I am using 7030BL transistor to control the power of Servo because when on 0 degree or 135 degree it keeps making noise and current draw is around 700ma i wanted it shut so i put this circuit, can anyone tell me if it is going to work or need any changes?
is 470uf capacitor is on right place? or should it be put after the +8 Power?
Why not just make sure the servo doesn't go to 0 or 135 degrees?
The most common reason for servos buzzing and taking lots of current is because they are stalled, often because you are trying to drive them past their end stops. Perhaps you ought to check that first...you could maybe use the example Knob sketch.
Also I hope you realise that if you cut off power to the servo it won't stay in position if there is any load trying to move it. Then when you add power again it will jump back into position.
Steve
Mark248:
I am using 7030BL transistor to control the power of Servo because when on 0 degree or 135 degree it keeps making noise and current draw is around 700ma i wanted it shut so i put this circuit, can anyone tell me if it is going to work or need any changes?is 470uf capacitor is on right place? or should it be put after the +8 Power?
You are low-side switching 8V power to the servo, yet it has a PWM input that is at 0V or 5V.
Think about this - if the servo is unpowered it will float up to +8V and see the PWM input as
either -8V or -3V. This will probably result in the Arduino pin being fried.
You need to high-side switch the power to the servo, and arrange that the PWM pin is set to
LOW or INPUT before powering down the servo.
MarkT:
You are low-side switching 8V power to the servo, yet it has a PWM input that is at 0V or 5V.Think about this - if the servo is unpowered it will float up to +8V and see the PWM input as
either -8V or -3V. This will probably result in the Arduino pin being fried.You need to high-side switch the power to the servo, and arrange that the PWM pin is set to
LOW or INPUT before powering down the servo.
Should i also put a resistor between PWM signal and servo too?
By switching the high-side will servo power be completely cutt off when i turn off the transistor ?
A resistor is good protection, a few k ohms is plenty (you don't want to slow down the signal too much).
The point is to keep the grounds commoned, its the reference voltage for everything.
By switching the high-side will servo power be completely cutt off when i turn off the transistor ?
Well if no current can flow into the supply rail of the servo, how is it going to get power? Power is the product
of current and voltage.
To switch on the high-side you'll need to level shift to 8V and then and use a p-channel MOSFET.
MarkT:
A resistor is good protection, a few k ohms is plenty (you don't want to slow down the signal too much).The point is to keep the grounds commoned, its the reference voltage for everything.
Well if no current can flow into the supply rail of the servo, how is it going to get power? Power is the product
of current and voltage.To switch on the high-side you'll need to level shift to 8V and then and use a p-channel MOSFET.
What if i turn on the transistor 3 second earlier then sending PWM signal to the servo? and don't worry about servo moving on torque because my design cannot do that it will be still but right now it keeps consuming ampere.
Mark248:
What if i turn on the transistor 3 second earlier then sending PWM signal to the servo? and don't worry about servo moving on torque because my design cannot do that it will be still but right now it keeps consuming ampere.
Huh? Whats this 3 second thing come from?
MarkT:
Huh? Whats this 3 second thing come from?
just to get the power on before receiving a pwm signal
Just curious, did you see this:
Power_Broker:
Why not just make sure the servo doesn't go to 0 or 135 degrees?
Or this?:
slipstick:
The most common reason for servos buzzing and taking lots of current is because they are stalled, often because you are trying to drive them past their end stops. Perhaps you ought to check that first...you could maybe use the example Knob sketch.Also I hope you realise that if you cut off power to the servo it won't stay in position if there is any load trying to move it. Then when you add power again it will jump back into position.
Steve
Why not just do a yourServo.detach()?
That stops sending the positioning pulse, so it won't be driving.
(Same caveat as above of course: if there's a mechanical load trying to move the servo away from the last commanded position.....)
