circuit no 1

Circuit board no.1

lochmaster 3.0 draw up

The circuit board consists of:
given readings:

12volt supply
2x 5 volt supply

LED :1.8v, 20ma

vce:0.04 volts bjt

WORKING:
R14;R15:
12v-1.8v-0.04=10.16v

R=V/I :10.16V/0.02A =508 ohms

R13;R16:

Beta=ic/ib.......ic=2omA, o.02A........ib= ?......beta=10o

Ib=ic/beta...o.o2A/1oo=o.o0o2A,

R=V/I 5-o.7 V/o.o0o2A...... subtract 0.7 from the supply voltage
4.3v/0.2ma= 21500 ohms

NOTE:The resistor im going to use is 560 ohms as 508 resistor does not exist going up to the closet resistance level. As the resistor R15 is in a parallel circuit with R14 the calculations are the same.

Components :

3 voltage inputs, v in 1 being 12volts, v in 2 & v in 3 being 5 volts, the circuit ends being grounded to earth.
Also consists of two different coloured leds both being 1.8v ,there are also two NPN type transistors.
4x resistors, two being 560 ohms R14 & R 15, the other two being 1k ohm resistors R13 & R16.

NOTE: After checking data sheet ib, 0.2mA is not enough current to open the transistor.Data sheet recomands transistor needs a 5mA current.
R13;R!6:5v -o.7v/5mA=...... 4.3v/0.o0o5A= 860 ohms same problem with R14;R15 i'll change the resistor to a 1 k ohm resistor as there is no resistor at 860 ohms.

Actual circuit board:

Explantion:

R14 at 560 ohms is in parallel with R15 also 560 ohms. R14 is connected to D1 the green LED 1,8 v in series to T1 the collector leg( NPN transistor),base being postive is linked to R13 1 k ohm resistor and then to 5volt supply,

From my 12 volt supply R15 (in parallel with R14), connected to D2 through the collector of T2, base is linked to R16 1 k ohm resistor.

Both T1 and T2 are grounded to earth through their emitter .


Reflection and results:

-With the given 12.07 volt supply and two 5 volt inputs, procceding with a voltage drop across R14=10.11v and voltage across LED=1.96v giving a VTof 12.07 in the circuit.

-the voltage drop from the base to the end of R13=4.88v, this must mean .13volts is lost in the circuit somewhere between the two components.

the voltage readings for R15 should be close if not the same as R14 as the two circuits are simlar

the same situation for R 16 should be the same as R13 as the two circuits are simlar