Hey there. I'm having a look at getting into this robot wars-style of robot building, and am wondering about the radio control. From a practicality point of view, is it possible to build a radio transmitter / receiver yourself that will not experience interference when amongst other radio controllers at a competition? I suppose what i'm asking is whether there is any way to escape the cost of buying a radio controller.

 

In a word no...
You dont state where you are..soo, in the States you have the FCC, in the UK there is another governing body similar....in Europe..well you got Brussels!

You would need to get type approval for your gear which aint cheap!!

Go buy some its easier...I fly R/C planes buying radio gear hurts the pocket but you just gotta do it...

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Eccentric millionaire financed by 'er indoors

 

I have looked into this and found the same as above. I'm getting into buying cheap radio controll sets, escpecially ones that are missing something simple like the battery pack, the serovs or the crystal, on ebay, garage sales, flea markets and the like. You have all the regulatory stuff taken care of as long as you don't modify it in a way that changes its power, or add a non approved crystal or otherwise modify the band it uses. And if you could have built your own you can certainly repair one. Just beware of older ones that are no longer legal, even ones made for your country might only be for the laws at the time they were made. Though I did make a very nice controller with the guts of a newer controller with broken knobs, and the casing of a nice brass finish and wood sided old unit that had unusable insides. Another possible option is one of these: Low cost Tx/Rx I threw one in my june bug order cause its cheap enough that i was sure I could learn something from it, and it can indeed send a on off signal, I haven't yet investigated its serial communication capabilities, but it looks like it could do some stuff for only $5, it is probablly sort of limited too. I was actually thinking of making a thread to investigate the possible uses of such a cheap device.

 

One more thing...Are you versed in the design of VHF equipment?

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Eccentric millionaire financed by 'er indoors

 

Just buy one of the Futaba FAAST or Spektrum 2.4GHz transmitters. THose do not intefere with each other because of the 2.4GHz Spread SPectrum Protocals required for devices operating on that band.

It is NOT cheapter to build one yourself. You're going up against economies of scale for a mass production product.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

it does however look like I'll be able to build a DC motor controller that works with a futaba reciver for cheaper than they sell those. But thats less common, and so less effected by economy of scale than RC transmitters since its just one of many accessories they sell for those.

 

Brushed motor controller? It's possible, but don't forget the cost of the PCB. You're still trying to beat mass production methods though so it's likely there's one out there that costs less. Brushed or brushless? What voltage and current do you need? Do you need reversibility? And what price are you trying to beat? Is there anything special you are looking for in the motor controller?

The two big problems about a radio are the radio part and the mechanical part (joysticks and casing and everything).

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

Yeah, the cost of all the mechanical parts also makes buying a controller, even one that needs repair, a bit easier.

My plan is for a brushed, variable speed pwm, reversable motor controller, that reads the signal from two ports of a normal futaba or traxxas type of transmitter, which is also pwm, and controlls two motors, for skid steering. But I won't go into too much detail about that cause it already has its own thread. As for the cost issue which is relavent here; I'll be using a L298 h-bridge chip (about $3) and a 18F1320 ($5ish), besides that all that is needed is a few resistors and small caps, a dip switch, a trimmer pot and a power regulator (total about $4) and a small perf board ($2), even rounding up to include solder and stuff thats under $20 for a customizable device, and I use the trimmer pot to make it so you can adjust the relative speeds of the tracks to account for mechanical variables and make it drive straight when you push stright up on both sticks. I've seen bi-directional controllers for as low as $8, but I would need two of them and I dont think thos cheapos are very adjustable or handle 4A. But anyway people get into electronics when customizing your own thing is worth more to them than saving time and money. And to be fair, I am using some economy of scale because im buying a premade motor controller chip to take care of 90% of what Im doing. I'm not just arguing to try to be right though, if you know of some speed controllers that could do this for cheaper, well it would deflate my project, but it would be good to know about.

 

4A is pretty low. No RC ground vehicles that I know of use that level of current. Planes yeah, but plane controllers are not reversible.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

R/C planes use more than 4 amps....Trust me I know...I fly them..

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Eccentric millionaire financed by 'er indoors

 

THe smallest ones can use around 6A and a 6A controller would be reasonable to use for 4A. 10A and up...not so much.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

the motors I'm using actually draw no more than 3.2A even stalled, so its working well for me. I'm not sure what a typical RC race car motor draws.

 

Oh....I stand corrected...
after flying for more than 25 years it seems I know nothing about electric flight either indoors or outside........What have I missed...?

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Eccentric millionaire financed by 'er indoors

 

There are large electric helicopters now and the smallest electric planes are foam, motorized kites or plastic wrap.

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Tanaka Sensei (avatar) says: Please spell it "ridiculous" correctly! Not "rediculous". ^^

 

I don't think he was trying to belittle your expierience Chippie, but they do make some very tiny cheap RC aircraft these days.