Re: Servo Compact Design Problems!!!
 

John,
What many of the people here are familiar with are the servoes used in Radio Controlled cars and airplanes. They are not designed for continuous use as a drive system. A servo takes a power supply voltage and a control signal and makes the output shaft turn to a particular angle. This is useful for steering and wing control.
When you spoke of a servo motor in an earlier post, you may have been referring to a stepping motor. This device is similar to a servo in that it can have very precise control of the motor shaft but it can rotate a full circle and is meant for continuous duty. The motor in a video cassette recorder(the one that drives the tape) is a stepping motor. Unfortunately a stepping motor requires very sophisticated electronics to drive it. So again it is the wrong motor to use.
You also did not specify the weight of the rover you are building. If it is in the 50 to 100 pound range, then any of the kit motors we use will be OK. You can get a lot of power from a little Fisher Price motor and you can buy the motor and transmission from many sources.
If you are building something that is only a few pounds, then small motors of the type in toy cars would work just fine. I don't know if Radio Shack has any stores in your country but they carry everything you need for a small project.
Let us know a little more about your project.

Re: Servo Compact Design Problems!!!
 

Thanks a lot guys, I'm really appreciate your help, In this message I will tell you about my robot, Here is the details

I will never describe my project as best as you will see now,

My project is a something that I hope that our army look for it, its a thing popular, you even know it, its a scout and carry on a gun.

Did you here about SWARD (http://www.foster-miller.com/) and (http://www.foster-miller.com/lemming.htm) These guys provide a complete mobile platform that will replace the soldier in the battlefields,

My Project is the same the above, But with little modification, If you the manual sheet provided in above link, then you will know my specification, But the diff between my rover and SWARD, that my one is simpler than the SWARD and will use transceiver,

Now after you know the rover I need to build and the Spic. I needed can you advice me what is the best choice in the motors and what is the convenient transceiver (range between 300 meter and 600 meter), And any advice you find that it will help me,

I'm really thanks for your help guys,




For turning it will not a big deal, cause the left 3 motor are separated from the right 3 motor, So I may send a signal to move the left group to forward and a diff. signal to the right group to move backward, so the rover will turn right, That's it, Of course if there are no another problem you may see, Tell me if you see a problem,


Thanks In Advanced For Whatever Help, And Please Advice Me...

Re: Servo Compact Design Problems!!!
 

John,
You have not mentioned any specs for size, weight or budget. I can recommend the chassis, transmission, CIM motor combination as being able to move anything up to about 150 lb. In sand, you will need some extra protection to keep the grit out of moving parts. You can't beat the Innovation First control system but I don't think it will give you the range you think you need. It is good for a couple of hundred feet, maybe as much as 400 feet in line of sight.
As far as budget, the above parts will cost several thousand dollars (US) If you are looking to go smaller, say about 50 to 75 pounds, then the Fisher Price motors and transmissions should do a good job. They are designed for children's cars and work pretty well for being plastic. Those can be had much cheaper and are available through surplus houses like American Scientific.
Let us know if there is any information you can give us for specifications.

Re: Servo Compact Design Problems!!!
 

Hallow,

After my last post, I asked the biggest mall in robotics in Egypt, I asked them about my requirement, and the surprise that a lot of components are not available there (Just is not like I saw in the net, But they have a collection of things that I think it will help, Its included below), But the good news that, there are another technique they tolled me to use.

Here is the technique I will use in my project, And here a good specs about my robot, to help you to help me,

Specs of my Robot:-
[*] The Robot Specs.....
*******************
1- The size of my robot is 60 cm height, 30 cm width,

2- It will use 4 DC Motors, these Dc Motors are connected to 2 tracks (such as tank), each track will include three wheels (These wheels are free, I mean not connected to any motors it's just used to pull up the track) (Its just like the tank).
[*] -> Details for stage (2)
----------------------------
-The DC #1 & #2 Will be in the right side and DC #3 & DC #4 Will be in the left side,
-The DC #1 Will be in the front of the rover that will take the front of track,
-The DC #2 Will be in the rear of the rover that will take the rear of track,
-In between the DC #1 And #2 (Front of Track And Rear) There are 3 Wheels.
###################

3- These 4 DC motors will derived from a DC Driver board that will take its power from a Motorcycle Battery (or similar)-(12 Volt and 20 A)->(Maybe I don't know yet), The battery will be recharged through 3 or 4 dynamo->(Maybe), So there is no need to unplug the battery to recharge it, and will provide long live mission,

4- The Driver board will connect a Main Board that will manage the direction of each motor, through the driver.

5- The Main Board of the robot (I don't have any information about it yet, but its on the shelve in the malls) assume it will connected to PC that will be inside the robot chassis, (Not complete PC, Just Mother, HDD, VIGA, Sound Card And Wireless Network Card (That will act as Transceiver (That will deliver and send info, to operator))).

