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Asked — Edited

Turn Dc Gear Motors Into A Servo

Hey guys,

Anyone tried something like this yet? This may be what I need to use for my arm motors.


High Power Servos

#21  
robotmaker
I would like for you to take a look at my idea for a servo mimic that I came up with. I t is different than the link I posted. It is listed later on in the thread on second page. I put up an idea for a servo mimic with several drawings. Wanted you thoughts on my idea.

Also thanks for the H-Bridge schematic. I would like to try that also.
#22  
RGORDON relays are the worst idea for controlling that old school design before h-bridge ,relay have a chatter problem,contacts wear out,plus draw alot of current
now limit switches can be used ,but not neededalmost because using a feedback pot on turntable
from the feedback position you can set the limits in the micro code
#23  
robotmaker

Thanks for your input. I don't have any experience yet with micro-controllers and programming and this was just way to save money instead of buying expensive high torque servos. I still may try it just to see if it works.

I appreciate you looking at it.
#24  
taking FUTABA S3003 servo apart and adding h-bridge wont need any programming
code i am talking about is scripts in EZB board ,and me or anyone else can help with that
#25  
@rgordon and others
i designed h-bridge design and pcb boards all info in zip file,made this design awhile back and sold many boards if anyone needs to buy the boards let me know,more that buy the boards the lower the cost to have it made ,boards are in 2 parts ,main reason is that the board is universal
logic circuit on one board and pwm h-bridge on another rated at 60 amp cont,but you can easy remove mosfets to save money,remove 4 of the 8 mosfets give you 30 amps
i dont get money from this and dont need it
HBRIDGE.zip
files in bmp and sch and parts list
#26  
Rgordon,
To answer your question about bending the waist.
I am going to have to take some pictures this weekend and start my own thread in Project Showcase. I made it pretty cheaply, and if you look at the pictures it is easy to figure out, but you will see that it is very hard to describe without looking at it. *confused*
#27  
rgordon Danger! is correct
yes bending the waist is very easy done it on a few robots ,not hard or high cost ,with already made parts or easy to make parts,mostly depend on the weight you need to bend and that would the torque needed to bend and return,
bending is very easy but returning needs alot more torque

on the h-boards i am selling adding a special stall and what i call under stall (i guess it can have a better name)
stall is easy its when your robot bumps into something or a gear gets jammed and you could burn out the motor or h-bridge

now on under stall.it when your robot goes on to a carpet or some thing and motor keeps spinning and does move there is a way to detect that
both conditions you can have to shut down the motor or go in reverse or turn off the robot
as you can see i love designing circuits 20 hours a day ,and sometimes think about when i am sleeping and passing it free to others
#28  
rgordon
If you are still interested in how I am making my robot bend at the waist, I have pictures
here.
It is all cheap hardware.
#29  
my RAD 4.0 will have bending at the waist ,using legs like on a person and using strong servo's ,has more then a 40 lb lift
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if you have a bigger robot,look at windshield motors very high torque
and i use a h bridge connected to a FUTABA S3003 BOARD ,i use this for my main robot arms to each lift near 50 lbs may be more,very high servo's
Spain
#30  
@ Rgordon: know these high-torque servos and low price (30kg: 72 pounds), I filisofia to find a powerful yet inexpensive servo I found these, now I have one mounted on the head of my robot RSP (soon I'll upload the photos) his strength is great! watch your fingers, you can attach a machacarlos.y if the servo pinion gear ring with a large and well make a speed reducer would gain much strength.
If you have occasion to balance the center of gravity of the robot arm with the axis of the servo (it may be impossible at times), but at least put some weight that is more useful patra balanced, this helps to reduce torque servo, here are some ideas that I implemented in my project, I hope some will be useful.

Big servo
#31  
Thanks! Wow, that's a good price. Strong too! 28.6 lb.-in. I may have to have some of these.
#32  
i buy alot from hobbyking,does take a very long time to get to usa *stress*
#33  
@Danger!
Thanks for the pictures of the waist mechanism. It gave me some ideas:)
#34  
@robotmaker

I like your RAD 4.0 robot. He's cool! I would like to use this kind of setup for my robot arm. Would you be willing to sell me a h-bridge rated for 30 amps connected to a FUTABA S3003 BOARD so I can control my dc gear motor like a servo? I would like to test one first then if it works out I would buy more from you.:D
#36  
I mean do you have an H-Bridge already connected to a FUTABA S3003 Board that I could buy that is ready to hook up to a motor?
#37  
Also, does it have to be a FUTABA S3003 or can any servo work?
#38  
most use t he futaba S3003 because it has schematic for it and pins easy to connect
mine are in robots
#39  
I'm.going.to come back.and read this after I've had sleep. I have the wrist motors and claws and maybe a shoulder that runs off 3 to 6v motors I need to interface with ezb.
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#40  
they will work perfect with FUTABA 3003 servo,and istead of the feedback pot can use two 2.6 k or 2.4 k resistors in series and use the center or use a trim pot and adjust the pulse width,in my design looking to use a servo motor
way you asdust it is set it for 1.5ms and adujst pot till motors dont move,mostly near center value of pot witch is 2.5 k ,same with 2 resistors 5.2k divided by 2 = 2.6k or using 2.4 k 's
mostle need to stay near 5k value when selecting two same resistors ,another name its called is 'dead center"