Technogumbo
New Member
Hi everyone. I am working on a small project for using USB to control an RC car. Basically what I am trying to do is allow uninterrupted PWM signals to pass through the device when USB is not hooked up, then prevent the PWM signals when USB is hooked up to the circuit. USB operates on 5V and I try and limit my devices to sourcing 400mA from the bus.
RC cars normally have a three pin PWM, V+, and GND line for each servo and electronic speed controller you want to control. The battery powering the circuit could be from 7.2 to 12v.
**broken link removed**
I am wondering if the attached schematic is even realistic? I was hoping to use a PNP transistor with base hooked to the 5v line of USB to essentially close the PWM line whenever I hook up the USB connector to the device, and supply my own PWM signal being generated from a microcontroller.
I am having doubts because the base of the PNP will be left unconnected when no USB cable is hooked to the device. Do I need to use a circuit like the following posted by user Hero999 in another thread?
**broken link removed**
Thanks for all the advice in the forum I have found it useful many times.
RC cars normally have a three pin PWM, V+, and GND line for each servo and electronic speed controller you want to control. The battery powering the circuit could be from 7.2 to 12v.
**broken link removed**
I am wondering if the attached schematic is even realistic? I was hoping to use a PNP transistor with base hooked to the 5v line of USB to essentially close the PWM line whenever I hook up the USB connector to the device, and supply my own PWM signal being generated from a microcontroller.
I am having doubts because the base of the PNP will be left unconnected when no USB cable is hooked to the device. Do I need to use a circuit like the following posted by user Hero999 in another thread?
**broken link removed**
Thanks for all the advice in the forum I have found it useful many times.