Author Topic: Help with component selection  (Read 566 times)

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Offline tuxgeekTopic starter

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Help with component selection
« on: January 24, 2012, 04:31:22 PM »
Hello all. I am looking at building a robot for a capstone project in a computer information systems class I am in. I am wanting to build something tracked that has a pan/tilt platform on top and I already have plans for the way I am going to build the tracks, I know what microcontroller platform I want to use, but the rest of it, I need help picking out parts for. The biggest issue is that I need to be fairly low budget. I want to start with a smaller version, which I see as a 8 inches to 1 foot long so I can use that to see if anyone I know would be willing to contribute financially towards the full size version.

1.   Motors - I can’t really get a feeling for how much power something has by just looking at ratings, so I have no clue what to even start to look at.

2.   Batteries - I need something with decent bang for the buck, without being too big or heavy for the rest of the thing. I like lead-acid because of the cheap factor, but would cheap cordless tool batteries work?

3.   Motor controllers – I can probably build something, but if there’s one that is affordable, even better

4.   Wireless system -  I plan to make it computer controlled by Bluetooth or WiFi in the end, but for testing, I will need a standard controller

5.   Accessory mount movement – I don’t know what to use to control the pan and tilt movement of the accessory mount.  I figured it would be best to use a servo for the tilt mechanics since it only needs at most 135 degrees of tilt control. The problem is I need it to be able to support a decent sized camcorder. For the rotation, I figured a motor would be the best idea since I need full rotation. I was planning on connecting the motor to the turntable via chain or direct gear and then using a rotary encoder on the turntable to sense where its facing.

If anyone is selling anything that would be useful for this, I would love to know. I have no objections to buying used.

I think I remembered the vast majority of my questions, and I look forward to your experienced answers.
Thanks :)

PS - Judging by the number of verifications, i have a feeling that some members like turning their creations free on the website...  :P

Offline tuxgeekTopic starter

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Re: Help with component selection
« Reply #1 on: January 24, 2012, 07:17:33 PM »
I just realized that I probably posted this in the wrong section, so if it needs to be moved, please do.

Related to my OP, I found this motor(http://www.allelectronics.com/make-a-store/item/DCM-130/24-VDC-135W-MOTOR-W/BELT-GEAR/1.html), and with enough reduction I think it will work just fine. What do ya'll think?

Offline Gertlex

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Re: Help with component selection
« Reply #2 on: January 25, 2012, 12:08:48 AM »
Got nothing on #1.

Quote
2.   Batteries - I need something with decent bang for the buck, without being too big or heavy for the rest of the thing. I like lead-acid because of the cheap factor, but would cheap cordless tool batteries work?

Ebay for 6V or 7.2V NiMH batteries like those used in RC stuff are probably good for this (and you can always cross check with non-ebay sellers). You'll also need a charger.  I suppose cordless tool batteries would work.

Quote
3.   Motor controllers – I can probably build something, but if there’s one that is affordable, even better

Here's a schematic for a motor driver that will probably suit your needs as long as you don't use crazy powerful motors.  http://forums.trossenrobotics.com/showthread.php?3907-Dual-Gun-motor-driver&highlight=motor  PWM to the 5V input can provide speed control.

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4.   Wireless system -  I plan to make it computer controlled by Bluetooth or WiFi in the end, but for testing, I will need a standard controller


What do you mean by standard controller?  Regardless, the approach that'd be best for testing would be a wired connection... Most microcontrollers have such.

Quote
5.   Accessory mount movement – I don’t know what to use to control the pan and tilt movement of the accessory mount.  I figured it would be best to use a servo for the tilt mechanics since it only needs at most 135 degrees of tilt control. The problem is I need it to be able to support a decent sized camcorder. For the rotation, I figured a motor would be the best idea since I need full rotation. I was planning on connecting the motor to the turntable via chain or direct gear and then using a rotary encoder on the turntable to sense where its facing.


One option is to use a 4-bar linkage to keep the weight off the tilt servo (you won't get as wide a tiltl range though).  Multi-turn panning is not something I'd try to do cheaply, I guess... Turn the robot instead (tracks are nice for that...). 

You could use a Wifi secuirty camera e.g. Trendnet IP110WN or the smaller, similar D-Link camera.
I

Offline tuxgeekTopic starter

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Re: Help with component selection
« Reply #3 on: January 25, 2012, 09:54:42 AM »
Quote
4.   Wireless system -  I plan to make it computer controlled by Bluetooth or WiFi in the end, but for testing, I will need a standard controller


What do you mean by standard controller?  Regardless, the approach that'd be best for testing would be a wired connection... Most microcontrollers have such.

I kinda meant like a standard wireless controller (like a RC car), but tethering would work

Quote
5.   Accessory mount movement – I don’t know what to use to control the pan and tilt movement of the accessory mount.  I figured it would be best to use a servo for the tilt mechanics since it only needs at most 135 degrees of tilt control. The problem is I need it to be able to support a decent sized camcorder. For the rotation, I figured a motor would be the best idea since I need full rotation. I was planning on connecting the motor to the turntable via chain or direct gear and then using a rotary encoder on the turntable to sense where its facing.


One option is to use a 4-bar linkage to keep the weight off the tilt servo (you won't get as wide a tiltl range though).  Multi-turn panning is not something I'd try to do cheaply, I guess... Turn the robot instead (tracks are nice for that...). 

Yeah, I think I will just turn  the bot. It makes it easier to engineer.

Motor wise, I am looking at:
http://www.robotmarketplace.com/products/0-HTIM1.html Its fairly cheap, but I am not really sure of the power output
http://www.robotmarketplace.com/products/0-DTXP5737.html Seems like a nice cheap motor, but it would need insane gears, and again, not sure of the power output
http://www.allelectronics.com/make-a-store/item/DCM-130/24-VDC-135W-MOTOR-W/BELT-GEAR/1.html I still think this would be good, but I need more opinions.

Now that I am looking at the price of the motors, I think I might wanna build it as full size from the start. I plan on it being 18"x9" for the platform with 2" wide tracks. I'm not sure yet. If I can get the motors cheap enough, I can scale up the rest of the components once I have the money. I don't really want to use the materials to have to build 2 frames for it, and it will be cheaper to just buy one set of motors. For most of the motors, I could also start out with one per track, but leave provisions to have 2 per track as an up-scaling method. What do you guys think?

 


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