What is a Logic Level Power MOSFET ?

snr090428Power MOSFET transistors are voltage controlled switches.  They begin to turn on at their rated “gate threshold voltage” or Vgs(th).  Most of the datasheet ratings are given for a fully saturated condition, typically 10 volts.  There is also a maximum allowable gate voltage, Vgs, that is typically 20 volts.  Any voltage greater than that will pierce the thin metal oxide layer that insulates the gate from the rest of the silicon die, destroying the device.  This is why uninstalled MOSFETS can be so sensitive to electrostatic discharge (ESD) damage.

Continue reading

Microchip PIC Microcontrollers for Motor Control: PIC16F648, PIC16F785 and PIC18F2331

While many of the PIC microcontroller models have at least one hardware PWM output channel that could be used to control an h-bridge, we’ll take a quick look at several models that are particularly well suited for servo and stepper motor control applications.  

Continue reading

How to Convert USB to Serial TTL Level Signals

If you’re designing a device that spends most or all of it’s time connected to a PC through a USB port,  it is probably best to design USB connectivity right into the device.  However, if the device only needs to be connected occasionally to change settings or download data logs, it might be convenient to use a separate adapter that translates USB protocol to TTL level asynchronus serial signals that talk to the microcontroller’s UART.  Also, if you’re a hobbyist, you may not want to spend a lot of time understanding the details of USB interfacing hardware and protocols.  I recently stumbled upon an adapter that makes this easy.

Continue reading