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Topic: Need some guidance for a school project. (Read 2 times) previous topic - next topic

cyclegadget

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Anyone have any idea of what motor I should buy?


The type of motor for a 1/10 scale RC vehicle like that one is called 540. 540 refers to the diameter and bolt pattern on the face of the motor. I would get a slow motor if possible because that car could easily be too fast, and make it too hard to operate.

jensPA


Only the manufacture that designed and built the motor is in a position to develop and publish a true datasheet for a specific motor. A given 'shop' may be able to perform their own measurements and give you an estimate of the key motor parameters, but I wouldn't count on it.

Remember, measure twice cut once.

Lefty


Ok, what is stopping the "shop" from linking that data sheet?

jensPA


The type of motor for a 1/10 scale RC vehicle like that one is called 540. 540 refers to the diameter and bolt pattern on the face of the motor. I would get a slow motor if possible because that car could easily be too fast, and make it too hard to operate.


Thank you, good to know. But the question still remains about the current because buying a regularly 540 RC motor would maybe not work I guess, need to much power and maybe too fast?

cyclegadget


  The slowest standard RC car motor that I know of is called "stock" and have 27 turns. Motors with less turns are faster.  10 turn is faster than 13. 13 is faster than 17 etc.  Also the higher turns, the less current required to run the motor.

I can't quote a amperage as I would be guessing. However, the easiest way to slow a motor down and reduce current is to lower the voltage. You can easily run a 540 motor on 4.8 volts. As a matter of fact smaller lighter cars 1/12 scale, often ran 4.8 volts for their races.

The slowest 540 that I know of without a gearbox attached to it would be a Mitsubishi 540 motor. It looks like the silver colored one part way down this page. http://www.modelersite.com/Dic2010/Thebest/English/Abarth_Eng.htm

Grumpy_Mike

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Ok, what is stopping the "shop" from linking that data sheet?

They are a shop, they are not engineeres. They probbly have no idea who made the motor they probbly just got a batch from a box shifter in China. It is a less than ideal world out there.

If you want a good motor with good provenance then go to a proper component supplyer. Mind you, you pay for it.

jensPA

#20
Feb 03, 2012, 06:25 pm Last Edit: Feb 03, 2012, 06:37 pm by jensPA Reason: 1
Ok.

I found the old original motor and did a little testing today. At about minimum voltage 6 V its current was about 1.1 A when spinning free and 2.3 A when stalled. But I also looked at other motor drivers today and found this http://www.pololu.com/catalog/product/1212

That should be enough, but my question is what is the difference in difficulty between the Ardumoto and this one? The description talks about many things I don't really understand, what would be the practical difference between this one and the Ardumoto?

Another question I just thought of would be if the motor in some way would interrupt the compass, anyone know?

Edit: I also got a mail from Traxxas today and the current stall specs. were secret, but I guess if I need a new motor should be looking in some better supplyer like Elfa here in Europe.

cyclegadget


The link you gave is a 2 channel motor control. It is more complex then you need and would take more programming skill to use it. I don't think it is the best choice for you.

You could use an electronic speed control "ESC" with reverse designed for remote control cars. The operate with the same pulses that servos do. It will simplify the code and it will easily handle the motor for your car.

Traxxas uses a motor made by someone else. For what they use it for, they are not concerned with precise amperage. They make their parts good enough to withstand much more than required.

I started to look for an ESC for you but, brush motor ESCs are harder to find than I expected. I am sure they are out there but, it will take some looking.

jensPA



The link you gave is a 2 channel motor control. It is more complex then you need and would take more programming skill to use it. I don't think it is the best choice for you.

You could use an electronic speed control "ESC" with reverse designed for remote control cars. The operate with the same pulses that servos do. It will simplify the code and it will easily handle the motor for your car.

Traxxas uses a motor made by someone else. For what they use it for, they are not concerned with precise amperage. They make their parts good enough to withstand much more than required.

I started to look for an ESC for you but, brush motor ESCs are harder to find than I expected. I am sure they are out there but, it will take some looking.


Ok, thanks.

The only affordable ones I can find is these two http://www.dealextreme.com/p/waterproof-marine-esc-electric-speed-controller-for-r-c-model-boats-50a-15759
http://www.ebay.com.au/itm/ESC-20A-Brushed-Reverse-Motor-Speed-Controller-1-16-1-18-CAR-Boat-BRAKE-OFF-/160704614055?pt=Radio_Control_Parts_Accessories&hash=item256abdcea7#ht_2000wt_905

Unfortunately they ship from Asia, but I guess I have to wait.

cyclegadget


Out of the two you have this one seems to be the better one. http://www.dealextreme.com/p/waterproof-marine-esc-electric-speed-controller-for-r-c-model-boats-50a-15759

It also has "integrated Battery Eliminator Cirsuit (BEC)"  5V/1A .... it might be good enough to power your Arduino from. That part would have to be checked and tested. If so, you will only need one battery on the car.

jensPA

I have now received my Uno and a IR sensor, this one http://www.sparkfun.com/products/242, and now I have a simple question. It works rather well, goes from 3 V to 0.8 V in its range 10 cm to 80 cm and even further maybe 110 cm, but then when nothing is in front of it it goes to 1.5 V. Is this normal?

Thanks again for all the great answers.

cyclegadget


According to the graph picture in your sparkfun link, the voltage should go to minimum with nothing in front of the sensor.

Maybe, you are getting interference from something else? Maybe you need some blinders "shields" between the sensor and beam output.

jensPA



According to the graph picture in your sparkfun link, the voltage should go to minimum with nothing in front of the sensor.

Maybe, you are getting interference from something else? Maybe you need some blinders "shields" between the sensor and beam output.


You mean I would get some interference from distracting light, I could try it in another room. I read the datasheet before and it said something about getting a by-pass capacitor of 10?F or more
between Vcc and GND near this product. Could that be the problem?

cyclegadget

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You mean I would get some interference from distracting light, I could try it in another room.


Yes, that is what I was trying to say. IR light from other sources could be causing the problem.



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I read the datasheet before and it said something about getting a by-pass capacitor of 10?F or more
between Vcc and GND near this product. Could that be the problem?


Adding the capacitor would at least eliminate that possibility. It is hard to say if that is the cause or not.

jensPA

#28
Feb 10, 2012, 07:44 pm Last Edit: Feb 10, 2012, 08:05 pm by jensPA Reason: 1

Adding the capacitor would at least eliminate that possibility. It is hard to say if that is the cause or not.


I have only a 100 mikroF home, you think that would work?

Edit: I switched room and it worked, once again thanks. Maybe it would be a good idea to build some sort of shield to minimize the distraction s you pointed out.

cyclegadget


It will still help. The smaller 10uf works better for high frequencies than the 100uf but, I would use the 100uf it that is all you have.

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