Amps, Volts, Power Converters and Power Supplies.

Step 2. Voltage.

Just as important as current, "Voltage" is something that needs to be considered when powering electrical devices.

Voltage is measured in "volts", and as you may already know, the symbol for volts, is a "V". For example, "240V" is a bigger voltage than "12V".

Like "Current" is a measurement of "Amps", "Voltage" is a measurement of the difference in electrical energy between the two different parts of a circuit. The bigger this difference in energy is, the higher the voltage becomes. The best way to describe "volts", is that it is the pressure that causes a current to flow like was seen in the pictures in the previous step.

An example of this could be that you have a tank of pressurized water. This is connected to a hose. When you increase the pressure in the tank, this will make more water come out of the hose. It's that pressure that is the same as voltage. Increasing the voltage will make more current flow.

Planning and care needs to be taken when building a robots electrical system, as you may have different electrical components that require different voltages. Using the EZ-B v4 for example, using EZ-Robot HD Servos connected to the v4's digital ports can be powered with a 7.4v LiPo Battery. The black "Ground" and red "Vcc" pins helps deliver the 7.4 volts to the servo.

Now you want to use an Ultrasonic Distance Sensor (ping sensor) on the digital ports next to your servo. The ping sensor is only rated for 5 volts. You plug the sensor in and fire up your EZ-B. Chances are you will burn out the ping sensor as you are giving it "7.4 volts" which is too much power.

(Whatever voltage the battery is capable of delivering, will be the same voltage on ALL of the unregulated digital Vcc (red) pins.) on the EZ-B v4.

Possible ways around this, is to use another power source that is the correct 5v voltage, or use power converters, which will be explained in step 8.


A Voltage Summery.

Let's take a simple 4.8 to 7.4 volt servo.

! Giving it 12 volts will fry it.

! Giving it 2 volts will under power the servo and could damage it.

! Following the correct specifications for any electrical device is always advisable.


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PRO
USA
#1  
Thanks for this info. Still not sure why everything says it will handle 20plus servos because power wise, they cant. also a 20amp fuse will probably to blow before ez-b blows. this would be great in the specs!!

Thanks again

Scott
PRO
USA
#2   — Edited
I'm not an expert, but there is common sense too.

Not all servos are equal: there are small torque and high torque servos, there are cheap servos (bad electronics, counterfeiter etc) and good servos (good engineering) and smart servos (with micro-controller e.g. Dynamixel with temperature, load, torque control). 

Servos/motors have different current rates e.g. idle, torque stall, peak, inrush. 

Some setups don't accommodate the Inrush/Peak current. Inrush Current is commonly used to describe the current that is required to energize an AC powered device when first applying voltage and power to it. If you have all your servos moving at same time you have a Inrush current during a brief period.

Some batteries have high discharges rates for example a lipo battery with 1000 mAh and a C=20 can handle 20 amps, but a niMH (AA) can't handle 20 Amps so the battery plays an important role.

And last not all fuses are equal there are quick-acting and time-lag (slow) a slow fuse can handle as much as 10 times the current for a brief period before blowing up...   

Without knowing all details we can't make assumptions.
PRO
Synthiam
#3  
I recommend using EZ-Robot HDD digital servos for prototyping you product development, because they're the highest efficiency that you'll find. PTP is correct, in that your post may be assuming a specific servo experience, which is impossible to generalize. The EZ-B can provide power to entire InMoov large servo configurations. Even the EZ-Robot JD humanoid uses an EZ-B v4 and has 14 hdd servos and powers off a single 7.4v battery. This conversation of power requires explicit details of the hardware selected for your product development - as it cannot be generalized. 

If you have questions regarding the EZ-B v4 manufactured by EZ-Robot, then you can visit their website at www.ez-robot.com to contact them directly. Otherwise, the opensource hardware and software for the EZ-B v4 design is available in the Synthian GitHub link at the footer of this website. Lastly, there's a number of supported hardware platforms for ARC in the Getting Started link on this website. Many options to ensure you experience positive results with your product development.