[Newbie question] Vdd vs Vin for servos while using a 9v battery
My Intro to Engineering class has been tasked with a robotics project using the Board of Education. I've built robots before, but not with Parallax products.
I've just gotten to point of using servos in the "Robotics with the BOE Bot" book that comes with the BOE. The book says to put a jumper (between the servo ports) over Vdd if using a 7.5V DC power supply or over Vin if using a 6V battery pack. I'm using a 9V battery, which obviously isn't either.
So, where do I put the jumper? If someone could explain why I put the jumper there (e.g. voltage is greater than 6V, or something), that would be helpful, too.
I'm using a BOE Revision D with BS2 Rev. J.
//Andrew
EDIT: By the way... our instructor pointed us to the forums if we needed any help. He's fine with us asking questions on here--it's not cheating/unwanted in any way.
I've just gotten to point of using servos in the "Robotics with the BOE Bot" book that comes with the BOE. The book says to put a jumper (between the servo ports) over Vdd if using a 7.5V DC power supply or over Vin if using a 6V battery pack. I'm using a 9V battery, which obviously isn't either.
![;) ;)](https://forums.parallax.com/resources/emoji/wink.png)
I'm using a BOE Revision D with BS2 Rev. J.
//Andrew
EDIT: By the way... our instructor pointed us to the forums if we needed any help. He's fine with us asking questions on here--it's not cheating/unwanted in any way.
Comments
Selecting "Vdd" with the jumper will send the 5V from the on-board regulator to the servo supply pin/s.
Your 9V dictates selecting "Vdd".
If "Vin" got selected then the 9V (too much) would be available for the servo (and wreck them.)
They don't last long anyway, but little 9V batteries are short-lived running servos on a BoE.
Thanks for the help!
//Andrew
With a BoE, you're better off using 4x AA batteries (like a BoeBot) to power Stamp and servos, using Vin.
As chips have evolved, it seemed that 7 volts was the highest a servo would tolerate - never 9 volts DC.
But now, even the brushless ESC for controlling r/c airplanes prove an extra +5 or +6 regulated DC output (often a choice to select one or the other) and this is just for the servos.
In sum, newer servos will fry if you go too high. You can salvage the motor and use an outboard h-bridge, but the electronics are NOT going to tolerate 9VDC for a New York minute.
Believe me as I have a nice new and very dead servo from momentary high voltage.
Enjoy!
Mike
Either the 4 AA's as erco suggests or a pair of Lithium Ion batteries would work better.
Fine needle nosed pliers and tweezers are a necessity for working with small components, particularly surface mount parts.