# Resetting Self-Latching Switch on Timed Circuit Power-Down

#### campionc

Joined Apr 24, 2015
6
I have a latching switch I purchased from Amazon along with a pre made adjustable timer circuit.

Pushing the switch activates the timed circuit, and pushing it again deactivates it (in theory).

I have all of this figured out, I think, except for this one thing. The switch is attached to constant power. How can I reset the latched switch once the timed circuit powers down?

The only thing I came up with was a capacitor-reelay contraption which had its own set of problems, would have been too big, and kind of stupid to put together just to reset a switch. Can someone please give me some ideas? My skill level is between novice and intermediate.

FYI, the circuits run at 12v and thd timed circuit runs another relay that runs a max load of 20a. Thanks!

Last edited:

#### Alec_t

Joined Sep 17, 2013
13,069
Welcome to AAC!
If the latching switch is mechanically latched, no amount of circuitry is going to magically unlatch it. What you need is an electrical latch circuit which can be set with a momentary switch and reset electrically.

#### campionc

Joined Apr 24, 2015
6
Welcome to AAC!
If the latching switch is mechanically latched, no amount of circuitry is going to magically unlatch it. What you need is an electrical latch circuit which can be set with a momentary switch and reset electrically.
I'm not sure if it's mechanical or not actually. Maybe you can tell from the description? It's also showing CarNetix part number "CBL-143 2".

Here's the description:
Black Pushbutton Switch with metal internal construction. Extremely solid construction. Diameter is approximately 18mm. Mounting Depth is approximately 40mm Contact resistance: ?50m? Insulation resistance: ?1000M? Dielectric Intensity: 2000VAC Operating Temp: -20?~ +55? Mechanical Life: 1,000,000 cycles Electrical Life: 200,000 cycles Operation Pressure: About 4N Operation Travel: About 1.5mm LED Life: 40000 hours 16mm diameter Switch Rating: 3A/250VAC Contact Configuration: 1NO1NC /2NO 2NC Operation Type: Latching The Front Shape: Flat Round The crust material: Black Plastic Ring Illuminated IP Degree: IP40

#### Alec_t

Joined Sep 17, 2013
13,069
That's a mechanical latching type.

#### campionc

Joined Apr 24, 2015
6
That's a mechanical latching type.
Gotcha. Thanks for all the help. I'll probably be back when I can't figure out how to make the latching circuit work. Lol.

Thanks again!

Joined Jan 15, 2015
6,835
Gotcha. Thanks for all the help. I'll probably be back when I can't figure out how to make the latching circuit work. Lol.

Thanks again!
If you explain in detail exactly what you want to do or what the objective is we can likely help you but a real good detailed explanation is required to get things going.

Ron

#### campionc

Joined Apr 24, 2015
6
If you explain in detail exactly what you want to do or what the objective is we can likely help you but a real good detailed explanation is required to get things going.

Ron
Basically, I need a momentary switch (that has a LED on/off indicator) that will turn on a 20 amp load for ten mintues (give or take), and then turn itself off, at the same time resetting the state of the switch. The switch has to be supplied with 12v constant power and that part is unavoidable. The other part is, I need to be able to terminate the timer early and turn the load off.

I can't really tell you what this is for because it's a restricted topic. But for all practical purposes, let's say I'm ru.nning an electric motor with it. Push on, push off, with auto shutdown.

I hope that helps explain a little better. Thanks!

Joined Jan 15, 2015
6,835
Basically, I need a momentary switch (that has a LED on/off indicator) that will turn on a 20 amp load for ten mintues (give or take), and then turn itself off, at the same time resetting the state of the switch. The switch has to be supplied with 12v constant power and that part is unavoidable. The other part is, I need to be able to terminate the timer early and turn the load off.

I can't really tell you what this is for because it's a restricted topic. But for all practical purposes, let's say I'm ru.nning an electric motor with it. Push on, push off, with auto shutdown.

