Re: Random timer!

On 2007-06-03, Baron <baron.nospam@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

500K slow rate
\
/\
.-\/\/\--+--------+--- +5V
/ / | . . . .|. . . .
\ | . VCC(8) .
/ 1.2M | . .
\ --RES(4) OUT(3)--------->
| . LM555 .
go-fast ----\/\/\-->|-+--------+--TH(6) DISmmm(7)-----.
10K 1N914 | . . |
+--TR(2) CV(5)-- |
| . . |
| . GND(1) . |
| . . . .|. . . . |
| | |
+--------|-----\/\/\-'
| | 33
===== |
10uF | |
--+--------+-- 0V

Can you confirm the resistor value between pin 2 and 7 please !
I read it as 33 Ohms ?

that's right the LM555 has a maximum current into the discharge pin
of 200mA, (and the CMOS version TLC555 or 7555 only 100ma)

33ohms is enough to keep the peak discharge current to a
sensible value with a 5V supply the capacitor will charge to 3.33V
so the peak dischharge current will be about 100mA

Bye.
Jasen
.

Relevant Pages

  • Re: Bright flashing light for fake alarm box?
    ... I think you left out the pin numbers so I put Pin One in. ... > Rt 470k ohms ... You can adjust the frequency of flashes by changing Rt or Ct. ... but it'll be hard to get a 10uF cap that is low leakage. ...
    (sci.electronics.basics)
  • Re: LM386 (audio amp) oscillates
    ... output as recommended in the app notes (10 ohms in series with .05uF). ... The oscillations will stop if I add a .05 cap across the input pot, ... The app notes show pin 7 open in the 26dB setup.But it looks like ...
    (sci.electronics.basics)
  • Re: PAD5
    ... John Larkin wrote: ... Pin 3 to pin 1 ohms as a diode ... In low current apps simple back-to-back diodes can cause distortion. ...
    (sci.electronics.design)
  • Re: PAD5
    ... Pin 3 to pin 1 ohms as a diode ... course they don't specify leakage. ...
    (sci.electronics.design)
  • Re: PAD5
    ... Pin 3 to pin 1 ohms as a diode ... Even if the rails have to be set up just for that purpose. ...
    (sci.electronics.design)