Setting Up the Zybot - Power Considerations

A very important part of any robotics applications is powering all of the parts on your board. Moving parts not only take a lot of power but, they don't always pull consistent amounts to current. For example the more you move around a servo the more current it requires. In other word you may have spikes in the current being drawn.

Another complication is that different components require different voltages, and certain components can easily get fried if you supply too much voltage.

So its important to know:

What components need power

What Voltage is required for each component

What is the maximum voltage you can supply to each component

Step 1: What Parts Need Power?

The Servos require 5 V to operate at full power. The Zybo board also requires 5V, but only 5V. The motors require 12V to operate at their full speed, which we need since we are putting a lot of weight on the Zybot.

The USB hub has an external power supply, but we found that if we power the board with full 5V it can power the camera, and the WiFi adapter just fine.

Since this is a fairly small application, keeping it to one battery was the optimum choice, so we chose the 11.1V Lipo batteries because they can supply the correct voltage.

Unfortunately the full 12V is too high for the Zybo and the servos, so we need a voltage regulator.

Step 2: Choosing a Voltage Regulator

When we originally built the Zybot, with a 5V supply we had a problem with the Zybo doing a full power reset. Meaning that something was pulling too much current away from the Zybo. When we scoped the various connections we found that, factoring in the spikes in current from the servos 2A would be an ideal amount of current for the servos.

So we found our solution, a voltage regulator would be able to supply 5V and more current than a 5V supply and allow us access to the 12V input. Unfortunately the Voltage regulator that we used isn't being sold any more, but I found 2 suitable substitutes.

A 12 to 5V regulator that can supply 5A but is linear.

and

A 12 to 5V regulator that can supply only 2A but is switching.

If you use the first option, you can use the same regulator for both of your 5V needs, but you battery will drain much faster because it isn't switching.

If you use the second option, you will have to use multiple regulators but the battery will last much longer because it is switching.

The regulator you choose is based on your preference.

Step 3: Warning

The Zybo can be fried fairly easily if you supply to much current, too much voltage, or reverse the leads. Make sure you measure everything in you power circuit to make sure you won't exceed what the Zybo can handle.

We ourselves fried two Zybos figuring out the best power option for the Zybot.