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Radio controlled...

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chris414

New Member
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.
 

Chippie

Member
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...
 

Triode

Active Member
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.
 

Chippie

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

dknguyen

Well-Known Member
Most Helpful Member
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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Triode

Active Member
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.
 

dknguyen

Well-Known Member
Most Helpful Member
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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Triode

Active Member
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.
 
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dknguyen

Well-Known Member
Most Helpful Member
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.
 

Chippie

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

dknguyen

Well-Known Member
Most Helpful Member
R/C planes use more than 4 amps....Trust me I know...I fly them..
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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Triode

Active Member
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.
 

Chippie

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

Well-Known Member
Most Helpful Member
There are large electric helicopters now and the smallest electric planes are foam, motorized kites or plastic wrap.
 
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Triode

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

Chippie

Member
I don't think he was trying to belittle your expierience Chippie, but they do make some very tiny cheap RC aircraft these days.
Yeah I know...I wasnt trying to turn this into a pi$$ing contest... :)

I'm feeling a little mischievous at the moment( dunno why must be my medication again...) I have a little indoor heli that weight less than an ounce and the motors are ever so small its unbelievable.....
 

adrianm

New Member
Is bluetooth an option?
I'm mainly asking for myself, because I was thinking about a remote controlled robot with a camera. The idea is to connect the motors and the camera (maybe a simple USB webcam) to a microcontroller or FPGA which in turn is connected to a bluetooth IC.
For the remote, a PC or laptop (maybe even a phone) with a client that takes user input and displays the image from the webcam.

(the only reason I'm thinking of bluetooth is that I need a way to transmit the video back)

P.S: I posted here because I think my question is related, but if you think otherwise, I'd be happy to start a new thread or ask a moderator to split the topic)
 

ronp849

New Member
I think the original post was about building robots for home use and not for commercial sale. If this is the case then any homemade system does not need CE approval and 2.4GHz systems are open for non licence holders. This is provided the power is kept below the regulation limits. With a System on a Chip, (SOC) device the output power can be set by software. The device I was thinking of is the CYRF6936 which has transmit and receive capability - so no problem with data coming back from the robot.
 

thomasPlam

Member
Default

hi guys,
am planing to make one rc helicopter as ma final year project. i would like to know about the calculation for the blades,its length etc. am planing to make one like in the site Proxflyer frontpage. plz give me your opinions .

regards
thomasplam
 
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