Here's my scenario:

I have an array of 120V LED fixtures that need to be turned on for 10 minutes when the following conditions occur:

  • It's dark out AND Someone walks in front of a motion sensor


  • Someone toggles a switch inside (this can be a standard light switch or a pushbutton that fits into a standard box and looks professional)

You would think that someone would have already done this and would be marketing it, but I can't find a time-delay dusk-only motion sensor with a switch input.

Basically if someone walks by at night, or if someone hits a switch, then turn on the lights for 10 minutes.

My Question:

I need a schematic that uses common parts (NE555P, discrete components, etc - no microcontrollers) to fulfill this logic. The total power of the lights is about 50W @ 120VAC. Normally I would be able to do this myself, but my attempts have ended up as scrap paper.

EDIT: I'm open to using a microcontroller, just make sure to give me very very very detailed instructions, since I'm not very familiar with their quirks.

To clarify: I am 100% open to building something from components/ICs. In fact, I would prefer that. I just need to know how to wire up the microcontroller and/or 555-monostable.

  • \$\begingroup\$ Why can it not use a microcontroller? This is 'easy' using an MCU. \$\endgroup\$ – gbulmer Jan 13 '16 at 2:05
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    \$\begingroup\$ Could be done with a 2-in OR gate, a 2-in AND gate, and an edge-triggered monostable 555 circuit (with 10 minute duration). Output of the 555 drives a relay. Depends what your input signals are - for "dark out" you would need further circuitry to generate a logic signal from some sensor - same with a motion sensor. Far simpler, more accurate, and more compact (and possibly cheaper) to get a PIC12F or other low end microcontroller. \$\endgroup\$ – Tom Carpenter Jan 13 '16 at 2:41
  • \$\begingroup\$ There are outdoor light fixtures available in home stores (such as Home Depot) that perform these functions ( I have one over my garage). It only operates when it is dark and the light on time is adjustable. You should be able to adapt one of these for your lights. \$\endgroup\$ – Barry Jan 13 '16 at 2:59
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    \$\begingroup\$ You have written out a specification in terms of AND and OR. This can be translated into AND and OR gates - or via a well known trick into NAND gates, which come in handy four-packs. A 10 minute delay is a bigger problem (without a CPU) and beyond the capability of a NE555. However there's a 4000-series chip with an oscillator and big counter made for the job. (4024? 4040?) \$\endgroup\$ – Brian Drummond Jan 13 '16 at 11:50
  • \$\begingroup\$ There are PIR modules with built in time delay. That should make your design much simpler. \$\endgroup\$ – Vinod Jan 13 '16 at 13:04

If you don't want to deal with making an electronic circuit, you could consider using a "delay on break" time-delay relay for the indoor switch. These are available in various control voltages and delay ranges -- and many can directly switch 120 VAC. (Some time-delay relays are multifunction devices where delay-on-break is one possible setting.) Cost is likely around $50. You may also need a small box and DIN rail to mount the relay.

A standard motion detector for outdoor lights can provide the motion-detection function.

The trick is wiring the time-delay relay contacts in parallel with a motion-detector output so that either the relay or motion detector can turn on the lights. At the very least, the motion detection must be a three-wire type (neutral, line, switched output) -- but it wouldn't surprise me if some motion detectors are fussy about another source energizing it's output.

  • \$\begingroup\$ I'm actually looking to build my own circuitry rather than purchasing commercial fixtures. From what I've seen they are very unreliable for my price range. \$\endgroup\$ – Daniel Jan 14 '16 at 17:53

The ready-made PIR sensor lamp is the simplest for the automatic part.


simulate this circuit – Schematic created using CircuitLab

Figure 1. Reset PIR switch by interrupting power.

I have observed that many of these lamps turn on for the set time when first powered up. A simple push-to-break switch or even a regular on-off switch can be used to interrupt the power for a few seconds and reset the timer. This would be fine if you only have to explain its operation to family.

Another minimum electronics solution is a pneumatic time delay push switch - popular in some stairwell applications. The user presses the button and the button gradually springs back out with speed governed by an adjustable screw air valve.


simulate this circuit

Figure 2. PIR sensor bypass by pneumatic time-delay switch.

To install the Figure 2 option requires running an extra wire from the button to the bulb.

  • \$\begingroup\$ That's nice, but I'd rather build something from components if possible. These commercial fixtures seem to be rather unreliable for my price range. \$\endgroup\$ – Daniel Jan 14 '16 at 17:53

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