XYZ Microscope Stage Controller Update - Self-sufficient Power Supply
In this video, I show you how I modified my XYZ microscope stage controller circuit to make it entirely self-sufficient. Previously, the microcontroller was not powered by an external power supply, but it was powered by a USB cable and a mobile charger. However, this is no longer the case. I added an extra voltage regulator to the circuit and now there's no need for another external cable connection to power the microcontroller. Also, although the microcontroller is externally powered, thanks to a simple modification, it can stay powered while it is connected to a computer via USB.
Additional details
So, as I mentioned, the modification involves the power supply of the microcontroller. Originally, when I designed the PCB, I did not want to have the microcontroller to be “self-sufficient”. I intended to have it either connected to a computer or used standalone and powered by a mobile phone charger. Also, the onboard voltage regulator provides 3.3 V and it is quite cumbersome to power the Teensy 4.0 via an external 3.3 V, and I did not want to add another voltage regulator. So, yeah, I did not add an additional voltage regulator to my design.
However, after some time, I was thinking about adding an external power source to power the Teensy 4.0, so I could get rid of an extra cable and I could make the operation simpler. A customer who originally inquired about the design of this board also requested this modification. So, I ended up adding the same voltage regulator that provides the 3.3 V to the rest of the board.
The Teensy 4.0 microcontroller can be powered through its VIN pin, which allows for a wide range of input voltage options. This pin accepts input voltages between 3.6V and 5.5V, making it versatile for various applications and power sources. So I can use it with the voltage regulator that is set to provide 5 V.
When connected to a suitable power supply, the VIN pin directly feeds power to the onboard voltage regulator, which then supplies the necessary voltage to the microcontroller and its peripherals. This capability simplifies circuit design by enabling users to provide power from batteries, wall adapters, or other sources, ensuring that the Teensy 4.0 operates efficiently in diverse environments while maintaining stability for signal processing tasks and other functionalities. In my case, the external power source is the MP2315-based voltage regulator. However, by default, VIN and VUSB are connected together. So, it is not possible to power the board externally and use its USB port simultaneously without a small modification.
To modify the Teensy 4.0 for separating VIN from VUSB, we follow these steps:
Locate the Power Path: Identify the traces and jumper that connect the VUSB and VIN on the Teensy 4.0 board. This information can typically be found in the schematic provided by PJRC, the manufacturer of the Teensy boards. But I show it on the pictures next to the text and in my video as well.
Remove the Jumper Trace: We can use a sharp knife or scalpel to carefully remove the jumper trace connecting VIN to VUSB.
Testing: Once the modifications are complete, it is a good idea to measure if the VIN is indeed separated from VUSB before powering the circuit. I showed this in the video in two different ways.
Teensy 4.0. One can see the VUSB trace going towards the corner of the board and the VIN/5V pin at the corner of the board. By default, they are connected on the bottom of the PCB (see below).
By completing these modifications, we gain the ability to independently control power to the Teensy 4.0. This enhances its utility in projects requiring specific power management strategies, especially in scenarios where external power sources and USB connections are utilized.
With this tiny but important modification, my automated microscope became a bit better and simpler to use.
Also, note that this modification is not specific to my circuit, but it can be applied whenever you would need to both power the Teensy 4.0 externally and also connect it to a computer via USB.
Check the project on my PCBWay project page:
Teensy 4.0 bottom. The VUSB-(VIN/5V) connection is clearly visible here. Cutting the trace between the VUSB and the VIN/5V pad allows the board to be powered externally while having it connected to a PC via USB.
