Motion sensitive RGB lamp can standby for 3 years

Ooooh, nice enclosure! This is a little motion sensing lamp which [Krazatchu] built a few years back as a Mother’s Day gift. The PIR sensor is easy enough to see as the white dome on the front of the case. But look closely below that and you’ll see the LDR which it uses to keep the thing asleep during the day. This is intended to save on batteries but the original version still ate through them like crazy. This year he gutted it and worked out a much more power-friendly design.

He moved to a TLC1079 OpAmp which greatly reduced power consumption when reading from the PIR sensor. The microcontroller was also upgraded from an ATtiny13 to an ATmega328, making the new version Arduino compatible. It puts itself to sleep and keeps the lights out during the day, drawing just 0.08 mA. When driving the RGB LED the lamp pulls about 50 mA. That should still last a while on three AA batteries but we’d still recommend using rechargeables.

Comments

  1. Bogdan says:

    There are some cheap $3 PIR sensors on ebay. The ones i bought are missing the LDR but there is space for it on the PCB plus another resistor. It’s much easier to use that than to make the actual PIR detector circuit.
    Also, to save energy on the LDR it could be powered just briefly by the micro when there is a motion detected.

    Other than that, the build looks very well.

  2. GR0B says:

    I would have used rechargeable batteries and then added a small solar panel or some other small power source to slowly top the batteries. Then you push the battery life well past 3 years.

  3. Bogdan says:

    that is 3 years of standby… no light. i think the batteries will drain much sooner due to usage…
    so in this case maybe rechargeable batteries are better.

  4. Whatnot says:

    Instead of an LDR you could use a solar cell, that way when it’s light it will not only know but be recharging.

    Oh and if not then rechargeable are a bad idea since they have a sizable internal discharge even when not used and even when you use the more modern ones that have less capacity but are designed to not discharge so much internally it would probably still be more than a classical batteries.

    Yo prrof the point I can tell you I have a remote-switch remote with batteries that I haven’t changed since I bought it more than 6 years ago, so your classical batteries really last when a device is made to only use power when operated.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

Join 92,288 other followers