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understanding an RC toy mainboard

Discussion in 'General Electronics Discussion' started by Jean Perret, Jan 3, 2013.

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  1. Jean Perret

    Jean Perret

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    Jan 3, 2013
    Hi all,

    I am trying to understand how a toy RC mainboard is made as I am in the process of boosting the speed of a toy grade RC New Bright 9.6V , 380 motor.

    My first step is to put a stronger battery with higher mah, about 2000mah NIMH instead of the standard 600mah NICD same voltage.

    Second change the motor to a better brushed 380 motor.

    Problem: Everyone is saying the mainboard will fry.. But then I would like to understanf WHAT will fry, is there a specific electronic part I need to change ( mofset? transistor?) or every single part of the mainboard would fry??? I would like someone to explain me what are the different parts of a toy grade RC their role and power limits etc..then can I put a small computer fan on the mainboard to cool it down enouph ??



    Thank you so much!
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    hi ya Jean
    welcome to the forums and a Happy New Year

    NO, you wont fry the circuit board if the battery voltage is rated the same
    going from 600 mAh to 2000 mAh will just give you a longer use time before the battery goes flat

    It wont make anything go any faster either ... ie. the original motor

    Improving the motor is the easiest of choices to initially try
    for that I couldnt give any recommendations, it may take some experimentation with motors of the same voltage but maybe higher RPM etc

    Dave
     
  3. BobK

    BobK

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    Jan 5, 2010
    Also note that going from a 600maH NiCd to a 2000 maH NiMH might even make it ruin slower! NiMH is not as good as NiCd at high current draws. Given the higher capacity, it probably will run the same or better, but if the capacity of the two batteries was the same, the NiCd would most likely run faster.

    I speak from experience here. I replaced the batteries for my electric drill driver (NiCd), with higher rated NiMH and it did not run well at all. I had to go back to NiCd.

    Bob
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The type "380" seems to denote mostly the size and form factor of the motor, You can find motors with different electrical chracteristics. If you want to use the old control board, make sure the new motor doesn't draw more current than the old one.
    Other wise "everyonde" may be right and you at least risk frying your board. You may need stronger driver transistors (assuming they are on the PCB as discrete components) or a stronger driver chip (if an integrated chip is used).
     
  5. Jean Perret

    Jean Perret

    37
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    Jan 3, 2013
    Thanks guys!

    So this where my skills in electronics stop... I don't understand much on how a rc toy board is built.. I know there's a crystal or a chip for the frequency somekind of pole with a winding around for the frequency as well and then a bunch of transistors and others stuffs , ( Do they all have mofsets?? ) Basically what really heats up on those boards and may fry?? What exactly transfers the power to the motor??

    Thanks!!! :) And happy new year!!!
     
  6. BobK

    BobK

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    Jan 5, 2010
    Depending on the board, there might be 4 bipolor transistors or MOSFETs, or there might be one or two chips that contain other circuits as well as these transistors.

    Look at where the motor wires do on the board. They will be connected to the transistors or chips that supply the current to the motor. If this is a powerful motor the driver components might have heat sinks on them, this would be a clue.

    Bob
     
  7. Jean Perret

    Jean Perret

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    Jan 3, 2013
    As far as it goes with New Bright mainboard I remember seeing only resistors and transistor with those 3 poles , Nikko on the other and use those mofsets with heat sinks. So in your opinion putting a faster motor would heat up every and each par of the mainboard or only specific elements and which ones? I know it would be lot easier to put hobby grade electronics but the challenge to boost a toy grade keeping most stock is a much rewarding challenge and learning process.

    Sorry about my ignorance.. thank you!
     
  8. BobK

    BobK

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    Jan 5, 2010
    The power transistors driving the motor are what are likely to need upgrading.

    Bob
     
  9. Jean Perret

    Jean Perret

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    Jan 3, 2013
    So i have to trace where the wires from the motor are soldered and follow the lines up to the first stuff and this would be a power transistor? What kind of different forms they could have or look like ?? Also what kills those electronic parts are the amps drawn by the motor? Do we have to check on the amps at no load, maximum efficiency or stall?

