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71
You are 100% correct and I love the RD->DC tutorial in the link you posted.  Well done! 
In my many hours of research I found a prefab TReX Jr which seems to do the same thing. 
Thank you again.
72
The picture you uploaded appears to be corrupt and I can't open it, but I'll attempt to do some guesswork without it.

From what I am guessing, is that your receiver is outputting signals for a servo, but you are trying to hook up a dc motor to it instead.  This isn't going to work for what you are trying.  To make it work, you need something to convert your servo signal into something appropriate for a DC motor.  Example Here (there are several things you can do to accomplish this.)

If I'm wrong in my guess, let us know: 
  • What kind of motor are you trying to hook up?
  • What (if any) circuitry you are using between the receiver and the motor.
  • What you want the motor to do (Stop/Start?  Start and move proportionally up to full speed?  Reverse to Forward and all speed in between?  Act like a servo?
73
Mechanics and Construction / Robot horse neck
« Last post by SvdSinner on December 07, 2020, 12:44:56 PM »
My 14yo daughter and I are building a robot horse.  I'm working on the mechanism to allow the neck to raise, lower, and move side to side.  My idea is to use 3 linear actuators in a triangle to create the motion.  the ends of the actuators will be free to swivel.  I am constraining the lower actuators to not point down (from the torso) and the upper actuator from not pointing up.   See the attached image of my first iteration of the mechanism.  (I'm new and couldn't figure out how to display the attached image inline)

Upon completing this first drawing, I worry that the weight of the neck might damage the stepper motors or the threaded rods due to high radial and axial loading.  (The neck and head frame weigh 3.9lbs bare and the head will eventually add 5-7 servos and a speaker, and it will eventually be covered in "fur".  The torque of just the frame is currently 3.3ft/lbs.  The center of the head and the weight of its future mechanisms is about 18" from the base of the neck, which adds an additional 3ft/lbs torque.  That means a static axial load of 8ish pounds on the top threaded rod and 4ish pounds on the bottom two.  Dynamic forces as the horse moves will be much higher.)  I am trying to figure out how to better support the weight of the front without hurting the steppers or the threaded rod.  I'd like the joint to be strong enough to prevent it from breaking the first time a child tries to pull down on the head.

Some ideas I've thought of (but am not fully sure of their value): 
  • I can move the mounts on the torso further towards the top and bottom (while keeping the mounts on the neck in the same position) to trade off some radial load for more axial load.
  • I can add a 608 bearing to the lead screws (mocked up on the bottom two steppers) to increase support.
  • I could/ "hang" the neck with some tension springs to off-set the weight of the head/neck.  I don't have much experience making custom springs, but I realize they would need to have a certain tension so that they don't make the axial forces worse.


1)  Does anyone know the rough limitations of Nema 17 steppers as far as axial/radial load? 
2)  How much radial would 608 bearing to be able to handle?  (It obviously isn't a thrust bearing, but is designed for some axial forces.)  For cost reasons, I'd rather use 1 (or more) cheap 608 bearings than dedicated thrust bearings, if possible.
3)  Any suggestions on how best to bear the weight and torque of the neck/head in a mechanism like this? 
4)  Any major flaws of this mechanism that I'm not seeing?
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Software / Re: Anyone tried Windows 7 for robots?
« Last post by elwishtwo on November 25, 2020, 11:21:28 AM »
I have downloaded the community edition but unable to install it. It’s asking for the .net framework. I tried installing the .net framework 4.5 / 4.6. None of them are getting installed on my system which is windows 7 . Have Installed SP1 as well. Could you please support me about what is to be done next.
75
Electronics / Re: charging two diffrent types batteries with one charger
« Last post by bdk6 on November 24, 2020, 06:16:00 AM »
Every type of battery has different charging requirements.  Lead Acid and LiPo are VERY different.  Each should have a charger especially designed for it.
You don't state what type of "charger" you are using.  I have a feeling it isn't intended for either type of battery.
LiPo batteries are subject to catch fire or even explode if charged improperly.  Lead acid is less dangerous but can still be damaged or destroyed.
I HIGHLY recommend you buy appropriate chargers designed for each type and use ONLY those.

There is a great deal of information on batteries and charging here: https://batteryuniversity.com/
76
Electronics / Re: PCB assembly company recommendation?
« Last post by bdk6 on November 24, 2020, 06:08:48 AM »
At work we have started using https://www.nexlogic.com/
I have been very happy with the quality and service.
77
Software / Re: Skid Steering (Differential Thrust) on a boat calculations
« Last post by bdk6 on November 24, 2020, 05:54:39 AM »
I'm not sure exactly what you are asking for, but maybe this will help.  If I'm not on track, let me know.  I may be able to clarify some things.
To restate the problem, you want the boat to move forward and possibly turn left or right some amount, based on an input variable from -1 (left) to 0 (straight) to +1 (right).

There are many ways to approach it.  This is one.
To move straight ahead both motors should turn the same speed.  Let's start with 50%
To turn left, the RIGHT motor should turn faster than the left.  Since there will be more resistance, let's keep the left motor the same speed and turn the right one faster to minimize speed change.
To turn right, the LEFT motor should go faster, similar to above.
Let's write some pseudocode to set two variables to the desired PWM percentage.

leftMotorSpeed = 50;       // First set both to 50%
rightMotorSpeed = 50;
differentialSpeed = turnVariable * 50;     // differential speed will be somewhere between -50 (for -1) and +50 (for +1)
// Now add the differential to the appropriate motor
if turnVariable < 0
   rightMotorSpeed = rightMotorSpeed + abs(differentialSpeed)  // add the absolute value since the differential is negative
if turnVariable > 0
   leftMotorSpeed = leftMotorSpeed + abs(differentialSpeed)     // doesn't really need the abs() but I like to program defensively
// if it is not greater than 0 or less than 0 then it is 0 and doesn't need to be added

Now you can convert those motor speed percentages to whatever values you need and send them to the motors.

Does this help?
78
For Sale / Professional and deepened robot chassis and duct cleaning robot
« Last post by Defy on November 22, 2020, 07:28:36 PM »
We specialize in the research and production of robot chassis and duct cleaning robots. If you are interested in them, you can visit our website for more details. http://www.zzavatar.com/special-robot/
79
Electronics / Re: PCB assembly company recommendation?
« Last post by Loveironsight369 on November 14, 2020, 02:11:56 PM »
I havent tried this one yet.https://www.pcbway.com but it seems good.
80
Robot Videos / Re: RoboOne biped battles flying robot
« Last post by Loveironsight369 on November 14, 2020, 01:51:20 PM »
 ;D ;D ;D ;D ;D ;D ;D I Guess great minds think alike and i'm new trying to see if theres room for to can of thing to go main stream. but biger and more stuff.This is the first thing i research on this forum was 'Battle' lol
im an inventor that trying to make my on design
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