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Tracker III radio issues

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Tracker III radio issues

Postby flying jeep » Sat Dec 31, 2011 9:56 am

I searched this forum for info on the Tracker III radio and all I found some very dated threads. I asked for help on this radio on the "General" forum with little response, maybe this is the better place to ask for help. I'm building the Revell Gato with Caswell's driver and servos. Everything looks great so far. The servos all seem a bit nervous. A constant chatter. I got a second receiver for Christmas and it does the same thing. I took the whole rig into the yard, away from the house, and it does the same buzz. I talked to John at Polks Hobby and tried recharging the batteries. I also tried using the gigantic servo included with the radio. It works fine!!! So I started trying all the other spare servos laying around the shop. They all buzz and chatter. I talked to John again and he seems as puzzled as I am. He is sending me some of his servos to try. I don't know what else to try.
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Re: Tracker III radio issues

Postby Pirate » Sat Dec 31, 2011 10:22 pm

Does the setup you got use a Mtronic speed control?
I had installed one of their speed controls on my Ohio. I had a constant chatter I thought was some kind of interference. I tried everything to eliminate interference and nothing worked. Don from Loyalhanna Dockyard told me to plug the speed control's lead to the receiver into a slot not meant for it-seem to remember it went into slot 7 or 8 meant for the power input. Once I did this the chatter stopped. This means you lose one of your other channels, but it worked for me. I ended up swapping out the Mtronics speed control for a new one that didn't have the same problem-- luckily.
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Re: Tracker III radio issues

Postby Ramius-II » Sun Jan 01, 2012 3:00 pm

Hi Pirate!
Typically chatter and jitter are caused by other digital signals getting onto either the power buss or the signal lines to the servos (typically the white wire on the servo leads). It can also be a function of the amount of current (amps) available from the power source. In the case of a power source problem basically the servo motor is told to move and at this exact instant it draws a large amount of "power" to start the motor turning. Power is equal to E x I or the voltage times the current. If there is not enough current available then the voltage drops. There are several ways to deal with this and one of the ways is to add a large value capacitor such as a 100,000 mfd across the power. The capacitor will charge and should keep the voltage up long enough for the motor to start and draw less current. While this next part may seem strange and confusing, adding small value capacitors such as a 1 mfd tantilum, .1 mfd ceramic, and .01 mfd ceramic will effectively short out high frequency noise problems. The biggest problem in trying to trouble shoot such a problem is that test equipment is necessary such as a voltmeter and even better an oscilloscope to look at things. The voltmeter will give you a clue as to the voltage while a scope will respond quicker to and also show "noise". My best guess is the since you are using "rechargeable" batteries the problem is the use of rechargeables as rechargables have slightly less voltage than non-rechargeable and often supply less current than other types of batteries. You may wish to try another battery pack with fresh Alkaline batteries. If this works then look at the current rating of your rechargeables they should be at least 900 mAh. Hope this give gives you a start.

Best, Ed
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Re: Tracker III radio issues

Postby flying jeep » Sun Jan 01, 2012 3:56 pm

Thanks Ed. Most of that went right the heck over my head, but one thing does stand out. John at Polks hobby told me to charge the heck out of the receiver battery. And I seem to get the same amount of "buzz" whether on the speed control BEC or the supplied nicad pack. So it could be a battery voltage problem. But what I don't understand is why one servo would work fine and all my other sevos buzz.
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Re: Tracker III radio issues

Postby Ramius-II » Sun Jan 01, 2012 4:35 pm

Hi Jay,
Sorry I did not mean to be so "technical" and it is difficult to write not knowing how much someone knows or does not know. Write too simple and you may insult the person, write too technical and you confuse the person. Basically servos wish to always see +5 volts DC. When the motor in servo is told to start turning for an instant it wishes a BIG amount of current (amps). When the batteries are asked for more current than they have available they sacrifice the voltage to supply the current as there is only so much power available. So your +5 volts now become something like +2.5 Volts which is not enough. At 2.5 volts things start to become "spritual" (technical term) meaning that sometimes they work and sometimes they do not. Rechargable batteries only produce 1.2 volts per battery and not the 1.5 volts as an alkaline battery will give. So 4 rechargables will only give a total of 4.8 volts while 4 alkalines will give 6.0 volts. What I was suggesting was adding a large value capacitor as temporary "storage" to overcome the initial request for more power. You can buy simple a simple volt meter for arround $10.00 and it is a worthwhile investment.

There are all kinds of devices connected to a receiver than can generate a "signal" telling the servo what to do and typically these signals will appear on the power. Some servos are just more sensitive to these signals. Your best bet is to only connect one servo at a time and see if it responds normally. Then start adding other devices until that which was working correctly stops working correctly. If you have ever watched an old movie about ships like the Titanic you will probably remember the radio transmitter that was used which produced a big "spark". Most motor produce sparks as I am certain you have probably seen. This means most motors are miniture "transmitters" and these sparks can be part of the command being sent to the servo. Each servo contains a motor so a servo can produce an unwanted signal that is send down the power then back to the servo via the "command" wire. This is why the second part of what I was writting were ways to deal with the sparks or what is often called "noise".

Aside from the above, another technique that often helps is to twist the servo wire together as tighly as possible. My main guess is that you are having a problem with the power. BEC are great and again, require capacitors on thier outputs. The way a BEC works is by switching on and off the power at a very fast rate and thus can produce an unwanted "signal" unless a capacitor is used to filter the signal. Most places that sell BEC's also sell the capacitors as an "add-on".

