如附图所示。555定时器连接成一个单稳态电路,其时间常数约为5s。当小偷刚打开点火装置时,555被触发,第③脚输出高电平,使继电器触点闭合,可以启动引擎。别急,约5s后,555定时结束,输出变为低电平。继电器释放,点火装置断开,引擎失效,不能启动。二极管D1和D2在输出降低时防止继电 As shown in the figure. 555 timer connected into a monostable circuit, the time constant of about 5s. When the thief just opened the ignition, 555 is triggered, the first pin output high, so that the relay contacts closed, you can start the engine. Do not worry, about 5s, 555 timer ends, the output goes low. Relay release, ignition off, the engine failure, can not start. Diodes D1 and D2 prevent relaying when output is reduced