Automatic turn off circuit or device (12v)

Thread Starter

Saluki

Joined Feb 23, 2019
78
I have an application (car door panel courtesy light) needing a SIMPLE as practical circuit to switch off said interior light if the door has been left open (eg overnight) to prevent the battery running down, light burning out, melting enclosure, etc. An inexpensive manufactured small board or module such as this might be ok too:

https://www.ebay.com/itm/253046146435?chn=ps&_trkparms=ispr=1&amdata=enc:1T5naSik9QbWG2pYIUXYv8g0&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=253046146435&targetid=1584739237574&device=c&mktype=pla&googleloc=9014659&poi=&campaignid=19894961968&mkgroupid=148855406073&rlsatarget=pla-1584739237574&abcId=9307911&merchantid=110903650&gclid=EAIaIQobChMIgNP5jYrwggMV7DjUAR3bdgm2EAYYBCABEgIkHPD_BwE

But that one, at least "as is" is only good for 10 seconds on time.

Additional Requirements:

No TRIGGER or (directly) user operated "on" switch: Just connect 12V (in this case the original 12v to the door lamp), output comes on in under 1 second, then after ~5 - 6 minutes the output switches off even if the input is still on. If input is off, of course, switch output off.

Zero or very minimal current draw by the control circuit itself when the output is "off".


A fade out after several minutes is preferable to a sharp turn off, esp. if the application was extended to a dome light, but, for the door panel light I can live with a sharp turn off.

I found a similar discussion here:

https://forum.allaboutcircuits.com/...-around-10-minutes-for-interior-light.144999/

But that's an old discussion and I do not see any recent activity by the OP, who seemed to find and put in use a fairly good solution. So I don't know of any easy way to ask him what module / board he actually bought, or if he has further experience / input / advice.

(SFAIK this forum does not provide for PM's?)

I do have some DE3175 LED lamps coming, the idea being to, at a 1st crack, simply reduce the current draw of the light itself.

Referring back to the eBay board (the below circuit is provided @ the link, but I'm not sure it actually matches the module?), would it be advisable to alter BOTH R1 and C1 to increase the "on" time?

1701537132177.png

1701537603432.png

1701537540021.png

Thanks!
 

dl324

Joined Mar 30, 2015
16,732
I do not see any recent activity by the OP, who seemed to find and put in use a fairly good solution. So I don't know of any easy way to ask him what module / board he actually bought, or if he has further experience / input / advice.
I'm surprised the eBay link still worked.
Arrived yesterday, fitted today. It is TINY. It took an hour to fit, not easy like they say,, considering also the stack of money I paid for it.

I had to change the wiring of the dome lamp and cut wires - not funny for a car undeer warranty but those have this already I guess. You need to solder or use crimps and crimp splices (I did not solder, for once, I know it is bad - oh well).

The original wiring was bringing +12V continuous, -12V continuous (ground) and -12V trigger from doors. The bulb inside the dome light is connected to +12V permanently and a slide switch connects to continuous -12V or door -12V (or nothing). This circuit feeds +12V to the bulb, so -12V must be continuous. So I had to change the wires around at the dome light entry and splice +12V, -12V and cut the door -12V and feed it to the light delay circuit. Bah... I did not use the ignition wire (so the light dims immediately upon closing the door, I don't see the use of that, it dims anyway after only 20 secs)

Oh, and also before dimming there is a jolt in the voltage , not nice to the eye. Also none of the times - dim and timeout, are adjustable. Waaay overpriced. If it dies, it goes to bin, cannot repair it.

Whatever... I fitted it regardless.
This seems to be what he went with:
domeLightTimer.jpg
It looks like it requires significant modifications. Is that what you want to do?
SFAIK this forum does not provide for PM's?
PM feature will be unlocked after you have around 10 posts.

Pictures of random relay boards with no commentary are not helpful...
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
I'm surprised the eBay link still worked.


This seems to be what he went with:
View attachment 308925
It looks like it requires significant modifications. Is that what you want to do?
PM feature will be unlocked after you have around 10 posts.

Pictures of random relay boards with no commentary are not helpful...
HNoted -
I'm surprised the eBay link still worked.


This seems to be what he went with:
View attachment 308925
It looks like it requires significant modifications. Is that what you want to do?
PM feature will be unlocked after you have around 10 posts.

Pictures of random relay boards with no commentary are not helpful...
I'm surprised the eBay link still worked.


This seems to be what he went with:
View attachment 308925
It looks like it requires significant modifications. Is that what you want to do?
PM feature will be unlocked after you have around 10 posts.

Pictures of random relay boards with no commentary are not helpful...
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
Thanks all!

When I'd first tried eBay I got an error message, but now the link from the OP / old thread indeed does seem to work for me, and indeed that module is quite pricy - ouch.

Those pics are of the board I asked the question* about and I posted the circuit the seller provided -- my intent was trying to figure out if the circuit the seller provided matched the board. Am I just not seeing, for example, tiny LEDs in the pics?

