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RC Tank Troubles, please help

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Traxtor

New Member
I'm new here so appropriate greetings to all.

I have made a start on an radio controlled tank project.

After putting it together i have found that at a very short range the motors begin to pulse instead of maintaining a constant speed.
I have witnessed the radio unit perform well at a desired 20-30 meters, although now attached to the tank the pulsing starts at around 4 meters.

I have done a little reading but as yet to no avail.
I am unsure if it is being affected by noise or electromagnetic interference from the motors or whether the power supply to the motors is the problem.

From what i have read, i think the problem could be solved by capacitors.
Can someone please verify this?
Also is there a circuit configuration which would allow the use of capacitors and for the motors to run bidirectional?

Thanks for reading

*I found this image, by my reckoning following it should allow for alternating the polarity and "hopefully" reduce interference. Just hope it solves my problem.
https://media.photobucket.com/image/great%20planes%20motor%20capacitor%20traxxas/suicideneil/otherstuff/solderingcapstomotors.jpg
 
Last edited:

audioguru

Well-Known Member
Most Helpful Member
My electric model airplanes have a 0.1uF ceramic capacitor from each wire to the brushed motor's metal case. The range is about 1km and there is no interference from the motors.
 

Traxtor

New Member
My electric model airplanes have a 0.1uF ceramic capacitor from each wire to the brushed motor's metal case. The range is about 1km and there is no interference from the motors.

That would be a 104 capacitor right?
It's those i was thinking of using.
Meanwhile i have moved the RF unit as far away from the motors as possible. I also placed my batteries between motors and RF unit. There is already an improvement in behaviour at range, can't wait for the caps :)

Cheers
(Sorry for the double post/edit)
 

mneary

New Member
If the motors use the same battery then the receiver could simply be starved as the motor draws the battery voltage lower.

In my experience, separate batteries is the easy way out of this.
 

audioguru

Well-Known Member
Most Helpful Member
Yes, a ceramic capacitor marked "104" is 0.1uF.

My electric model airplanes originally used one 8.4V Ni-MH battery (7 AAA cells) but one flight lasted only 5 minutes. Now I am using one Lithium-Ion battery made from two cells of a laptop's battery (nominally 7.4V) and it provides a lot more power for about 20 minutes per flight. The motor gets very hot and the battery gets hot.
 

Traxtor

New Member
If the motors use the same battery then the receiver could simply be starved as the motor draws the battery voltage lower.

In my experience, separate batteries is the easy way out of this.

The receiver does use the same batteries. There is a notable difference as it distributes the power to both motors in full spin. I was thinking of using seperate batteries but thought that would add a little too much weight to this poject, besides, i'm not very capable in the electronics department (I'm guessing that would require gate switches of somesort??)

I have plans for a another (bigger, better etc) tank project. I would like to implement independent power supplies for the motors but not sure where i'd start. I have 2x nikko evolution sprint motors ready and waiting but am struggling to find gearing to match the 9 tooth bevelled pinions fitted to them.
My next step was going to be fitting my corrugated belts to be driven directly from the motors but that seems a little crude to me.

Audioguru, using laptop batteries? Sounds like an amazing hack. I need a leaf from your book.

Thanks for the help people :)
 

Traxtor

New Member
Can anybody point me in the direction of a circuit diagram displaying the use of transistors as a switch in a situation which allows me to drive motors back and forth.
I am having difficulty understanding how to implement independent power supplies for my motors. (e.g how to allow the use of transistors in a situation where the polarity is reversible)

The RF unit i am using acts as 2 DPDT switches, I would like for this to switch the transistors, allowing a larger 6v supply to drive the motors. This appears to me to be pretty simple if driving the motors in one direction, my problems start when trying to complete a circuit in both directions as the transistors won't allow for the current to travel in the opposite direction when it is reversed and + becomes -.
I imagine i would need 4 transistors (1 for each wire from the RF unit)

I hope this is understandable as i am obviously fairly confused about it.
I appologise for my ignorance in advance. Any help would be appreciated.
 
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