I have one project where I am driving a bunch of servos and another where I am driving a large amount of LEDs. In both of these projects the teensy sends signals of low current and the LEDs and servos have their separate large current inputs. The servos share their ground with the signal ground however, which I guess means that at least the ground of the teensy has to be able to survive a lot of current in order for it to work. The LEDs are driven by MAX7221 chips. I am using teensy 2.0 and USB chargers capable of delivering 3A. The two problems are:
A) How to connect the charger to the teensy to allow for the servos or LEDs to also connect to its power and ground. Looking at the teensy 3.0 schematic, it appears there is no place to connect to power and ground before the 500mA fuse, as both Vusb and Vin are located behind it. On the other hand, the teensy 2.0 appears to have a direct connection between the power of USB and Vcc, with no fuse or anything to take damage inbetween. Wouldn't this mean that it ought to be possible to pull a rather large current from Vcc? How about ground?
In the case of the servos, they have a separate power input which I ought to be able to split out from the USB cable, but they share their ground with the ground of the signal. I think I may have to sink a notable current to ground because of this.
In the case of the LEDs, they have separate ground and power, so I can create a junction in the USB cable right before the teensy and pull and sing current straight to it.
B) How to connect the charger to the teensy to allow for the servos or LEDs to also connect to its power and ground WHEN LOADING THE TEENSY with a new firmware. At that time the USB connector is connected to the computer and it can only deliver 500mA so the secondary charger needs to be connected somewhere. I see potential issues with different ground levels.
What is common practice in cases like these? I seem to find a lot of information regarding teensy 3.0 and 3.1 regarding separating Vin from Vusb but that option isn't available for the teensy 2.0. The 2.0 also appears to be missing a fuse. Schematics of teensy 3.0 and 2.0 are attached below for convenience. Thanks
Teensy 3.0
Teensy 2.0
A) How to connect the charger to the teensy to allow for the servos or LEDs to also connect to its power and ground. Looking at the teensy 3.0 schematic, it appears there is no place to connect to power and ground before the 500mA fuse, as both Vusb and Vin are located behind it. On the other hand, the teensy 2.0 appears to have a direct connection between the power of USB and Vcc, with no fuse or anything to take damage inbetween. Wouldn't this mean that it ought to be possible to pull a rather large current from Vcc? How about ground?
In the case of the servos, they have a separate power input which I ought to be able to split out from the USB cable, but they share their ground with the ground of the signal. I think I may have to sink a notable current to ground because of this.
In the case of the LEDs, they have separate ground and power, so I can create a junction in the USB cable right before the teensy and pull and sing current straight to it.
B) How to connect the charger to the teensy to allow for the servos or LEDs to also connect to its power and ground WHEN LOADING THE TEENSY with a new firmware. At that time the USB connector is connected to the computer and it can only deliver 500mA so the secondary charger needs to be connected somewhere. I see potential issues with different ground levels.
What is common practice in cases like these? I seem to find a lot of information regarding teensy 3.0 and 3.1 regarding separating Vin from Vusb but that option isn't available for the teensy 2.0. The 2.0 also appears to be missing a fuse. Schematics of teensy 3.0 and 2.0 are attached below for convenience. Thanks
Teensy 3.0
Teensy 2.0
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