| Transcranial direct current stimulation(tDCS)is a kind of non-invasive nerve stimulation technology.It can regulate the activity of cerebral cortex nerve by applying specific,low-intensity current to specific brain areas through electrodes.Its portable,non-invasive,low-cost and safe features make this technology a promising brain stimulation technology.At present,the main foreign companies developing transcranial direct current stimulator are Neuro Conn of Germany and Soterix of America.There is no professional transcranial direct current stimulation equipment in China,and the safety of human experiments is unknown.In addition,at present,the impedance detection of equipment at home and abroad is mainly to determine whether the impedance detection is passed by setting impedance threshold.This unified artificial setting of impedance threshold will make the impedance detection lack objectivity and may cause skin burns,so how to realize personalized human impedance detection is a problem that needs to be solved at present.Therefore,a portable transcranial direct current stimulation system with personalized impedance detection technology is studied and designed independently in this paper.The transcranial direct current stimulation system developed in this paper is mainly composed of hardware circuit and personalized impedance detection technology.Hardware circuit design includes current test circuit,impedance detection circuit and real-time monitoring current protection circuit.After the selection of components,schematic drawing,circuit design of each module,PCB layout,circuit board welding and debugging of software and hardware,the parameters of the prototype are tested.The output of current test is from-2000?A to + 2000?A,and the step length is 200?A.The actual current value is collected from the host computer.The error between the actual value and the set value is calculated.The maximum error of current test is 10?A and the maximum error percentage is 2%.In the impedance detection test,the maximum error of the collected resistance is 2.4 k? and the maximum error percentage is 10%.The accuracy meets the impedance detection requirements in the field of transcranial electrical stimulation.In addition,the power consumption of the system is tested.It is found that the maximum output power can stand by for about 20 days for a long time.Finally,the current output waveforms of different stimulation modes are shown in InfiniiVision 1000 X series.The waveform output satisfies the experimental requirements.Personalized impedance detection technology mainly draws the relationship curve between current and impedance according to the change of individual impedance with current,and establishes their mathematical model.When different individual impedance is detected,different impedance thresholds are selected for different stimulus currents.Finally,the portable transcranial direct current stimulation system with personalized impedance detection designed in this paper can provide a better platform for clinical experiments of nervous system diseases. |
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