pulsating power supply for pump

Hi there

I want to make a 12 volt liquid pump go slower but because it has to pump some very thick liquids I'm afraid I'll burn it if I just set the voltage back and I can make it go slower if it pulsates. So I thought of making a powersupply that pulsates short pulses of 12 volt to slow it down and use an arduino to control it. I was thinking of using the pwm of the arduino to drive a transistor of an old amplifier to pulsate the power with a pot to set the speed.

so it would be like this arduino->transistor wit old computer psu->pump

A is this a good plan to pulsate the power any way? B What is the best way to do it?

Thanks in advance Wybren

PS if you think dude that's all wrong please tell me I'm quite new to this.

sounds about right. Use the computer power supply to provide a stable 12V, and use the arduino PWM to control a power transistor which then drives the pump as shown here: http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads

Thanks I'll start on it tonight. i'll keep you posted.