hi
i recently built a RC boat which has a small dc motor, i built a speed control based on a 555,
mark/ space ?

the problem is that at low speed settings, all i get is a lot of whistles and squeeling and not much else.apparantly this is a problem with this arrangement.
is there another approach ?
the motor is a small dc motor taking around half an amp, due to space restrictions i have to use a 9v pp3, instead of a perhaps a better matched 6 volt AA supply.(not ideal but i get nearly half an hour)
thank you
doug

 

Do you have a schematic?

You don't "have to" use a PP3 battery for running a motor, and AA are not the only alternative; there are plenty of superior and inexpensive battery options available today that would outperform either of these.

 

Unfortunately this is a down side of motor control without feedback of some kind, essentially you are running open loop velocity control and this does not provide the torque at low mean current levels, I assume you mean PWM for mark/space?
IOW the mean current drops at low rpm but the torque requirement can remain the same.
Max.

 

A lower frequency will help, and you can set it very low if it's driving a boat.