constant to Separate momentary on off

[Textinstar]

Can someone help me with a circuit to monitor an existing switched 12v+ signal
& output separate momentary on & off pulses, whilst consuming minimal to no power in the off state.

EG.
Separate momentary outputs in response to an On/Off switched DC input
The pulsed outputs, xxx? milliseconds long triggered during the Change of state from On and Off.
Something like https://www.electro-tech-online.com/custompdfs/2012/04/599.pdf
Or like the attached circuit but separate on & off outputs.


Purpose.
In the attached (B/W) image You can see a momentary SPDT ON-OFF-ON switch,
I would like to replace this switch with a circuit triggered from a switched 12v+ input,
that will output a control signal for the (BRN) & (ORG) wires.

 

[ccurtis]

To be clear, this circuit you want has one input: A SPST toggle switch closure to +12V or open? Two outputs: one output pulses to +12V (for some to be determined amount of time) and then to 0V (or open circuit?) only when the input switch is closed, and the other output pulses to +12 (for some to be determined amount of time) and then to 0V (or open circuit?) only when the input switch is opened?

The pulse width (time) needs to be specified and the load that the pulses are driving needs to be specified. Also, are there any restrictions on the how the outputs of this circuit behave when power is applied to the circuit, ie., must the outputs stay zero volts when power is applied, or can either one of them pulse when power is applied.

 

[alec_t]

It would help if you could answer Ccurtis's questions. In the meantime, this might suit your needs as I understand them.

 

[Textinstar]

Thank you both very much for the quick replies,
As for the pulse width (time) I'd be guessing at 500 milliseconds, my objective is to replace a momentary switch.
(The momentary switch In the attached (B/W) image)
The link below has the specs for the solid state relay In the attached (B/W) image.
http://bluesea.com/category/78/79/productline/385
As for the load in the Bluesea Systems specs it states "<7.0 Amps" , but the link from the place I bought it from states
" Amperage Operating Current 100mA when changing state", see link below.
**broken link removed**
Unsure how to answer the "restrictions on the how the outputs of this circuit behave when power is applied",
Other than to say I would like it to consume little to no power when it has 0v (open circuit) on its input.
And would prefer if outputs stay zero volts when power is applied.

Also thanks alec_t for Schematic, at a glance it looks perfect for the job. (will build tomorrow)
Although if you could give your opinions using this extra info, just to make sure I'm on the right track.

Thanks again

 

[alec_t]

Hmm, I think I'd prefer to use the manufacturer's figure of "<7A" when designing a circuit to switch that particular load. My circuit in post #3 is only a timing circuit with a 200mA drive capability, so don't build it yet! It will need modifying considerably to cope with driving the Blue Sea relay. I'll have a think and get back to you.

 

[Reloadron]

Unfortunately this link does not seem to work and should be the instruction manual for the actual switch (contactor). I tried it in Firefox and MSIE and it seems to be a corrupt .pdf file. I was able to manage the first page. They specify a Amperage Operating Current of 100mA when changing state. Looking at the posted controller unit Pulsed Switching Module that would pretty much make sense. However, I don't get the reference to the <7 Amp? The actual Relay, Contactor or Switch seems to have 5 wires exiting it. This is where the destruction, err instruction, manual would be nice. If the pin out or wires out in this case were know, the user could momentarily hold the On or Off with 12 volts applied and measure the coil current needed. I can't help believe the answer lies in a corrupt PDF file. Attached is what I was able to download of the Instruction Manual .pdf file.

I doubt the magnetic latching coil(s) require much current but it becomes a guessing game.

Ron

 

[alec_t]

Well if it only takes 100mA to operate then the post #3 circuit could do that providing the relay has in-built catching diodes to protect the 555s from back-emfs. However, to be on the safe side they could be added.

Here's an alternative circuit with the 555s replaced by Schmitt NAND gates wired as two ~500mS monostables. Paralleled gates are used to drive high-side P-MOSFETs to switch +12V to the brown and orange wires at the start and end, respectively (if that's what you want....if not, just interchange them), of the 12V 'In' signal. The FETs should easily handle 7A (Load1 and Load2 in the sim are ~7A loads), so 100mA would be a breeze.

 

[ccurtis]

As I read it in the Overview section of that manual the contact closures need not be momentary, at all, and an ordinary SPDT switch (not momentary) can be used.

Edit: Later on it indicates a momentary action, probably to reduce to current required to drive the relay when not needed? But, wouldn't the relay need to remain on anyway until the switch is moved to OFF? It's not clear what the device is doing. Is it connecting the battery to the rest of the boat, or is it used to start the engine? If it is used to start the engine then the momentary action time is dependent on how long it takes to start the engine? Maybe dumb questions, but I see things like "solenoid switch" in the manual.

