1) Mach bo v qu dng:S mch:
a) Nguyn l hot ng:u tin ta t p t vo chn 6 ca Opamp th 2(mch so
snh) . c th iu khin c mch bo v theo dng qua ti. y ta iu chnh khi
dng qua ti ti a l 3,83A:Lc in p trn in tr 0,11 l 0,11x3,83= 0,42Vp
ra ca Opamp th 1 (mch khuch i thun) l Vout1 = 11* 0,42= 4, 63VT ta
t p t Vdat 4,63 VKhi Vout1 > Vdat th lc Vout2= 12v , chn G ca
SCR b kch, t r le b kch, bo v mch.Khi ngt ngun cho SCR th mch hot
ng li bnh thng.b) Kt qu o Cch o:Vn ng h kim v thang o p DCt que en
mass chung, (chn s 2 ca 7812 mch bo v qu p)t que vo cc v tr chn s
1, 6 ca IC LM358 c kt qu trn ng h.Khi mc ti 4.53 (2,65A): i vi mch
khuch i thun+ p ra trn chn s 1 l 3,2 V+ H s khuch i: 10, 7 gn ng vi
tnh ton l 11 i vi mch so snh:+ p t trn chn s 6 ca Opamp th 2 l 3,2
V i vi SCR:Khi SCR khng hot ng th p vo chn G xp x 0v, p VAK=12VKhi
SCR hot ng th VAK xp x 0,9V
2) Mch to xung dng IC555
a) Nguyn l hot ng:Khi cp ngun th t C s np t Vcc qua tr 10k qua
diode D27 qua bin tr R24 qua t xung mass. Khi in p trn t nm trong
khong 1/3Vcc n 2/3Vcc th in p ra chn 3 l mc 1 (12V). Khi in p t ln
hn 2/3Vcc th t bt u x theo ng t t qua bin tr R24 qua diode D28 qua
chn 7 v v mass. Lc ny, in p chn 3 ca IC555 mc 0(0v)Cho n khi in p
trn t nh hn 1/3Vcc th t C li c np, mch lp li chu trnh.b) Kt qu o: o
dng sng np x t:Ta c kt qu nh hnh v:
Trong : Volts/ DIV chnh mc 2VTime/ DIV chnh mc 2mS o dng sng chn
3 ca IC555
