Instructables

how do i reverse polarity to/control a "hobby" servo using an arduino chip and motor shield?

i am new to programing and electronics/circuits i.e. breadboards etc, and i have been looking around on this website and YouTube to reverse the polarity to a linear servo motor to make it go forwards and backwards. i am also having with the servo going to far forwards and backwards and locking up the motor to the point where i have to manually spin the gears to free the motor, how do i fix this?
The servo/motor i am using is a AS2000L 1.7- Gram Linear Ultra-Micro Servo and i am using 2 types of this servo, one with just positive and negative wires and the other is the full version with the chip and receiver/transmission wire here is the link for the servo,http://www.spektrumrc.com/Products/Default.aspx?ProdId=SPMAS2000L the specs for it that are on the back of the package are:
Torque: 2.8oz of force
Speed: .14 sec @ 3.7V
Dimensions: 22 x 16.9 x 8.2mm
Weight: 1.7g
Voltage Range: 3.2V - 4.2V
Stroke: 9.1mm
Connector Type: JST
In the beginning i used a 9V battery and just switched the ends that the wires touched and that was how i was reversing the polarity, now i am using the same method but with 3 1.5V  AAA batteries connected together.

quatch2 years ago
You should also look up general motor control. You generally need more current than an arduino pin can supply, and a diode is a good idea when working with motors and relays. Reversing motors is also generally done with an "H-bridge", although I have no experience with those to advise you.

Have a look at the servo control shields and libraries, then you'll know what parts and code you need weather you build your own or buy a kit.
quatch quatch2 years ago
also, a 9V is more than that servo wants! you could damage it.

Alsoalso, a 9V will give you low current (I think they max out around 24mA or so, but that might be sustained), whereas 3x1.5V will allow much more. I expect it to act quite differently between the two batteries.

The product you link says it comes with a special cable to reverse direction. Figuring out how that works will allow you to replicate it in software.
THE STIG37 (author)  quatch2 years ago
i just looked on the link and now i see what you are talking about but that would require me to use there receivers and transmitters and i am trying to stay away from them
THE STIG37 (author)  quatch2 years ago
As of right now i am using the version without the chip because i need as much room as i can get and the chip gets in the way of mounting it so if i use the servo with the chip i will solder on some new longer wires and move the chip around but i cant use the transmitter/reciever that they want me to use and i think i missed where it talks about that reversing wire, could you tell me where it is. Also i didnt notice any change in how it operated
I hope you haven't switched the supply wires around on the full version.....

The two wire version probably needs some limit switches to make sure you don't strain the motor at the ends of the travel.

THere is a library for the Arduino that you use to drive the servo version.