# How to calculate the needed voltage and current to supply for Arduino

I have Arduino MEGA and I'm connecting to it 5 servomotors.

``````{ 3 TowerPro M995
Basic Information

Modulation:  Digital
Torque:  4.8V: 130.5 oz-in (9.40 kg-cm)
6.0V: 152.8 oz-in (11.00 kg-cm)

Speed:  4.8V: 0.20 sec/60°
6.0V: 0.16 sec/60°

Weight:  1.94 oz (55.0 g)
Dimensions:
Length:
1.60 in (40.7 mm)

Width:
0.78 in (19.7 mm)

Height:
1.69 in (42.9 mm)
Motor Type:  3-pole
Gear Type:  Metal

2 Towerpro M996R

Basic Information

Modulation:  Digital
Torque:  4.8V: 130.5 oz-in (9.40 kg-cm)
6.0V: 152.8 oz-in (11.00 kg-cm)

Speed:  4.8V: 0.19 sec/60°
6.0V: 0.15 sec/60°

Weight:  1.94 oz (55.0 g)
Dimensions:
Length:
1.60 in (40.7 mm)

Width:
0.78 in (19.7 mm)

Height:
1.69 in (42.9 mm)
Motor Type:  3-pole

}
``````

So how can I calculate the voltage and current needed to supply this Arduino?

• Use a LiPo battery then you never need to worry about current again :) Jun 7 '16 at 4:10

Drive all your components simultaneously from an external supply at appropriate voltage. Measure current draw in series (set your multimeter's red cable on the 10A port and set it to 10A, and connect red to VOUT, black to ground). Don't hold the wires in your hands, use clip-ons. Let it run for a while, and pay attention to current fluctuations. Read the current requirements on the display. A power supply with a bit more amperage than necessary is a Good Thing(tm).

Edit: remember to get both normal load and stall measurements. It is wise to add some way of turning stalling motors off, since stalling is motor death. And sometimes power supply death - those segway-for-kids things come to mind (and make me snicker ... WHEN I WAS A CHILD WE HAD OUR FEET FOR TRANSPORTATION, AND SHOES, IF WE WERE LUCKY!).

Voltage is simple - a device has a requirement and that is what you have to provide. In the case of the servos that is a range of voltages that it can use. So 5V is a good voltage. The Arduino can take 5V if you feed it in to the 5V pin or the USB port, or 7-12V if you feed it in to the barrel jack.

The current you cannot calculate. You haven't provided enough information. The calculation, when you have the information, is quite simple: for all the devices on the same power supply add the currents requirements together. The supply has to be able to provide at least that amount of current.

• I couldn't find information about the current anywhere :/ this is the info provided by the main website.. the servos are connected in arduino ... so they are taking the volt from 5V in arduino ..
– O2M
May 7 '16 at 18:04
• Then you will have to measure the current with your trusty DMM.
– Majenko
May 7 '16 at 18:05
• Measurements in ordinary cases will not be a reliable indication of what can be encountered. The servos should not be powered through the Arduino. Expect that they can draw up to several amps when loaded, especially in combination. Jun 6 '16 at 19:15