Good morning Friends..when i was started to make RC crafts in all means,the speed controller was my ever nightmare.at begining i was using a simple on and go type controls like any cheaper RC cars.but as i progress i started to use my knowledge in electronics to my applications. as a result i made several types of speed controllers still working nicely after years of gruelling service.i am posting this article here because i know many of my friends are need it..when i asked for a speed controller here at Chennai Town,they gave me a price list.and was
shocking while looking in to it.for a single channel speed controller, the price was Rs 4500/00-!!!!  with that money,i can buy a good quality DVD player, or a 20 inch CTV, or a Dual Core Mother board, or a good digital camera.!!!!...

   and if you ask for a two channeled one its 6000/00-almost...and for a motor differential one..9000/00..ohhhh...and can only work as the home made one..so i decided to make my controllers even better than before.now all it works nicely and flawlessly...
   
   to make a good quality solid state speed controller, you need heavy and expensive equipents and ample of money and ultimately a good knowledge in electronics..?  sure..? rethink..NOOOO....you need nothing, but some patience and mechanical mind with some time to spend.

here we are...you need only some handy things from around you...and sure a soldering iron in to 25 watt, a three pinned one to avoid leakage.soldering flux and good solder wire.you need not even a multi meter  !!!!!!!...   
   first of all find a sliding or rotating type volume controller can found at scrapyards or can buy at any electronics shop within

alf a dollar.if you are taking it from an old source the value of the potentio meter is not an issue...any value will work.so if you are buying one try to get it within 50 Kilo Ohms, and Linear type one.if you are using a conventional servo, the sliding one wll be the best bet.
and if you are using a toy RC a rotating type will be best.but you can use either for either use.

   i took this old tape recorder main board to take needed parts to me.here you can see some good sliding controller looking at me..
"hey Rachu we are waiting for you"...hi..hi..

desolder it from base carefully...now its free...
now we got the main part of the controller..the variable resistor, or a potentio meter...its value here is 50 Kilo Ohms.

now we need a power transistor to drive our motors, lights, or anything you need...here some inexpesive but ever classic silicon, and Germanium transistors, from, MJE 3055 up to 2 Amps..TIP 3055 up to 5 Amps..and 2N 3055 for 30 Amps or more as you can bridge it.
the TIP 3055 also can be used instead of 2N 3055 to save space. you can place these or this transistor anywere you like so you can save space and weight.and a heatsink is a must for higher amps.no fan is needed to cool it as most of these PTs can withstand temperature up to 180 degree of heat..

and here you have a second alternate for PT, is Darlington pairs..means two transistors in one..with this you can achieve a good soft start and stop..good for light crafts..

now its fixed and wired..you can see how simple it is..here i have wired it in a rough way..but you can simply place and wire neatly as you can...so everything will be tidy..a 470 ohms resistor is used with controller to protect the transistors from stalling current,when a stalling of motor occurs.as the TIP 3055 is employs a thermal protection inside you need not worry about burning it out while a short circuit happens...no worry...reverse polarity is not a matter here as we use a diode in series with this circuits.there is nothing to go wrong  with it so you need not worry about splashes of water..if this goes to water nothing happen..wait untill dry..and then works again..no money loss...

now i glued a piece of aluminium sheet on to the arm of servo, with many holes on it to adjust the stroke length of the actuating arm,as we need...

Make a hole at the tip of the controller..carefully..dont tear it....

ow yo can simply fix it as shown,all with foam boards,because it can absorb excess throw and shock,made out of servo if you switched of the transmitter first...no steel or plastic structure is needed...i used a brass rod here..its only for a guidance..you can simply do on
your way with your own ideas...

now our controller is ready for the ordeal..but still lack one thing..a reverse switch..here i used a DPDT switch, can foud any land phones, or can buy at any electronics shops..much cheaper..here it costs only a 5 Rupees...

now wire a second line in reverse with wires from transitor out..and place the switch at the neutral position of the arm, after checking the play of servo arm..place the main throttle stick at this position as neutral...mark it or keep it in mind..

Now its ready...with a motor..this motor was actualy a toy motor, for 3 volts..and i reworked on it for 9 volts and 700 ma..and in to 6000 Rpm..for my KAAKKA..means the Raven,from strw board and bamboo sticks..a flying model of my own..have to compleate it..

And here i am adding some useful proven circuits , all tested and with me now,is first one is simple but effective inexpensive but works almost same as professional one.its much simpler , and using the ever basic principle of transistor biasing.here the base voltage is controlled via a variable resistor, our volume controler in this case,so the out put will remain as constant untill we alters the base voltage.

Second one is based on MOSFET( Metal oxide semiconductor field effect transistor),for greater amperage handling.you can simply fix a RS 500 or more powerfull motor to it.if feel bad can bridge same one with exsisting one so it will handle your load nicely.here you can see
that the circuit is more complicated, because this unit is based on PWM, or pulse width modulation. so it may generate some SAW, (Surface Accoustic waves)means some radio disturbances, so we must use good quality wires, and must use a shielded wire to connect
the variable resistor.

Third one is even more complicated because here we are using a CMOS Ic for making pulse.(Complimentary Metal Oxide semiconductor).
the Ic is easily available, and cheap.
   The next circuit is based on Darlington Pair transistor means two PTs in one.here is the circuit. its too easy to make and an ameter is connected in series to output, so you can simply determine the load current in output.this circuit is meant for only under 2 Amps.
you can also use this circuit as a battery charger and voltage eliminator for electronics service...its based on BD679, a cheap PT to buy.
   so..now its on the way..woooommmmm....try it...and you can save ample of money...and you can do many other things with those saved money...

and sure..if there is an idea..there must be a video...see here...http://www.youtube.com/watch?v=SS3gkDgQSz4

now you all may think that it will only work with less powered motor...no...here is...i am adding the same circuit with a powerful RS motor...from a drill...

and wedded to a prop..

and se here...

now friends..time to wake up...do some thing for yourselves for you...save a lots of money...sharpen your creativity...and with saved money you can make more models for you...and se the video here...http://www.youtube.com/watch?v=9-HSQ1Ubeek

Do note that these designs will only work with brushed motors. Also, except for the PWM design, the dissipation in the power transistor would be high at low voltage and high current.

OK for small motors.

Sushil..you are absolutely WRONG....i will post a detailed brushless cofiguration,. here as i got time, and not for small motors...i think you commented this without looking in to ful postings...the last postings shows a big RS motor, and droping more than 6 amps...and you can bridge the transistors so you can go with up to 50 amps...but i am advicing you that you need not any power ful motor to drive a craft in to high speed as i can show you here one of my craft, is working on 3.6 volts and a reworked toy motor...http://www.youtube.com/watch?v=kKh6NGzlXJg