Section 6: Trinamic Power Requirements

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Current sense resistors are two low-resistance resistors that are placed near the IC. The driver sends its entire current through the resistors which is why they are so large.

The IC reads back the voltage and is able to figure out how much current it is using at any moment in time.

What matters most is the value of the resistor, because the value will determine the maximum current the driver will use.

Let’s go to page 49 of the datasheet and look at this table:

Look what happens when 0.10 Ohm resistors are used, which is what the VAL-2000 uses

Looking at the chart, it means that the max current that can be used by this board is 1.92A RMS.

Ok, so now what does RMS mean?

This is important because it determines what size power supply we need! If your power supply is too small, it may overheat and cause a dangerous situation!

RMS means Root Mean Square. It is the average current the motor is using. Sometimes it’s using less, sometimes it is more, for example when a load goes up, so will the current.

To determine max current, take the RMS and multiply it by 1.41. Why that number? Because Trinamic says so.

RMS x 1.41 = Max Current

If our RMS is 1.92A, our max current will be 1.92 * 1.41 = 2.71A

Since the ESP32 requires at least a 500mA power supply as stated in the ESP32 datasheet, this will give us a max current draw of 2.71 + 0.5 = 3.21A

We need to purchase at least a 3.21A power supply to make sure it does not get overloaded or overheated if you want to run the device at max power. Of course you can choose to keep the current low in the firmware and use a smaller power supply.


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