Constant 12v to momentary contact

[wmacdonald250]

Hello,

My circuit design experience is extremely limited, and I've done a ton of searching but can't seem to find what I am looking for.

Some background: I have a diesel generator that is started by tapping a momentary start/stop button, and stopped by the same action.

I am trying to control it remotely via my off grid inverter, however the inverter just puts out +12v while the generator is supposed to be running and then cuts voltage when it is supposed to stop.

I am trying to come up with a relay or circuit that will take a constant 12v and when it is applied make a momentary contact (to start the generator) and then when the voltage is disconnected it makes another momentary contact thus shutting down the generator.

Any advice or direction is much appreciated.

Thank you

 

[Les Jones]

I would suggest using a cmos exclusive OR gate One input would be driven directly by the 12 volt control signal. The other input would be driven by a delayed version of the 12 volt control signal. The delay would only need a resistor between the 12 volt control signal an the gate input and a capacitor between the same gate input and ground. This will provide a short pulse when the input changes state. (Either low to high or high to low.) I would then use this pulse to trigger an NE555 (Or the cmos version) configured as a monostable. Gooleing "XOR edge detector" and "555 monostable" will give you examples of the circuits.

Les.

 

[alec_t]

I have a diesel generator that is started by tapping a momentary start/stop button, and stopped by the same action.

There seem to me to be two possibilities: 1) the button press triggers a microprocessor or other module to perform an electronic toggle on/off action or 2) the button actuates a toggle-action mechanical latching switch. Can you confirm which one of these applies?

 

[wmacdonald250]

There seem to me to be two possibilities: 1) the button press triggers a microprocessor or other module to perform an electronic toggle on/off action or 2) the button actuates a toggle-action mechanical latching switch. Can you confirm which one of these applies?

Picking it up in a few days, will confirm and snap a couple photos of start / stop circuitry. Thanks for the interest.

For the sake of simplicity, I am also considering accomplishing this by going the electro mechanical route and using a spring loaded motor or servo that will spin or push past a reed switch and then return to its original position making contact again on the way back when power is removed. I was hoping there was an out of the box product that could accomplish this

 

[AnalogKid]

What is your skill set for building circuits? Can you wire up a chip and some R's and C's on perf board, or are you looking for an all wiring solution with small modules from ebay?

ak

 

[wmacdonald250]

What is your skill set for building circuits? Can you wire up a chip and some R's and C's on perf board, or are you looking for an all wiring solution with small modules from ebay?

ak

R&C's? Relays and capacitors? I'm capable of putting together just about anything, sadly just don't have the knowledge to design an appropriate circuit

 

[MikeMl]

... I have a diesel generator that is started by tapping a momentary start/stop button, and stopped by the same action.

I am trying to control it remotely via my off grid inverter, however the inverter just puts out +12v while the generator is supposed to be running and then cuts voltage when it is supposed to stop....

The following circuit, while a bit complicated, does what you ask. It has a relay output, so you can wire its (totally isolated) contacts in parallel with the existing generator's push-button without needing to understand the grounds or voltage levels in the generator.

You will need fused 12Vdc @ 130mA to power the circuit. The good news is that the circuit only draws power for the duration of the timing pulse while the 12V sugar-cube relay (**broken link removed**) is actuated.

The duration of the relay closure is controlled by the time-constants R1C1 and R2C2. As shown, the duration is about 0.5s.

In the simulation, V(in) is what comes from the inverter, and I plot the relay coil current to show when the contacts switch. You can do anything with the relay contacts you like. Likely, you will want only the Normally-Open contacts wired in parallel with the genny's push-button.

 

[wmacdonald250]

The following circuit, while a bit complicated, does what you ask. It has a relay output, so you can wire its (totally isolated) contacts in parallel with the existing generator's push-button without needing to understand the grounds or voltage levels in the generator.

You will need fused 12Vdc @ 130mA to power the circuit. The good news is that the circuit only draws power for the duration of the timing pulse while the 12V sugar-cube relay (**broken link removed**) is actuated.

