ONE momentary switch to switch states of latching relay

I just came over something I've heard of before, but know nothing about: Bistable.
And it seems to be the key to control a latching relay with only one momentary switch.
Is there a way to make a bistable driver or such to switch an ordinary latching relay with a momentary switch, without programming chips?

yes

everything that is possible in integrated logic is also possible in discrete relays

Jakob E.

Thanks,

Do you know a direction to point me in, circuitwise?

google "bistable multivibrator" or "flip-flop" (not the shoes).

JR

Thanks,

I found a circuit that I simulated.


+Vcc=12v
R1=R4=1k
R2=R3=10k

I get 11v out on one side and 50mv on the other.  The switch in this circuit is still a latching one, not momentary though...

I found another circuit called "Sequential Switching Bistable Multivibrator" and seems to be closer to what I need. It says:

Switching between the two states is achieved by applying a single trigger pulse which in turn will cause the “ON” transistor to turn “OFF” and the “OFF” transistor to turn “ON” on the negative half of the trigger pulse. The circuit will switch sequentially by applying a pulse to each base in turn and this is achieved from a single input trigger pulse using a biased diodes as a steering circuit.

Click to expand...

Playing around with logic gates is a much more simple approach, correct?

Example: (Still needs two momentary switches)

What about this one?

This is commonly done with a 4013 D-type flip flop.

I like the simplicity. Can you (or someone else for that matter) explain what happens with the switch is pushed?
I guess the the purpose of the circuit is to change the direction of the fan. That seems kind of impossible, as the + of the fan is connected to the +12vdc rail. The - side however, changes from +12Vdc to +0.175mVdc (fan swapped for a 1k load). So the fan can either get (almost) +12vdc, or 0vdc across. Whats the point?  Note: I'm using latching relays.

merlin said:

This is commonly done with a 4013 D-type flip flop.

Click to expand...

> fan can either get (almost) +12vdc, or 0vdc across. Whats the point?

On/Off??

> switch an ordinary latching relay with a momentary switch

Hmmm.

I thought the point of a latching relay was to stop drawing current as soon as it switches states.
In this case, a short pulse, long enough to switch the relay would make sense.

PRR said:

> switch an ordinary latching relay with a momentary switch

Hmmm.

Click to expand...

Haha...you're right. Lack of sleep on my part.

PRR said:

> fan can either get (almost) +12vdc, or 0vdc across. Whats the point?

On/Off??

Click to expand...

Sorry, I missed the part about it being a *latching* relay!

Maybe the answer is easier if I use a "bistable" two coil relay?

Back up. Your question is muddy and I think we've all been barking a wrong tree.

> know nothing about: Bistable.
> And it seems to be the key to control a latching relay with only one momentary switch.

The "latching relay" IS a bistable flip-flop.

There is no one "ordinary latching relay". I have on my desk just what you need: a coil yanks a ratchet which turns a cam which works the switch. Holding your hand-finger on the coil-power will not cause a second ratch- you have to release power so the lever-finger slips back. I'd planned to use it for cellar lighting (at multiple points).

But that is out of production, very expensive. The modern latching relays come in two forms: two-coil and one coil with reverse polarity.

You would think you could use a DT contact on the relay to switch coils (or a DPDT to reverse supply). Problem is that you hold your button until the relay switches. Now the opposite signal is given and the relay switches back. It is about impossible to release your button at the instant that the relay has started to move but has not yet made contact.

This is an old problem in logic. In chippery we like a "master/slave" flip-flop. One flop holds the input (user intention); the other does the actual switching. In MML we can fool with a capacitor to "hold" one state. This is how all the BOSS pedal switches do it.

While most flip-flops give a steady output, you can cap-couple them to the latching coil so it goes Thunk and then current fades to zero. You have to consider recharge path and minimum time between button presses.

Unless you are in a very retro mood, logic chips get you there with less pain. (Today a $1 PIC gets you there cheaper.)

The attached plan is NOT thought-through but sumthin like it should work.

I've started to consider it (ordered a programer yesterday.) But I'm not sure about the "less pain"-part. I know nothing about programing. (I don't even know how to spell the work correctly, it might be "programming".) And I don't think I'm smart enough to program something like this.  :-\
Your circuit was useful, as you said.
Well. I'll take the leap and go the programing route I think.

PRR said:

Unless you are in a very retro mood, logic chips get you there with less pain. (Today a $1 PIC gets you there cheaper.)

Click to expand...

There may also be some specialized ICs that could come in handy.  This one's one of the first I found for "latching relay driver":

https://www.fairchildsemi.com/datasheets/FA/FAN3240.pdf

Looks like, if that type of relay is the configuration you're looking at, you could drive the open/close inputs from a toggle flipflop's Q and /Q outputs, using a momentary switch for the input.

PRR said:

The "latching relay" IS a bistable flip-flop.

Click to expand...

Yep.

The modern latching relays come in two forms: two-coil and one coil with reverse polarity.

You would think you could use a DT contact on the relay to switch coils (or a DPDT to reverse supply). Problem is that you hold your button until the relay switches. Now the opposite signal is given and the relay switches back. It is about impossible to release your button at the instant that the relay has started to move but has not yet made contact.

Click to expand...

I wonder if this sort of relay is the brains of a Useless Box.

This is an old problem in logic. In chippery we like a "master/slave" flip-flop. One flop holds the input (user intention); the other does the actual switching. In MML we can fool with a capacitor to "hold" one state. This is how all the BOSS pedal switches do it.

Click to expand...

The kids might need a definition. MML is Mickey Mouse Logic.

supersonic said:

I just came over something I've heard of before, but know nothing about: Bistable.
And it seems to be the key to control a latching relay with only one momentary switch.
Is there a way to make a bistable driver or such to switch an ordinary latching relay with a momentary switch, without programming chips?

Click to expand...

How about this?

> How about this?

Yup.

But you lose one pole. Otherwise, yup.

PRR said:

> How about this?

Yup.

Click to expand...

merlin said:

This is commonly done with a 4013 D-type flip flop.

Click to expand...

Sorry, I know this thread is old, but I'm kind of muddled at the moment, because I came across a similar on/off (bypass) circuit in one of my very old guitar effect pedals (Danelectro Mini series from early 2000) which doesn't work anymore. I thought maybe the momentary switch is the culprit, so I took it out, and I temporarily wired another one, and when I pressed it, I could see the CLK input goes HIGH and then goes LOW, but no matter how many times I press the switch, the Q output is always at HIGH state so the effect is always on. I have checked the traces, and every resistor, and capacitor involved in the circuit, and they're ok.

Is the 4013 busted?