Analysis the working principle of the design of touch switch and key switch

Touch switch is an electronic switch, which can be switched on by pressing the switch button lightly. The switch is disconnected when it is released, and its internal structure depends on the force of metal PIN to achieve the on/off

Because of its small size and light weight, touch switch is widely used in household appliances, such as audiovisual product, digital product, remote control, communication product, household appliance, security product, toy, computer product, fitness equipment, medical equipment, money checker pen, laser pen key and so on. But touch switch has its shortcomings, frequent pressing will make the metal PIN lose elasticity and become ineffective due to fatigue. So now most of the electric buttons are directly replaced by conductive rubber or hardware PIN of pot switch, such as computer keyboard, remote control and so on.

Design and development of touch switch
Travel switch also known as limit switch, which can be installed on a relatively stationary object (such as bracket, doorframe, etc.) or moving objects (such as vehicle, door etc.). When animals approach the stationary object, the connecting rod of the switch drives the contact of the switch causing the closing contact to break or the opening contact to close. The action of the circuit and mechanism is controlled by the change of the opening and closing state of the switch contact.

Micro switch - touch switch. Structure: The switch panel and the raised button connected with the switch panel, its characteristics is the button and panel as an organic whole by its either side arc connection with the panel, it is better to plastic injection of button, connecting strip and panel from a complete mold, the shell of button has a cover which is preferable., the new type of arc connecting strip has certain elasticity because of its thin strip. When the central button is pressed and then released, the elasticity of the arc connecting strip will make it reset, so there is no need to set the reset spring under the button. at the same time, the structure can be simply realized by an integral injection molding, thus greatly facilitating the manufacture and assembly. Classification of working principle of proximity switch: working principle of proximity switch: working principle of inductance proximity switch. Inductive proximity switch belongs to a position sensor with switching output. It consists of LC high frequency oscillator and amplification processing circuit. When metal object approaches the oscillating inductor which can generate electromagnetic field, eddy current is generated inside the object. This eddy current reacts on the proximity switch, attenuates the oscillation ability of the proximity switch, and changes the parameters of the internal circuit, thus identifying whether there is a metal object approaching, and then controlling the switch on or off. The object that the proximity switch can detect must be a metal object.

Working Principle of touch switch

After 220V AC passes through the bulb H and bridge rectifiers, becomes a DC pulsating voltage, which acts as a forward bias and is added to the thyristor VS and R branches.. In the day: when the brightness is greater than a certain degree, the photodiode D presents a bottom resistance state to cut off the transistor V. Its emitter has no current output, and the SCR VS is blocked because of no trigger current. At this time, the current flowing through the bulb H is less than 2.2mA, and the bulb H cannot emit light. Resistor R1 and voltage regulator diode DW make the bias voltage of triode V not exceed 6.8V and protect the triode. Night: when the brightness is less than a certain degree, the photosensitive diode D presents a high resistance state ≥ 100K, which makes the transistor V forward conduct and triode with a voltage of about 0.8V, which makes the SCR VS trigger-on and the bulb H bright. RP is a brightness selection element for switching in the morning or evening.

Installation and adjustion

When installing, put the welded PCB into the transparent plastic box and fix it. Connect it with the controlled lamp H in series, and make it face to the sky curtain or the brighter space in front of the lighting window of the house, so as to avoid the direct illumination of the night light within 3 meters. Debugging should be carried out in the evening, adjustment the resistance of RP so that the controlled lamp H starts to light up at the appropriate brightness.