Hey guys, I'm having some problems that I hope one of you can easily fix.
Here's the deal - I'm trying to drive 4 different resistive loads (similar to heating elements) with the PWM outputs of an AVRtiny45. I'm essentially trying to use PWM to modulate the power delivered to the loads. The resistive loads each require up to 500mA of current. They are roughly 10 ohms each, though they can vary slightly. Since the tiny45 can't drive this much current, I'm trying to use P-Channel MOSFETs to switch the current on and off. I'm using P Channel instead of N Channel because I figured it's safer to connect my load to the ground side of things (?).
The problem is, when I turn on the PWM outputs, the AVRtiny45 chip resets.
To make things worse, everything works fine when I remove my resistive loads and instead use LEDS in series with 470ohm resistors. The LEDs dim and get brighter and work just fine, but the load resistance is much higher than my original load.
I'm assuming it all comes down to me trying to power everything from the same 5V power supply - the AVR, the resistive loads, everything. This is the preferred scheme in my application. I only want 1 power line.
I'll try to attach a schematic. What could be causing the chip reset when driving the "high" current PWM?
Other important info:
-P Channel MOSFET is FQPF7P06
-PWM freq is 244Hz
-AVRtiny45 is running off internal 8Mhz Oscillator
-RESET pin is disabled and used as IO instead
-VCC comes from the output of a 7805 chip, which is powered from 9V
-The PWM outputs are changed by I2C communication to the tiny45