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Author Topic: New Robot Builder here  (Read 1988 times)

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Offline MichaelSchaapTopic starter

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New Robot Builder here
« on: May 09, 2015, 10:39:39 AM »
Hey all!  My name is Michael.  Ive got an electronics degree but for various reasons I never used it.  It's my birthday today and last week I decided to attempt to build the robot in the Building your first Robot section.  Parts are starting to come in.  2 things are bothering me.

1.  Ive got a servo picked out, though have not bought them yet.  I'm very confused with how to attach it to the two wheels.  I decided to not use cardboard for wheels.  Ive found some robot places that sell wheels that are designed to attach to the servos..... I'm almost just throwing up my arms and getting the set.  I did a search here which lead me to a few threads though I still don't get it.  Do you screw the servo arm on the wheel then push the wheel on the servo?  I'm confused because Ive seen some arms screwed on the servo.  If you screw the arm to the wheel, how do you screw the wheel/arm to the servo?  I'm just basically confused to how do you attach the wheel to the servo?

2.  Batteries.  I've read the specs of the Uno R3 board.  Voltage can be from 5 to 12 volts I believe.  Amazon has a RC battery that is rated at 9.6 volts.  What I'm concerned about is the current.  The battery is rated to produce 2000mAh.  Here is the link to the battery:

 http://www.amazon.com/dp/B001BA292A/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=24ZVCZNGHP7EP&coliid=I3D2V1640BDEGE

Would this battery blow the board?  I also bought the Motor Shield.  I'm guessing the motors will be controlled there.  What do you think?  I was going to get a 6 V battery but I read that when it drops below 5V the board will stop working.  Since I've got a range im dealing with I picked the middle to give me some room.  So.... Would the above battery be good for this robot?

Thanks in advance!

Michael

Offline mklrobo

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Re: New Robot Builder here
« Reply #1 on: May 10, 2015, 12:57:39 AM »
 :) Hello! I would offer my opinion, where permissible..
Your first question;
Do you screw the servo arm on the wheel then push the wheel on the servo?  I'm confused because Ive seen some arms screwed on the servo.  If you screw the arm to the wheel, how do you screw the wheel/arm to the servo?  I'm just basically confused to how do you attach the wheel to the servo?
In reference to this, I could only offer generic info, based on the information
that you have presented. My first response would be, analyze the mechanical
load you expect to drive, then buy a generic servo already set up for your
purposes. This saves time, money, and logistics of repair/programming.
The second question;
9.6 volts at 2000 Mah }{ 5 - 12 volt required, do not drop below 5 volts.
Would this battery blow the board?  I also bought the Motor Shield.  I'm guessing the motors will be controlled there.  What do you think?  I was going to get a 6 V battery but I read that when it drops below 5V the board will stop working.  Since I've got a range im dealing with I picked the middle to give me some room.  So.... Would the above battery be good for this robot?
The Milli - Ampere hour level of the current, is a good battery, relative to the use
you have for it. Small, time limited robot programming uses will suit you, from your
description. 2 amps should provide you with what you need for now, depending on
the demand of your motors. If you use a MCU that demands a steady voltage, I would
use a regulator to feed that board. Try to use a seperate battery for the MCU, to avoid
spikes for the motor usage. (in reality, you could get by with no problem, but personal
property invokes tender loving care on robots. $$)
Good Luck!!    ;D ;D ;D

In addition, I will try to address your programming/motor issues and more in my post in the Miscellanous section, Analyzing the Axon series: Coding, Construction, and Contraptions.
« Last Edit: May 10, 2015, 01:00:40 AM by mklrobo »

Offline bdeuell

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Re: New Robot Builder here
« Reply #2 on: May 10, 2015, 01:35:03 PM »
the hobby servo wheels I have seen/used mount directly to the servo. you would remove the servo arm and replace with the wheel. The servo has a splined connection (you will want to make sure this is compatible as different suppliers have different standards). The screw is used to hold the wheel/arm onto the servo.

as for the battery:

The uno board has an onboard linear voltage regulator, this can accept a voltage in the specified range and will supply a constant 5VDC to the microcontroller. the on board linear regulator can not handle a very high current especially at higher input voltages. the regulator is more than sufficient to power the microcontroller but a advise against powering the servos through this regulator. For this reason i recommend picking a battery that has a voltage that matches your servo specs. you will also need to be sure that the battery voltage remains in the Uno's specified input range throughout its discharge.

you want to pick a battery with a GREATER discharge current than your system requires. the battery will only supply the amount of current that your system draws. the discharge current is usually rated in terms of "c" where "c" is equal to the motors capacity (a 2000mah battery has a c=2000ma). a very common maximum discharge rating is 1c but some batteries have higher ratings. You will also want to consider the runtime for your robot and size the battery accordingly.



Offline MichaelSchaapTopic starter

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Re: New Robot Builder here
« Reply #3 on: May 10, 2015, 04:28:03 PM »
Thanks much. I decided to go with the Continous Rotation servos and Wheels that are sold here.

http://www.imagesco.com/

They already drilled the holes in the wheels to directly attach to the servos. What's more is for every servo you buy you get a FREE WHEEL!

Thanks again for the input!

Michael

P.S.  The amount of questions this board asks to prove you are human is ridiculous. Oy.

Offline bdeuell

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Re: New Robot Builder here
« Reply #4 on: May 10, 2015, 06:41:19 PM »
the wheels (unlike the ones i have used) appear to mount to the hobby servo horn/arm... please disregard my above comments regarding the servo wheel mounting in this application.

 


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