HXT900 Servo Mods
Only Duane will care, but FYI:
I started modding a Hobby King HXT900 9-gram (tiny) standard servo last night for continuous rotation (CR), for possible use as a small robot drive motor. Many 9-gram servos are not CR candidates since they only have a half-gear sector on the output shaft. The HXT900s are hailed as some of the better cheap servos since the gears are beefier.
I made slow progress last night as I had to work with a sick baby on my lap, but it was quality bonding time. With Father's Day approaching, I can't shirk any duties!
Anyhoo, the HXT900 uses the feedback potentiometer as a rotary bushing and significant structural component of the output shaft, so it's not a simple "yank the pot" hack like some other servos I have modded. I ended up just chopping the pot contacts out so it could rotate 360, and cutting a mechanical stop off the output gear so it can rotate 360, then I routed the pot wires outside and reassembled it. Still have to add an external pot for nulling, but it rotates cleanly. Additionally, I need to finish & test the modded servo to see how useable it is. Some servos are extremely sensitive to pulsewidth and lack fine motor control. Will advise.
Even if it does work well, I suspect the pot shaft may wear quickly. I have plans to make a delrin insert & steel shaft to replace the pot entirely. So good news, bad news, campers.
I started modding a Hobby King HXT900 9-gram (tiny) standard servo last night for continuous rotation (CR), for possible use as a small robot drive motor. Many 9-gram servos are not CR candidates since they only have a half-gear sector on the output shaft. The HXT900s are hailed as some of the better cheap servos since the gears are beefier.
I made slow progress last night as I had to work with a sick baby on my lap, but it was quality bonding time. With Father's Day approaching, I can't shirk any duties!
Anyhoo, the HXT900 uses the feedback potentiometer as a rotary bushing and significant structural component of the output shaft, so it's not a simple "yank the pot" hack like some other servos I have modded. I ended up just chopping the pot contacts out so it could rotate 360, and cutting a mechanical stop off the output gear so it can rotate 360, then I routed the pot wires outside and reassembled it. Still have to add an external pot for nulling, but it rotates cleanly. Additionally, I need to finish & test the modded servo to see how useable it is. Some servos are extremely sensitive to pulsewidth and lack fine motor control. Will advise.
Even if it does work well, I suspect the pot shaft may wear quickly. I have plans to make a delrin insert & steel shaft to replace the pot entirely. So good news, bad news, campers.
Comments
I also noticed the pot shaft is being used as an axle.
I haven't had a need for this small of a CR yet. I thought about it back when there was some talk about making a mouse bot.
I'm guessing where the shaft meets what's left of the pot is the weak link in your CR servo.