Recent Posts

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21
Electronics / Re: Replacing two analog POTs in mobility scooter bot
« Last post by tgibbons on July 13, 2014, 04:24:56 PM »
Thanks for the feedback on the voltages. That had not occurred to me. You were correct that 2.5v on the main control circuit was stop and 0v was full reverse and +5v was full forward.

Since this was a control voltage, I was able to control it with a PWM output from an Ardunio Uno. I was happy to find a digital PWM output would work for this, so I was able to replace both pots with the digital output from the Ardunio. 

Now on to replacing the mechanical steering...
22
Electronics / Re: Servo Problems
« Last post by Billy on July 13, 2014, 02:39:33 PM »
i first tried grounding everything together, that worked but the twitching came back
i also tried changing the batteries which also worked for a little while but the twitching returned


In every system where there are issues that can be attributed to noise, one of your first actions should be to stabilize the supply. Think of the batteries as the power source for your power supply. The power supply at each part being bypassing capacitors.
http://en.wikipedia.org/wiki/Decoupling_capacitor
On each of your power lines, and including at the battery, try install a 10uF electrolytic cap in parallel with a 1uF ceramic cap. Install these at the batteries, and if possible at the power connectors to the servos.

You said you power the uC from a 9 volt battery. That is OK but the negative terminal of the 9V battery must be connected to the negative end of the AA battery pack. That assumes you do not have any isolation between the servo circuit and the uC. Isolation is an advanced topic that you should consider if you still have issues.

Final thought: your description makes it sound like a noise issue, but of course it's possible you have a SW issue and the pulses to the servos are simply irregular.
23
Software / real time operating system
« Last post by ansh on July 13, 2014, 08:26:04 AM »
    
I am not really going to design I just want to learn something before design
I want to design my real time operating system , so I need features , requirement component and tool

I need to develop program For real time operating system
my effort
1)basic tool
compiler
linker
debugger

2)language
c language

3)requirement
requirement of real time os should be fast

features
kernel - micro kernel
scheduler - real time scheduler
multitasking - multitasking
scheduling - preemptive scheduling


I think I have forgotten some features
24
Electronics / Servo Problems
« Last post by vipulan12 on July 12, 2014, 06:19:05 PM »
hey guys, I was working on a biped robot that uses the UNO and 10 servos, and by changing the angles i should be able to make the robot walk however for some reason my servos tend to twitch like crazy
i am powering the 10 servos using 8 AA batteries(6 volts in parallel) the arduino is not powering any of the servos
the arduino is being powered by a nine volt battery (seperately)

i first tried grounding everything together, that worked but the twitching came back
i also tried changing the batteries which also worked for a little while but the twitching returned

a friend said that I should power the servos using the batteries and the arduino in parallel(could this potentially damage my arduino?)

what exactly is the cause of these twitches?
they mainly occur at  the moment the servos are powered(just by flipping the switch pn the battery pack)
25
Electronics / Re: Odometry "like" an Optical Mouse
« Last post by bdeuell on July 11, 2014, 05:58:15 PM »
I had to look up how an optical mouse works ... (http://computer.howstuffworks.com/question631.htm) but it seems to me like you could build a scaled up version with a light and camera. The challenge seems to be in the software to process the images ... and i'm not much help there. However if my understanding is correct I don't see why it couldn't track orientation as well. My thought is the software would compare two images and find the transformation that provides the best fit. The best fit would look for a transformation that would include translation in x and y as well as rotation about the z-axis. Of course adding another degree of freedom (rotation about the Z-axis) to the transformation increases the processing required.

I am looking at a sensor for a project at work that detects translational motion using Laser Doppler Velocimetry. There is a version that can detect both x and y translation but not rotation. I would think you could use two sensors a fixed distance apart and calculate the rotation from the difference in the two sensor movements. However these sensors run about 10k for a single axis detection capability so they are probably outside of your price range.

... just some thoughts on the problem, probably not very helpful.

If you do find any sensors capable of measuring the translational movement of an irregular surface without contact (even if it is only in one axis) I would be interested.
26
Electronics / Re: Odometry "like" an Optical Mouse
« Last post by Billy on July 10, 2014, 08:24:04 PM »
That might be something that roborealm could accomplish.
Of course to work like a mouse your robot would need to always face the same direction like a mouse does if you want to use it track location.
It may work as a distance/speed indicator and coupled with a compass give you a reasonable idea of where the robot is.

I have used roborealm in a different manner for tracking location of a lawnbot. The bot is painted a bright orange and camera is mounted on roof line of the house looking into the yard.
I use roborealm to find the robot (based on color) and then I know where the robot is in the yard. Roborealm comes with easy-to-use APIs that I've embedded in a visual basic application does the high level thinking for the bot.
27
Misc / Re: Solar Panel
« Last post by GaleTonkin on July 10, 2014, 10:25:19 AM »
Does anyone know how i can get a 12volt Solar panel to power a 12volt inverter, i have briefley tried and had no such luck. the inverter runs of the electronic cigarettes lighter in a car so is obv battery powered, which makes it DC, is a solar panel AC and therefore why it doesnt work??? Please Help!!!  :)


Thanks


Well my personal opinion about these panels are not good. Very expensive with little efficiency..
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29
Electronics / Odometry "like" an Optical Mouse
« Last post by getSurreal on July 10, 2014, 09:15:20 AM »
For starters, I'm not talking about hacking a computer mouse.

Does anyone know of a project that takes the concept of how an optical mouse tracks and scales it up to work for an outdoor robot?  I was thinking of some sort of cmos camera that can be several inches above the ground and be able to work without a fixed focus since the terrain could have blades of grass or other objects at various heights.
30
Software / Re: Problems uploading to Axon II using McUber
« Last post by Admin on July 09, 2014, 07:35:50 PM »
Just a silly question to get it out of the way . . .

Did you install the USB drivers, and does your PC properly recognize that the Axon is plugged in?

ps - I deleted your double post.
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