The decoupling caps shouldn't be needed for the crude tests you are doing. But in general they provide stability and noise reduction to the circuit.

Look up the datasheet for the part and they will usually provide a recommended circuit (sometimes several) including recommended capacitor types and values as well as other notes that can be very helpful.

To rule out flaky breadboards, make your connections directly to the pins of the IC using either grabber leads or soldering wires to them.

 

You have an IR emitter/detector pair at the top and bottom step. The LEDs are out, and you walk up the stairs, they come on and turn off when you pass the detector at the top. But what happens when you go down the stairs? When you broke the beam at the top before, it turned off the LEDs. But in this case, you want to turn them on. Or if you start up the stairs, change your mind and turned around to go down? Or as I do all the time, you take one step (breaking the beam) and immediately turn around.

Have you thought of these situations?

 

Can you expand on the decoupling capacitors? I didn't put any capacitors into my circuit....perhaps that's the root of my problem...what are decoupling capacitors? Where would they go?
Sorry for the ignorance, and thanks for the info!

Decoupling capacitors are there to minimize voltage ripple at the regulator's output, and are not related to the problem you're experiencing.
Did you double check the regulator's connection to ground as was suggested?

 

43 Posts, I've just checked the loads in my 45's.

Physically connect +12v to input pin, make sure the centre pin is connected to 0v, Ground or -12v
Connect the 1k0 load between the Output pin, and 0v, Ground or -12v
With the voltmeter black lead connected to 0v, Ground or -12v & the red lead connected to the output pin.
It should measure approx. 5v
Good luck...........

 

There's more, look at "Designing a simple alarm circuit using microcontroller" #7 for a schematic (7805).
In todays forum.

 

You have an IR emitter/detector pair at the top and bottom step. The LEDs are out, and you walk up the stairs, they come on and turn off when you pass the detector at the top. But what happens when you go down the stairs? When you broke the beam at the top before, it turned off the LEDs. But in this case, you want to turn them on. Or if you start up the stairs, change your mind and turned around to go down? Or as I do all the time, you take one step (breaking the beam) and immediately turn around.

Have you thought of these situations?

I have thought about some of those situations....haven't thought about the starting up and turning around scenario....I think what I may end up doing is reading the two sensors...if one goes high, turning the lights on for a pre-determined time, then shutting off. I do realize that if someone goes down the stairs immediately after I go up, the lights may turn off on them. But I've been drilling this idea around in my head for weeks, and can't come up with a solution to address all the possible scenarios, so may just have to settle. I'm really new to all this, so my ideas and knowledge are growing as I learn more. But I don't know how to address all the different scenario's...any suggestion?

 

Just an idea. Consider a pair of sensors at the top and bottom. Then you can detect whether a person is going up or down

You might also have to inhibit the pair of sensors, once they are activated, to ignore the second leg. Sorry, no ideas for a dog.

 

Just an idea. Consider a pair of sensors at the top and bottom. Then you can detect whether a person is going up or down

You might also have to inhibit the pair of sensors, once they are activated, to ignore the second leg. Sorry, no ideas for a dog.

Thanks for that...the pair of sensors might be the ticket...at least the sensors would know if someone was coming or going. I suppose setting up variables could help determine if someone turned around as well...I'm gonna let that percolate and see what I can come up with...although it might just be easier to set the lights to stay on for x amount of time and be done with it...although trying to figure it out will be fun either way!! So I have one other question if I can? I'm cutting a 12v 5050 led strip into sections of 3 leds/stair, ...15 stairs; which will be attached under the lip (I think). I'm using an Arduino to run the program. I was planning on sending the output from the Arduino through a ULN 2003 to drive all the LED's. I was prototyping this (although the 5m LED strip was still all intact), the 2003 got very hot. I have ordered heat sinks, but the heat has me a little worried. 2 ideas...1. would breaking the 15 sections of lights into two (8 stairs and 7 stairs) and driving them from two different Arduino pins and two input/output pins on the 2003 reduce the heat? or would using a relay to drive the lights (with the 2003?) be a better option? This is all fairly new to me, and installing them in a house has me questioning everything!
Thanks again for you thoughts and expertise!