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71
Mechanics and Construction / Re: step speed regulation problem
« Last post by bdeuell on February 16, 2015, 10:04:18 PM »
you could use a feedback controller (with an encoder or other sensor to measure the motor speed) to ensure constant velocity by enabling the PWM controller to ramp up the duty cycle when the load increases. this is not a particularly simple solution so it would not be my first choice.

On a related note you could look at back EMF speed control. essentially the motor windings are used to sense its own speed and adjust the PWM control accordingly. 

If you are truly stuck with the current motor i would try to find a mechanical means of slowing the speed down. can you fit a smaller sprocket on the motor?

perhaps a cable drive would work for this application, it looks like you only need 180 degrees of motion for the step. im picturing a cable that is attached to the outside of a pulley at the step. then a threaded rod at the motor for it to wrap around. ideally you would custom cut a helical groove with a rounded profile to match the cable but a standard thread can work. che cable would then continue back to the pulley at the step and attach to the same place or near where it started.



72
Electronics / Re: Robotic Telescope.
« Last post by bdeuell on February 16, 2015, 06:14:01 PM »
Perhaps a friction drive, basically a rubber wheel that would ride on the edge of the filter disc. it could be mounted somewhere near where you have indicated but you may need a mounting bracket to get it in the right place
73
Electronics / Re: 3.7 v lipoly powering micro servo? bad idea?
« Last post by bdeuell on February 16, 2015, 06:01:46 PM »
Having said all that, I would like to know the potential problems.  What would be the harm of lower than recommended voltage?  Could it damage the battery or the servo?  And what is the harm of reduced torque on the servo itself?  Could that also be something that could damage the internal components?
I doubt you will cause any harm to the servo electronics. The low voltage could cause them to be underpowered resulting in higher currents when compared to the same torque at rated voltage. If run for a period of time this could overheat and burn out the motor. caution that servos are often powered even when not moving this allows them to maintain their position if a load is applied. basically at the lower voltage you still do not want to exceed the motors rated operating current for a given duty cycle.

Reduced torque should actually help the life of the mechanics inside the servo.

The battery life is often dependent on the charge discharge cycles you put it through. Typically deeper discharge = reduced life, faster discharge = reduced life, higher temperature = reduced life.

With regards to using a voltage booster, the batteries I want to get actually have a voltage of 4.2 v when fully charged, and they go down to 3.7 v when fully depleted.  What impact would that have on the ability of the voltage booster to output adequate voltage?  Would that make any difference?  Does 3.7 v provide enough voltage to be boosted to 4.8 v?  And is there a danger of boosting it too high?
A boost converter is designed to give a constant output voltage for a range of input voltages, the allowable input range depends on the converter and would be given in the specs/datasheet.

The servos I am thinking about using require somewhere between 100-200 ma.  Would a 3.7 v battery be able to supply that much amperage?
This depends on the battery specs. No battery should be discharged at a rate greater than its specified maximum and lithium batteries are particularly sensitive and at risk to blow up if discharged too quickly, over discharged, or overcharged. youtube has plenty of videos if you want to see this i would recommend avoiding it yourself.  ;D Most lithium batteries you find will have a built in protection for these conditions but i would not rely on these to protect the battery, you should design your own protections for these conditions into your system.

I have also considered using a 7.4 v lithium polymer battery, and using voltage regulators to provide the right voltage for the microcontroller and servos.  Does using a voltage regulator reduce the amount of amp hours that a battery can provide?  And by how much would it be reduced?
It does not directly reduce the capacity of the battery but a regulator/booster will waste power and reduce the overall efficiency of your system, how much depends on your regulator type/design. However battery capacity is dependent on discharge rate so drawing more current from your battery will shorten its run time.

A related question is, do I need separate voltage regulators for the microcontroller and the servos?
Depends on the voltage you supply for the motors, microcontrollers are usually not very flexible on their input voltage. However its not a bad idea having a separate linear regulator for the microcontroller can eliminate a lot of problems by isolating the power.
74
Software / Re: Help with PID line follower
« Last post by bdeuell on February 16, 2015, 04:56:13 PM »
basically you need to add a condition (if statement) in your code that tells the robot to go straight if it does not detect a line otherwise (else) follow the line using PID or any other algorithm. Im not sure how you have your sensors wired to the robot but the theory is, if none of the sensors detect a line assume there is no line and drive straight until it appears again.

Make an attempt to figure out how to implement this "condition" into the code, if you are struggling with this post back with specific questions about what part you are having trouble with. If you plan to use this copied code you will really need to read through it and understand how it works so you can add these modifications.

BTW it looks like the code you are using is actually a PD control loop.
75
Software / Help with PID line follower
« Last post by Cycloned on February 16, 2015, 11:59:09 AM »
Hey everyone. I have a line following competition this weekend and I have prepared a simple robot for it. My robot is tracing lines pretty well, the only issue is that when it comes to the end of a line, it rotates in one place. I want to change it so that it continues to go forward after the line finishes because the competition track has several gaps in the line. Since I am very new to Arduino, I must admit that I have copied the program from online, and have only experimented with the values to get the line tracing to work. I have an understanding of the way the code works but I do not have enough time to go in depth into it and recode things myself. I will however be making my own program after the competition.

Could someone help me out with how I can accomplish this?

http://pastebin.com/hnmUHcxQ
76
Misc / Re: FAA finally proposes rules for drones
« Last post by Ibaeni on February 15, 2015, 06:57:37 PM »
This is very interesting because I'm currently working on an autonomous quadcopter. (Links in signature). At this point, it is interesting to see the standpoint of the US in comparison to other nations. As mentioned by the article, many other countries have made the commercial use of drones a much easier process. Hopefully as UAV's are further researched/developed, lawmakers won't hinder that research. UAVs offer an amazing opportunity to improve overall quality of life. Whether it's farming, search and rescue, or military applications, I see UAVs having an important role in our society the same way other developments have like cars and telephones. That development is a ways away, but it has great potential.
77
Misc / FAA finally proposes rules for drones
« Last post by Admin on February 15, 2015, 01:50:54 PM »
78
I've added a few new features recently - including the ability to cut perfect-sized circles and elipses.  I'm considering adding more features, like cutting from drawings, lines and other measured-motions, gear-wheels, and precise arbitrary shapes created "immediately" using the joystick...  if anyone is interested, let me know and I'll post my code.
79
I agree! It is great software for modeling and designing things in general. It's very powerful but simple at the same time. I actually just use the free student trial software for my modeling, as I don't have thousands of dollars to spend on software, but it is near fully functional and allows me to make & create anything I'd need to. That would be very helpful for designs to be in autodesk format, but it's not essential! I could help anyone take their idea from just an idea to a solid part as well!

I'd love to see some of the custom parts you need made when you get some designs ready mkl!  8)
80
 8) Hello!
I have to learn the software myself, which does not
seem to daunting a task, which is a tribute to the people
who made the software. I will start with simple drawings
for simple parts, but may proceed to more complicated
3-D drawings for more intricate parts.(blow - out diagrams)
If this software is easier for you to absorb for processing
your mechanical orders, then anyone in the forum could
use this too,
to insure smooth transitions. It would be a good
investment for me to use the software, if I will depend on it
in the future. What do you think?  ;D
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