Vex Servo

What is maximum/minimun rated operating voltage?

The operating range of the Vex Controller is 5.5 – 9.0 Volts which will be applied to the Vex Servo. If the Vex Servo was not connected to a Vex Micro Controller, the Vex Servo has a range of 4.4 – 15 Volts on the power inputs. Servo life will be reduced operating outside the Vex Controller range.

What is the wiring diagram for the Vex servo? I have a Radio Shack Beo Bot kit which came with Basic Stamp 2, and would like to know if the Vex servo will work at all with the Basic Stamp (Voltages and control signal). The Beo Bot kit uses the Samp’s pulsout command for control. Would I use the same for Vex and if I do, what parameters should I use?

**There are 3 wires on the VEX Servo Module: Black, Orange, and White. The Black wire is Ground. The Orange wire is for + Voltage. The White wire is for the PWM Control Signal. A Standard Servo and the VEX Servo have a PWM range of about 1 – 2 ms and operates from the white wire at TTL voltage levels. The orange wire voltage range is from 5.5 to 9 volts. The connector may vary and need to be modified.

I am not familiar with the Boe-Bot, but if you created the standard PWM signal using Basic Stamp 2 and the wiring and voltage output is the same, the VEX Servo should work with the Boe-Bot.**

There is no appearance difference in the four motors in my kit. The manual states I should have three motors and one servo. How is a servo marked? How do I tell it apart from a motor?

The only difference between a Motor and a Servo from the outside is the silkscreen marking on the back cover. The Motor will be marked MOTOR MODULE and the Servo will be marked SERVO MODULE.

Is it possible to realign the servo’s neutral position? I have a servo centered in a square construct but the neutral position is nowhere near the correct orientation when attached to the robot. I have biased the orientation by moving the servo when starting up, but the usable range is reduced by the amount of the bias. I’d like to get the whole range back if it’s possible.

No, it is not possible to realign the servo’s neutral position. You can change the center position with code or by using the Trim on the Transmitter but, this will reduce the range of the servo. If possible, try mounting the Servo on a moveable bracket so that you can position the Servo in the orientation you require.

Using the Vex Programming kits along with the servos, we find that the servos pulse mechanically when the microprocessor switch is turn on. It appears that the imbedded software wants to send the servo to its neutral position. We can understand this for the ist time on. For the subsequent times on, a few minutes later, we would not expect any movement of the servo. However, the servo pulses mechanically the same way as first startup. This action is deletarious when gears, flywheels and other mechanical advantege devices are connected to the shaft of the servo. Can you explain?

Unfortunately Radio Shack did not specify the power up, power down or power off state and therefore the response under these conditions can not be determined.

How can you reprogram a servo to become a continuous spinning motor. I have hitec servos which you can just take out the electronics and it will run freely but can you do this with vex too?

No. You can not convert a Servo to become a Motor. The electronics inside interpret the input PWM signal to create the proper control to the Motor.