The duration of the relay closure is controlled by the time-constants R1C1 and R2C2. As shown, the duration is about 0.5s.

In the simulation, V(in) is what comes from the inverter, and I plot the relay coil current to show when the contacts switch. You can do anything with the relay contacts you like. Likely, you will want only the Normally-Open contacts wired in parallel with the genny's push-button.

Thanks for taking the time to either draw that up or share it, and while I have to say in all honesty I don't understand how it works, I am perfectly capable or ordering the components and sticking them together. I'll wait for the generator to show up to test and get exact contact timing for start up and shut down in case there needs to be a modification. Your power requirement sounds very specific, I will look into a supply that is 12v 130ma exactly.

Again thanks for taking the time, I will take some time and try and understand the circuit.

 

[KeepItSimpleStupid]

Out of the box:

There is, sort of, It's called delay on make and delay on break with a monostable output. The devices may likely be found in a "multi-function timer".

What you could do is use a "smart relay". These would satisfy your "off the shelf" minus the programming. Idec, schneider electric and there's Teco - **broken link removed**

Cost, unfortunately, tends to do weird things.

I know your asking for Start/Stop right now, but there could be other functions that are needed.
e.g. Oil level low prevents start and causes alarm
Input must be valid for some time before it's taken as valid.
Exercise of generator - usually done in xfer switch.

You really don't want the states to get messed up. So, other inputs can actually verify what's expected. e.g. engine running and engine stopped.

Some scenarios. What if the generator is exercising and you get a power fail wanting the generator to start? The generator is already running.

Think carefully.

 

[KeepItSimpleStupid]

I will look into a supply that is 12v 130ma exactly.

This is a concept that sometimes causes a misconception. You house has say a 200 Amp 208 V service. You put a 7 W night light on it.

Your car battery can deliver 400 A cranking. You turn on a dome light,

The power sources just have to greater than the anticipated draw for DC anyway.

For AC, the term VA (Volt-amperes), Power factor and inductive loads make things weirder.

But still the source power has to be greater or equal than the load draw.

 

[wmacdonald250]

Out of the box:

There is, sort of, It's called delay on make and delay on break with a monostable output. The devices may likely be found in a "multi-function timer".

What you could do is use a "smart relay". These would satisfy your "off the shelf" minus the programming. Idec, schneider electric and there's Teco - **broken link removed**

Cost, unfortunately, tends to do weird things.

I know your asking for Start/Stop right now, but there could be other functions that are needed.
e.g. Oil level low prevents start and causes alarm
Input must be valid for some time before it's taken as valid.
Exercise of generator - usually done in xfer switch.

You really don't want the states to get messed up. So, other inputs can actually verify what's expected. e.g. engine running and engine stopped.

Some scenarios. What if the generator is exercising and you get a power fail wanting the generator to start? The generator is already running.

Think carefully.

Thanks for the link and info, price isn't too bad. Fortunately the inverter we are using is pretty top shelf, and has all of the generator functionality programmable ie: checking AC inputs to see if it's already running prior to trying to start it, going as far as to check the HZ to make sure it's running stable , as well as programmable quiet times, exercise scheduling etc, however it is designed to run a more high tech generator, and to actually control cranking time etc, whereas this generator has that all automated.

Generator will auto shutdown on low oil pressure or high block temp etc and this will generate an error on the inverter control panel as well as send a page through our monitoring software.

By and large I think between the generators own safety features and the control and monitoring features of the inverter it should pretty much cover everything.

The programming on these units doesn't look terrible difficult for what I would like to accomplish either.

Thanks!

 

[wmacdonald250]

This is a concept that sometimes causes a misconception. You house has say a 200 Amp 208 V service. You put a 7 W night light on it.

Your car battery can deliver 400 A cranking. You turn on a dome light,

The power sources just have to greater than the anticipated draw for DC anyway.

