View Full Version : Can i use UPS power supply as my SMPS supply?

05-17-2006, 02:34 PM
hi friends,

my objective is to supply max 5V DC power supply to my Stepper motor driver chip UCN5804B ,so can i use UPS output for it. But my problem is that the UPS supplies 12V DC power so, how to step it down?

Though the UCN chip can take max. of 12 V DC as VCC but it's given in the circuit to use 5V as its power input.Plz help.

the Datasheet of UCn chip is:

05-17-2006, 06:58 PM
Only if the UPS you have - can supply current MUCH MUCH more than the current required by the Stepper Motor.

(This "much much" maybe atleast 20 times or more depending on the motor, and UPS)

This is because UPS output maybe - most probably - a Switched Power Supply - which can become unstable easily in case of erratic (motor like) loads.

If you dont mind burning up the UPS in your experimentation, than it would be an interesting and maybe fruitful attempt.

Moreover if your UPS is of the Computer Power Supply - its all the more hard because its current is too low for a motor - please read the max current value on yours.

It would be better if you insert a small "heating element resistor - 1or 2ohms" in series and then begin your experiments .

To get 5V, simply use LM7805



05-17-2006, 11:11 PM
why don u try out smps...
gives u both 12v and 5v...

02-27-2010, 11:16 PM
Many places u get 12v smps .... at 100rs u can use , check the current ratings 12v 2A+ needed
use one of the following :

1)LM7805K it delivers 3Amps current use a heatsink if needed
2)http://www.linear.com/pc/images/product/thumbnail/1279_1.jpg with LT1083
3)7805 can be combined with other components to provide an output of up to 3 amps,
like the TIP2955

Hope u will select one of thse

02-28-2010, 10:04 AM
12V UPS??? Do you mean the DC UPS for car batteries??? What is the size of the stepper motor you are using?? Does it really need that much current?? if IT does then you are better off changing your stepper motor rather than looking for massive power supply units for it.

02-28-2010, 11:21 AM
power units are not massive .. some steppers need high peak currents .PSU sd be abe to deliver .. if the work is very small like a pen plotter .... tiny motors can do

for projects like CNC machines the motors need to be powerful