1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

timer 555 circuit once or continues loop?

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Monaco, Nov 24, 2002.

  1. Monaco

    Monaco New Member

    Joined:
    Nov 16, 2002
    Messages:
    26
    Likes:
    0
    Location:
    Holland
    I want to make this:
    http://www.uoguelph.ca/~antoon/circ/555test2.htm
    But what will happen if I press swish S1 and keep it
    closed? Are the leds just going on once or will they go off
    and after 2,5 seconds on again.
    And so making a continues loop?
     
  2. mechie

    mechie New Member

    Joined:
    Sep 4, 2002
    Messages:
    591
    Likes:
    3
    Location:
    Lincolnshire, England
    The 555 Timer

    All three of these 555 timers are connected as monostable multivibrators; so a single cycle will be seen rather than continuous. The switch [S1] simply kills the power to the monostab IC3 and the 74107 IC5.
    This means that ICs 1&2 will time out soon after power is applied to the circuit and then sit dormant until power is isolated and restored :?: regardless of the position of S1.

    The only way I can see this circuit working is if S1 kills the power to everything (an on-off switch) :?

    Although this way of testing a 555 seems OK it doesn't check the discharge transistor. I wonder if a simple astable circuit would be more thorough - it would just mean watching an LED to observe flashing for OK or steady for faulty.
     

Share This Page