Control Led for defined periods from battery

I would like to develop a project to use a human motion detector to switch on/off a Led strip during a defined period of time each day. The Led strip will illuminate a cabinet which is difficult to access, and not close to a mains supply, so I want to power this from a battery.
My initial idea is to use a Pro Mini in Deep Sleep mode, because of its power efficiency, for most of the day to maximise the battery life. Use an interrupt from a RTC to awaken the Arduino and empower a microwave sensor (RCWL 0516). In turn the sensor would be connected to the base of a 2N2222 transistor which, when activated, will connect the battery (4x18650 Li-ion) to the Led strip. I haven't figured out the OFF switch yet but the ability to change the on/off times is important.
I’m sure this is not the first time this has been done, but to date I have failed to find anything. Does anyone know of a relevant resource I could reference?

Your post was MOVED to its current location as it is more suitable.

Thank you

Have you experimented with the RCWL-0516 device?

How often would you wake it up to see if anything was moving in its detection area?

Does it work well being waked and slept?

A PIR motion detector that can run continuously at a very low level of current might work better. Use it to wake up the Arduino, which can then turn on the LEDs if the time is right.

Lights stay on for some time (30 seconds? adjustable) after the last motion is detected.

Just expanding and exploring a bit here.



I haven't experimented with the RCWl yet - I am still awaiting its arrival.

The reason I chose it was that I believe it covers a wider angle than the 100° of a SR501. If restricted to 100° I would need to use two sensors - hence doubling the current draw.

The idea is that the motion detector would be ON for 100% of the 'defined time', but I do not know, yet, what current it draws while doing this.

When motion is detected the sensor will send a signal to the Arduino, which in turn triggers the base of the transistor with a delay built in.

You will have to. They work well. Sometimes a bit too well - a detector I deployed here for um research purposes kept “seeing” through walls and from behind. I googled and someone actually recommended pairing the RF with a PIR. :stuck_out_tongue:

At a glance the RWCLs use ~3 mA current. You don’t get 15 mW RF for nothing.

This is 50 times the current of a PIR motion detect. Passive is good in some circumstances. :expressionless:

So it may be that 3 mA would be OK for hours. Certainly that’s a small fraction of what the LEDs will draw when on.

If not, then two PIRs could be used.

Sry I misread your description, I got the feeling you were waking up periodical to take a look, so to speak, rather than being woken up because there is something to see,



? pairing the RF with a PIR ?

I also have a pair of SR501's on order

I'm not certain that Arduino & interrupt is the way to proceed with this because I have read that any function run during the interrupt should be 'short and sweet' or it could disrupt the timers. The majority of Arduino interrupt project that I have found so indeed work on the basis of "waking up periodical to take a look".

Having said that I find it hard to believe that someone has not already invented this

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