I built a circuit with a simple 555 timer output feeding an astable multivibrator also using a 555. I just want to reverse (alternate) the output polarity of the astable multivibrator every time I start the timer. I have a dpdt relay that will reverse the polarity but how do I latch and unlatch the relay coil alternately every time the circuit gets triggered? The relay has a latching coil. Thanks,

 

You can use a D-FF, such as a CD4013, configured as an alternating latch (/Qout to D input), to change states each time the circuit is triggered.

Instead of a relay, you could use an XOR gate such as the CD4070 to reverse the polarity of its output.

Edit: If you use a relay to reverse polarity, the load must not be connected to circuit common.

 

Thanks, I think the D-FF will be perfect for my application because I want to feed the output from 2 astable mutivibrators into this and the relays are too big anyway. Where is the best place online to order components like this? I am in Canada and my local electronics supply store is out of stock on the CD4013.

 

This might seem like a very elementary question but how do you maintain your supply voltage when feeding the output from one 555 timer to become the supply voltage to the next 555? I have a monostable o/p feeding an astable multivibrator and would like its final output at or close to the original supply voltage. Is this even possible? Thanks

 

This might seem like a very elementary question but how do you maintain your supply voltage when feeding the output from one 555 timer to become the supply voltage to the next 555? I have a monostable o/p feeding an astable multivibrator and would like its final output at or close to the original supply voltage. Is this even possible? Thanks

Why do you want the output of a 555 to be the supply voltage of a second?

Not the way to do it. You use the output to trigger the second 555. The 2nd is always powered.

 

Don't use one device to power another device. This is inviting trouble.
As djs says, use the output of the first device to trigger the second.

 

Why do you want the output of a 555 to be the supply voltage of a second?

Not the way to do it. You use the output to trigger the second 555. The 2nd is always powered.

That’s kinda what I was thinking. Does that mean I would not jumper pin 8 and 4 which it shows on most circuit diagrams?

 

Don't use one device to power another device. This is inviting trouble.
As djs says, use the output of the first device to trigger the second.

That’s kinda what I was thinking. Does that mean I shouldn’t jumper pins 8 & 4 like it shows on most circuit diagrams?

 

That’s kinda what I was thinking. Does that mean I shouldn’t jumper pins 8 & 4 like it shows on most circuit diagrams?

That is something else totally unrelated.
Pin-8 is Vcc supply connection. You connect this to +V supply.
Pin-4 is the /RESET input. Connect this to pin-8 when you are not using the RESET control function.

 

I am in Canada and my local electronics supply store is out of stock on the CD4013.

Can you do mail order, such as from Mouser or DigiKey?

If you don't use a relay to invert the signal, then you will also need a XOR gate, as I mentioned.