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Grand Robot Master
05-19-2009, 06:07 PM
is it possible to use standard (non digital) servos on lynxmotion's electronics?
i was thinking of getting some robophilo servos if they are cheaper. mind you that i know little to nothing about servos.
does anyone know where to get servos cheap?
did i already ask this question?
Will Grand robot Master EVER make it to robo games 2010?*dramatic music*
stay tuned.......*more dramatic music*

Adrenalynn
05-19-2009, 06:40 PM
PWM servos will work on PWM controllers. Even digital PWM servos.

Any reasonably standard PWM driven servo will run on the SSC32 from Lynxmotion.

You're not planning on building a walking robot with cheap servos, right? I'm sure Darkback2 can chime in with an edgumacated opinion on that one...

darkback2
05-19-2009, 09:58 PM
Ok...so I'm the king of cheap...I know there are definite draw backs to this recommendation...but I've gotten by on Tower Pro MG 995s...and here is a link to MG 996Rs (http://www.hobbycity.com/hobbycity/store/uh_optReviewReadExec.asp?idProduct=6221&description=Towerpro+MG996R+10kg+aircraft+servo). I think zenta used them somewhere on his apod...and charlie and squidword use them in the ankles...for the guns, and in a few other places. At $10 a servo you can't really beat the price...making a scratch built 18 degree of freedom hexipod for under $200...same for a 12 degree of freedom quad.

Again, they work...not the best, and not all the time...but they work...and in todays economy maybe they work well enough to get you through for a while.

Another method is to get a set of really nice servos, and use them in several different robots. HS 645s are a good servo for a multi legged as in hexapod...or with work a quad...with levered legs...Any less than that and weight management becomes an issue

HS 5990s...buy one a month for the next year and your not just good your golden. My current plan with squidword is to do that...get bye on mg995s for the next year while I buy 1 HS 5990 a month for the next year. I've already got 4 on there...and they are freeking beautiful.

DB

Grand Robot Master
05-20-2009, 08:26 PM
would you recommend them for a tripod?

darkback2
05-20-2009, 09:56 PM
probably not...

To be honest...I don't know. If your conservative with them, then...maybe!?


Ok...here is my two cents...Your asking your question a bit out of order. Ok...so you want to make a tripod...
what is your budget?
How are you planning to control it?
What tools do you have access to?

I believe I remember you saying you have no experience...so why are you starting with a tripod again? (read a tripod is harder than a quad is harder than a hexapod...

DB

Grand Robot Master
05-21-2009, 09:49 PM
my budget is fairly limited, around $500-800 max.that limited in robotics, right?
i felt that the tripod requires less servos, therefore less $$$$.
i'm willing to accept the difficulty
my machining resources are litlle to none. about all i have is a soldering iron and some electronics stuff. ill probably use lynxmotion servos brackets.
i plan to controll it with a wireless ps2 controller, people are saying its fairly easy.
i tallied up the price and it came to a bout $800, pretty close to my range. i'd like to start with a quad or hex, but they're so expensive. i'm liking the kowatec mini hex, but i can't find a price on it, let alone anything else on it.
im also waiting for the micromagic systems microbug to come out, if it even does, ive heard different price ranges on it.
id probably make a quad first thoug because id like to enter it into the mechwars competition next year.
*HUFF* *HUFF* so... ive rather done my homework on information......basically
oh yeah....whats the drawback to these $11 servos?

lnxfergy
05-21-2009, 10:10 PM
my budget is fairly limited, around $500-800 max.that limited in robotics, right?
i felt that the tripod requires less servos, therefore less $$$$.
i'm willing to accept the difficulty
my machining resources are litlle to none. about all i have is a soldering iron and some electronics stuff. ill probably use lynxmotion servos brackets.
i plan to controll it with a wireless ps2 controller, people are saying its fairly easy.
i tallied up the price and it came to a bout $800, pretty close to my range. i'd like to start with a quad or hex, but they're so expensive. i'm liking the kowatec mini hex, but i can't find a price on it, let alone anything else on it.
im also waiting for the micromagic systems microbug to come out, if it even does, ive heard different price ranges on it.
id probably make a quad first thoug because id like to enter it into the mechwars competition next year.
*HUFF* *HUFF* so... ive rather done my homework on information......basically
oh yeah....whats the drawback to these $11 servos?

The drawback to $11 servos is that they can't even lift themselves. If you want to carry anything.. or even walk at all, you need powerful servos -- power is expensive. You wouldn't try to win the indy 500 with a V4 hyundai now would you?

-Fergs

Also, on the topic of less legs == less money. Thats a fallacy. You still need to typically carry the same payload (in the mechwars scenario, a camera, gun, batteries, etc). Less legs carrying the same amount of weight means that the individual servos will cost significantly more although there may be less of them.

Quantum
05-21-2009, 11:44 PM
The problem with powerful servos is that alot of people assume thats what you need. You need to account weight and torque into your design. Lynxmotion brackets are great for someone that doesn't have access to machining equipment or doesn't even want to mess with that aspect of the design. These things are heavy. You need the bigger servos because their general brackets and made that way. Along with the extra wieght from the bracket you have to include the wieght of the servo as well. All I have to say it takes alot of time and money to make a smaller servo work. I know this and I will show this as well. Just finishing up test code and about finsihed with it.

