555/556 reset pin question

[unseen wombat]

I'm trying to make a circuit using a 556 timer. I want both timers to be astable, such that when the first one is high, it sets the second one oscillating, then they both shut off when the first one goes low again.

I need to know, what do I connect the output of timer A to in order to get this to work?

I thought I would connect it directly to the reset of timer B, and when I model it that way on electronics workbench, it seems to work fine (except the first pulse is quite a bit longer than the following ones. I don't know why), but when I try it for real, it seems the reset pin doesn't actually do anything, except when it's grounded, of course. So far, I've only tested timer A on my real 556, but it oscillates whether pin 4 is connected to Vcc or not, (unlike what happens in my model).

So what should I do? Attached is a picture of what I'm trying to do, but even though it works in multisim, it won't work IRL, because pin 4 has nothing to do with making the timer work. I suppose I could use two 555's and connect pin 3 of the first one to pin 8 of the second, but Vcc is shared in the 556.

 

[Roff]

I'm not sure what you're doing.
Reset is active low. If you tie it to Vcc, or let it float, the timer will function. To reset it you must tie it to ground.

 

[unseen wombat]

Ok, what I want to do is have the first timer control the second timer. I want the first one to stay off for about 10 minutes, then come on for 3, off 10, on 3, etc. While it's on for the three minutes, I want that to cause the second timer to give a one second flash once every 30 seconds.

That's what I'm trying to do. Any ideas as to how I can use one astable timer to control a second astable timer? I'm thinking now maybe I should take the output from timer A and feed it through B's R1 resistor to pin 7 and not connect pin 7 to 8 on timer B. That will in effect power up timer B, right?

 

[unseen wombat]

Nevermind, I figured it out, I just need a pulldown resistor from pin 4 of timer B. That way it's grounded as long as the output from A is low, but when it goes high, pin 4 gets some current.

 

[Tiger555]

Nevermind, I figured it out, I just need a pulldown resistor from pin 4 of timer B. That way it's grounded as long as the output from A is low, but when it goes high, pin 4 gets some current.

Hi mate, will you please tell me how to get a 1ms pulse in every 20sec. I am not at all into electronic. But i fig some 555 timers circuits. Looking ahead to solve.. thanks in advance.

 

[thecritic]

Hi mate, will you please tell me how to get a 1ms pulse in every 20sec. I am not at all into electronic. But i fig some 555 timers circuits. Looking ahead to solve.. thanks in advance.

IMO, best way to learn 555 isn't by memorizing circuits and formulas for monostable, astable, astable with duty cycle < 50% etc etc. If you understand basic principle of operation, you can come up with any form of solutions.
555 Timer IC Working Principle