Display cabinet - pir motion sensor & led circuit 555

Hello 555 timer community,

I am making a clear display case for a model. I would like LED lights to activate when a viewer walks pass the display, and to stay on for a short amount of time say 10-15 secs. Display case size 400 x 400 x 400mm.

I am hoping to make a very simple circuit using a 555 chip assembled with through-hole components onto a breadboard, linked to a primary cell batteries.

I believe I will need to use a passive infrared sensor (PIR) and approx 5-15 LED white LED lights for the display.

I would really appreciate any advice and feedback as to if this is a suitable project for using the 555 chip, and also:

  • Any recommendations for a circuit
  • Advice on how to calculate a running time of 10-15 secs.
  • Best arrangement of LED's, multiple standard through-hole or can you buy a spaced strip arrangement?
  • Advice on a suitable PIR.

Any help much appreciated, I am continuing my research in the background, but can offer to report back my progress and work in progress shots for your interest.


You would be best off buying a battery powered PIR lamp (osram make them) and using that. I've got one in the garage, the batteries last years.
Hi Fleck,

Thanks for your reply. That is quite and interesting idea. I have seen this one below on amazon and will give it a try.

I will test to see if it gives the desired lighting effect and motion detection when place inside the lid of the box.. even perhaps disassembling it and remounting the sensor to the front of the box could work.


Much appreciated.

Any alternative ideas or 555 circuits still appreciated.

Have found this cheap:
Pyroelectric Infrared PIR Motion Sensor Detector Module HC-SR501

Am trying to understand if I would need to link up to a 555 timer circuit, or if it could drive a strip of LED's directly.



It looks like that sensor you linked to on eBay will time delay up to 18 seconds and I would bet you could just hook your led strip right to the output pins. For the .99 cost it would be worth a try. You would most likely have to add the transistor circuit like in the video to handle multiple led's. I doubt the item from eBay would handle more than 1-2 led's by itself, so you want to use that module to trigger the transistor that allows current to pass through your led strip. I hope I made sense, I just got home from a long night at work so let me know if I just wrote a bunch of garbage LOL.

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Hi George,

Many thanks for your time to reply.

I have the PIR Sensor HC-SR501 from ebay and it can be tuned to output a signal for the 10-15 second period I am looking for, the infra red range works perfect for my needs too.

You are right, one LED connected straight to the output pin of the PIR is ok. However, connecting anymore in parallel and they become dim, I don't know the technical term but it doesn't seem to have enough 'umphh' (current output?).

I rigged up the PIR with a transistor circuit (see diagram below - transistor 2N4401), which I was hoping would let me utilize the full 6V of the power source. This works in that I can run multiple LED's in parallel, however, the LED's are not quite as bright as I had hoped for.

I want to run the LED's at 3.2V 20mA, and therefore with a 6V battery used a 150 ohm resistor, this is fine in a simple test LED/battery circuit and I see 3.2V measured across the LED' with a multi-meter. However, putting them into the transistor circuit below I only measure 2.8V across the LED's, even if I remove the resistors before the LED's?

How can I get the LED's to run brighter (3.2V)?

I am also unsure if:

  • Does there need to be a resistor limiting the input to the Base of the transistor?
  • Have drawn/made the circuit in the correct manner?
  • Estimated battery life (using x4 AA Duracell coppertops in series for 6V)

Here is a video of the circuit with the light display set at a few seconds:

Any help much appreciated, as I am very close to getting this there!


PIR Sensor HC-SR50 Datasheet

Transistor 2N4401 Datasheet