For AC, the term VA (Volt-amperes), Power factor and inductive loads make things weirder.

But still the source power has to be greater or equal than the load draw.

Ok so the output from the AUX which I believe is 12v 0.7A would be fine?

 

[KeepItSimpleStupid]

Idec has emulators, but the cost is a bit pricey.

 

[KeepItSimpleStupid]

Ok so the output from the AUX which I believe is 12v 0.7A would be fine?

AUX could possibly be a AUXillary contact rated for 12V, 0.7A. i.e. Designed to activate a relay. I'm just reading between the lines.

If it's a power source then anything < 0.7 A is OK.

 

[MikeMl]

...Your power requirement sounds very specific, I will look into a supply that is 12v 130ma exactly...

The power supply can be anything from 11V to 15V. It could even come from the starting battery in the generator.
When I specify a 130mA power supply, it just means that the supply must be capable of at least 0.13A.

Think of it this way, the starting battery in your car is technically a supply capable of delivering 1200A at ~10V (during cranking), yet it works just fine to power your cell-phone charger which draws ~1A.

KISS's points are well meaning, but I suspect that the generator has its own in-built logic to prevent you starting it if there is no oil in it, or if it is overheated...

 

[wmacdonald250]

AUX could possibly be a AUXillary contact rated for 12V, 0.7A. i.e. Designed to activate a relay. I'm just reading between the lines.

If it's a power source then anything < 0.7 A is OK.

"The Radian inverter has two sets of terminals which can respond to different criteria and control many operations. The 12V AUX terminals provide a 12 Vdc output that can deliver up to 0.7 Adc to control external loads. The RELAY AUX terminals are “dry” relay contacts rated up to 10 amps (at 250 Vac or 30 Vdc)"

I have the option of a dry contact or a powered output

 

[wmacdonald250]

Really considering the programmable relay option, interesting units and could potentially be used for a variety of things. Just downloaded their programming software and simulator, not quite as simple as it looked but going to mess around with it, If I can manage to make it work in simulation I'll order one.

 

[AnalogKid]

I did this a while ago with a one-transistor circuit. Just gotta find it...

ak

 

[wmacdonald250]

The following circuit, while a bit complicated, does what you ask. It has a relay output, so you can wire its (totally isolated) contacts in parallel with the existing generator's push-button without needing to understand the grounds or voltage levels in the generator.

You will need fused 12Vdc @ 130mA to power the circuit. The good news is that the circuit only draws power for the duration of the timing pulse while the 12V sugar-cube relay (**broken link removed**) is actuated.

The duration of the relay closure is controlled by the time-constants R1C1 and R2C2. As shown, the duration is about 0.5s.

In the simulation, V(in) is what comes from the inverter, and I plot the relay coil current to show when the contacts switch. You can do anything with the relay contacts you like. Likely, you will want only the Normally-Open contacts wired in parallel with the genny's push-button.

Hey Mike,

I've decided your circuit is probably the simplest and most cost effective method. Can you help me with a couple of rookie questions, what software did you design the simulation in?
I'd like to get a copy, I'd also like to get the contact time down to about 1/4 of a second on both the inital and the final connection.
Lastly when I am sourcing the components what voltage am I looking for as I see dozens of different resistors that are 100k and caps that are 2.2u etc.
Sorry for the elementary questions. And thanks for your help

 

[MikeMl]

..., what software did you design the simulation in? I'd like to get a copy,...I'd also like to get the contact time down to about 1/4 of a second on both the inital and the final connection.

LTSpice. Free download at www.Linear.com. I will post the .asc (sim) file which you can use as a tutorial, except that you will not have the relay library, so when simulating, just use a ~85Ω resistance (~resistance of the coil of the automotive sugar cube relay) in place of the relay coil.

Lastly when I am sourcing the components what voltage am I looking for as I see dozens of different resistors that are 100k and caps that are 2.2u etc...

I would use **broken link removed**
**broken link removed**, + on the right end.
C1,**broken link removed**, + on the left end.