I'm using a 556 Timer and want to do the following with it:
When the external Mercury switch of the 1st timer on the 556 is closed then opened it will sound a Buzzer for approximately 2 sec. At the same time it will supply power to the 2cd timer of the 556. When the second external Momentary switch is closed and then opened it will turn on a LED. The LED will continue to stay on till the fist Mercury switch is activated once again, which starts the cycle over again. I hope this make some sense, especially since I am new to all this. I would surely appreciate it if anyone could make up a schematic or something to get me going in the right direction. Please contact me if more information is needed.
ok, so i guess you could use a one shot timer on the first one via the use of the Reset, use it's output to release the reset line of the second one, use the second switch to set the trigger of the second timer which should if memory serves switch on the output of the second timer.. this output can run an LED etc..
so basically, you want a momentary latch of your second switch only while the first one has tripped the timer for no longer than
2 secs or so.. and when the first timer expires, it should also kill the output of the second timer and hold down the reset .. i guess i was to think about it some more it would be simple. I would think a Data type flip-flop from the first timer would do what you want. oh well.
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If I had the buzzer only come on while the 1st switch is close would I even need a timer? If that's the case how do I give power to the second switch, which when closed turns on the LED till the first switch closes again? Remember the first switch is a momentary switch and may close for different periods of time. Would I even need a timer for the second switch? How could I accomplish this? I don't know anything about flip-flops or latches, if something like that would even work. If you can give me any information along with part numbers or schematic showing how it would work I would surely appreciate it.
Thank You so much for all the information, I hope it did'nt take you to long . Where did you get your smarts from? I'm going to go through this and try some stuff out. If you don't mind, I will probably need to contact you again. Your a great help! Thanks!
ok, some more info is needed his. If i read you correctly. I think what you need is a is a data flip flop. Look about half way down on this page and read alittle about them.
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Basically, you have a Data input, this would be for example your switch 2 input. then you have a C (clock) input, this would be from your switch 1.. depending on the type of D-FF you want to use. for example, the C input (clock) goes from low to high using your switch 1, it will take what ever state the D (input) is in and place that to the Q output and thus hold that state until the next time the C input gets a low to high transition input, which will repeat the process over again. the Q output can be used to light up an LED if you wish. now when i said there are different kinds of data flip-flops? i meant there are different types of triggering styles for example. the one i just used would be a Positive edge which means that it takes the D input status and transfers it to Q when the C (Clock) goes high. so that means while the C is being held to low (common), the Q output holds the current value that was there before. Now, if you used a negative edge type, it will capture the state at D and transfer that to Q when C goes low (ground). both edge types ignore changes taking place at D while the C input is being held at the trigger level. this means, it will only capture what D is at the time of transition of the CLOCK level change per type that your using.
Now, you have level type D-FF's, and they have high capture logic for the CLock, and what this means is, while the Clock is in the high state, Q will reflect all activity of changes from D until C goes back to the low state at which point Q holds the last state of D..
I hope you understood that and i didn't get anything twisted here.
I noticed that the sight i gave you has their description of the level type miss leading. I double checked some doc's i have here to make sure, they state that Q holds the last value until C goes low, that wouldn't really make sense because why would you need a Negative edge FF ?, so the statement there is a little incorrect, D will show at Q it's value while C is high, and when C goes low, Q will hold the value at transition time.
Basically, if your attempting to create some synchronizing circuit where you need an output to appear when switch 1 is on and switch
2 is on to show that you have sync, this would be the way to do it. because the next time also remember that you will need a deboucer on the Clock input because if you have a poor connection there, it will trip that input multiple times. if you plan on using a contact switch, i would suggest using a small capacitor on the input to common. something like a 0.01 uf.. Also, if you require a minimum time for Switch one to hold it's state? you can adjust the cap size on the clock input. just remember to select the type of flip flop you need and to drive an LED, use a TTL type. the 74xx series is good for that. other wise you will need driver transistor. Like many other Flip Flops, many have Set and Resets.. all this means is, you can force the Q output to what you want at start up if you wish..
A positive Edge D-FF
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One with 8 D-FF's with common Clock for all.
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A list of Quads etc.. http://www.ortodoxism.ro/datasheets2/1/03ldaq2whf1qu7dlj4g216t704py.pdf
they come in different varieties, just remember the 74xx, 74xxx series are TTL which can handle the current of the LED and is 5 volt logic etc.. other types are static sensitive. the 74HCxxx series allow for a wider range of supply voltages.
--
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
Sorry - this was a little harsh for the .basics group. I'll try to cancel the post. I've broken the fundamental rule of s.e.basics - the only dumb question is the one you don't ask.
But, it does sound kind of like you're looking for an R-S flip-flop for your second stage.
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