Controller question

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101

Aah, if you want your robot to walk, not just dance in place, it’s going to need some knees! You can add another set of servo motors to control them, or if you’re happy with the robot just walking forward and turning you can make some passive (not motor-controlled) knees by cutting the legs in half, then taping them back together on one side with something like electrical tape, so that they only bend one way. I think you’re going to need another support, in addition to your trailing wheel to support the robot while it’s moving its legs, at least to start.

That line-following robot project you link to looks like a great beginner project, go for it!

And please feel free to use any of the code I’ve posted for any of your projects. It’s been made totally public by putting it on this forum, and I probably copied large parts of it from someone else’s code to begin with.

Good luck in the contest!

-Adam

102

Hi again!

I just tought of a cool project so i wanna ask you some questions.

The idea was to make a small motorised vehicle. The plan was that it would be RC, and that i could sit in it, and drive around (im not hoping for many miles pr hour :P)
Im guessing the weight will be around 80 kilos all together.

So i found some products that i tought might be usable on this site:
http://www.trossenrobotics.com/store/c/2666-DC-Motor-Controllers.aspx
I looked at the RC ones with 10A.

And perhaps a strong motor from this site:
http://www.trossenrobotics.com/store/c/3086-BaneBots.aspx

A question as well, i know a motor controller is needed for this project, but if u buy a RC motor controller do you still need a servo controller? Couse if im not wrong isent the servo controller/microcontroller to handle code signals, which will not be needed for a RC project?

I know there is some math to take in mind, about torque, weight and stuff. But if you’d just tell me if this plan is able to go through without buying too expensive parts (50-80 is an ok price if needed)

Im not very familier with the taking in mind how many Amps needed for this project, so i tough you might be able to help me with this :wink:

Btw: Motors are the best choice for this i guess? Not servos :question:

-Thanx

103

You’re correct that DC motors (rather than servo motors) would be the right choice for a vehicle large enough to carry you, since you’re going to want the wheels to spin continuously, and with more power than you can get out of any hobby servo. Also, what kind of control signal you need to generate (servo pulses or otherwise) depends entirely on your motor controller.

Some of the stronger motors on this page look like they would be able to drag a person around…slowly. Used or surplus power wheelchair motors are popular because they usually have integrated gear-heads and supported output shafts so you can just mount them and stick on a wheel. You can also look at retrofitting electric scooters or skateboards, which should have built-in motor controllers. You’ll need some serious batteries to power all of this, probably sealed lead-acid.

Of course the most important thing in a project like this would be safety. You would be dealing with powerful motors and large batteries, plus a massive and powerful vehicle that could do some real damage. You would definately want to design in some fale-safe systems so it couldn’t go bonkers if it lost your remote control signal.

I don’t want to talk you out of trying, I guess I’m just saying you should be careful!

-Adam

104

[quote=“nexisnet”]

I don’t want to talk you out of trying, I guess I’m just saying you should be careful!

-Adam[/quote]

Well i dont know if its even worth trying this, it will probably be a expensive project and the speed, as you said, would be very limited. I just want to do a cool project, something to use for something cool, not just a robot that can run around on the floor and avoid walls. Still trying to find new ideas :wink:

It also may be smart to do some basic projects first, to build up a bit more knowledge.

105

Hi again! 

About the electrical vehicle idea.

I’ve listed links to different products; it would be nice if you’d give me some feedback on if you think this torque/rpm is enough to move me for more then 3 km/h :P.

Motor: goldenmotor.com/ >Printed motor

(I tought about the PM-12E)

Battery: trossenrobotics.com/store/p/ … -Zeus.aspx
Or trossenrobotics.com/store/p/ … -Pack.aspx

I also have a CAD of how the vehicle hopefully will look:

http://s173.photobucket.com/albums/w60/sotu_maskot/?action=view&current=vehicle.jpg

I just want to know if this torque and power is enough to possibly drive me.

If you have any parts better qualified for this job then those i listed, plz name them.

106

Those motors look pretty nice, and so does your CAD drawing. The PM-12E could probably pull you faster than 3km/h.