I hope that helps explain a little better. Thanks!
OK, sounds to me like you want a "one shot" timer. Push a momentary push button switch and the timing cycle begins, your load be it a motor or whatever will run for a preset period till the timing cycle times out. Then nothing happens till the button switch is pressed again. However, you also mention:

I can't really tell you what this is for because it's a restricted topic. But for all practical purposes, let's say I'm ru.nning an electric motor with it. Push on, push off, with auto shutdown.
Really matters not what the load is other than inductive like a motor or resistive like a heating element for choosing a contactor, all that needs known is load voltage and current. I spent a 45 year career working with classified systems, been there and done that. Also need to know if you are switching AC (Single or Multi-Phase) or DC for the load.

With the above in mind I'll make a suggestion. I haven't a clue what your electrical background is like so rather than build I will suggest a pretty much turn key canned idea. You also do not mention a budget? I will also assume an industrial business type application. For a timer I would start with one of these and use the 12 volt model which is a part number TMM-0999M-466. Granted this is slightly overkill because it offers several modes and you could shop for strictly a one shot timing relay but I like these and have used them in many designs for their mode capabilities. You are looking at about $90 USD. Timing is settable between 1 sec. and 999 min. Use a normally open push button switch to start a cycle and if you want an illuminated LED push button which the LED is on during the cycle that can be worked in. The down side is if you want to interrupt a timing cycle once it begins another normally closed push button momentary switch is needed. The contacts of this timer would in turn drive a large contactor for your 20 amp load. AC coil contactor voltage? DC contactor coil voltage? Ron Thread Starter #### campionc Joined Apr 24, 2015 6 OK, sounds to me like you want a "one shot" timer. Push a momentary push button switch and the timing cycle begins, your load be it a motor or whatever will run for a preset period till the timing cycle times out. Then nothing happens till the button switch is pressed again. However, you also mention: Really matters not what the load is other than inductive like a motor or resistive like a heating element for choosing a contactor, all that needs known is load voltage and current. I spent a 45 year career working with classified systems, been there and done that. Also need to know if you are switching AC (Single or Multi-Phase) or DC for the load. With the above in mind I'll make a suggestion. I haven't a clue what your electrical background is like so rather than build I will suggest a pretty much turn key canned idea. You also do not mention a budget? I will also assume an industrial business type application. For a timer I would start with one of these and use the 12 volt model which is a part number TMM-0999M-466. Granted this is slightly overkill because it offers several modes and you could shop for strictly a one shot timing relay but I like these and have used them in many designs for their mode capabilities. You are looking at about$90 USD. Timing is settable between 1 sec. and 999 min. Use a normally open push button switch to start a cycle and if you want an illuminated LED push button which the LED is on during the cycle that can be worked in. The down side is if you want to interrupt a timing cycle once it begins another normally closed push button momentary switch is needed. The contacts of this timer would in turn drive a large contactor for your 20 amp load. AC coil contactor voltage? DC contactor coil voltage?

Ron
Thanks for the detailed info! I suppose you could look at it like a controller for a car's rear defroster. It's the same thing, really. I am using a heating element, but it has its own relay. So the timer only needs to turn on another relay. Like the car example, it is all 12 volt, and I also need to have it work the same way, with a single button. I even looked into finding one of those automotive switches, but wouldn't know how to hook it up.

Joined Jan 15, 2015
6,835
The single button is a minor headache but shouldn't be a big deal. Let me think about it and see what I can come up with. Much like my truck's rear window defroster. Turn them on and they remain on and time out, push the button before they time out and they shut off. I have an idea.

Ron

#### campionc

Joined Apr 24, 2015
6
The single button is a minor headache but shouldn't be a big deal. Let me think about it and see what I can come up with. Much like my truck's rear window defroster. Turn them on and they remain on and time out, push the button before they time out and they shut off. I have an idea.

Ron
Yep, that's it! I do have a timer circuit, at least part of it, already. It came from Amazon. Here's the link:

http://www.amazon.com/gp/aw/d/B00E1JNLTS

Thank you so much!