Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Geoffrey on October 17, 2010, 04:20:53 AM
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Hi, I'm planning on building my first robot sometime before the end of the year, and I'm going to be buying the following:
12 Tenergy Premium AA 2500mAh high capacity NiMH Rechargeable batteries
1 Sharp GP2Y0A02YK0F Analog Distance Sensor
1 Pololu Ball Caster with 3/4" Plastic Ball
2 2-5/8" plastic Black wheels Futaba servo hub
3 Power HD High-Speed Digital Sub-Micro Servos DSP33
1 Axon Microcontroller
In your honest opinion, what have I done horribly wrong in picking these materials, and what have I done right?
I'll be building a basic, smallish, differential drive robot that uses a distance sensor to decide which way to turn to avoid walls.
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Sub-micro servos won't be able to drive your wheels anywhere.
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Then how's 3 Power HD Micro Digital Servos HD-1581HB?
Or do I still need more torque?
Also, dumb question, but to connect the sensor to the controller, do I need male-female, or female-female terminators?
Nevermind, I just realized...
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Sounds good to me except the following:
12 Tenergy Premium AA 2500mAh high capacity NiMH Rechargeable batteries
3 Power HD High-Speed Digital Sub-Micro Servos DSP33
3 Power HD Micro Digital Servos HD-1581HB?
Is there a reason you will be getting 12 AA's? Are you looking to power the servos separate from the Axon, or are you just looking to have a backup battery pack? A single battery pack is more than capable of powering 3 servos, the Axon, and the Sharp IR rangefinder.
Secondly, is there a reason for going with Micro's and Sub-Micros? With the wheels you plan on getting, you will have more than enough ground clearance for regular servos. For example, the HS-311 (http://www.servocity.com/html/hs-311_standard.html) is half the price and has more torque than the Micro's you have listed. They aren't digital, but do you have a need for digital servos? Also for inexpensive lightweight servos to mount sensors on, I use SG-90's. If you shop around you can get them for as little as $2 USD shipped.
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@OP:
It's not about torque, its just that servo wheels are designed for normal-sized servo splines, and won't connect to micro/submicro ones. Digital servos have better angular control, but for wheels, you don't really care about that... just build some encoders later. An HS-311 should do fine, as knossos said.
As for the batteries, I thought that the point was to have 3 sets to swap in/out... correct me if I'm wrong?
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Yeah, I spaced. Getting the HS-311's.
And I'm swapping the 12 batteries for a single 6v pack.
And no need to pay extra for continuous rotation on the servos as I can modify them for that for free right?
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Yes, that's right, you can modify your own servos easily enough (There's a tutorial on it in SoR that's pretty nice and detailed)
Your robot sounds pretty fun. Be aware, though, that the output from a Sharp IR rangefinder is nonlinear... I believe the GP2Y0A02YK0F (20cm-150cm?) is something like 65*voltage1.10 for reasonably accurate readings.
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Also, where can I get a hitec cable that will connect to the sensor and axon? I am having horrible luck finding cables.
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A lot of sites sell the 3-pin JST connector for the Sharp IR rangefinder. For example RobotShop (http://www.robotshop.com/lynxmotion-sirc-04-cable.html) and Sparkfun (http://www.sparkfun.com/commerce/product_info.php?products_id=8733). Also, if you're just looking for wire, there is this wire from ServoCity (http://www.servocity.com/html/servo_wire__bulk_.html) that works fairly decent (its reasonably flexible and durable).
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Okay, thank you so much everyone, you're awesome.
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I get my sensor cables from hobbyking: here (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9769)
They have a futaba connector, which is similar to a hitec one. But they will still plug right into the axon's header pins.
Just solder the lead wires right onto your sensor (ex: potentiometer)