Hi everyone,
I was wondering if any of you could help with this circuit , in making the output current variable. Is it as simple as changing the Zener diode , Z1 , for a potentiometer and careful selection of R3 and R4 resistors ? I need a power supply that outputs a constant current with variable voltage , as this is the best method for anodising. It would however be preferable if that current could be adjusted up or down depending on the surface area of the anode. Thus far I have done some math and found as follows :
R3 = 22000Ω
R4 = 0.85Ω ( 0.25 + 0.25 + 0.25 + 0.1 , all 5W)
Z1 replaced with 5k Potentiometer
When POT is at 0Ω , collector current = 0A due to no voltage at Q1 base. When POT is at max 5000Ω , collector current = 3.839A , and Q1 base voltage is 3.963V. If my theory is correct , this increased voltage at Q1 base causes an increase in Q1 collector current , but more importantly that current is fixed and can thus be controlled by the potentiometer. Any ideas anyone?
I was wondering if any of you could help with this circuit , in making the output current variable. Is it as simple as changing the Zener diode , Z1 , for a potentiometer and careful selection of R3 and R4 resistors ? I need a power supply that outputs a constant current with variable voltage , as this is the best method for anodising. It would however be preferable if that current could be adjusted up or down depending on the surface area of the anode. Thus far I have done some math and found as follows :
R3 = 22000Ω
R4 = 0.85Ω ( 0.25 + 0.25 + 0.25 + 0.1 , all 5W)
Z1 replaced with 5k Potentiometer
When POT is at 0Ω , collector current = 0A due to no voltage at Q1 base. When POT is at max 5000Ω , collector current = 3.839A , and Q1 base voltage is 3.963V. If my theory is correct , this increased voltage at Q1 base causes an increase in Q1 collector current , but more importantly that current is fixed and can thus be controlled by the potentiometer. Any ideas anyone?