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71
Electronics / Re: Simple microprocessors?
« Last post by ootbrobo on June 19, 2014, 11:38:56 PM »
If you are asking the question of which micro is simplest I take it you have not messed with microprocessors before?  If that is the case I would recommend buying an off the shelf solution like an arduino.  That will allow you to focus on your application from the getgo, and less on the howtos of processors.

As for your project description, I see a red flag.  Those membrane based flex sensors are not super repeatable, at least they weren't when I was working with them in the past.  You more or less have to calibrate them often to get a consistent result. If I recall correctly this calibration involved depressing the sensors once or a couple of times to essentially warm them up.  I could be crazy though, check the spec for your specific senor.   My two cents, what you may actually want is a load cell, or a linear potentiometer rigged with a compression spring.  In each case your sensor has a pretty consistent sensitivity to load.
72
Mechanics and Construction / Re: bandwidth of two wheel inverted pendulum
« Last post by ootbrobo on June 19, 2014, 11:22:22 PM »
Okay,

So that document is pretty involved so I honestly just skimmed it.  The setup in the doc seemed to be referring to the use of encoders and a gyro not an accelerometer.  So I assume you are using the Accel for your pendulum gravity vector, and the gyro for the rate?

As for using a physical filter at the output of the accelerometer, I would suggest going with a digital filter instead, such as an IIR.  This ought to be a more powerful and robust solution.  Keep in mind you may need to compensate for a lack of an FPU though depending on the processor you are using.

The natural frequency of the sensor?  I don't think that is what you are looking for.  If you need a natural frequency at all it ought to be of the pendulum.

The problem I think you may run into here is that an accelerometer + gyro combinaton here does not give you sufficient information without some assumptions, or references.  Point being the accelerometer picks up three distinct vectors 1) gravity 2)centrpital accel due to pendulum angular rate 3) linear acceleration of the robot as a whole.  You can derive #2's contribution from the gyro, but you do not have direct feedback for the forward motion of the entire robot.  I would recommend adding encoders to get position/ rate data from the wheels in reference to the pendulum mast. 


 
73
Mechanics and Construction / Re: I look for a term for what I'm looking for
« Last post by ootbrobo on June 19, 2014, 10:39:41 PM »
Ron,

You are basically looking for an arm with three degrees of freedom. all of which are rotational, I take it?  I would be inclined to go the servo route with cascaded pan and or tilt mechanisms.  That's probably one of the best COTS (completely off the shelf) solutions out there.
74
Electronics / Need help selecting an RC transmitter
« Last post by pterrus on June 19, 2014, 08:56:36 PM »
So I recently acquired this thing for cheap and the plan is to mount an arm kit or something to it and make it into an RC robot.  What I need is a transmitter that has at least 4 channels (2 for drive/steering and at least 2 for the arm servos).

The problem is I'm a total RC noob and have no idea what to buy.  I gather the crystal on my base is 27.145 MHz.  I've looked at stuff like the FlySky FS-T6 but it's unclear to me that this will do what I want.  When it says 2.4 GHz, is that the crystal frequency or something else?  Should I not be looking at digital transmitters?  Am I even asking the right questions?  Googling isn't getting me anywhere, so any recommendations/clarification would be helpful!
75
Mechanics and Construction / [advertisement] New Channel Connector Plate
« Last post by ServoCity on June 19, 2014, 12:55:43 PM »
These plates make it easy to create a strong joining point between our channel pieces!
$3.99 / 2 pack


http://www.servocity.com/html/channe...l#.U6Mrz_ldV7s

We recommend using 6-32 socket head machine screws with this plate (sold separately)



To see additional ways to attach channel watch
https://www.youtube.com/watch?v=UjJ8yy6-kBM&list=UUfOty7yWBfSXfAPAq2AI_DQ
76
Electronics / Re: Need help- 24vdc motor driver
« Last post by jkerns on June 19, 2014, 07:13:48 AM »
It appears from the picture that the input to your motor driver is a PWM from 0 to 98% duty cycle. (on 0% to 98% of the time)

The "Standard" output from the typical RC system is a pulse modulated system that does not provide the above type of duty cycle. (don't recall the details off the top of my head, google it.)

So, unless you can make your radio output a duty cycle instead of the standard servo pulse signal, you will need something to translate from RC style signals to a duty cycle.
77
Software / Re: Making a robot that solve a rubik's cube.
« Last post by Mehal on June 18, 2014, 09:40:44 PM »
Well ,I couldn't get any proper help from the internet, so I decided to try it on my own. I have made a simple program in C which asks me to input the colors on each facelet and then in output it shows where does each piece belong and how it needs to be oriented. But how to find the neccessary algorithm using this data?
78
Electronics / Need help- 24vdc motor driver
« Last post by mr_rendell on June 18, 2014, 06:59:06 PM »
Hello,
First of all thanks for allowing me join this group.
I need help figuring out electronics on my lawnbot,
I am using:
2ea wheelchair motors
2ea 12vdc 35ah batteries
Lawn mower (of course)
Super e t4 fhss digital proportional radio system (4ch)
And... 2 ea (china made) ebay
DC 15-24V 40A Brush Motor Driver Module Drive Board 80A Max
(Was gonna get sabertooth 2x25) but a bit pricy

Now..
I am not sure if I need arduino to control my motor driver board or use it just like sabertooth
When I try to plug it with my batt and receiver, I was only getting 9vdc on the motor poles.
Has anyone use this motor driver?
Thanks in advnce!
79
Software / Re: Problems uploading to Axon II using McUber
« Last post by Webbot on June 17, 2014, 07:46:29 PM »
Ok - can't vouch for the board - but maybe Admin (the manufacturer) can.

Could try Webbot Studio  http://webbot.org.uk/iPoint/50.page at least I can help with the log output from that.


 
80
Software / Re: Problems uploading to Axon II using McUber
« Last post by Hero I on June 16, 2014, 04:45:45 PM »
I even went on Yeta Corp's website last week and sent them an Email asking them about the problems I'm having with McUber, but haven't heard from them yet.

http://www.yetacorp.com/products/mcuber/
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