Re: speed controller help [TANKS]

[Frank Pittelli <frank-at-rctankcombat.com>]

Carla and Joe Devine wrote:
> 
> Can any one out there help me? I can't seem to wrap my head around how 
> they work. I would like proportionality, but I can't figure how to make 
> it work. I am totally out of my element here folks any help is greatly 
> appreciated.

Given the high amount of current that our drive motors require, there is 
really only one way to provided "proportional" speed control and that is 
with an Electronic Speed Control (ESC).

Commercially available controllers usually include a microprocessor that 
reads the signal from the R/C receiver and then turns one or more power 
transitors on/off as needed to drive the motor at the desired speed. 
ESCs are rated by the maximum voltage and maximum amount of current they 
can control.  The higher the maximum current, the higher the cost.

However, if you are proficient with soldering iron, you can make your 
own proportional controller without the need for a micro-processor, 
which is the way it used to be done.  Quite simply, you use a venerable 
555 to create a simple timing circuit controlled by a 5K pot, when the 
pot is turned by a servo, the timer speeds up.  Such 555 timing circuits 
have been around for ages and you can find many such designs on the Web. 
Connect the output of the timer to a bank of FETs and you can drive as 
large a load as you want.  As with all electric circuits, there's plenty 
of little things to take care of, but that's the essential operation. 
Such ESCs can be found in the scooter industry, where the pot is turned 
by the operator to speed up or slow down.  Rick Schultz used such 
controllers in his Leopard and they worked great.

        Frank P.