Robot Control

[Matt]

I need to conrol my robot using rf signal. Does anyone know of any schematics of the tansmittter and reciever? If not, what do you have to control your bot and where did you get it?

[hlreed]

Matt, I would use model airplane type radios and receivers. They are relatively cheap, common and available. The receivers run servos directly, so it is fairly easy to do steering.

[JDerr32]

I agree that RC radios-n-receivers are the way to go - quick w/o hassles. When shopping for a radio, you may want to plan ahead for other functions such as implements or weapons. I only needed two channels for tank-style steering, but opted for a four channel HITEC FM radio (75 Mhz). <p>I am finishing my senior design project, a lawnbot. It uses two motors in the rear (one left, one right) and a separate 24 VDC electric motor for the grass cutter. For safety sake, I am using the third radio channel for engaging the grass cutter motor via a control card from Diverse Electronics Services (www.diverseelectronicservices.com) that houses a TYCO relay, instead of simply turning the cutter on with a toggle switch. <p>I worked for a lawnmower company and did projectile testing and know that I DO NOT WANT TO APPROACH THE BOT IN THE GRAVEL DRIVEWAY IF IT SHOULD RUN AWAY AND TRY TO TURN THE SWITCH OFF WITH IT THROWING GRAVEL!! HA HA. <p>So I would buy a little more radio than u need now so you don't wind up with a box full of xtras because they are limited. I think I paid $110, but you can buy simple 2-channel pistol types for around $50 and some four channels run under $100. Check out Diverse Elec's website for motor controllers (really robust). Carl is a great guy to do business with.

[josmith]

Airplane control radios come on 72mhz. For ground control you are required to use 75 mhz which usually has to be special ordered or converted.

[hlreed]

Is some cop going to get you because your robot "airplane" does not fly?

[Matt]

The FCC will be after you. Local HAMs would track the interferance to your location and the FCC would be knocking on your door with a fine.

[chessman]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Matt:
The FCC will be after you. Local HAMs would track the interferance to your location and the FCC would be knocking on your door with a fine.<hr></blockquote><p>I highly doubt that.<p>The radio systems are used so commonly that the interference is all over...I'm sure the HAMs are used to it by now.<p>If you're worried about it still, you can get an "Experimental Radio License" for $50 from the FCC that will allow you to conduct any type of radio transmission you want on any declared frequency. I was going to get myself one of them, but I didn't feel like that license was worth my $50 (I have car payments!!!)

[hlreed]

You can buy a model airplane radio at any hobby store. I have done that and used for experiments in a rotary wing monstrosity I made once. There is a model airplane field here that is devoted to radio control. They all have assigned frequencies so many can be in the air at one time.
If you are alone, it makes no difference if it is a robot or airplane, since you are the only one doing it.
If you are making a tele robot, this is the best way to go.

[Matt]

I'm not saying its likely that the fcc will be after you, but it CAN happen. I'm not worried, just trying to weigh the decisions.

[desterline]

There's a big field connected to my back yard. Sometimes I take my airplane out there and fly it (on 72Mhz), sometimes I take my RC car out and run it (on 75Mhz). Same field, same wattage, what's the difference? I don't see one.<p>Denny

[Rodney]

Unless you have very deep pockets and lots of spare money, do not, REPEAT do not use an aircraft frequency, use the ground frequency. The cost is the same but; if you shoot down one of those bigger planes (cost is upwards of $1000.00) plus any damage the crash might cause will be your responsibility. That is why the guys who fly planes belong to clubs where the freqency can be monitored and controlled. If I or another flyer catches you using the 72 MHZ frequency for ground controlled equipment, we will most certainly make sure the FCC is notified.

[chessman]

if you're so worried, they make aircraft radios on CB frequency<p>Oh yah, I'm sure anything you build, or I build, will go over with the FCC real well <p>You could get the experimental radio license that I talked about....$50.<p>[ June 26, 2003: Message edited by: chessman ]</p>

[rionredinger]

AND just what is the FCC gonna do about using a frequency for testing? and why not use a R/C car controller? It does about the same thing and with a little bit of programming it can be made to do pretty much anything. I say use the car frequency so you can avoid the thought of the FCC or any R/C pilot jumping on your back. Just a thought.<p>Oh one more thing, lets keepit to about 20 decibels in here ok.
Thnx,
Tux

[Matt]

The FCC has laws on what fequences can be used for. Its like transmiting on your local police frequency. You can't just pick and choose what frequency you want to use. Visit www.fcc.gov to see what will happen if you transmit on the wrong frequency. I really don't care if I use an airplane frequency for the ground, but I am telling what COULD happen, not what probably will.<p>[ June 28, 2003: Message edited by: Matt ]</p>

[davee]

Why take the chance? First off, it is a federal offense to broadcast illegally. This comes with a hefty $25,000 fine.<p>Second, an airplane flying around 2 or 3 miles away on the same frequency could crash as a result of this 'deliberate' interference and I'm sure you don't want that! This is why they seperated the frequencies in the first place.<p>Third, most radios used for aircraft RC can be retuned to the ground vehicle variety by switching the crystals they use to tune to a specific frequency. Worst case scenario is the radio will have to be adjusted to work in the other band. This usally involves the use of some test equipment and a screwdriver.<p>As for whther or not you will ever be caught, thousands of HAMS do spend an inordimate amount of time tracking things down, just for the fun of it. We have equipment that can pinpoint a transmission in just under 3 seconds. They are wonderful for putting jammers out of business. Just one complaint to the FCC could result in somebody beginning the process.<p>Why risk it when you can be legit. Also if you want to just control the device via simple RC, a simple radio is fine. If you want to have some real fun a digital setup is what you'll need. 802.11 comes to mind but there are hundreds of solutions available.<p>[ June 30, 2003: Message edited by: davee ]</p>