Hello all!
I have designed the following circuit, but I am hoping some one can check it for me please.
The designed function is as follows:
Once the circuit is switched on, a time delay begins at TD1, and once it expires Pump1 turns on, and the Bladder inflates to a preset maximum pressure. At this point, the pressure switch sends a current to the NPN transistor, which in turn energizes the relay, diverting power to TD2 and Pump1 turns off. After the preset delay, Pump2 turns on, deflating the bladder to a preset minimum pressure. At which point the relay is switched back to TD1 and the cycle starts again.
The pump speeds are controllable via PWM1 & PWM2 Modules.
The system has a battery backup and regulated 12VDC supply to the circuit. I have an UPS module and a 12V regular Module as shown from the 240AC power supply.
Calculations:
I have first calculated the resistor values over the SMC pressure controller and the transistor switch base current etc, as follows:
Parts Specifications:
SMC pressure controller Specs: http://www.smcaus.com.au/files/imm/IMM_ZISE30_GB.pdf
Current Consumption Ismc = 40mA
Find Resistance for SMC pressure controller - Rsmc:
Rsmc = 12V/0.04A
Rsme = 300ohms
Relay1 12V DPDT
30mA Coil
400Ohm
All Diodes are to be IN14001 or IN14004
Transistor BC547A
he = 110
Vbe = 0.7
First find Ib for the Transistor.
Ib = (Load Current / Hfe) x 2 to ensure saturation.
Ib = 0.030A / 110 x 2
Ib = 0.27mA x 2
Ib = 0.54mA
R2 = Vin - Vbe / Ib
R2 = (12 - 0.7) / 0.00054
R2 = 20925 Ohm or 22K
Assuming the Resistance of the SMC controller and R2 are in paralell.
R1 = 1 / (1/Rsmc + 1/R2)
R1 = 1 / (1/300 + 1/2092)
R1 = 295 Ohm
TD1 = 1.1W when Relay is on.
I = W/V
I = 1.1 / 12
I = 0.091A or 91mA
R4 = V / I
R4 = 12 / 0.091
R4 = 131 Ohms
R4 = R5
R5 = 131Ohms
R6 = R7
I = W (pump) / V
I = 2.5 / 12
I = 0.208A or 208mA
R6 = 12 / 0.208
R6 -= 57.6 Ohm
R6 = R7
R7 = 57.6Ohm
---------------------------------------------------------------------------------------------
Some questions I have are:
1. Will this circuit work as planned?
2. Do I need a resistor for the path accross RC1 coil?
3. Are the formulas and calculations correct?
4. Are the Diode and Transistor suitable?
Any advice would be appreciated, I am running out of time and just need a hand, any help would be appreciated please.
Thanks very much,
Grant.
I have designed the following circuit, but I am hoping some one can check it for me please.
The designed function is as follows:
Once the circuit is switched on, a time delay begins at TD1, and once it expires Pump1 turns on, and the Bladder inflates to a preset maximum pressure. At this point, the pressure switch sends a current to the NPN transistor, which in turn energizes the relay, diverting power to TD2 and Pump1 turns off. After the preset delay, Pump2 turns on, deflating the bladder to a preset minimum pressure. At which point the relay is switched back to TD1 and the cycle starts again.
The pump speeds are controllable via PWM1 & PWM2 Modules.
The system has a battery backup and regulated 12VDC supply to the circuit. I have an UPS module and a 12V regular Module as shown from the 240AC power supply.
Calculations:
I have first calculated the resistor values over the SMC pressure controller and the transistor switch base current etc, as follows:
Parts Specifications:
SMC pressure controller Specs: http://www.smcaus.com.au/files/imm/IMM_ZISE30_GB.pdf
Current Consumption Ismc = 40mA
Find Resistance for SMC pressure controller - Rsmc:
Rsmc = 12V/0.04A
Rsme = 300ohms
Relay1 12V DPDT
30mA Coil
400Ohm
All Diodes are to be IN14001 or IN14004
Transistor BC547A
he = 110
Vbe = 0.7
First find Ib for the Transistor.
Ib = (Load Current / Hfe) x 2 to ensure saturation.
Ib = 0.030A / 110 x 2
Ib = 0.27mA x 2
Ib = 0.54mA
R2 = Vin - Vbe / Ib
R2 = (12 - 0.7) / 0.00054
R2 = 20925 Ohm or 22K
Assuming the Resistance of the SMC controller and R2 are in paralell.
R1 = 1 / (1/Rsmc + 1/R2)
R1 = 1 / (1/300 + 1/2092)
R1 = 295 Ohm
TD1 = 1.1W when Relay is on.
I = W/V
I = 1.1 / 12
I = 0.091A or 91mA
R4 = V / I
R4 = 12 / 0.091
R4 = 131 Ohms
R4 = R5
R5 = 131Ohms
R6 = R7
I = W (pump) / V
I = 2.5 / 12
I = 0.208A or 208mA
R6 = 12 / 0.208
R6 -= 57.6 Ohm
R6 = R7
R7 = 57.6Ohm
---------------------------------------------------------------------------------------------
Some questions I have are:
1. Will this circuit work as planned?
2. Do I need a resistor for the path accross RC1 coil?
3. Are the formulas and calculations correct?
4. Are the Diode and Transistor suitable?
Any advice would be appreciated, I am running out of time and just need a hand, any help would be appreciated please.
Thanks very much,
Grant.