Servo Voltage

Jerry Elya

O have several Homework Boards and the "What's a Microcontroller?" book. In the book it takes great pains to remind to use ONLY a 9V battery with the Parallax servo; no wall warts, etc. Why?

My understanding is, 5v runs the BS2, and unreg 9v runs the servo, which is a bit high.

Can I power the board with a 9v battery, and the servos with 4 D-ells in series, and both common-grounded together?

I also have a bunch (dozen) of really small servos, labeled "Mystery". Can I assume they're not of some weird voltage? Aren't; most 7.2V? Finally, if I go to FIVE D)cells, (7.5V), would that over-voltage be a problem? I'm asking that because today I fed 5.0V to a sound toy and it popped!

erco

Jerry: You're quite right. Most servos can be safely used at 6 volts; 4 D cells is a good source. And yes, just connect the grounds (battery negatives) together. A small 9V battery drops in voltage when the servo demands a lot of current, so it is relatively safe to use one while experiment with servos.

7.2 volts or 7.5 volts (5 alkalines) directly into a servo is pushing it. Those 9G Mystery servos are plentiful & cheap (I have some too) and they'll last longer at 6V!

W9GFO

Jerry Elya wrote: »

In the book it takes great pains to remind to use ONLY a 9V battery with the Parallax servo; no wall warts, etc. Why?

A wall wart can supply much more current than a 9 volt battery.

Most servos are rated at either 4.8v or 6.0v. You can get away with using a 9 volt battery because they are so poor in high current applications. But if you replace that 9 volt battery with a 9 volt wall wart, there will be much more current available - which can damage the servo.

Rich H