Latching ON/OFF Circuit with Single-Wire Remote Control & Indication from Multiple Push-Buttons 2015-02-23

[crutschow]

crutschow submitted a new article:

Single Wire PB Controlled Alternate-Action Relay with Remote Indication - Momentary PB controls remote relay ON/OFF with PB LED status indication using a single wire.

Here's a circuit that will light a momentary-action LED PB switch based upon the bi-stable state of a remote relay using only one wire from the switch to the relay (and the chassis ground, of course) with no added circuitry at the switch.

Here's an LTspice simulation of the circuit:

**broken link removed**

The key to the circuit is transistor Q1 which is used to detect the current from the relay driver to the switch LED (the LED is lit when the relay is energized).
The transistor action...

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[crutschow]

crutschow updated {articleTitle} with a new update entry:

Momentary PB to Gnd controls remote bistable relay circuit with PB LED status using a single wire.

Here's a modification to the circuit that allows the remote control and indication of a latching relay circuit with a PB connection to ground using a single wire, thus requiring no power at the PB.

Here's the LTspice simulation of the circuit:

**broken link removed**

When the relay is ON, current flows through D2 and R7 to light the LED indicator at the PB. This voltage also saturates Q1 so the output at Node 3 is low.

Momentarily pushing the PB grounds Node 1 which turns off Q1,...

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[Tony Stewart]

In the old days we might have used Schmitt NANDs to make a retriggerable one shot and any flip flop or even a CD4040 counter which has the Schmitt Clk input for /2 on the 1st stage, Q1.

CD4040B's are still very cheap. 3M //0,2uF gives a 0.5s monostable pulse.
Make sure to add the reverse coil diode for the relay.

 

[crutschow]

crutschow updated {articleTitle} with a new update entry:

PB Latching High Side Switch with LED Indicator

Below is a modification to the original circuit which uses a high-side MOSFET switch instead of a relay to switch the load.

View attachment 96360

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[Gasboss775]

I find circuits like this ingenious, allowing signalling in two directions, somewhat reminiscent of circuits used in telephony. I have a few questions though:

Iam not entirely clear on the functioning of the "PB" as Iam unfamiliar with the circuit symbol used to describe it.

What is the source of power in the "PB"?

Is the mains ground used as the common connection in the circuit?
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In the old days we might have used Schmitt NANDs to make a retriggerable one shot and any flip flop or even a CD4040 counter which has the Schmitt Clk input for /2 on the 1st stage, Q1.

CD4040B's are still very cheap. 3M //0,2uF gives a 0.5s monostable pulse.
Make sure to add the reverse coil diode for the relay.
View attachment 91360

I prefer the 4060 as it has extra gates to allow for an onboard oscillator RC or XTAL.

 

[cowboybob]

Iam not entirely clear on the functioning of the "PB" as Iam unfamiliar with the circuit symbol used to describe it.

"PB" = Push Button.

The circuit SIM is just a timed switch to emulate someone pushing a PB.

 

[Gasboss775]

There is mention of a power source in the PB, is it from a battery, do you think?

 

[cowboybob]

There is mention of a power source in the PB, is it from a battery, do you think?

The power source (V1) is a component of the "Simulated PB Switch" (note the dotted lines) and, as such, is not a component of the latching on/off circuit. I don't use LTSpice very much but don't think it has a timed switch element, so one has to be made from parts, thus the "Simulated PB Switch".

 

[Tony Stewart]

I find circuits like this ingenious, allowing signalling in two directions, somewhat reminiscent of circuits used in telephony. I have a few questions though:

Iam not entirely clear on the functioning of the "PB" as Iam unfamiliar with the circuit symbol used to describe it.

What is the source of power in the "PB"?

Is the mains ground used as the common connection in the circuit?
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I prefer the 4060 as it has extra gates to allow for an onboard oscillator RC or XTAL.

I agree, I meant the CD4060 as well
The PB running off Vcc is edge detected using the XOR gate (aka frequency doubler) then uses a monopulse stretcher to debounce then goes into a D FF /2 circuit (aka toggle memory) These are like classic chess moves in these configurations.

 

[kinarfi]

I had a need for a single button that toggled and the circuit I had worked but was iffy and after messing with it and watch the voltages with a scope, I thought I had it working good, then I disconnected the scope and it started not staying off, if I hooked my Fluke meter to it, it stabilized again, so I added the 100k for the meter and the 4 nf for the scope, may not be needed, and I had noticed that the voltage on the cap had to decay to about 2 for it to switch, so I added the bright white LED to keep the voltage near 2 (zener?) . Now it switches consistently and rapidly and will be put to use in my off road vehicle.