Hi,
I've got a Teensy 3.6 that's having power-on problems.
I've got a 7805 with a 10uf output cap (fed by a 9V power supply with a maximum output of 1amp), and I'm feeding the nice clean 5.0V to the Vin on the Teensy. I also cut the VUSB trace as the instructions say to do when you're using external power. However, the Teensy won't seem to boot. When I check the Vin pin and the 3.3V pins, they all read what they should (the Vin has about 4.97V, and the 3.3V are all reading 3.31V). When I ground the reset pin, it doesn't do anything. However, if I plug in the USB to my computer with the external 5V power on, it starts up, and then I can remove the USB and it continues to run on the 5V external power. If I ground reset though, it doesn't work again. If I leave both the USB and external power connected, then grounding the reset pin works as expected.
Anybody have any idea what's going on here? Is there a *standard* way to drive the Teensy 3.6 with external power that just always works? I wanted to be writing code here, not screwing around with power supply issues. Is there an external power supply circuit that just works? I've tried an LM7805, and a TSR 1-2450 (miniature switching supply that's a drop in replacement for the 7805) -- in both cases I get the same result -- only works if *both* the USB and the external power are connected initially, and then continues to work when the USB is removed. I tried removing the LM7805's output cap (since technically I shouldn't need it, and I read somewhere that it could cause slow start ups), but that made no difference. I also tried the TSR 1-2450 with and without the cap, made no difference.
Any help you could provide would be greatly appreciated.
Thanks,
calphool
I've got a Teensy 3.6 that's having power-on problems.
I've got a 7805 with a 10uf output cap (fed by a 9V power supply with a maximum output of 1amp), and I'm feeding the nice clean 5.0V to the Vin on the Teensy. I also cut the VUSB trace as the instructions say to do when you're using external power. However, the Teensy won't seem to boot. When I check the Vin pin and the 3.3V pins, they all read what they should (the Vin has about 4.97V, and the 3.3V are all reading 3.31V). When I ground the reset pin, it doesn't do anything. However, if I plug in the USB to my computer with the external 5V power on, it starts up, and then I can remove the USB and it continues to run on the 5V external power. If I ground reset though, it doesn't work again. If I leave both the USB and external power connected, then grounding the reset pin works as expected.
Anybody have any idea what's going on here? Is there a *standard* way to drive the Teensy 3.6 with external power that just always works? I wanted to be writing code here, not screwing around with power supply issues. Is there an external power supply circuit that just works? I've tried an LM7805, and a TSR 1-2450 (miniature switching supply that's a drop in replacement for the 7805) -- in both cases I get the same result -- only works if *both* the USB and the external power are connected initially, and then continues to work when the USB is removed. I tried removing the LM7805's output cap (since technically I shouldn't need it, and I read somewhere that it could cause slow start ups), but that made no difference. I also tried the TSR 1-2450 with and without the cap, made no difference.
Any help you could provide would be greatly appreciated.
Thanks,
calphool
