Advice on power supply for 2 7.4V servos and 5V laser

Projects General Guidance
1

Hi there,
I am new to arduino. I am quite confused when it comes to powering various components.

As I understand, the arduino can only output 5V. I don't really understand electricity all that much so I'm not sure what I have to do to power the devices.

My main questions are...
Do I need a 7.4V power source for each of my servos?
Can I power the laser from the arduino, or should I use an external power source?
Better to buy batteries or get something that plugs into the wall (any recommendations welcome)?

Any advice on a power configuration for this is greatly appreciated!

Here are the servos I am planning to purchase:
http://www.servocity.com/html/hs-5496mh_servo.html

and here is the laser:

Cheers!
Jason

2

As I understand, the arduino can only output 5V. I don't really understand electricity all that much so I'm not sure what I have to do to power the devices.

The power to run the servo doesn't come out of the Arduino. The Arduino just sends the control pulse for the angle/position information. The servo should have 3 wires, power, ground, and control? (I don't know if "control" is the proper terminology).

The laser at 35mA can run directly off one of the Arduino output pins (rated 40mA maximum)

Can I power the laser from the arduino, or should I use an external power source?
Better to buy batteries or get something that plugs into the wall (any recommendations welcome)?

Batteries are probably "easier". But, do you want to replace or recharge the batteries?

Stall Current (6.0V): 1200mA
Stall Current (7.4V): 1400mA

To be "safe" and reliable, your batteries or power supply needs to supply that current for each servo (1400mA = 1.4 Amps).

And, a battery rated at 1500mA-hr won't really supply 1500mA for one hour... But, it will provide 1mA for about 1500 hours. (You'll probably need a bigger battery than that.)

7.2V is a bit unusual for an off-the-shelf power supply, but you might find one that's adjustable. Or, maybe the servo companies sell a pwer supply??? You can build a power supply with an "adjustable" regulator set to 7.2V (voltage is set by selecting resistors) but linear regulators are usually limited to 1 Amp (sometimes 1.5A) and switching regulators are trickier to build.

3

Thanks for your response! Are there other sources to learn more about the arduino and power sources?

I have pretty hefty access to batteries at work... would AA batteries in sequence suffice?

What if My voltage ends up being something like 8V, but I need 7.4V... Do I need to use a voltage regulator or resistors?

If you have some sources, I will be happy to read those!