time delay voltage pulse
heyy guys.. i im baffled how to creat a a time delay voltage pulse ckt, that genrates a +5v voltage pulse after every 6 seconds (without using a 555 timer,or any timer at all) i want this for trafic light signal systemi.e my logic design project. I ve designed the rest of it. I waz thinking about using a diode clipper or sum sort of a RC ckt.
Why make things hard? These products are aviable just for this purpose.Originally Posted by Master Mind
Lions and tigers and bears, OH MY!
i knw but we hav a restriction!
i knw but we hav a restriction!
Which is what?
Lions and tigers and bears, OH MY!
Do you also have a restriction to use transistors?
Proper Planning Prevents Piss Poor Performance
Transistors we can use...
Last edited by Master Mind; 25th October 2009 at 04:28 PM.
COME on GUys i need a soloution ASAP!
You've given no details on your restrictions. Yet you expect us to give you a solution, and bail you out.Next time don't wait so late to ask, and give the information when requested.
Last edited by BrownOut; 25th October 2009 at 06:21 PM.
Lions and tigers and bears, OH MY!
gosh man i went to get me a cofee!!You've given no details on your restrictions. Yet you expect us to give you a solution, and bail you out.
read the thread! i cant use a timer! but i can use a transistor or a RC circut or even a diode!!!
How about this. Use a transistor as the main switch, at it's base use a series of diodes that will have a forward drop of about 5 volts. Do the math to find an RC time constant of 6 seconds to reach five volts and feed that into the base of the diodes that go to the transistor base. When voltage is applied to the base of the RC network it will charge to 5 volts, at which point the diodes will begin conducting triggering the transistor on. You'll have to chose your R value carefully though as it will need to limit current to the base to keep it from frying as well as still provide enough current to saturate the transistor.
Last edited by Sceadwian; 25th October 2009 at 07:32 PM.
"Because I be what I be. I would tell you what you want to know if I
could, mum, but I be a cat, and no cat anywhere ever gave anyone a
straight answer, har har."
Program a PIC to output a pulse ever 6 sec. Technically, a PIC isn't a timer.
Last edited by BrownOut; 25th October 2009 at 08:24 PM.
Lions and tigers and bears, OH MY!
If you can use an opamp you're all set, they're easy to configure as a comparator. I played around with the transistor idea, but I couldn't find a low enough R value that would saturate the transistor without an absurdly large capacitance, the transistor was always in it's linear range and burning a lot of power, and in the real world itself up, you might be able to use two or more transistor in a darlington array to do it though.
Last edited by Sceadwian; 25th October 2009 at 08:29 PM.
"Because I be what I be. I would tell you what you want to know if I
could, mum, but I be a cat, and no cat anywhere ever gave anyone a
straight answer, har har."
I was bored so I played around with it in LTspice cause I don't generally create new circuits from scratch. It's pretty crude, but it works. The major problem being the turn off delay is the same as the turn on delay. Sorry about the size of the image, I didn't bother trying to make it small, was just a hack job. The blue line is the triggering input (in the shematic it's the pulsed voltage supply) and the green line is the load current. I used a 100ohm resistor as a sample load. The response will be much more square and less lossy in the transistors if the load is less. You could probably increase performance dramatically by changing the components used, perhaps to a true darlington. Just as a learning example I'd like comments from other users on how that circuit could be improved without adding significant complexity.
Last edited by Sceadwian; 25th October 2009 at 08:52 PM.
"Because I be what I be. I would tell you what you want to know if I
could, mum, but I be a cat, and no cat anywhere ever gave anyone a
straight answer, har har."
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