Dsg d  n q  &f&i page &p of &nArialdo z @ E?"@y X"hX0.20(#PFPFz" F47K  H? H?">BH"@H@ "">B>~@@~@z"z" u`1K pp "KVPBC237B ; ; 8^ 8^ `"=`8   4 4 4"h81N40010W0W(#0WPF">N"N @ z""8Hz(">B@ @z"">Bgg@g@g">Bg@@g"">K,,@,K,"""KK~KK""DR%3">Kgg@gKg"8H`n"DR`n" KKgKgK"" KBgKg@g@"z" $u`1K p "s`470K1.00 H?H?y"\ 100   h. h." >~B~H"@~H@~e@~ ""DR" ,,H , H,H"" ^B~gg`g@~gy" N 22   @ h. h.",,He,e,Hy"",, , ,y"z" @10K  H? H?"^bg``gz""Xh`ny"  22 4 h. h."Xh",b`,y""^b,b`,` ``z"""  # ,ppж#"^{b{g`{`{g#"H"HH #"z(">~" @~ "C"C C C#">~B~F@~ @~)@~Fy"">~B~g"@~ @~@~g""8wH`n">~"Cgg@~g Cg"C"Cg C Cg#" <(J`n"^^b```#" XhXh"^b^F```Fy"" 8wHz(" 8wH"^B~@~`y"y"" %3"K,,K"%3AO" ,bgH,H,g`gd'`{{\rtf1\ansi\deff0\deftab254{\fonttbl{\f0\fnil\fcharset0 Arial;}}{\pard\qr \x\fs16 Design by Phil Townshend\par \qr \x\fs16 www.edutek.ltd.uk} }"fD1N4001(#0Wjg(#Xzh(#"!Bgg g@g""8H`n"">Bg"@g@ ""0@e@ehhh"#~,,""xVPBC213 ;@8 8^`T `"$^{b\gg`{g`\g"89h1N40010W0W(#0WPF"Xth`n"%Cb{gg`{g Cg""XUhc`n"&^\gB`\gg@@""""ȷ%3"'^\°,,`\,`\"""(C°~ C""<(J")>~"C C@~y"d@  {\rtf1\ansi\deff0\deftab254{\fonttbl{\f0\fnil\fcharset0 Arial;}}{\pard\qc \x\fs24\b FRIDGE ALARM\par \ql \x\fs20 \par \ql \x\fs20 The fridge alarm was designed to prevent the fridge door being left open but if the timing is turned down, can also be used to alert anyone that the fridge is being raided!\par \ql \x\fs20 \par \ql \x\fs20 This circuit is activated when a light is shone upon the LDR which in this application would be the light from a fridge when the door is opened. This causes Q1 to conduct and activates the relay, The relay provides power to a standard 555 monostable that activates a buzzer when the output returns low after its timing period. The length of delay before the buzzer is activated can be adjusted by VR1.} }d F`{@@/{\rtf1\ansi\deff0\deftab254{\fonttbl{\f0\fnil\fcharset0 Arial;}}{\pard\ql \x\fs20 The standby current of this device is very low. In complete darkness, a typical LDR will have a resistance of around 1Mohm. This results in a standby current of around 1uA. A PP3 battery should last at least 6 months.} }d"h<8@1009 (# PF PF"*>b5ge@e@g`5gd"""+>B @ @@d""8H",>K@K  x4 $100F Electrolytic Capacitor 0 1 010K Resistor (1/4W) 0 1 01K Resistor (1/4W) 0 2 01N4001 Diode 0 3 0#22F Electrolytic Capacitor 0 2 0470K Variable Resistor 0 1 047K Resistor (1/4W) 0 1 09V Battery (100mA) 0 1 0BC213 PNP Transistor 0 1 0BC237B NPN Transistor 0 1 0Buzzer (6V) 0 1 0LDR (ORP12) 0 1 0 NE556 Dual Bipolar Timer 0 1 0SPDT Relay (6V) 0 1 0@ @?"@