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Thyristor Responder circuit

Published on Apr 18 2011 // Switch Control Circuits

Thyristor Responder circuit.

Circuit shown in Figure 1. Close the power switch K, with the 1.8kO resistor divider after 3kO, A point potential of about 2.2V, B point potential of 0V. After the host announced the answer in the beginning, set a button (assuming K1) pressed, the corresponding one-way thyristor SCR1 turns on, L1 light. SCR1 turns on, the two 1N4007 diodes to clamp the B point potential of about 1.4V, all SCR cathode potential are as 1.4V. When the other group and then press the button, connected to the SCR trigger the very existence of 0.7V on the voltage drop across the diode, so the trigger voltage between the electrode and the cathode is only about 0.1V, which can not make the corresponding SCR conduction, the corresponding indicator will not light. Answer in the first round after the host disconnects the SCR off K, and then close the K can answer in the next round. The figure for the power indicator LED, the circuit can be arbitrarily extended answer in number of groups. For a while in the audible lights can be used to point B and the negative power supply voltage between 1.4V IC or as a music information Xiangqi audible trigger voltage. Figure 2 is a printed circuit.
Experimental Comments:
SCR uses MCR 100-8, L1, L2, L3 are used 6V light bulb, take a good line in Figure. When you press K1, the light L1 light, but at this time when pressing the K2, L2 is also bright, as when at K3, can not be achieved Responder function.
Analyze the reasons, in the SCR1 conducting, the measured potential of A point of 2.2V, B point potential of about 1.2V (diode forward voltage drop as discrete, two diode forward voltage drop less than 1.4V), AB voltage between about 1V, so the voltage may cause SCR2 or SCR3 conduction. Then adjust the R3, when R3 1.5kO notes when, SCR1 turns on, after, SCR2, SCR3 not turn, can be achieved as described in the text answer in function.
In addition, the power instruction slip, the proposed strike by the following formula R1: R1 = (U1-U2) / I, where the supply voltage U1, U2 for the light-emitting diode drop, typically 1.8V, I was light-emitting diode current, usually 5 ~ 15mA, therefore, the figure is about R1 5kO appropriate choice.