Digital Servo Holding position after disable

[Jared Russell]

We had this problem with the servo on our hood until we got a Hitec servo compatible with this guy so we could reprogram it: https://www.servocity.com/html/hpp-2...l#.VvVqMJYrKL8

[Kevin Sevcik]

Originally Posted by Jared Russell

We had this problem with the servo on our hood until we got a Hitec servo compatible with this guy so we could reprogram it: https://www.servocity.com/html/hpp-2...l#.VvVqMJYrKL8

Bought that programmer with the HS-7954SH servo. If I turn fail safe off, it freezes in place when it loses signal. If I turn fail safe on, it servos to the fall safe position and holds there. Doesn't seem to be a setting to kill it when it loses signal. Maybe different hitec servos can do different things.

Anyways, my solution has been to buy another servo. Servocity says futaba digital servos just die when they lose signal. Those weren't available around town, but Savox were. I can personally confirm the Savox die when they lose signal. It looks like just hitec hold position.

[who716]

i am spit baling here as this is little out my league but could a simple fix be attaching a spring to the servo to overpower it every-time you cut power to it or turn it off. we did this on our scalier as a break so that if we dont get up high enough when the match ends and they cut the power the spring will take affect turning the servo to place the break mechanism on the scalier.

[Ether]

Originally Posted by who716

i am spit baling here as this is little out my league but could a simple fix be attaching a spring to the servo to overpower it every-time you cut power to it or turn it off.

Unless I'm misreading the previous posts, the problem is this:

1) A way to cut the power has not been identified, and

2) When the signal is turned off, the servo tries to hold the last commanded position.

Assuming the above is correct, if you add a spring load sufficient to overcome the servo, all you'll do is prevent the servo from moving and possibly burn out the motor.

[Kevin Sevcik]

Originally Posted by Ether

Unless I'm misreading the previous posts, the problem is this:

1) A way to cut the power has not been identified, and

2) When the signal is turned off, the servo tries to hold the last commanded position.

Assuming the above is correct, if you add a spring load sufficient to overcome the servo, all you'll do is prevent the servo from moving and possibly burn out the motor.

This is correct for the Hitec digital servos. At this point we've solved our problem by buying a Savox servo, so this thread should now mostly be seen as informative for anyone that does/doesn't want a servo that will hold its last commanded position after it's lost signal. I need to test tomorrow if the hitec holds position even in Disabled, because I'm sure that would be a fascinating feature to some teams. For instance, IF it holds position, it means who716 could have gotten a hitec programmer and set his brake position as failsafe, and the brake would automatically engage at the end of the match.

[who716]

Originally Posted by Ether

Unless I'm misreading the previous posts, the problem is this:

1) A way to cut the power has not been identified, and

2) When the signal is turned off, the servo tries to hold the last commanded position.

Assuming the above is correct, if you add a spring load sufficient to overcome the servo, all you'll do is prevent the servo from moving and possibly burn out the motor.

that what i thought but it turns out that the servo is strong enough to pull the spring, but without power the spring pulls it back.