Hi,
I have two hard switches A and B that need to be linked in a certain way.

A is a toggle switch (on / off ) that powers a circuit .
B is a normally open pushbutton switch.
B must be physically removed and replaced by the following action triggered by A:



A manually goes from OFF to ON and powers one circuit.

3 seconds delay..

And automatically B is briefly closed just to start another circuit (different from the first) and remains open.

Nothing happens when A manually goes to OFF again.



I know this could be ridiculously easy to do with timer stuff but I´m on the mechanics side.
Thanks.

 

HI ADRIADI
"is briefly closed just to start another circuit"
do you mean cycle
could you do us a rough sketch of what you have in mind,

 

Basically A switch triggers a cyle in B pins 3 secs later (b is not there anymore, just two pins)

 

forgive my crude drawing my copiers off at the moment see pic

just using a relay analogy to start with

so when you close switch A there is a 3 second delay before the relay operates momentarily sending a pulse to circuit B ?

are you ok with electronics ?

 

adriadri

i hope were talking low voltage stuff

 

Thank you!
Yes the analogy is exact. 12 volts is the voltage.I just need a simple circuit to do that .

 

something like this
the output can drive a normally open relay or a power transistor, depends on your circuits really,

im a bit of a newbie, i was hoping one of the experts would show us the way, they must be all up the pub,

 

sorry ,the first input will need a differentiator? to provide the negative trigger pulse,
sounds complicated but i think its only a diode /resistor

will get back with this info

hows your maths?

 

if using a relay it will generate a back force on switch off so a diode is needed here to protect the second 555.

 

Thanks for your help Tibbles, I´ll look into this circuit. I´m good in Maths (not counting electrons, but RPM´s)

 

A couple of options:

A positive-edge transistor-triggered 555 monostable: The leading edge of a zero-to-positive pulse on R1 will trigger the 555. Depending on what the input to the B circuit looks like, the 555 output might drive it directly, or through a relay or an opto-coupler.

A "relay monostable": The ON-period depends on the value of C1 and the resistance of the relay coil. The diode prevents it from being an "edge detector".

Ken

 

Thanks for your circuits Ken!
If I´m not wrong the "relay monostable" result is just the relay acting a
given amount of time "the on-time"?

If so, I don´t need this.
What I need is that when I manually move a toggle switch from ON to OFF, (this could be one half of a double toggle switch, the other independent half powers the A circuit that has nothing to do for what I need),
two pins- absolutely independent from that circuit-are momentarily shorted
-say the time a PC keyboard key is pressed when you type-.

The time delay from the toggle switch change till the momentary short occurs, is 3 or 4 seconds.

 

Oops! missed that. I'll re think this.

Ken

 

here´s a pic of what I need.Thanks!

 

sorry adriadri

your inititial project shows 2 black boxes, do you need only 1?

 

Yes. In fact the toggle switch is double. So one part triggers the irrelevant (not shown now) first box and the other part is exclusively dedicated to trigger the sequence I need, which means you must see the toggle switch as isolated from everything but the black box of the last attachment.

 

im having a discussion on this forum about attaching thumbnails, how do you do it?

if you still need the delay a similar approach will apply
as there is no indication of polarity/voltage on the two bottom pins, the relay route would provide isolation

 

kens relay circuit looks good, just use the normally open contacts,
save a lot of electronics,

 

Thanks for your help!
Well, the thumbnail is uploaded using the "MANAGE ATTACHMENTS" button
in the additional options dialog.(keep in mind you don´t have to use the "quick reply" option to get this dialog available)
just use "Post reply".

 

(this could be one half of a double toggle switch, the other independent half powers the )

if you use a double pole switch double throw switch, you can maintain isolation at this point as well so you can choose your own power supply polarity etc.

need to look at kens relay circuit to check if the relay is initially closed or initially open, either way just use the relevant contacts.