6- The sensors (GPS, Temperature, Compass, Camera And Mic), will connected directly to the pc through its ports,
[*] -> Details for stage (6)
----------------------------
I have an interface board called K8000 from velleman.com that have an parallel interface to pc, this board have an 4 input analog & 16 in/out digital & 9 Output Analog, It will be use for temperature sensor and the switches that will used for interrupt the pc (Example if I push a witch, then this will interrupt the pc and my SW so it will activate a voice recognition program, or activate the autonomies mode, and so on), The rest of sensors I will ask for there interface port.
I think that the camera & Mic & Temperature sensor are not the problem, (cause its interface is known and easy),
The problem will be interfacing the compass and GPS (I think it will be the problem cause I don't know what is the output of these sensors), I have question here, can I attached them to my interface card or to any port on my mobile PC??
###################

7- The robot maybe include 2 or 3 Motorcycle Battery that will automatically recharged from dynamos.

8- The Robot Mobile PC will take its power from battery #1, And motors take its power from Battery #2 And Sensors and other components may take its power from battery #3 (And all these Battery will be recharged automatically)

9-the load of the rover will be 35 or 40 KG or More, so I will buy a stronger DC, that will achieve these constraints (I think that there are such these motors for this load??!!)

10-Indeed the DC will contain a gearbox (Its the hardest problem, Cause there is no body here have these gearbox and its hard to build it, and its hardest to get it from outside the country.)

11- Please If any Important Specs. are not mentioned Please PM me,


************************************************** ********

(*)The Operator Specs.....
1-Its a personal computer that attached to it a wireless network card, Just it,
2-There will be access point between the Robot PC and The Operator PC,
3-The range of this wireless network is 300 Meters line of sight, If the access point in the middle between the Robot PC and Operator PC, and the range will be 150 Meters if the access point is beside the operator,

************************************************** ********

(*)The SW Specs.....
1-Its normal network program using Winsock.ocx that will retrieve the real time video and sound and sensors reading from Robot PC to Operator PC and Send instruction From Operator PC To Robot PC That will execute it,

************************************************** ********

Here is my Specs, Tell me what is your Opinions, And what is problem you may found here, Please Help me,
And by the way, What is the Fisher Price motor ??

Any Help will be appreciated, Thanks in advanced for whatever help, Thanks.

Re: Servo Compact Design Problems!!!
 

John,
I think you are taking on a big project for a first time robot builder. The only hardware I know is the Velleman I/O board. It is meant to be part of a computer control system that will accept input from sensors and output control. It can be used for remote control of a system such as a small broadcast radio transmitter. It would be used through a modem to turn on the transmitter, adjust output power and take meter readings and sense the temperature of the room, etc. It may not be able to handle the real time tasks of driving the robot. With a robot of only 30 cm wide and 60 cm high you will not have enough room for a big battery let alone three batteriesand a computer. The wireless network link setup midway on the course is a good idea for maximum range but if your onboard computer fails to connect you lose the control of the robot.
So this leaves you with this...I am guessing you mean that the robot base is 30 square cm (30cm x30cm x 60cm h) A few small motors of the type in model cars would work if you choose an appropriate gear ratio and keep the robot slow. You did not indicate what task the robot must perform but if you intend to add GPS then you might just program it to run autonomously and you wouldn't need the network interfaces. You only need the tank tracks if you need to pull some other weight or the robot will be climbing a hill. I suggest four wheels where two wheels are the power for drive and two wheels steer just like a car. The fisher price motor and gear box are still too big for you application but you could take the drive system from a large RC model car and adapt them to your project. Before you go to far, get a driving base that is wired to a control system. Don't try the wireless until you can drive a wired base. If you can't get a base to drive, all the rest of your project will have no use. There are several books on building robotic models that you should check out. Do you have a library near your home that you could check into? Are you near a university that might have a good library you could have access to? Does your school have a library?

Re: Servo Compact Design Problems!!!
 

I'm sorry if you mismatche my wards,

The Velleman I/O Board will used to take meter readings and sense the temperature of the room, Its not designed for controlling robot, i mention that i will use it for the reasons above, not for controling the rover, there will be another board that will control the rover and i'm said that i don't know much about it right now.

The robot size maybe greater that this dimention, there is no problem, because if i have a strong DC then there is no problem to have a big dimention rover.

I don't know what is the solution if the network disconnected?? Did you have a solution? (But i think if I establish the connection befor let the robot go away then the robot may not disconnected I don't know, Do you have any better idea?)

Please what is ment by fisher price motor?
And what is the output of GPS and Compass?
And how can I Interface the GPS and Compass to my project (And can I attched the to Velleman I/O Board)?

Thanks In Advanced For Whatever Help

Re: Servo Compact Design Problems!!!
 

John,
I did understand the Vellemen circuit operation. It is a standard input/output interface for computers that allow control and data recording.
I do not have a solution for loss of wireless network. You may need to have software running on the robot that has error checking and switches to an internal program until the network is reconnected.
A Fisher Price motor is one of the motors that is supplied with the Kit of Parts that we build the FIRST robots with.
The data output of a GPS receiver and compass vary with manufacturer. Most should be a serial data stream, either RS422 or USB.
The interface is up to you and the needs of the equipment you purchase. This equipment does not follow any standard and I do not know if what is available for purchase in this country would be available in your country.
The VEX robotic kit that Radio Shack sells, appears to have most of what you would need to build the base and drive around. It has mechanical parts, wheels, motors, and a controller. The chassis looks like it could be at least 50 x 50 cm when you bolt everything together.
I don't have any idea what your budget is. The equipment we are discussing can get very expensive and to ship to your country may be more than you can afford.

Re: Servo Compact Design Problems!!!
 

Thanks alot for your help