature sensing circuit. The DSP master control circuit includes a powersupply circuit, a clock circuit, a JTAG interface, a reset circuit, PWM wave outputpins, an A/D conversion circuit and a Serial Communication Interface (SCI). TheH-bridge driver circuit is composed of a photoelectric isolation circuit and anH-bridge amplified circuit. Besides, we use the TEC and Kapton heating plate tocontrol the temperature of PCR and the thermal lid. Choosing the thermal resistorPt100as the temperature sensor, we design a bridge sensing circuit of eliminatingnonlinear error.The lower computer software includes a software initialization subprogram, anA/D conversion subprogram, a PID algorithm subprogram, a PWM wave outputsubprogram, a SCI subprogram and Flash-programming.At last, we have debugged our developing temperature control system. Theexperiment results show that the relative error of the A/D conversion is0.16%. Thetemperature change rate of the TEC is4℃/s and its control precision is±0.25℃. Theheating rate of the Kapton heating plate is2.2℃/s and its control precision is±0.3℃.Electrophoresis results show that the system meets the condition of PCR. Thetemperature data can be transferred to PC by SCI with the Baud rate of9600and thetemperature curve can be drawn by the PC software. We have already tested ourdeveloping temperature control system consecutively for a long time, the system can run stably.