Edit again: Alec, I had something more in mind similar to your second circuit (using a single hex schmitt inverter and BJTs on the output instead), since it is simpler and has much less quiescent current, but it will pulse one of the outputs when power is applied to the circuit, which output depending on what position the input switch is in. Hard to say if that is an issue or not since the switch device being driven will be powered up with the same voltage.

 

[alec_t]

@ccurtis
I'm guessing the relay is a dual-coil latching type, so it only needs a brief pulse on one coil (brown lead) to set it and a pulse on the other coil (orange lead) to reset it. So as the datasheet says, it draws no current except when changing state.
I've played around with the sim of the post #7 circuit and neither output gets energised at circuit power-up (though I did find that a problem with earlier trial designs).

 

[ccurtis]

I've played around with the sim of the post #7 circuit and neither output gets energized at circuit power-up (though I did find that a problem with earlier trial designs).

I don't want to belabor the point, but if the capacitors start off with an initial charge of zero and the power supply starts with zero volts, then upon application of power one of the gate outputs driving its capacitor will rise to +12V initiating a pulse at the output of the one-shot output gate.

But, since the latching relay in the unit being controlled is latched in one state anyway, then I would guess that it is still latched in that state upon power up of the unit. If it is the OFF state latch that gets the initial pulse at power up from your circuit, then the unit also powers up in the OFF state.

 

[Reloadron]

Question? The switching module outputs a 100mS pulse. While this may be useful when used with a more elaborate controller if all that is needed is a pulse on and pulse off to a magnetic latching contactor why not a pair of N/O momentary push buttons. One PB for On and another for Off? Wouldn't that work? While I may be off base or missing something that would seem a simple approach.

Ron

 

[Textinstar]

Thanks to all for the help & information.
I've attached a full copy of the Blue Sea Systems manual.
Thanks Reloadron, found a link other day but didn't work properly for me ethier, the link you posted works fine for me now though.
As for "pair of N/O momentary push buttons", to make it short I can only wish it were that simple.
As for "measure the coil current needed", the ML-Series Remote Battery Switch unit has yet to arrive.
As for "If the pin out or wires out in this case were know", the black & white attachment in post #1.
Thanks again alec_t for 2nd Schematic, I will probably build the one from Post #3 first, replacing S1 with the contacts of a solid state relay.
Mainly because I already have these components in SMD, if I fry the 555's or they can't drive the load, I will use the outputs from the 555's to drive two more solid state relays.(again as I already have the relays)
If the output pulse at turn on or anything else ends up being a problem, I will build the 2nd Schematic alec_t posted.(post #7)

Thanks again to all for the help, will post PCB artwork when finished & tested.

 

[alec_t]

According to the sim there shouldn't be any output pulse at turn-on for either the post #3 or post #7 circuit. Well, that's the theory, anyway .

I will probably build the one from Post #3 first, replacing S1 with the contacts of a solid state relay.

That will work, but I was under the impression you already had a source for a control voltage which went from 0 to 12 then 0. If so, then the SSR isn't needed; just apply the control voltage to R1.
Keep us posted on progress.

 

[Textinstar]

Thanks for the info
I must have misunderstood "neither output gets energised at circuit power-up (though I did find that a problem with earlier trial designs)."
Self taught & no high school education (just read alot & do alot), so bare with me if I'm not getting my jargon right.
As for replacing S1 with SSR, I Know it is overkill but the 12v+ switched wire I have access to is coming from a sensitive expensive piece of equipment.
The switched 12v+ wire is not accessible enough to 100% know exactly what it is already driving, so not wanting either circuit to interfere in the others operation in anyway,
I figured it best to use some sort of Opto-isolated input & the SSR's were the first thing I could find lying around. (my whole house is packed up to move so **** is hard to find)
Although have since found some 4N25's so will use one instead, that is unless you think Opto-isolated input is extreme overkill.(don't mind a little overkill)
Again bare with me in the 2nd Schematic is it possible to replace the CD4093 Quad 2-Input NAND Schmitt Trigger, with CD4011 Quad 2-Input NAND Gate?(as I already have some)

Thanks again for all the help

 

[alec_t]

Overkill understood.

in the 2nd Schematic is it possible to replace the CD4093 Quad 2-Input NAND Schmitt Trigger, with CD4011 Quad 2-Input NAND Gate?

Should be ok, but with long time constants (500mS) used here the Schmitt inputs are recommended for stability. Suck it and see, using a dummy inductive load such as a spare relay.
Talking of stability, the circuit should be adequately decoupled and screened to prevent false triggering from any picked-up interference.

 

[Textinstar]

I would just like to say thanks again alec_t.
Been a while but finally got back to this project. I haven't had time to make a proper PCB yet, but the proto-board version is running perfect so far.

 

[alec_t]

That's good to hear!