Looking for a timer that activates in less than a second and stays on for 2 minutes

[f1r3z1m]

Hello, it's my first topic at this forum
well i'm trying to do a system for my building to put at the stairs...
when a person pass between the infrared sensor its turn on the light about 2 minutes
but now I have a problem with the timer because I was think to do with capacitor but it have to recharge in less than a second
I just can't find a circuit to active in less then a second and stay on for 2 minutes
if someone already have the circuit ready please post it here

when my circuit is over I will put here all the circuit since the powersupplie to the system that turn on the lamp

thanks!

PS.: I'm sorry for my english... its because i dont pratic this a long time

 

[sigint]

Re: Help with timer

Your timing cap should easily charge in less than a second, unless you have a limiting resistor in series with the charging source, if you are using a 555 you may want to switch to a simpler transistor switch.

SiGiNT

 

[IanP]

Re: Help with timer

How about using 555-timer as edge-trigger ..
Infrared sensor activates timer which generates output pulse determined by R[t]-C[t] ..
See picture below ..

IanP

 

[f1r3z1m]

Re: Help with timer

How about using 555-timer as edge-trigger ..
Infrared sensor activates timer which generates output pulse determined by R[t]-C[t] ..
See picture below ..

IanP

hi
i try to do this circuit at my home and isis but it doesn't work
I don't know what happens
:s
and i search on the web I try many circuits but anyone works

i dont know more what to do

 

[IanP]

Re: Help with timer

Circuit(s) with 555-timer should work without problems ..
Post the diagram of your circuit and include values of resistors and caps that you used ..

IanP
:|

 

[f1r3z1m]

Finally I have done this project
I was very busy but I got sometime and finished it

This is the project how I promissed

**broken link removed**

**broken link removed**

and to change the time has to change the resistor R1 and capacitor C1

 

[erikl]

The serial circuit of D2 - Q1(CE) - Q2(BE) without any current limiting is dangerous: the current through these 3 devices depends on B(Q1) and on the operating voltage 5VCC, hence is rather undefined. A different (higher) current gain B of Q1 or a 5..10% increase of the 5VCC could (have) blow this serial circuit.

You might want to insert a limiting resistor in series with D2, about 100Ω.

 

[f1r3z1m]

erikl
yeah I did it but i forgot to put it in the schematic
I maded it at protoboard... I put a 220R and its work perfectly

thanks to remind it