The NiMH battery pack you link to doesn’t really have much capacity, and can only safely output 5 amps, not enough for those pancake motors. Sealed Lead Acid batteries are relatively cheap and can handle a lot of current, but they are quite heavy. Small battery powered vehicles are going more and more with Lithium Ion battery packs these days, which are quite light. They’ve been coming down in price recently, but they’re still quite expensive.

Did you see that the website you found those motors on also sells battery packs and motor controllers? Well, they sell power scooters too, but what fun is that?

-Adam

P.S. I haven’t had a chance to play with Google SketchUp yet, what do you think of it? Are you using the free version?

107

Mostly i need a battery pack which is as small as possible. And i can only see batteries providing 24 or more voltage, and i cant run 24 volt on a 12 volts motor without it ending in meltdown can i :S?

Yes i do use the free version. Its brilliant!
So easy to use for the amateurs and can still be used by the pro’s, all depending on how much time you use in your project. Still i haven’t learned everything, but i know the basic of how to build structures, and its the best CAD software i have tried.

Did you see any price listed on the motors?

Edit: Ive updated the the vehicle to how it will look (the foot steps indicates where to stand): http://s173.photobucket.com/albums/w60/sotu_maskot/?action=view&current=vehicle2.jpg

Btw, how many amps is needed to drive that motor we agreed on, you think one of theese will do?

V Ah Mål mm (lxbxh) Vekt Tilkopling Art. Art nr Pris Antall
(Til tilkobling F1 passer flatstifthylse 35-758 om kabelen er 2,5 mm², og 35-761 om kabelen er 4 mm².)
6 4,5 70 x 47 x 101 0,91 kg F1 (4,75 mm) 80-402 74,90 kr
6 12 151 x 50 x 94 2,25 kg F1 (4,75 mm) 80-404 169,00 kr
12 1,2 97 x 43 x 53 0,6 kg F1 (4,75 mm) 80-405 84,90 kr
12 4,5 90 x 70 x 101 1,8 kg F1 (4,75 mm) 80-409 129,00 kr
12 7,2 151 x 65 x 94 2,7 kg F1 (4,75 mm) 80-410 179,00 kr
12 10 151 x 65 x 112 3,3 kg F1 (4,75 mm) 80-411 229,00 kr
12 12 151 x 99 x 95 4,3 kg F1 (4,75 mm) 80-412 269,00 kr
12 18 181 x 76 x 167 6,3 kg F3 (for M 5) 80-413 449,00 kr

Sorry for the text (norwegian)
-Sotu

108

You’re right, you should not run a 12V rated motor at 24V, as this will damage or destroy the motor. You don’t have to limit yourself to 12V motors though, motors made to run at higher voltages tend to be more energy efficient, and there are higher voltage battery packs.

Your drawing still looks good, but I think the design was a little better as a tricycle. You’re going to have trouble keeping that wide thin front axle from bending, and by turning the axle rather than individual wheels it’s going to be difficult to steer and tend to skid as you turn.

I’m not sure what those things on your list are (sorry, my Norwegian is a little rusty), but I have an idea for your project. Rather than trying to match up a motor and a battery+charger and a controller, you could get a conversion kit for an electric scooter or skateboard which would have all three bundled together, and would work well together for sure.

-Adam

109

OK, sorry for making those numbers and all so difficult, all i want to know is how many Ah is needed for that motor? Or does the Ah only decide how long the battery will last? Xampl, how long will that PM-12E motor last with:
Power(W)
160
Voltage(Vdc)
12
Current(A)
18

With theese Ah’s:
1,2
4,5
7,2
10
12
18

And what you mean by conversion kit? Can you link me to any in my interest :D?

110

Amp*Hours is a rating of how many hours a battery can supply 1amp, so for example, the 18Ah battery should be able to run your 18A motor for 1 hour. The 12Ah battery should run your motor for 40 minutes, and so on. In reality the battery won’t be able to supply power for quite that long, and the battery voltage will drop during this time so (depending on your motor controller setup) your motor power will slowly decrease as well.

