Hey,
i am new to rc controls and servos. i am wantnig to build a very large almost go cart sized rc car. i need a very large servo to steer it. I am thinking of using a windshield wiper motor or something similar but i do not know how to connect it in to rc reciever on the car. I have seen ways of connecting the motor outputs from the servo to an h-bridge circuit and using the servo pot to provide feedback to the reciever. Is this the only way? or is there a better way? Any help would be appreciated. thanks
You may want to look into using a linear actuator to move the stearing linkage. I think somebody makes a 6v servo compatable version, but I don’t think it is cheap. The main problem is cheaply controlling 12v motors with 5v control signals.
ok. I had never thought about using an actuator but see how it could work. I see linear actuators at servo city. the one i see has 5 wires to connect. red and black for pos and neg, then it has 2 reference and one for position signal for the pot. how would you hook this into the reciever? do you need to use a micro controller?
thanks
Be careful to check the speed specs on any linear actuator you chose. Many are strong, but slow. You could end up with a lock to lock steering delay of 10 seconds. lol 
I was forced to find a solution to a similar problem myself. For my senior design project I built a 150lb robotic pack mule but didn’t have the budget for a jumbo servo or fancy controller.
My solution was to use a linear actuator from surplus center controlled using a Victor 883 electronic speed controller from IFI Robotics. The Victor was likely overkill but it was what we had on hand. Sadly I was unable to utilize the built-in potentiometer feedback so it was incapable of auto-centering when the transmitter stick was released. We understood the basics of how to accomplish this but didn’t have the budget to implement it. What we hoped to use was a microcontroller which could be programmed to receive the commands from the receiver then read the potentiometer to determine the actuator’s position versus the desired position. The microcontroller would then send commands to the ESC to move the actuator as desired.
One feature I was able to make use of was the built in limit switches. For my application, a mechanical limit was reached before the actuator reached it’s own design limits. To prevent binding and damage to the actuator, I removed the limit switched and diodes from the actuator and installed the switches on the frame so the mechanical components would activate the switch. All I needed to do then was simply extend the wires to hook everything back together.
My last bit of advice relates to Jim’s comment. While linear actuators are quite strong, this strength comes at a cost of speed. For my robot, I needed to overvolt the actuators to 24V in order to steer at a respectable speed. The robot only traveled around 5mph but this was too fast for the actuator originally. While overvolting the actuator did provide the speed needed, as always this technique will result in a severly reduced life span for the component. It was sufficient for the school project but definitly not a long-term solution.
Hope this insight helps some. Good luck with your project!
Dan Toborowski