Grand Robot Master
05-25-2009, 09:51 PM
in that case i will probably put the tripod on hold for now and start with a quad. that or mod a robophilo i own. you can see the ideas i have for that in another thread i started.

Sigma X
05-25-2009, 11:58 PM
I also have a servo question for starters I plan on using Hs805 servos for my biped x2 for the leggs
do you think using them is a good idea or would I have to use somthing better?

Adrenalynn
05-26-2009, 12:11 AM
Their weight-to-torque ratio is much lower than some modern digitals.

darkback2
05-26-2009, 01:08 AM
Charlie started out using nothing but MG 995s. they cost $5 a piece at the time, and have gone up to 10 over time. 996Rs have a lower torque value...and are probably crap...I don't know...ask zenta.

in anycase, that was how I built charlie for under $100! and she worked...she caught on fire a few times...but she worked. (one of the back leg lift servos overheated to the point where the case burned all the way through. I've had this happen with 4 or 5 mg 995s...which is were I don't recommend them...I strongly don't recommend them.

I also didn't have much in the way of tools at the time. I used a saber saw, a drill press, and a vice to make all of the brackets.

the saber saw cost me $10 at the thrift store...I love that little guy.

Check out the "so you want to make a mech" tutorial (http://forums.trossenrobotics.com/tutorials/how-to-diy-128/building-a-mech-using-dbs-bracket-system-3099/)...or whatever I called it. You can print and cut out all of the brackets to make either of my mechs. I use a $100 band saw.

Hope this helps.

DB

Sigma X
05-26-2009, 01:32 AM
I see so I would need somthing better but what?

darkback2
05-26-2009, 12:33 PM
Ok...just a thought.

As for the expence of building a robot vs the number of legs, I would argue that it has more to do with the number of degrees of freedom, or joints, or leg segments, coupled with the quality or torque requirements for each segment.

Charlie is a 10 + pound quad with 12 degrees of freedom. Because the torque requirements for each segment is relatively low I was able to get away with mg 995s ($10 each) for a while, and definately with HS 645s ($36 each, I'm currently using 8). I can get away with this because charlies legs use levers for lifting. current cost per leg $85 or so.

Squidword is under 10 pounds...actually last check he was around 5, but he has put on a lot of weight since then. with 12 degrees of freedom. Because of the torque requirments for his lift servos, squidword uses 4 hs 5990s ($125 each) in addition to 4 hs 645s and 4 mg 995s... current cost per leg $175 or so...

Just for comparison, Connors shadow scout uses 5990s and 5995s...(5995s were discontinued so you would have to use 5990s) each leg has 6 DOF (degrees of freedom) thus the cost of a similar bot would be $750 a leg...

Of course none of the above include brackets, servo wire extendors, or even the screws and bolts that it takes to put everything together.

As far as the which servo question...

Tower pro servos have price going for them...they probably won't last forever, but I've still got 8 or so of them left on charlie, and 5 on squidword because I had them laying around...and they will probably get me through for the near future.

Hitec servos seam a lot more robust, and will probably last me a lot longer.

HS 645s for leg segments that don't have to hold too much weight, or for light weight walkers
HS 5990s for heavy lifting

Hope this helps

DB

Sigma X
05-26-2009, 03:47 PM
yes it does thanks alot

xx2747
05-31-2009, 08:32 PM
speaking of cheap servos (I look for these a lot; don't have a big budget) looks like the Hextronik 10kg servo is the same as mg995 but I don't know if they can be more reliable. This company makes alotta cheap servos. Look at this robot made from these servos. It's a biped too!

YouTube - Runbot's 3D printed prototype
it shows how shaky the biped can get though.

Grand Robot Master
06-07-2009, 09:02 PM
would hitec HS-475s work?
how about the robophilo servos?

Adrenalynn
06-07-2009, 09:36 PM
would hitec HS-475s work?


Nope.

DresnerRobotics
06-07-2009, 10:48 PM
On that video, two things to note:

1) Tethered. Why? Because those servos aren't strong enough to carry an onboard power supply.

2) Look how jerky they are. Why? Cheap internal feedback circuits on them, they have a ton of deadspace and tend to overshoot their mark and go into oscillation trying to self correct.

You absolutely get what you pay for with servos with one exception; AX-12s. No better value out there, you get more than what you pay for. I know I sound like a broken record, but it is the truth.

xx2747
06-10-2009, 12:37 AM
I've always wondered if ax-12's were easy to work with.
I think they're great servos, but aren't the controller choices limited?
Correct me if I'm wrong please - I don't know anything about dynamixels.

Adrenalynn
06-10-2009, 12:45 AM
Technically, the "controller choices" are infinite. You don't need a "controller". Anything that talks serial (which is, effectively, everything created for as long as I've been in computing, a good thirty years or more) can drive the AX-12 *to some extent*. Properly driving them needs fast serial.

lnxfergy
06-10-2009, 08:48 AM
I've always wondered if ax-12's were easy to work with.
I think they're great servos, but aren't the controller choices limited?
Correct me if I'm wrong please - I don't know anything about dynamixels.

At the moment, the only end-to-end pose and capture and playback device that requires minimal to no programming, is the CM-5. After that, you'd have to program. There are currently several libraries available for controlling AX-12 servos using AVR microcontrollers. Issydunnyet, my mech, is built out of AX-12 servos with an AVR controller board that I built... and you might notice I said, at the moment above....

-Fergs