Friday, February 5, 2010
Chapter 3 - Exercise 15 Part 3
Today I wired up the alarm system portion of the breadboard... once again, I lacked two 2.2 microfarad resistors so I substituted a 4.7 microfarad for C3 (in Figure 2-113). When I wired up this noise maker using that combo, it worked... but probably didn't sound exactly like it should with two 2.2 microfarads...
I also modified the relay circuit to look like the one in Figure 3-95. When I break the magnetic switch, I hear the relay kick in and it locks, too - resetting the magnetic switch doesn't turn it off.
I hooked up the speaker... flipped the power... broke the magnetic switch... and nothing.
(Keep in mind that I'd already used my multimeter to test voltage/current settings - there was a charge of almost 12V built up on C1 capacitor... and about 11V on the two wires I used to connect to the speaker... so... faulty speaker?
Instead, I connected an LED in place... and it worked. The LED lit up just fine... but shouldn't it pulse? I rechecked all my wiring and components... everything where it should be and voltage across the LED... enough to light it at least. But not enough to get me any noise from the speaker. So I'm back to testing... probably won't get to it until tomorrow, but I'm anxious to build this device, so I'll do my best to figure it out... suggestions or tips welcome.
Movie of the LED lighting up below...