    Thanks!
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    Jean,

    after seeing your comments in the last few posts, I would venture to say that
    you are really wanting to do something that is way way out of your depth of experience

    is there anyone in your area who is a skilled electronics tech that can mentor you and help you work with this face to face ?

    Dave
     
  11. BobK

    BobK

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    Jan 5, 2010
    I was thinking that you could actually add on new driver transistors without modifying the board at all. You could use the two wires from the motor as signals to control the 4 transistors needed to make a full bridge. This could be a pretty safe way to do it without blowing out the existing controller board.

    Bob
     
  12. Jean Perret

    Jean Perret

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    Jan 3, 2013
    You're right Dave .. I am to total disaster when it comes to electronics :eek:)) Believe me I have tried to ask a lot of people about this project and always same answer.. Switch to hobby grade.. Black magic and electronics go together for a vaste majority of people..That's why I am counting on you guys to take me out of the darkness!
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    I have no experience with RC stuff so take this with a grain of salt.

    The usual way a motor is driven is called an H-bridge. See http://en.wikipedia.org/wiki/H_bridge

    This arrangement allows the motor to be driven in either direction. If PWM (pulse width modulation) is used, the motor speed can be varied. http://en.wikipedia.org/wiki/Pulse-width_modulation

    For simplicity and efficiency, the H-bridge is usually made with MOSFETs. These may be in the TO220 package (http://en.wikipedia.org/wiki/TO-220) or in a smaller package such as TO-92 (http://en.wikipedia.org/wiki/TO-92), or they may be part of a driver IC such as the L298 shown in the first Wikipedia article I pointed you to. An H-bridge can also be made using bipolar junction transistors (standard transistors) but these are generally lossier than MOSFETs so MOSFETs are preferred.

    There may be smaller H-bridge drivers available in smaller packages such as 8-pin DIP (http://en.wikipedia.org/wiki/Dual_in-line_package) but I don't know of any off-hand. You could make a list of all the ICs on the control board, and google them all, or post the list here, to find out which ones are H-bridge drivers.

    The H-bridge, whether it's implemented with discrete components or on a chip, has to carry the current that is drawn by the motor. Therefore it is the thing that will be stressed if you use a larger motor with a higher load current. Problems are more likely to occur when the motor is starting up, changing direction, heavily loaded, or stalled, since it draws more current in those situations.

    BobK's suggestion could be a way to allow you to buffer the output of the existing H-bridge without having to know exactly how it works. You can use the existing motor connections to drive a more powerful H-bridge, and drive the motor from that.

    I suggest you try to find out more about the existing motor drive circuitry on the board first. There may be an easier way to boost the output current capability.

    I assume you are going to keep the voltages the same; you simply want to use a more powerful motor with a higher current consumption, is that right?
     
  14. Jean Perret

    Jean Perret

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    Jan 3, 2013
    Thank you so much for your infos! You are totally right, my point is to see how far you can boost a toy grade RC and not falling in the easy way to just switch all electronics to hobby grade..So yes as 9.6V is already on the high side ( hobby grade using about 7.2V-8.4V) but putting a higher mah battery let's say at least 1800mah vs the standard actual 600mah and change the motor assuming actual one at best is a Mabuchi RS 380 SH by a Tamiya 380 sport tuned, but still I can't find any specs on that motor as amp draw etc...

    https://www.tamiyausa.com/product/item.php?product-id=54393

    Here is an interesting thread about someone who has tried modifying a toy RC and seems one of the mofset burnt out

    http://www.ultimaterc.com/forums/showthread.php?t=161984
     
  15. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    It might be worthwhile posting some photos of the board. Use plenty of illumination (outside on a sunny day out of direct sun is probably best) and get as close as you can without losing focus. Both sides could be helpful.

    As for the motor's current consumption, you can measure it if you connect the motor to a battery with an ammeter in series. Get readings for slight load, heavy load, and stalled. Stalled will probably be highest.
     
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