Hey guys,
I'm building an alarm clock as a personal project.
Basically, instead of making noise (which wakes my roommate before me), I am building a board that will drive a set of blue LEDs to simulate a sunrise in my otherwise dark bedroom.
I have found these commercially, but they are very expensive (like, over $200 for the LED version)
Plus, I like to build things.
So, on to my problem.
I've put together a quick board with a pair of 555 timers on it. The first is an Astable Multivibrator operating at ~750 hz. The output of this goes to a monostable 555 with a Resistor/capacitor circuit to slowly raise the divider voltage. The output of the Monostable 555 goes to the gate of my MOSFET to drive the ~30W LED string.
The goal of all of this is to slowly increase the light instead of just blasting me with light in the morning. The second goal is to learn more about the 555 timer as it seems ubiquitous.
I have a good squarewave coming out of the Monostable 555, and power to the MOSFET's source, but when I put a scope looking at the Drain to ground voltage, I see a 12VDC flat line with spikes at the triggering frequency.
When examined closer, the spikes are a single sinewave cycle, dropping first then climbing, then returning to 12VDC.
Response time of the MOSFET is supposed to be ~20ns. (obsolete part NDP4060, had a few laying around)
I have changed the MOSFET twice now. switching between viewing the Drain and the gate shows a clear discrepancy between what is being sent and what is being received.
Any help would be great!
Thanks,
Dan
I'm building an alarm clock as a personal project.
Basically, instead of making noise (which wakes my roommate before me), I am building a board that will drive a set of blue LEDs to simulate a sunrise in my otherwise dark bedroom.
I have found these commercially, but they are very expensive (like, over $200 for the LED version)
Plus, I like to build things.
So, on to my problem.
I've put together a quick board with a pair of 555 timers on it. The first is an Astable Multivibrator operating at ~750 hz. The output of this goes to a monostable 555 with a Resistor/capacitor circuit to slowly raise the divider voltage. The output of the Monostable 555 goes to the gate of my MOSFET to drive the ~30W LED string.
The goal of all of this is to slowly increase the light instead of just blasting me with light in the morning. The second goal is to learn more about the 555 timer as it seems ubiquitous.
I have a good squarewave coming out of the Monostable 555, and power to the MOSFET's source, but when I put a scope looking at the Drain to ground voltage, I see a 12VDC flat line with spikes at the triggering frequency.
When examined closer, the spikes are a single sinewave cycle, dropping first then climbing, then returning to 12VDC.
Response time of the MOSFET is supposed to be ~20ns. (obsolete part NDP4060, had a few laying around)
I have changed the MOSFET twice now. switching between viewing the Drain and the gate shows a clear discrepancy between what is being sent and what is being received.
Any help would be great!
Thanks,
Dan