Maybe this will also assit in understanding everything. You have AC (alternating current) and DC (direct current). Your receiver and servos and all only wish as pure a DC as possible. A capacitor electrically acts as a "short" to any AC without causing any adverse effects.

Again I hope all this assist you and will cure the problem.

Best, Ed
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Re: Tracker III radio issues

Postby Pirate » Sun Jan 01, 2012 5:50 pm

And Ed, you told me all of this when I had this problem with my Ohio, and I tried all kinds of grounding and interference techniques you suggested to alleviate the issue, but it still chattered until I plugged the Mtronic speed control into a different slot on the receiver.

All I'm saying is could be the problem and it only takes two seconds to switch the plug and find out. Sure beats spending weeks insulating, wrapping, twisting and shielding everything in sight to no avail.

This was my experience chasing down a ghost in my system. Thanks to Don at Loyalhanna Dockyard with this strange occurrence with the Mtronics speed controls or I never would have found it.
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Re: Tracker III radio issues

Postby Ramius-II » Sun Jan 01, 2012 7:35 pm

Yes you are probably correct and keep in mind that a speed controller works by "pulsing" the power to the motors off and on thus it is producing "pulses" that travel down the power wires and can affect a servo. Depending upon the design of the receiver, changing which output from the receiver drives the speed control could easily isolate the speed control from the servos. Aside from the use of capacitors, diodes could also be used but again I have been trying to keep everything as simple as possible. The use of relays can also cause big problems and if you look at most typical connections to a relay you will see a diode across the coil.

Best, Ed
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Re: Tracker III radio issues

Postby flying jeep » Mon Jan 02, 2012 11:37 am

Thanks, Guys. I'll try putting power into a different channel. I've tried three (speed control BEC) and I've tried six (battery) so far. Adding one servo at a time does not work as the first servo I plug in chatters. The only one that works well is the humugo standard size servo that came with the radio. I wish there was a way to post a short video so you can see what this thing does.
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Re: Tracker III radio issues

Postby Ramius-II » Mon Jan 02, 2012 11:54 am

Hi Jay,
One suggestion may be to take everything you have, put it in a box and take it to your local hobby shop where they can do things like try a different receiver.

Best, Ed
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Re: Tracker III radio issues

Postby JWLaRue » Mon Jan 02, 2012 12:10 pm

Jay,

Are you located near Carmel? You could also try to arrange some time with some of the SubRon6 / Indy Admirals folks. Having another pair of eyes on the problem is often useful.

-Jeff
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Re: Tracker III radio issues

Postby flying jeep » Mon Jan 02, 2012 5:12 pm

Ramius-II wrote:Hi Jay,
One suggestion may be to take everything you have, put it in a box and take it to your local hobby shop where they can do things like try a different receiver.

Best, Ed



My wife gave me another receiver for my "target" tug. It does the same thing, maybe worse. Good idea though!
Jay
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Re: Tracker III radio issues

Postby flying jeep » Mon Jan 02, 2012 5:14 pm

JWLaRue wrote:Jay,

Are you located near Carmel? You could also try to arrange some time with some of the SubRon6 / Indy Admirals folks. Having another pair of eyes on the problem is often useful.

-Jeff


You know what? I've put off joining the admirals long enough, I need to get off my butt and do it. Probably not much going on this time of year in Indy though. And I still have not figured out how you join the local Subron group.
Jay
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Re: Tracker III radio issues

Postby Ramius-II » Mon Jan 02, 2012 6:44 pm

Hi Jay,
How about if we start from the beginning? First the receiver needs to be powered only by an Alkaline battery pack with fresh batteries, no NiCad’s or BEC. It truly would be helpful to beg, borrow, or steal a volt meter to make sure you have the necessary voltage of at least 4.5 volts dc and that this voltage does not change when the servo is being operated. Then plug in only one of the servo’s that chatters and see if it chatters. If it does then this would indicate a bad servo. Here is a link that explains a servo: http://www.seattlerobotics.org/guide/servos.html Chatter can be caused by the servo trying to find the correct angle for the output shaft. If the internal “pot” (referenced in the article on servos) is dirty, for example, then it will never find the correct angle and will keep looking for it. The reason for recommending a straight Alkaline battery pack and a volt meter is to eliminate any other possible problems from other devices trying to tell the servo to change and to make certain you have the necessary power to drive the servo. Again I hope this helps.

Best, Ed
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Re: Tracker III radio issues

Postby flying jeep » Tue Jan 03, 2012 7:16 pm

Thanks Ed,

Yes, I have a very nice Fluke digital meter. I found it laying in the middle of the road! I sent away for a new LCD display and fixed it my self. I'll have to look in the junk box for a battery holder. I just may have one, gotta look. Don't you think that it's strange that ALL my servos in the shop are buzzing except the one that came with the radio? I just remembered that my Tamia Tiger Tank is 72mhz as well. I think I can tell the receiver to go to the same channel and try the other transmitter. I'll go charge it up and let everyone know later tonight.

Jay
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Re: Tracker III radio issues

Postby JWLaRue » Tue Jan 03, 2012 8:16 pm

flying jeep wrote:You know what? I've put off joining the admirals long enough, I need to get off my butt and do it. Probably not much going on this time of year in Indy though. And I still have not figured out how you join the local Subron group.

Send Chris Campbell a PM. He can be reached here as "admiral commander". Chris is tied into both the Indy Admirals and SubRon5 so can get you the details for joining both.

-Jeff
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