### Author Topic: Need help to pick right components for my first robot  (Read 2337 times)

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#### Dar0n

• Beginner
• Posts: 5
##### Need help to pick right components for my first robot
« on: August 05, 2015, 07:08:03 AM »
Hello!
I assume such topics are the most popular on this forum I am absolutely new in robotics, but have to face a chalenge to build one. Also I am not sure if I can get this kind of support on this forum, but I would appreciate any help(including redirecting to other websites).
Right now my question is not about how to build a robot, but how to pick right and cheap components for it. I've attached a (very) rough scheme of what I need.
This machine is planned to use in the following way: we put a sample on the bottom part of component A, then we use component C to move down the sample to liquid(marked B on the scheme), and then move up again. So, in principle it really reminds drilling devices like this one: http://www.purrosregulator.com/images/Img/image/DrillingMachine02.jpg
But I need to construct something perfectly feeting for my project.
Crucial moments:
-component A should be possible to align ideally in horizontal plane(that is perpendicular to Z axis); Since the tables can have different angles, would be nice to make this part with programable angles(something like 2 perpendicular wheels).
-distance l is supposed to change from 0 to at least 8 cm, so component C must provide this distance difference.
-Also it would be nice if component C could provide different speed - I plan to move the sample down with lower speed then move it up. If accurate numbers needed, I would say - 0,2-0,5mm/sec down and 1cm/sec up speed.
-Would be nice not to connect this device to computer, but to make and program its own keyboard(let's say, 4 buttons to control position of component A and 4 buttons to control movement - low and high speed for both moving up and down)

I think, other things can come up, but right now this is more or less everything I have in my mind:)
So, I need names of components(maybe with links) which I can use to build something like this - including balks.
Total size is not very crucial parameter - important is l distance only. But, of course, it should not be too big:)
I will be glad to answer any questions on my project or to get any advices:)

#### cyberjeff

• Full Member
• Posts: 114
##### Re: Need help to pick right components for my first robot
« Reply #1 on: August 05, 2015, 11:36:09 AM »
Mechanisms for working in 3 linear dimensions are readily available.

But, we have two unknowns which may make this very expensive. How much weight and how accurate? Since you linked to an industrial scale drilling machine, if you need that kind of power, you need to look elsewhere.

Otherwise...

3D printers are now widely available, they are highly accurate. On the hobby scale they can't handle much weight.

I've mentioned actobotics here recently, it helps to read around a bit first.

https://www.servocity.com/html/actobotics1.html

Note also their recent ad for a 7 rotation servo, which geared down could be useful.

Programming all this is a different matter. 3D printers have their own assortment of "languages" of which I know little. If you are more build it yourself, c++  is common and there are a few limits depending on what microcontroller you are using. Programming space is precious.

#### Dar0n

• Beginner
• Posts: 5
##### Re: Need help to pick right components for my first robot
« Reply #2 on: August 05, 2015, 02:02:00 PM »
Quote
But, we have two unknowns which may make this very expensive. How much weight and how accurate?
The weight I plan to put on the bottom of A component is really nothing - it's a mettalic plate 1mm height and 1cm diameter. I assume it weights several dozens of grams.
What exactly do you mean by accuracy - angles or vertical positioning? Again, I can only assume, but I think, for angles accuracy up to 1 degree is enough(in both directions). For vertical positioning the more accurate the better:) I think 0,1-0,3mm is good enough.
Quote
3D printers are now widely available, they are highly accurate. On the hobby scale they can't handle much weight.
Do I understand correctly that you suggest me to use 3D-printer to make backbone for my device?
As for programming, I think C++ is better for me. I'm not a programmer, but I had a course on it and learnt some basics.

#### cyberjeff

• Full Member
• Posts: 114
##### Re: Need help to pick right components for my first robot
« Reply #3 on: August 05, 2015, 06:18:06 PM »
Quote
But, we have two unknowns which may make this very expensive. How much weight and how accurate?
The weight I plan to put on the bottom of A component is really nothing - it's a mettalic plate 1mm height and 1cm diameter. I assume it weights several dozens of grams.
What exactly do you mean by accuracy - angles or vertical positioning? Again, I can only assume, but I think, for angles accuracy up to 1 degree is enough(in both directions). For vertical positioning the more accurate the better:) I think 0,1-0,3mm is good enough.
Quote
3D printers are now widely available, they are highly accurate. On the hobby scale they can't handle much weight.

3D printers need the same 3 axis that you need here, kits of just the mechanical parts are available, or you can build it out of the actobotics. A tenth of a mm is pretty tight. If the scale of the machine is small you can gear it down to gain  accuracy.
Do I understand correctly that you suggest me to use 3D-printer to make backbone for my device?
As for programming, I think C++ is better for me. I'm not a programmer, but I had a course on it and learnt some basics.

#### Dar0n

• Beginner
• Posts: 5
##### Re: Need help to pick right components for my first robot
« Reply #4 on: August 06, 2015, 04:08:38 AM »
I would prefer to build it out of the actobotics details.
So, what is common accuracy for such motors? And, btw, how are they called correctly?

#### Dar0n

• Beginner
• Posts: 5
##### Re: Need help to pick right components for my first robot
« Reply #5 on: August 06, 2015, 06:53:15 AM »
After some searching I realized that I probably need some linear actuator as a component C. Also I could combine 2 RC servo motors as A component, but it would be better to use 1 part instead of 2. So, maybe there is some device that can provide horizontal alignment.
Quote
The weight I plan to put on the bottom of A component is really nothing - it's a mettalic plate 1mm height and 1cm diameter. I assume it weights several dozens of grams.
I just checked - the mass of sample in fact is less than 1 gram, so the total mass linear actuator will have to lift is only the mass of device itself.
Can anyone advise something according to requirements above mentioned?

#### cyberjeff

• Full Member
• Posts: 114
##### Re: Need help to pick right components for my first robot
« Reply #6 on: August 06, 2015, 11:16:52 AM »
They are called servos. Here is a database:

http://www.servodatabase.com/

You need a digital and probably coreless. What the gear is made out of will affect lash, durabilty (under stress/shock) and wear. Durability, since you have little weight, is not a concern.

Accuracy depends on a myriad of things including gear lash in your mechanism.

You can multiply the "fineness" of the servo by gearing it down.

I have limited experience with robotics and none with linear actuators (you will probably build your own out of actobotics) so specific recommendations I can not give. Whether anyone else will weigh in is in doubt. I suggest you browse around.

#### Dar0n

• Beginner
• Posts: 5
##### Re: Need help to pick right components for my first robot
« Reply #7 on: August 06, 2015, 02:45:06 PM »
Quote
They are called servos. Here is a database:

http://www.servodatabase.com/

You need a digital and probably coreless. What the gear is made out of will affect lash, durabilty (under stress/shock) and wear. Durability, since you have little weight, is not a concern.

Accuracy depends on a myriad of things including gear lash in your mechanism.

You can multiply the "fineness" of the servo by gearing it down.

I have limited experience with robotics and none with linear actuators (you will probably build your own out of actobotics) so specific recommendations I can not give. Whether anyone else will weigh in is in doubt. I suggest you browse around.
Thank you for your help, of course I will browse around more. At least now I have a very common idea of what I want:)

Anyway, if somebody knows the device that provides alignment in 2 directions at the same moment - please, reply:) And, of course, if you have some other suggestions on the topic - I will be glad to hear other opinions.