Published:2011/4/22 19:15:00 Author:Nicole | Keyword: timer, fixed preset time | From:SeekIC
The foot 13 between valve value 1 and valve value 2 will suck the transistor base current. If relay releases, after recovery time 0.5s, to press key then it will start to switch process again.
The timer is composed ofwindow discriminator TCA965 to. After pressing the key Ta , decision time capacitance C will charge. transistor T1 obtains base current from 2 foot of TCA965, power supply provides current. The process is timed ahead of 10s. During this time, the indicator light LD57 on. When the capacitance charge voltagesurpasses valve value 1 , the relay pulls-in. Once it reaches valve value 2 which is set by potentiometer Rp, the relay will release again. The relay pull-in time is in the range of 0~18s, it is adjustable.
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