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Topic: motor (maybe servo) hardware choices? (Read 2877 times) previous topic - next topic

xl97

Hey gang-

my goal is to spin something.. (like a tube/turret).. upon button interaction..

my code is all set-up..etc.. working fine.. and I thought adding this effect to the existing code would be a nice addition to the overall effect..

if the button is pressed one time.. I want to 'jog' the motor a certain distance..(pulse it real quick?) (accuracy is not very important.. its more for 'effect')

if the button is held down...I want the tube/turret (motor) to keep spinning..



from reading, I understand that I can run 1 servo directly off my Arduiono

(got a cheapie, small servo from dealextreme..and tested it out)

the default servo sketch(s) seem to work..

problem with a servo, is it only goes 180 degrees... looked up mod'ing one.. but wasnt sure it can do 360 degrees (continuously...ie: spinning around consistently after the mod???)..

-AND- it seemed rather slow....  not what I was going for.... unless there is way to speed them up?

Next...

moved over to a motor based solution... found this kids toy that had a motor in it (wand type toy with led 'feelers' on the end that spin around...kinda neat how they gave power to the pcb/leds that were spinning.. [motor shaft/spring combo..etc]...)

gutted it..put it on my PSU.. it seemed to work at under 5v..

hooked it up directly to my Arduino.. (after more reading.. I read thats bad to do...but would really like to use the less parts the better motor here)..

no go..  (probably needs to much current to run?   (I tested pins on Adruino after to ensure they still work fine..they do)

so Im looking for a very small motor... (to fit inside of a toy/prop-nerf gun)...and spin the turret/tube when the button is pressed..stop when let go....etc..

I want to run up to my local radio shack and grab a few things to test this out before final implementation..

can anyone guide me on what motor(s) to check out?

if there is one I can drive directly.. GREAT!..

but if not.. Im not 100% sure what other components I need.. a transistor? and some resistors?  (some threads mention a diode?)

If I try to use one of these:
http://www.radioshack.com/product/index.jsp?productId=2914700

can I just remove the un-balanced weight at the end.. use as regular motor/shaft..and drive it directly?

Thanks.

xl97

bump..

I made this quick schematic.. using some diagram I found on-line..

and the actual part #'s I have on hand...


Im wondering if anyone can take a peek and see anything 'wrong'?






from looking at it myself.. it seems to me I would need to have a 3.3v vRegulator in the mix.. on the motor? (or get a motor that can take bigger voltage?... trick is.. I need a fairly small one in siz.e.with enough torque to move a 'barrel/turret' (like a gattling gun style movement)


I am also a bit unsure as to the pin choice.. (NEEDING) to be a PWM pin?

I am using this in conjunction with a 'waveshield'..  and it is used/shares the timers on certain PWM pins..etc..

when testing a straight motor in the mix.. there was a HUGE/LOUD noise being made..  I assume some sort of interference.. with on the power lines.. or the PWM...  (which is more what i suspect..as the noise co-incided with the PWM'ing of the motor speed...again.. no other components.. so no isolation)

thanks!

miros

what abouth stepper motor.they are slow bot strong and you can cotrol their move. only one disadvantage is conncection and price.
http://arduino.cc/en/Reference/StepperBipolarCircuit
if this didn't  help then i guess there are servos that can turn 360 degrees but they are pretty rare.

xl97

hi-

thanks for the reply.

a servo is pretty slow from what I could tell.. (got one form www.dealextreme.com to play with)..  is there a way to 'speed them up'?

(I also believe you can mod them to be 360..but is it continuous?)

I dont think a stepper will help either..

I need it to go 'sorta' fast..

at least faster than I have see the servos..etc go.

I want to basically pulse/jog the motor (maybe just a quick on/off will work).. when I press/release the button.. and to continuously run/turn if I press & hold...

the motor also needs to be small enough to fit in a nerf gun (maverick).. with enough torque to spin the barrel, like a gattling gun type effect..


beige

Have a look at heli tail rotor servos, some of the higher end ones are ridiculously fast.

As for continuous rotation, all you need to do is fix the feedback pot so the servo thinks it's always trying to catch up, on most servos you'll also have to cut the buffers off the output gear.

miros

you can try DC motor with encoder. that is clasic DC motor that ca read how much it rotates.
http://www.pololu.com/catalog/product/1218

xl97

accuracy isnt a concern at all..

I actually took some motor from a toy (see first post).. and wired it up as I posted..

Im really only giving the motor juice for a split second.. (when the trigger is pulled)..

and more if in AUTO mode..and the button is held down..

anways.. I used a simple digitialWrite() high/low when i needed and it works GREAT!..  (no worries about PWM or timers now either...since this is used in conjunction with a 'waveshield' (more or less)..

my only concern now is the torque.. which is obviously not going to be enough.. as I can simple stop it with my finger....

I ave NO specs on this motor at all.. (from a kid toy)..

but its roughly the same shape as the one I posted in the schematic.. (the 1.5v-3v motor from Radioshack.com)
here is the one I want to try and use in my final project though.. (hoping it works the same as the one I have now..but with enough torque to move something)
http://www.radioshack.com/product/index.jsp?productId=2102828

says 1.5v-3v.. but some comments are saying they have been giving it up to 9v even? (wow)..

again.. Im concerned with torque.. but keeping it at a size that fits in my project.. (this size is maxing out that room)


miros

DC motors have a lot rpm but they are weak. you will to use gearbox otherwise you will be able to stop them with finger. for your project i should recommend gear ratio abouth 10:1 or higher. try to find something ;)

xl97

I wouldnt have any idea on where to even start on looking (making/finding?) a gearbox for this?  (especially one with a 10:1 ratio)??

Thanks for the feedback though!.. any suggestions on where to start researching for this?


Tumbleweed

Einstein once said you don't really understand anything until you can explain it to your Grandmother

zoomkat

Quote
a servo is pretty slow from what I could tell.. (got one form www.dealextreme.com to play with)..  is there a way to 'speed them up'?


http://www.youtube.com/watch?v=wCx52hT4pu8
Google forum search: Use Google Search box in upper right side of this page.
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

xl97

thats a pretty sweet servo hack for speed!  thanks!

(might have to give it a try!)


to update.. I have my motor working fine.. (motor. not servo).. as I needed speed. (somewhat... not alot..but faster than stock servo)

the problem I think I'll be facing now.. it the TORQUE on that motor..


I havent tried the motor I got from Radioshack yet.. (because it  was only rated at 1.5v - 3v?)  I'll have to find a 3.3v vReg..and fiure out where to put it in line with my current motor wiring/diagram

which is like this:



Im thinking I can just throw in a 3.3v vRegulator... to help not kill the motor being driven off the battery/transistor like that.. but not exactly sure where to place it so it doesnt affect the rest of the circuit..

thanks

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