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Combination Lock

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DerStrom8

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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
 
Why are you using timers to do a combo lock? There are simpler circuits for that purpose that use static gates. Check these.
 
I wanted to see if it could be done with timers. I have a bunch of 555s, but I don't have many other chips at this point. I was hoping I could design a lock circuit using timers ;)
 
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Here is Another Simple Lock that works Good.

**broken link removed**
 
ok..best of luck.... does any one of you know about USB stepper motor controller?....
i was trying to make one parallel port stepper motor controller but it seems that parallel port does not work very well...it is lot messy...
so any one of you know about a usb controller . and yes i dont have a IC programmer...

i am trying to make a 3 axis CNC ...

plz help
 
I made a really simple combo lock using a 4017 and some NAND gates. It worked on the bread board, but when I tried to transfer it things got complicated and then it didn't work. That's probably because it had so many connections. I made a newer version that uses a Parallax RFID reader connected to a F-F, and that works perfectly every time :)
 
Here is Another Simple Lock that works Good.

**broken link removed**

That was one of the first circuits I had looked at, but I don't have any 4013s (or any other flip-flops, for that matter). That's why I was looking at 555s, because I've got five or six of them. Thanks a lot, though. If I can get my hands on the 4013s, I'll give this one a try.
 
ok..best of luck.... does any one of you know about USB stepper motor controller?....
i was trying to make one parallel port stepper motor controller but it seems that parallel port does not work very well...it is lot messy...
so any one of you know about a usb controller . and yes i dont have a IC programmer...

i am trying to make a 3 axis CNC ...

plz help

I suggest you start a new thread. I'm sure plenty of the members would be happy to help you out.
 
Hey, thanks a lot! That's a lot simpler than what I was thinking ;)
I'll give it a try this afternoon!

So, I put this circuit together and got it to work, but it didn't quite have the style of operation I was hoping for, but I think I can tweak it a little bit to suit my needs. Many thanks!
 
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