*Perhaps I should have broken up & reworded that question as follows, for better clarity:

-----Referring back to the eBay board / (the below circuit & pics are provided @ the link), does the circuit provided actually match the module shown?

-----Would it be advisable to alter BOTH R1 and C1 to increase the "on" time?

Um, I'd rather not have to modify a $40 board...

Since the dome light DOES auto-off, I suppose I could tap off that for control, particularly depending on if I can find the wires supplying it under the dash. However, local control in the door panels sure looks easier from a physical "getting to stuff" standpoint.

Noted on the PM's.

Thanks again! :)
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
Oh, I forgot to ask, any guess as to input impedance of the circuit I posted a copy of? C1 needs to be low leakage?
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
Note that 1st circuit can function as an off timer, but it does so by energizing the relay and opening pins 1-2, so I'd just be trading the current draw of the load (LED light in the door panel) for the draw of the board / relay. Pffftt!
 

MisterBill2

Joined Jan 23, 2018
17,881
Unfortunately, in many more recent vehicles, the delay turn off as requested is included in a body control computer module that controls many of the lights and costs at least $400 for an OEM replacement. Possibly, if the TShas access to older auto scrap yards, a module could be salvaged from an older vehicle, because at one time that function was provided by a separate module. I think our 1969 Dodge had such a feature.
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
Unfortunately, in many more recent vehicles, the delay turn off as requested is included in a body control computer module that controls many of the lights and costs at least $400 for an OEM replacement. Possibly, if the TShas access to older auto scrap yards, a module could be salvaged from an older vehicle, because at one time that function was provided by a separate module. I think our 1969 Dodge had such a feature.
Heh, yes, this is in a 2009 Subie Outback, and the computer controls the dome lamps but not the door panel lamps. :rolleyes:

But... I think I've found a timer module that will do the trick with no mods needed:

https://www.ebay.com/itm/262570726188?var=564893912583

:)
 

MisterBill2

Joined Jan 23, 2018
17,881
Heh, yes, this is in a 2009 Subie Outback, and the computer controls the dome lamps but not the door panel lamps. :rolleyes:

But... I think I've found a timer module that will do the trick with no mods needed:

https://www.ebay.com/itm/262570726188?var=564893912583

:)
If you power the module from the switched side of the circuit, when it switches off there will be no current draw. YES, that might get a bit complicated, possibly.
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
If you power the module from the switched side of the circuit, when it switches off there will be no current draw. YES, that might get a bit complicated, possibly.
Yes, it really shouldn't be THAT hard to come up with a circuit that completely shuts itself down unless Vcc is cycled off and then back on (to merely shut down yet again), but I seem to have a mental block...

The funny thing is, I have a little 4x AAA battery powered "undercabinet" light above my computer desk that turns itself off after maybe 10 minutes, to preserve the batteries. Well, it used to be battery powered - I ended up converting it to run off a spare 6v wall-wart supply, but it still has the turn-off feature. Which feature is actually more of an annoyance than useful, in that application.

I have this: https://www.amazon.com/gp/product/B06XBWS3T2/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1

And one 3-LED module powered by 9v is plenty bright, so I'm half tempted to rig one up with a switch @ my desk and tear the present "undercabinet light" apart and see if I can figure out or make use of the circuit.
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
It is probably a bare-die IC flip-soldered to the PCB with a blob of black epoxy over it, No visible ID at all.
Well, true...

But I do have another of these same under-cabinet lights, unused, it turns out. So, with a few components I might be able to "rig" them as, instead of lights, triggers, to turn on a relay or transistor to power those door panel lights. I also MAY be able to track down and tap a trigger off the dome light IF I can find the wires under the dash...

My hope that someone here has a circuit up their sleeve has just about faded. :(
 

MisterBill2

Joined Jan 23, 2018
17,881
Now I recall an article about a circuit to mute a radio for a while, and then unmute it That used a MOSFET with a large value capacitor to hold the gate voltage on after the press of a button charged it. possibly a variation of that concept would solve the issue. A button-press switches on the light and then when the capacitor charge leaks off the light dims and goes off.. That could be easy and cheap.
 

Thread Starter

Saluki

Joined Feb 23, 2019
78
Now I recall an article about a circuit to mute a radio for a while, and then unmute it That used a MOSFET with a large value capacitor to hold the gate voltage on after the press of a button charged it. possibly a variation of that concept would solve the issue. A button-press switches on the light and then when the capacitor charge leaks off the light dims and goes off.. That could be easy and cheap.
I was thinking the "factory" turn on transient (when the door is opened) could be used to trigger a timed "on" period...
 

sghioto

Joined Dec 31, 2017
5,369
My hope that someone here has a circuit up their sleeve has just about faded.
How long do you need the lamp to stay on?
Is the door light turned ON by grounding one side of the light or switching +12 volts to the lamp?
 
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