Futaba s9254 servos

[jessli]

I'm using a boe bot right now and I wanted to buy a lot faster servos and bought the futaba s9254 ones because of a recommendation from a friend. They forgot to mention, however, that I needed to modify them before i could use them. do i have to just mod them for continuous rotation or do i need to do some other stuff? if anyone could tell me how to do it, that would be a great help.
thanks!

[Duane Degn]

jessli,

What do you want to use the servo for?

If you're going to use them to turn a wheel like the servos on a Boe-Bot then you will want to modify them to make them continuous rotation versions. You wont be able to control the position of the servo once it has been modified; you'll just be able to control its speed.

So before you modify them let use know what you're trying to accomplish.

BTW, welcome to the forum!

[RonP]

jessli,

Check out this thread about the s9254. The s9254 is a Heli rudder servo I belive it has a different centering position but that dosn't matter if what you want to do is make it continuous rotation.

Welcome to the forums.

Ron

[Ttailspin]

Might be something in > this < thread for you?
And welcome to the forum jessli.

-Tommy

[spiked]

I've never used one in robotics, but I have in heli's for which they were designed. A couple of things come to mind, the 9254 was ONLY used with the higher end gyro, and it was indicated NOT to hook it up straight to a receiver. I'm not quite sure why but that raises a flag to me. Also, for any of the digital servos, we had to make sure it was set as a digital channel in the transmitter. Again I'm not sure what that did exactly but if we did not do it, the servo got red hot. Again, something to research and be comfortable with before using it in robotics. I think the 9253 is about identical, except did not have the gyro use only restriction. My helis used 9253's everywhere except the gyro controlled tail that used a 9254.

[Duane Degn]

I have a S9254 servo modified for continuous rotation. I was just trying it out with my QuickStart servo tester. It seems to behave just fine with the 50Hz signal from the Prop. The siganl from the Prop should be the same as if using it with normal RC equipment. I ran it for several minutes and it didn't get hot.

I do remember reading that the S9254 servos souldn't be powered with more than 5.1V. I don't recall reading anything about only using it with a gyro.

[spiked]

You are probably right duane - I went looking, and it's the 9256 that says gyro only. I probably remembered it wrong. sorry.

[erco]

I have a S9254 servo modified for continuous rotation.

That's a pricey digital servo to mod for CR. I've done plenty of analog servos. When you modify a digital servo for CR, do any of the extra digital features still work? Feedback, ramping, etc?

[Duane Degn]

That's a pricey digital servo to mod for CR. I've done plenty of analog servos. When you modify a digital servo for CR, do any of the extra digital features still work? Feedback, ramping, etc?

I modified this servo several years ago when I was very new to the microcontroller world. I was working on a camera mount that I wanted to keep steady using RC helicoter gyros. My original configuration limited the speed too much. I have since used a non-modified version to steady the camera.

I think some of the digital features still work. I'm pretty sure it can be refreshed more frequently than 50Hz. I don't know what I'd be looking for with the other features.

In general, I don't think these are a good choice for CR modification but based on the other thread about "fast servos" it does look like these do go faster than standard servos. I'm sure there are less expensive ways of getting a bot to go faster than using these.

I wish I had asked more questions here on the forum, earlier in my bot building life, about what parts to use for which tasks.

I really wish I had Gordon's RRB4 twenty five years ago.

[jessli]

Thanks everyone for the help

they're being used to turn the wheels. the boe bot is for a maze competition and i need to use servos as fast as these to have a shot at placing. also, i've already paid for them so i have to use them. So from what i'm hearing, i have to mod for continuous rotation and then they should work? I'm not the most hardware savvy person, which is why i'm working with a boe bot, so it would be awesome if anyone had a link or explained how to mod them.

and maybe for future reference, does anyone have any recomendations for servos that would work just as well but not need modifications?

-Jessica

[erco]

Parallax sells Futaba servos already modded for CR: http://www.parallax.com/StoreSearchR...rotation+servo

and/or search "continuous rotation servo" on Ebay: http://www.ebay.com/sch/i.html?_from...All-Categories

Larger wheels will make any given robot go faster. Is everyone using a BoeBot for your competition? That would keep things fair, except it sounds like you're free to use faster CR servos for driving. Hope you don't go up against a 3pi robot, those are ridiculously fast and optimized for line-following mazes: http://www.youtube.com/watch?v=mJV-KDqHgDQ

Good luck!

[Duane Degn]

Here's an Instructable on it. You shouldn't need to do any soldering though. The motor is attached to the circuit board but the whole assembly should be removable.

