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Giant Robo
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Joined: 17 Jun 2004
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Location: Marayong NSW


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Excellent,,,, Twisted Evil He has the bug! Laughing

Post Sun Jan 02, 2005 5:30 pm 
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dyrodium
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Joined: 24 Aug 2004
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Location: Sydney


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hehe... Yeah Smile
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Post Sun Jan 02, 2005 6:12 pm 
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dyrodium
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Oh also, has anyone used physical speed controlers before? They look like another cheap alternative. Can they reverse?
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Post Tue Jan 04, 2005 3:24 pm 
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dyrodium
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http://www.hobbyco.com.au/product/show_item.php?plu=FA4YF
Is this a good radio?
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Post Tue Jan 04, 2005 3:27 pm 
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Nick
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Joined: 16 Jun 2004
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That radio looks fine and 4 channels is more than enough unless you are trying something really tricky. You might hold off buying a 'stick' radio until you have also tried a wheel radio like http://www.hobbyco.com.au/product/show_item.php?plu=FA3PDF . Most builders develop a strong preference and Glen bought a wheel radio from the US for a really amazing price.

I'm not sure what you mean about physical speed controllers. Do you have a link or description?
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Post Tue Jan 04, 2005 4:02 pm 
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andrew



Joined: 16 Jun 2004
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Location: Castle Hill, Sydney. N.S.W


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by physical u mean servo pishing something.

only thing i have tried r switch controllers and drill speed controller.

the drill speed controllers worked well last time. will let u know net chance i get to use them.
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Post Tue Jan 04, 2005 6:07 pm 
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Nexus
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I think he means the old mechanical speed controlllers found in RC cars. They where just a servo pushing thing but i think that they allowed one or 2 speeds as they acted something like a modified pot.
Most RC esc's are made to replace these units
Dont know about reverse but prob possible
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Post Tue Jan 04, 2005 6:30 pm 
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ffej
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Joined: 22 Jun 2004
Posts: 595
Location: Kurrajong, NSW


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I think he's talking about the ones described on the Onslaught website, team vertex made one of thse for vertex I think, they can explain them much better than I can, so ill leave it to them.
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Post Tue Jan 04, 2005 6:42 pm 
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Knightrous
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Joined: 15 Jun 2004
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Location: NSW


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Andrew built a set of rotary speed controllers for Vertex, they worked okay untill we started using the the B&S motors and then we started having smoky brushes Razz The rotary controllers are very large and i don't see them being too possible in a featherweight unless you went relay reverse and minimised the ramp rate.
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Post Tue Jan 04, 2005 7:32 pm 
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Totaly_Recycled
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Joined: 15 Jun 2004
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I think he was refering more to the Tamia 3 speeds that use resisstors for sped control we have used them at first but they are unreliable and tend to stick on at times as they arent desighned for the higher voltage and currents we use in robots
they do have reverse though

Post Tue Jan 04, 2005 9:34 pm 
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Giant Robo
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Joined: 17 Jun 2004
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Location: Marayong NSW


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Angus, That silver SkySport radio your looking at is the one several of us use and it`s the one I recomended. Iv`e got 2 of em. Nick and Glen probably swear by wheel radios because they are used to them and have IBC`s. but you get used to steering with whatver system you have with practice, so compared with the radio Nick showed, the SkySport is cheaper and has 4 chanels. Then, as you advance in your`e bot designs, you don`t need to buy a better radio, you can have 2 active weapons or a spare chanel for some kind of "special effect"

I`m not knocking the wheelies. you might actually prefer it if you tried, but the SkySport is my own preference.

Cheers,
Jeff.

Post Tue Jan 04, 2005 11:37 pm 
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Big AL
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Joined: 16 Oct 2004
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yeah the mecanical speed controlers do have reverse and i'm looking into modifing resisters to handle the voltages we run them at but iv'e got couple of them in Dragoonnaire and they seem (seem) to be able to handle 9.6 volts.
i just know don't run them at half speed every where or you'll blow the resistor
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Post Wed Jan 05, 2005 12:50 am 
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dyrodium
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Joined: 24 Aug 2004
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Location: Sydney


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So mechanical speed controllers can't handle 12v? You would think they would be unblowable.
This is where I got the idea from;
http://coolrobots.com/builders/topframe.html

Quote:
"If you really want to save money you might have to use a physical speed control. A physical speed controller is essentially a swiper attached to a servo arm. But don't despair! At least you already have some servos that came included in your radio kit. And you will not have to worry about burning out any electronics with a physical system."

You would think they would be like variable resistors attached to the servo arm.

I am going to get the Skysport this weekend. Smile
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Post Thu Jan 06, 2005 3:52 pm 
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ffej
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Joined: 22 Jun 2004
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Location: Kurrajong, NSW


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Variable resistor = bad idea

The current that the motors draw will quickly burn out just about any variable resistor you can buy from dick smith / jaycar. All their talking about there is servo switching.

A better way of servo switching is to pull the servo's apart, keeping the servo and trimpot intact. You then take the output of the servo, and use it to drive the base of a transistor which then drives a relay. This also requires the use of a filtering cap (about 100uf will do) between the resistor base and ground to filter the output of the servo (which is PWM) an extra 12V battery (you can use the main bot battery at 12V if your really skimpy on weight, but its not reccomended) and a 4K7ish pulldown resistor.

Assuming the servo is trimmed to neutral, when you push the stick forward, one side of the servo lead goes positive, the other negative, and when you push it backwards, the opposite happens. If you attach a transistor to the side that goes positive, it will turn on and allow the power to flow from the battery to the relay coil, which is then energized, and the relay allows current to flow through it to the motor.

I can draw you a schematic with exactly how to build a propper bang bang speed controller for your bot ( dual H bridge setup) if you like, or just catch me on msn and ill explain it better there. A plus with this setup is that you dont need a failsafe, as when the servo looses signal, it just turns off, which kills power to the base of the transistor, turning the relay coil power off.

BTW, this is how the controllers on Catalyst and the original version of Singularity worked, except they used hacked up oatley controllers that output the same signal as a servo does.

Theres nothing wrong with servo switching, it works fine, I just hate things that are not solid state when they could be . . .

BTW X2, you might wanna get a V-Tail mixer when you buy that radio, that way you can use one stick to control the bot.
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Post Thu Jan 06, 2005 4:59 pm 
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dyrodium
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Joined: 24 Aug 2004
Posts: 6476
Location: Sydney


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Ok. Got the skysport radio (the sticks are so spiky!). Now, what is the best way to wire up the servos so that you can control the bot with one stick using micro switching, and leaving the other stick for weapons control. BTW, the kit came with 3 servos, so that's how many I have. Very Happy
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Post Fri Jan 07, 2005 6:04 pm 
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