DerStrom8
Super Moderator
Hello, all!
I'm in the process of designing a combination lock using several 555 timers wired as monostable pulse generators. The idea was to have a tactile push-button switch between pin 2 and ground on each of the timers to trigger the output, which is then connected to the base of an NPN transistor. The collector of the first transistor is connected to +9 volts, and the emitter is then connected to the collector of the next transistor (whose base is connected to the output of the second 555) and so on. My problem is that I need a way to keep the device (an LED right now, for testing) off until all of the correct transistors (with the push-buttons) are switched on. The emitter-base voltage doesn't allow this to happen, and I would like some help with this. I can try to post the schematic of my idea if it will help.
Thanks a lot!
Der Strom
I'm in the process of designing a combination lock using several 555 timers wired as monostable pulse generators. The idea was to have a tactile push-button switch between pin 2 and ground on each of the timers to trigger the output, which is then connected to the base of an NPN transistor. The collector of the first transistor is connected to +9 volts, and the emitter is then connected to the collector of the next transistor (whose base is connected to the output of the second 555) and so on. My problem is that I need a way to keep the device (an LED right now, for testing) off until all of the correct transistors (with the push-buttons) are switched on. The emitter-base voltage doesn't allow this to happen, and I would like some help with this. I can try to post the schematic of my idea if it will help.
Thanks a lot!
Der Strom