Once you have the motor out, remove the potentiometer that is held in with a small screw.

You can enlarge the hole the three wires pass through so they also accommodate the three potentiometer wires. You can either use this pot to center the servo or switch it for a muli-turn 5K Ohm trimpot. I used a trimpot on my S9254.

You'll need to trim the plastic stop off the last gear as shown in the Instructable.

Edit: erco bet me to it.

BTW, I said there were less expensive ways of getting a robot to go faster but this is likely a relatively easy way of getting more speed out of a Boe-Bot without needed completely different code.

[erco]

Yay for Duane, 2000 posts! You're hot on my heels. I better post some more useless Ebay stuff to keep YOU at bay...

[Duane Degn]

Yay for Duane, 2000 posts! You're hot on my heels. I better post some more useless Ebay stuff to keep YOU at bay...

At 1.46 posts a day, it might take a while to catch up while you're making 3.81 a day.

I hadn't noticed I was getting close to the 2000 mark.

@Jessica, Since I've been in the "upload stuff to YouTube" mood today, I made a rambling video about modifying a S9254 servo. It probably wont finish uploading for over an hour yet.



Good luck with the Boe-Bot and keep asking questions.

Edit: I just put my S9254 back together. The gears in this servos are a bit harder to get back in place than most servo's gears are. If you need help getting your servo back together, let me know.

[Duane Degn]

Jessica,

This thread has made me remember back to the first time I modified some servos to continuous rotation. All those gears were very intimidating.

These S9254 servos are kind expensive servos to experiment with. I figure you'll probably want to learn to do the modification yourself but you might want to start with a less expensive servo.

The HX12K from HobbyKing is a relatively easy servo to modify. It would probably be a good servo to experiement with. If you do modify a HX12K, you'll want to remove the mechanical stop from the final gear with a set of pliers. The stop is a metal pin (the HX12K has metal gears) that can (usually) be pulled out with a pair of pliers (though, I've had a few that I had to cut off). Of the servos I've modified, the HX12K was probably the easiest to convert to CR (if I didn't have to cut the metal pin off with a Dremel).

If you'd like, you could send your servos to me and I'd modify them to CR for you. Or, if you try to make the mod yourself and can't get the servo(s) back together, you could send me the pile of parts and I'll put them back together.

Of course you'd save time and a little money (from postage), if you could find someone locally who could help.

If you would like me to make the modifications, let me know and I'll PM you my address.

[jessli]

Thank you so much for the video, its really helpful. I'm going to try to modify it on friday with a friend who's good at this kind of stuff and i'll keep everyone updated on how its going.

[Rick Brooks]

Jessica,

Are you preparing for the National Robotics Challenge in Marion, Ohio?
Our group started using those servos two years ago on two test BoeBots. Last year we added two more BoeBots and this year we may add more.
They run both the tactile and non tactile maze events and normally do well.
Hint #1 Build a version of the maze at home so that you can practice. There isn't enough time to begin to set up a robot on the day of the event.
Hint #2 Get your robot running the maze perfectly on standard servos before you try the faster servos. The extra speed makes programming far more critical.
Hint #3 Run the servos off of the BOE voltage regulator. The regulator will not overheat and the performance will be more consistent as the batteries drain.
Hint #4 Replace the batteries every run at the event.
Hint #5 Replace the rubber bands on the wheels with high traction molded tires and clean them between runs. The ramps do get dusty and slippery.
Hint #6 Practice.
Hint #7 Practice.
Hint #8 Practice.
Well, you get the idea.
Good Luck

Rick Brooks
Indiana Tech Explorer Post 2829

[Duane Degn]

Hint #3 Run the servos off of the BOE voltage regulator. The regulator will not overheat and the performance will be more consistent as the batteries drain.

I thought these servos were limited to 5.1 Volts anyway? I'm pretty sure they aren't supposed to be powered with higher voltages.

@Jessica, good luck modifying the servos. Let me/us know if you need any help.

[jessli]

@rick yeah actually i am, I'm entering in a tactile maze bot and coding sumo this year. i'm guessing you're from indiana tech. The "friend" that recommended these servos to me was Austin. I met him last year and became friends with him and Kevin. Thanks for the tips too! and good luck to you guys at the competition this year, although I don't think you'll need it since you dominate most of the categories.

[Rick Brooks]

Jessica
I just got home from a heavy sumo meeting at Austin's house and Kevin was there (he lives across the street from Austin).
They haven't even set up their maze, yet. So it may be a good year to grab a win from them.
If you need any help, post it here and I'll keep an eye on this forum.
Good Luck

Rick