
Kit Description:
is Alarm Kit can be triggered manually by either pushing a local pushbutton switch S1
on the PCB or activated by a remote switch S2.
Circuit Description:
e Silicon Controlled Rectier (SCR) acts like a latching
switch and keeps the alarm on once either S1 or S2 are acti-
vated until power is disconnected.
e SCR has three pins an Anode (A), a Cathode (C) and a
Gate (G).
SCR1 is triggered to conduct current from the Cathode to
the Anode when the Gate is driven positive.
S1 closing provides a positive voltage from the battery through R2 resistor and D1 diode.
S2 opening provides a positive voltage from the battery through R1 resistor and D2 diode.
Either switch being activated results in the gate being driven positive.
Once an SCR starts to conduct a positive voltage on the Gate is not needed to maintain
current ow between the Cathode and the Anode. Current will ow until power to the
Anode is interrupted.
General Assembly Guidelines:
Good soldering technique is the most important factor in successfully assembling your kit.
A small pencil type soldering iron 25-40 Watts is recommended.
e tip of the iron should be kept clean at all times by wiping it oen on a damp sponge or
cloth.
Touch the component lead and the solder pad junction with the soldering iron tip.
Apply solder to the junction. It should not take more than 1-2 seconds for the solder to
melt.
A good solder joint will appear shiny and conform to the lead.
Refer to the Abra website at www.abra-electronics.com using the part number if you can-
not identify a part in the part list.
Parts list:
Tools Required: •Soldering Iron •Solder •Diagonal Cutters •9V Battery
C
SRC Picture:
Item ABRA Part# Description Quantity
Buzzer PKB8-4A0 Piezo Buzzer 1
C1 CD104 Capacitor .1uF 1
D1,D2 1N4001 Diode 2
LED1 LED-5R Light Emitting Diode (red)) 1
R1 R1/4-47K Resistor (yellow,violet,orange) 1
R2 R1/4-100K Resistor (brown,black,yellow) 1
R3 R1/4-470 Resistor (yellow,violet,brown) 1
S1 NO-110-PC Normally Open Push Button 1
S2 NC- 110 Normally Closed Push Button 1
SCR C106B Silicon Controlled Rectier 1
9V CLIP 29-130 9V Battery Clip 1
WIRE 22 HW36 Wire 36 inches 2
PCB Board2 Alarm Kit PCB 1