Thursday, April 14, 2011

Design the circruit No.3

Built and test the circuit shows below:

1. Components
   3 1N4001 diodes, 3 LED, 2 0.1uF capacitors, 1 9V1 5.6mA zener diode, 7 resistors, 1 LM324 opamps.

2. Calculation
   R6=10KR Vr6=9.1V-0.63V=8.47V, Ir6=Vr6/R6=8.47V/10Kohms=0.847mA
   There is no current can flow through the input of opamps, so Ir6=Ir7=Ir8=0.847mA
   R7=Vr7/Ir7=0.23V/0.847mA=271R  
   R8=Vr8/Ir8=(0.63V-0.23V)/0.847mA=472R
   Vr5=Vs-Vd2-Vd1=12V-0.6V-9.1V=2.3V   Ir5=Ir6+Id1=0.847mA+5.6mA=6.447mA
   R5=Vr5/Ir5=2.3V/6.447mA=356R
   Vr2=Vs-Vd1-Vled=12V-0.6V-1.8V=9.6V  Ir2=Iled=9.5mA
   R2=Vr2/Ir2=9.6V/9.5mA=1010R
   Vr3=Vs-Vd1-Vd4-Vled=12V-0.6V-0.6V-1.8V=9V  Ir3=Iled=9.5mA
   R3=Vr3/Ir3=9V/9.5mA=947R
   Vr4=Vs-Vd1-Vled=12V-0.6V-1.8V=9.6V  Ir4=Iled=9.5mA
   R2=Vr4/Ir4=9.6V/9.5mA=1010R
   

3.Design the circuit
   I found the terminal numbers of LM324 show as below

   I designed the circuit show as below


4. Built the circuit
   First time the circuit I build is not working. I checked the circuit board connection if that same as I done on lochmaster, then I find out i soldered the bridge wire of terminal 11 to the wrong strip. I fix this mistake and the circuit board works fine.
   I chose R2=1.2KR R3=1KR R4=1.2KR R5=390R R6=10KR R7=270R and R8=470R.
When sensor input voltage is lower then 0.22V
Green LED glows

When sensor input voltage is between 0.22V to 0.63V
Yellow LED glows

When sensor input voltage is higher than 0.63V
Red LED glows

5. Measuring and Explain
No matter what the sensor input voltage is, the Voltage drop cross the following components won't change.
Vd2=0.70V
knee voltage of diode
Vr5=2.23V
R5 is in series circuit with supply, one diode and the whole parallel circuit of zener diode.
Vc1=11.49V
C1 is in parallel circuit after one diode from supply.
Vc2=9.26V
C2 is in parallel circuit with the zener diode, so the voltage drop cross C2 is even to zener voltage.
Vd1=9.27V
The zener voltage of the zener diode.
Vr6=8.63V
Vr8=0.39V
Vr7=0.22V
R6, R7 and R8 are in series circuit share the zener voltage 9.26V.


When sensor input voltage is 0.9V and Red LED glows:
Vr2=8.57V
The available voltage after D2 minus voltage drop cross red LED and terminal 7.
Vr3=8.25V
R3 is in series circuit with terminal 8 and share the voltage came from terminal 1 after D3.
Vr4=0V
No current flow through R4.
Vd3=0.68V
The knee voltage when D3 works.
Vd4=0.51V
The knee voltage when D4 works.
Vled-red=1.98V
The available voltage after D2 minus voltage drop cross R2 and terminal 7.
Vled-yellow=1.76V
Yellow LED share the voltage difference between available voltage after D2 and available voltage after D3 with D4.
Vled-green=1.27V
Difference between available voltage after D2 and available voltage after R4 from terminal 14.


Available voltage of terminals:
V1=9.83V V2=0.63V V3=0.90V V4=11.43V V5=0.63V V6=0.90V V7=0.80V
V8=0.91V V9=0.90V V10=0.23V V11=0V V12=0.90V V13=0.22V V14=10.14V


When sensor input voltage is 0.9V, it is higher than terminal 13 in-, terminal 10 in+, terminal 5 in- and terminal 2 in-. So inverting voltage for terminals 7 and 8, non-inverting voltage for terminals 1 and 14. Terminal 7 to earth and red LED glow. Terminal 1 connect to "+" of supply and gives voltage to yellow LED circuit, low the voltage cross the yellow LED and switch it off, and current flow through terminal 8 to earth. Terminal 14 is non-inverting, so green LED is reverse bias, it doesn't glow.


When sensor input voltage is 0.2V and Green LED glows:
Vr2=0V
No current flow through R2.
Vr3=0V
No current flow through R3
Vr4=8.55V
R4 is in series circuit with terminal 14, green LED and share the available voltage after D2.
Vd3=10.20V
The different voltage between terminal 1 and the centre of yellow LED and R3.
Vd4=0.7V.
The knee voltage of D4.
Vled-red=1.28V
The different voltage between available voltage after D2 and terminal 7.
Vled-yellow=1.07V
The different voltage between available voltage after D4 and terminal 8.
Vled-green=2.02V
Green LED is in series with R4 and terminal 14, share the available voltage after D2.


Available voltage of terminals:
V1=0V V2=0.63V V3=0.20V V4=11.46V V5=0.63V V6=0.20V V7=10.17V
V8=10.17V V9=0.20V V10=0.23V V11=0V V12=0.20V V13=0.23V V14=0.88V


When sensor input voltage is 0.2V, is lower than terminal 13 in-, terminal 10 in+, terminal 5 in+ and terminal 2 in-. So inverting voltage for terminals 1 and 14, non-inverting voltage for terminal 7 and 8. Terminal 7 connect to earth and green LED glow. Red LED and Yellow LED are reverse bias so they don't glow.


When sensor input voltage is 0.5V and Yellow LED glows:
Vr2=0V
No current flow through R2
Vr3=6.54V
R3 in series with terminal 8, yellow LED and D4, share the available voltage after D2.
Vr4=0V
No current flow through R4
Vd3=7.44V
The different between terminal 1 and the centre of yellow LED and R3.
Vd4=0.65V
The knee voltage of D4
Vled-red=1.27V
The different voltage between available voltage after D2 and terminal 7.
Vled-yellow=3.41V
Yellow LED share the available voltage with terminal 8, D4 and R3.
Vled-green=1.27V
The different voltage between available voltage after D2 and terminal 14.


Available voltage of terminals:
V1=0V V2=0.63V V3=0.50V V4=11.46V V5=0.63V V6=0.50V V7=10.17V
V8=0.86V V9=0.50V V10=0.23V V11=0V V12=0.50V V13=0.22V V14=10.17V


When sensor input voltage is 0.5V, it is higher than terminal 13 in- and terminal 10 in+, lower than terminal 5 in+ and terminal 2 in-. So inverting voltage for terminal 1 and 8, non-inverting for terminal 7 and 14. Because terminal 7 and 14 are non-inverting, the green LED and Red LED are reverse bias, they dont glow. Terminal 1 and 8 are inverting, so yellow LED is forward bias, it glows. Because of the D3 is reverse bias, the current can only go through R3 and terminal 7 to the earth.

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