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Topic: Power supply building technical help required (Read 1 time) previous topic - next topic

bforu_gs

Hi friends,

Thanks all for reply,

dc42:
I am looking forward as per your recommendation, I do have one ATX PSU, but have few queries regarding it. 
Have a look at its specs

1) It is having much more ampere capacity then my requirement, won't it blow up my sevos,dc motor and stepper drivers (In my present PS I have connected ground to arduino ground, I think ground connectivity wont blowup my arduino board)
2)How much (exact) load requirement will be there and one which line(5v or 12v), I tested that ATX without any load with multimeter and it gave right readings.(12.03 v and 5.12v).


arduinoadrian

I won't estimate the motor current in the way explained above. Motor's currents are not the simple Ohm's law calculation from the windings resistance. The current varies depending on the mechanical load applied to the motor, that is, how much force they are doing to move the load. Thats' why they get burnt when mechanically overloaded. Better to place an ammeter (your multimeter measuring current) in series with the motor and measure the real current with the motor working with its normal mechanical load. That's the normal current it will take from the power supply. Remember if the mechanical load increases it will take more current. I don't think the relationship between force and current is even linear by the way (I have to check). Therefore, careful with the calculations and estimates...
Perseverance is 90% of the solution. The remaining 10% is more perseverance.

dc42


I won't estimate the motor current in the way explained above. Motor's currents are not the simple Ohm's law calculation from the windings resistance. The current varies depending on the mechanical load applied to the motor, that is, how much force they are doing to move the load. Thats' why they get burnt when mechanically overloaded. Better to place an ammeter (your multimeter measuring current) in series with the motor and measure the real current with the motor working with its normal mechanical load. That's the normal current it will take from the power supply. Remember if the mechanical load increases it will take more current. I don't think the relationship between force and current is even linear by the way (I have to check). Therefore, careful with the calculations and estimates...


The stall current of a DC motor at a known voltage can be calculated from the voltage and the DC winding resistance. Since the stall current is then worst case value (unless the motor is forced to rotate backwards while power is applied), it is the stall current that you need to know when choosing the peak current rating of an H-bridge and power supply used to drive the motor.
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0AlphaOmega

dc42, I was also going to suggest using an old PSU from a puter. There are some very good instructions on the web for converting them to standalone PSU's - Lots of grunt and pretty stable! :)

e.g. c/w 3.3V http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/

Lots of other similar pages.

Beware of mains when the unit is open!
For whom does the clock pulse? It pulses for you!

bforu_gs

#9
Jan 26, 2013, 05:32 pm Last Edit: Jan 26, 2013, 05:35 pm by bforu_gs Reason: 1
Hey guys thanks again for reply,

But for using ATXPSU only my concerns are as below.
1. This is having much more ampere capacity then my requirement as you can see in above posted image, won't it blow up my sevos,dc motor and stepper drivers.
2. How much (exact) load requirement will be there and one which line(5v or 12v), I tested that ATX without any load with multimeter and it gave right readings.(12.03 v and 5.12v), so is there requirement for dummy load resistor or dummy light bulb...


Thanks,

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