Ps3 power supply convertion to bench supply.

[nazar1000]

Hello,
I have got an power supply from ps3 and I would like it to convert it in bench supply.
The power supply produce output of 12V, 18 apms,
First my DT teacher told me to use 12 ohms resistor to decrease the amps down to 1 amp. ( I want to connect it to small motors which take about this much)
However when I connected 12 ohm resistor it burned.
This was probably caused by 12 watts being produce when resistor was connected and resistor was only resistant up to 0.6W.
So now the teacher told me that I need to buy 25W Arcol Power Resistor (Aluminium Clad) HS Series, this one here
http://www.rapidonline.com/Electronic- Components/25W-5-Arcol-Power-Resistor-Aluminium-Clad-HS-Series-517872
(delete space between "Electroni- Components)
Here come my question will this work ? and if yes which one should I buy 15r ?
Thanks for response

[pebe]

Using a 12ohm resistor is not the best way of reducing voltage for a motor. You would only get 1A if the motor voltage were very low. A 3V motor would only get 0.75A and a 6V motor would only get 0.5A.

A much better way would be to use a ‘buck’ converter. These devices used the ‘switched mode’ technique to reduce the voltage with very little (about 5%) loss of power. These types are typical of the devices you can get. All are from Hong Kong, are inexpensive, and I can vouch for their quality.

A simple buck converter giving up to 3A is this one.
http://www.ebay.co.uk/itm/1-DC-DC-Buck- ... 5d44cfdcc7
If you exceed the 3A max, the unit will shut down for safety.

This is the same type with an inbuilt voltmeter
http://www.ebay.co.uk/itm/DC-4-5-28V-To ... 565fd043f7
Note that with both of those you will lose about 2V from the supply, so you could only get 10V from your PS3 supply.

A better type to use would be this one, that also gives a variable maximum current adjustable from 100mA to up to 5A. It is a ‘buck/boost’ type so you can either increase or decrease the supply voltage from 0.8V to 28V
http://www.ebay.co.uk/itm/5-30V-to-0-8- ... 3a8900d308

Finally, the Bolls-Royce of these devices, a buck/boost converter that from your supply would give 0.8V to 29V with an adjustable current up to 3A (5A with a heat sink), with built-in voltmeter and ammeter. My son uses one of these as a battery charger for his fishing bait boat – it’s the only way to charge a 12V battery from another 12V battery.
http://www.ebay.co.uk/itm/DC-Boost-Buck ... 2589b65615

If you wanted easier adjustment, you could replace the preset controls of any of these items with standard pots and control knobs.

For more alternatives, go to Ebay and search for 'buck converters' or 'buck boost converters'.
I hope that helps.

CORRECTION!
Since replying, I have looked again at the specs for the last two converters. Although advertised as buck/boost converters, they state in their specs that they can only reduce the voltage. They are therefore NOT boost converters. From a 12V supply they can only output 10V. If you want to go higher than 10V, the best thing would be to use a boost converter first to raise the voltage. For example, this converter could lift the voltage to 30V
http://www.ebay.co.uk/itm/XL6009-DC12V- ... 35d119584d
You could then apply that voltage to the buck converters to get any output from about 2V to 28V.

[nazar1000]

Thanks for response!

I am beginner in electronic and therefore I don't want to start anything hard yet.
I just wanted to decrease the amp to at least 1amp or less so the motor will not burn.

I will think about your response and see what will suit me the most.
Sorry for my English, it is not my home language.
Thanks

[pebe]

The best way to stop the motor burning out is to provide it with the correct voltage. It will then only take the current (amperage) that it needs.

The simplest and cheapest way of doing that is still the buck convertor I mentioned before:
http://www.ebay.co.uk/itm/1-DC-DC-Buck- ... 5d44cfdcc7