I was thinking of a cheap electric skateboard, like this one. It has a small motor, gear-train, wheels, batteries+charger, all just bolted to a plate. I don’t know if this particular one has speed control, or just on/off motor power, but I know some higher end ones have proportional speed controllers. Search around for “electric skateboard” and see what you find.

-Adam

111

Still trying to find a 12/24 volt motor that fits my project, but goldemotor still havent responded, after 2 emails. I looked at the EL skateboard you linked, looks like they dont ship outside the USA tough :frowning:

Let me know if you accidently come over any motors :wink:

-Sotu

112

Im leavin for a class trip to Berlin for 5 days. The result of the robot contest im in, will be decleared the day before i come home. So i just want to say, if you liked my robot, and havent voted for it yet, but would like to support me in this contest, now is the time to vote. Create youreself a user on the http://www.societyofrobots.com/robotforum then go to http://www.societyofrobots.com/robotforum/index.php?topic=4011.0 to vote.

You dont have to if you dont want to, just wanted to tell you before i leave :wink:

Btw, i gave up the electric trisycle idea, not my thing. Instead om on a new robot, an RC one.

113

Good luck in the contest, and have fun in Berlin!

-Aadm

114

Hi again :slight_smile:

Berlin was fun and the contest went quite good :slight_smile:

Just wanted to say i landed on a non price (but mentioned among winners) place in the contest.
Winner had 8 votes, and me and second place had 7. Dont know/why the admin chose him over me when it was a draw but its ok, ill do better in the next upcoming contest. :wink:

115

Im upto a new project :slight_smile:
Im going to develope my skills by creating a servo controller.
Ok, so i’ve read through the job of each component, and im going to list all the components, and why i need them, underneeth. It would be great if you could check them and give me feedback, of whats right and wrong.
The job of the controller will be to control around two servos from the computer.

Components list:

  • A breadboard | to make the circuit on.
  • Resistors | To limit/control the power going through the circuit board.
  • Capacitors | To save up power for immidietly power drains, and to limit noise and such.
  • LED’s | To indicate that the power is on.
  • USB-B | To connect the USB cable to. / or perhaps i should use the paralell port?- ATmega8 AVR microcontroller | To handle the power going through the board, and controlling the code to the right servo, basicly the brain of the board.
  • Power source | Batteries to give power for the microcontroller and servos to work / This might be done through the USB as well?
  • Male break away headers | To connect the servos onto.
  • Voltage regulator? | To control the low power drop out (Is this needed for a small project like this?)

Also, if you would be so kind to check out my knowledge about some pins on the ATmega8.

  • GND - Ground (electricity), would guess this has something to do about the ground input of components and power?
  • VCC -Voltage at the Common Connector, plus power connecter instead of minus (ground)?
  • If i’ve understood right, the ATmega8 has three multi-bit multipurpose I/O ports. PORTB, PORTD and PORTC (Like the microcontroller is devided into different categorys, with different purposes/jobs?)

For this simple task, will all of theese pins be used? :S

That will be it :slight_smile: I really need importent info like this to manage this task. What also would be great (if not to much work) is a drawing where you point out what pins on the ATmega8 the most importent components will be connected to, for example: what pins to connect the power to, the I/O pins (break away header pins) to and so on. or just a drawing where you point out the jobs of the pins with what task they have in a project that im planning.

116

It sounds like you’re on the right track, but a little off on some things. For example, a voltage regulator maintains the constant, correct voltage for your microcontroller, which can be destroyed if the applied voltage is too high. Also, you cannot connect a USB port or a computer serial port (RS-232) directly to an ATMega8 without some sort of level/protocol shifting adapter.

I would suggest you work through the first two SparkFun Beginning Embedded Electronics tutorials:

  1. Background and Power Supply: Will show you how to set up a voltage regulator on a breadboard, using batteries or a DC wall power supply.

  2. How to Get Code Onto a Microcontroller: Deals with setting up a microcontroller (an ATMega8 even) on a breadboard and wiring up power and a programmer.

Once you have that working, you might want to look at the later embedded electronics tutorials.

Good luck!

-Adam