speed controle for motor

[nickk1]

Hi I need help again please I have 24v / 100 va supply coming from a transformer to power a small motor. I need to be able to vary the speed from full power to 0 I know I will need a potentiometer but I am unsure of the size to use or if any thing else needs to be used as well as this.
Nick

 

[rjvh]

I have 24v / 100kv supply coming from a transformer to power a small motor.

100kv

what kind of motor??

And to giv you an i dea you need a bit more than a potentio meter

Robert-Jan

 

[nickk1]

small dc 24v, what else might I need could you work a circuit out for me?
NICK

 

[rjvh]

does the motor say how many amperes it consumes

i would make a PWM control to control the speed

can be simple made with a 555 a few other components and a FET as driver

do you have already some experience or is this the first project that you want to make ???

 

[nickk1]

This is my first project motor amperes is not marked on it but I know its will run at 24v as I have ran it on a 24v 1.5amp supply ,is there a way I can work out the ampage of it.

 

[nickk1]

sorry quoted 100 kv in stead of 100 VA no wonder you were suprised

 

[rjvh]

100VA at 24v than the transformer wil suply roughly 4 amps

if you ran it already on a 1.5 amp suply than i don't see anny problems
the easyst way to find out how much amps it consumed is measure it with a amp meter

I will post a schematic but that's a little later this day (have to work also and it's a busy day for me today)

Robert-Jan

 

[rjvh]

here the schematic like prommissed

if anybody have sugestions to improve it feel free

the assumption is that you feed it with a AC voltage if you have already DC voltage you can skip the 2 diodes in the power line

the advantige of of a PWM is that you use less energy on lower speeds
and you have a beter torque (stronger and more resposive) on lower rpm

if you use only a potentiometer (like you sugested in your first mail) you will burn a lot of energy in the potentiometer which required a big wattage potentiometer (= expensive and hard to get)

good luck

Robert-Jan

 

[bunghole]

i'm looking for a pwm, could a use a ssp60n06 mosfet (the same as phillips BUK456-60A). the mosfet is 60amp.

 

[rjvh]

could a use a ssp60n06 mosfet (the same as phillips BUK456-60A). the mosfet is 60amp.

I am not familiar with that mosfet and it's one I can't buy overhere

keep in mind that they sell the mosfets amperage as it is measured by a single puls at a certain frequency and certain duty cycle at a certain D/S voltage

in real life they handle a lot less because its a repetitive puls with a variable duty cycle and higher voltages where you working with

also the cooling factor is importand (have a look into this mater verry intresting)

the easyst thing to do in order to handle more amps is to put 1 or 2 parralel

don't do to many (your driver will not be able to steer them anny more deu to an increasing gate capacitance)

Robert-Jan

 

[Roff]

i'm looking for a pwm, could a use a ssp60n06 mosfet (the same as phillips BUK456-60A). the mosfet is 60amp.

I checked the datasheet of the ssp60n06. Rds(on) is only 18 milliohms. Even with 4 amps, it would dissipate less than 300mW when on all the time.

 

[jawadlateef]

hey guyz why are u confusing nickk1. he just want to control speed of a simple 24v DC motor.
As far as PWM is concerned it is a real good suggestion if he understands.
Good Luck Nickk1

For motor ampere if u know the exact voltage u can calculate its coil resistance and get the rough amps idea.