555

Pin 4 is usually held high. Are you reseting the thing with pulses on pin 4 - or was that a typo?

Ed

Bascially as John said.

If you go from a low to high transition on the reset pin, the output will go high straight away. Has nothing to do with any duty cycle you have set up.

Well, it will have a marginal delay, which will be shown in the data sheets.

Don...

Pin 4 is the "reset," it is held high by being hard wired to Vcc for astable operation, so this must be a trick question.

You should google for this real basic stuff before posting.

That is what I was thinking.

Two 555s with pin 3 of the first connecting to pin 4 of the second.

The first has a lower frequency that the second. The result should be a short repeating series of pulses. Each series is separated by a distinct pause.

I am sure that there are other ways of achieving this.

- or was that a typo?

No trick. See my reply to an earlier post.

Thank you for your no nonsense answer.

On Tue, 22 Sep 2009 12:32:46 +1200, Roger Dewhurst wrote:

--- You're welcome. :-)

BTW, in response to one of your other posts, here's how to do it using logic gates:

Version 4 SHEET 1 1300 680 WIRE -112 -224 -272 -224 WIRE -80 -224 -112 -224 WIRE 32 -224 -16 -224 WIRE 240 -224 80 -224 WIRE 272 -224 240 -224 WIRE 384 -224 336 -224 WIRE -112 -192 -112 -224 WIRE 240 -192 240 -224 WIRE -272 -96 -272 -224 WIRE -224 -96 -272 -96 WIRE 80 -96 80 -224 WIRE 128 -96 80 -96 WIRE -112 -80 -112 -112 WIRE -112 -80 -160 -80 WIRE -96 -80 -112 -80 WIRE -64 -80 -96 -80 WIRE 32 -80 32 -224 WIRE 32 -80 0 -80 WIRE 240 -80 240 -112 WIRE 240 -80 192 -80 WIRE 256 -80 240 -80 WIRE 288 -80 256 -80 WIRE 384 -80 384 -224 WIRE 384 -80 352 -80 WIRE 448 -80 384 -80 WIRE -96 -48 -96 -80 WIRE -64 -48 -96 -48 WIRE 256 -48 256 -80 WIRE 288 -48 256 -48 WIRE -224 -32 -272 -32 WIRE 32 -32 32 -80 WIRE 128 -32 32 -32 WIRE -272 0 -272 -32 WIRE -272 128 -272 80 FLAG -272 128 0 SYMBOL cap 336 -240 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 1e-7 SYMBOL res 256 -96 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R1 SYMATTR Value 1e6 SYMBOL Digital\\\\and 160 0 M180 SYMATTR InstName A1 SYMATTR Value2 vhigh 5v trise 1e-6 tfall 1e-6 SYMBOL Digital\\\\and 320 0 M180 SYMATTR InstName A2 SYMATTR Value2 vhigh 5v trise 1e-7 tfall 1e-7 SYMBOL cap -16 -240 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value 1e-6 SYMBOL res -96 -96 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R2 SYMATTR Value 1e6 SYMBOL Digital\\\\and -192 0 M180 SYMATTR InstName A3 SYMATTR Value2 vhigh 5v trise 1e-6 tfall 1e-6 SYMBOL Digital\\\\and -32 0 M180 SYMATTR InstName A4 SYMATTR Value2 vhigh 5v trise 1e-7 tfall 1e-7 SYMBOL voltage -272 -16 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5 TEXT -264 104 Left 0 !.tran 10 uic TEXT 448 -80 Left 0 ;> OUT TEXT -224 -120 Left 0 ;HC02

JF

Oh. Usually my mind reading ability is much better. Sorry.

^^^^ Aarghhh!!! .............HC00

JF

Accepted. None of us can get through life without the occasional cockup.