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Power supplies-Types, and EZ-robot Use


In this tutorial, we'll learn about the different types of power supplies, and their use with the ez-b and other hardware, to help you find the right method to power your robot.


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Requirements, and Power Statistics

To select a power supply, you need to know 2 things:

What voltage do you need?
What amperage do you need?

All power supplies provide different levels of each, so it can be tricky to find the "prefect "one.

All Ez-robot heavy duty servos run at a max of 7.4V(Minimum 4.8V). This voltage is provided by the battery found in the store. The EZ-b V4 does not regulate power to the DIGITAL pins, so whatever goes in comes out. Other servos often have a max of 6V. This will require you to regulate the power to the servo, or run a 6V power supply.
The EZ-b has an operating range of 4.5V-16V.

The Ez-b V4 uses around 80mAh. The camera, around 100mAh.

Quote about Ez-b Capabilities:


I know it has floated around the forum that the digital power pins can handle 5 amp per digital pin, but that's not the case. It's max of 2 amps per pin and a combined constant amperage of 5A for all the digital power pins. While you can have a spiked (pulsed) current up to 20A, the ez-bv4 is only rated for 5A of constant current.

If you find you are drawing much more than this we would recommend externally powering your motors directly from the battery power supply to the motor drive electronics (it's good idea to add a fuse in between them).

Servo power is best to come from a 7.4V LiPo battery (with protection) but you'll need servos that are rated for 7.4V, if you don't have servos that can handle this high of a voltage you'll need a
voltage regulator.

The thing to watch out for with regulators is how much current draw they can handle, like most motors, servo motors can draw huge spikes of current when first initialized so you'll likely want to double or triple the current rating of your voltage regulator compared to the operating current of the servo so you don't experience a brown out. Brown outs result in the voltage dropping below a certain level and will either effect the operation of the servo or the electronics controlling them.

EZ-B Data sheet
Servos, for example, the heavy duty servos in the store, and used on all Ez-robots, pull a suggested max of 2A-3A. This can cause a problem for robots with many servos, and will often cause "brown outs", or a sudden shut down of the EZ-b to protect it.

For example, here's a JD robot:

User-inserted image

He has:
Ez-b--------------- 80mah
12 servos-------22A- 8HD, 4 mini
RGB led array-~50mah

Which totals---22.2A Max draw.

And due to the 20Asurge and 5A continuous limit, this would require most servos and modules to be powered directly from the battery, if servos are moved often and together

That's a lot for a little robot.
So now you need to power that little guy...