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Misc / Tech Tip - The Measurement of Torque
« Last post by ServoCity on Today at 08:42:38 AM »
In our latest Secret Life of a Servo series Jason dives into the world of understanding the measurement of servo torque!

Electronics / ac motor get stuck when changing direction
« Last post by assaf on April 16, 2018, 10:59:05 AM »
Hi everybody,
I am building a motion driving simulator.
it has six ac motors (400v 2 pole 3 phase 750w)
and six vfd's (telemecanique altivar 16 750w)
i bought a controller that someone builds for simulators that connects to the pc and control the six vfd's.
this controller send speed and direction commands to the vfd's (by changing voltage)
every vfd is connected to a resistor that acts as a brake.

only one of the motors get stuck sometimes when changing the direction of rotation.
when it gets stuck the vfd shows its output current is about 1A.
sometimes it get unstuck after a few seconds. sometimes not.

when i disconnect the GND between the controller and vfd and reconnect it gets unstuck.
also if i press and release the STOP button on the controller board it gets unstuck

tried connecting the motor and vfd to another output on the board. works fine

Software / Re: problem in understanding and implementing pure pursuit algorithm
« Last post by rouncer on April 12, 2018, 08:40:15 AM »
Just some basic trigonometry here, it should definitely work when you get it finished.

But I think it could be alot simpler than this.

Just get the difference of the target and the current position.

then get the angle of the vector.

then subtract the angle from the cars angle,  and the tricky thing with this way,  is you have to decide to wrap the circle or not.

Keep going,  its a basic program youll get it,  its in lots of old arcade games - this code,  for running spaceships around like asteroids or space pilot.  (you should be right by yourself.)
Robot Videos / Re: My robot taking its first (and wobbly) steps
« Last post by Sebediah on April 12, 2018, 03:30:25 AM »
Hey there! Sorry for such a late response, I've been in the middle of a move so haven't had time to keep up with all the forums. To answer your question: Yes I certainly do! Lately I've been upgrading Dorian's hardware to make him more stable and capable of proper interaction with people. I'm planning on actively developing Dorian for at least another two years, even though I will begin prototyping a new robot later this year.

My main plans for Dorian is to bring him outside to events and also just generally expose him to people in various places. Hoping I can develop him in a way that will make people engaged and curious about social robots in general  :)

If you're interested in the upgrades and the stuff coming up this summer, keep an eye on my youtube channel!
Software / Re: problem in understanding and implementing pure pursuit algorithm
« Last post by vhaa on April 12, 2018, 03:03:48 AM »

I am trying to implement the same tracking path algorithm. Did you solved your problem? Can you send the code?
Mechanics and Construction / Very quiet, high torque 150rpm motor advice
« Last post by rhysonic on April 10, 2018, 05:47:58 PM »
Hi I am designing a musical percussion instrument based on a spinning wheel. I have been using a power drill to spin the wheel, but when I try to record in in a studio or if I am on a really quiet stage the sound of the power drill really stands out.
Here is a video of an older version of the instrument (using a drill)

I have bought a couple motors recently but have had issues with all of them. This one for example, is a bit heavy, has quite a bit of low hum especially when mounted in a wooden box, also the amount of torque it has is I suspect overkill. I have had to put it in a box, inside a box, inside a box to reduce the vibration hum :(

This other (crouzet dcmind) very quiet motor I bought recently is a bit small and doesn't have enough torque

I can explain the amount of torque I need like this: If I pinch the rotation shaft really hard between my index and thumb and I can slow it down by no more than 10 percent then it probably has enough torque

The dcmind motor spins at 3000 rpm which is way too fast, but when I lower the voltage to 3.5v it gets down to maybe 300 rpm, but when I give it the pinch test I can stop it completely.

I really don't want to use a geared motor if I can avoid it ( I know this is wishful thinking) because I absolutely want the motor to be as quiet as possible so that I can record in the studio with it.
I am not sure if maybe stepper motors are quieter?
or maybe there is a special gearbox I could attach to the dcmind motor which would be quiet enough?
Also if anyone has any advice about sound insulating the motor that would be appreciated :)


Software / Help with iRobot Create Gen 1 Model 4400
« Last post by ScottH7a9 on April 10, 2018, 10:14:12 AM »
Hello: This is a little bit of a lengthy post and is probably asking a lot, but any help would sure be appreciated.

I have a generation 1 iRobot Create, Model 4400 to be exact. It has the optional command module which uses the Atmel ATmega 168 chip. The command module manual is here: http://www.irobot.com/filelibrary/pdfs/hrd/create/Command%20Module%20Manual_v2.pdf

The robot came bundled with WinAVR and Programmers Notepad. It also had drivers and instructions to use a USB port to communicate with the Command Module. Many years ago on a Win XP machine I built one of the example programs that came with it, was able to build and load it on the command module. Now when I try that I get errors that it can't create dependency files (The error is actually that it can't find the files but I believe the problem is they are not getting built earlier in the build process).

I am pretty ignorant about this level of programming (this close to the hardware that is), I Googled and found an AVR forum, the folks there suggested forgetting WinAVR and using Atmel Studio 7. I have installed it, I can build the example programs on my local Windows machine, but I am confused as to how this then gets transferred to the iRobot Command Module.

The Command Module has a bootloader and is supposed to handle the transfer along with the connection to the PC and the Programmers Notepad software. I'm not sure how this can be adapted to the Atmel Studio 7 or other software.

So a short version of the question would be: could anyone help me out with building and transferring a program to the Command Module (which again is an ATmega168 based device) over a USB?

Even some nudges in the right direction would be greatly appreciated. Thanks  :)
Misc / Second Largest SALE of the Year - ServoCity
« Last post by ServoCity on April 09, 2018, 11:33:36 AM »



Software / Re: Axon I/II with Arduino IDE
« Last post by Admin on April 06, 2018, 12:40:21 PM »
The Axon uses the ATmega640, which is exactly the same as the ATmega2560 used in the Arduino Mega. The one difference is the 2560 has more memory. If you can get 640 compatible software, you are good to go.
Electronics / Thesis Research Help
« Last post by Mbakori on March 28, 2018, 06:29:40 PM »
Hi guys!

I am a MBA student at California State University, Northridge. As my culminating experience in the program, I am part of a team of MBA students that is working as a business consulting group for a local company. Our client manufactures unique technology that fuses high-quality uncompressed video with precise time stamping, and accommodates a huge array of other user-defined parameters, such as temperature, pressure, windspeed, camera angle, etc. Our client already sells to organizations such as the US Military and other government agencies, NASA, SpaceX, Boeing, Lockheed Martin, Cessna, Lear, Northrop Grumman, and more. The company?s equipment provides invaluable, unparalleled video-analysis capabilities for many engineering and testing applications. Part of our role as consultants is to help our client discover new use-cases and markets for his technology.

I am reaching out to you to see if you would be willing to help us in our research by completing this very brief survey and distributing it among your colleagues. Any help would be tremendously appreciated. Thank you for your time.

Just click on this link to access the survey:
Thank you,
Kori conemac
MBA candidate
California State University, Northridge
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