Low Voltage Light Sensor Circuit for 12 LED Lights

Thread Starter

truwebs

Joined Apr 2, 2016
78
Go HERE to see where this project started or I could also say stalled.

Thanks to DickCappels and AnalogKid for the direction they gave me in my final product.

So not to bore you all with the non-electrical part of the project I will only be including the core images of this project. In other words, the BRAINS of the project.

shemeatic.jpg

This was by far the most challenging part of the project for a NEWBIE such as myself.. But, it is what gives this clock its Bling! This feature sets this clock apart from all the other Shotgun Shell clocks on the Internet. None of which I found on Instructables. This might be the only Shotgun Clock in this community.

When I first thought about this project, I thought I would be able to find a light sensor module somewhere online (Ebay or Amazon) that I could easily throw into this project and I would be done. I was wrong. I just do not think they exist.

The closest I came was a 12 volt light sensor relay switch. While it would work, the 12 volt battery pack you need to power it posed a problem. There was not enough room inside the box to house a clock mechanism, relay switch, and battery pack. (8 AA batteries). Now this might be an option for you if your design will be a larger box.


Problem Solution

First let me say this is MY FIRST circuit built with any components other than wires and manufactured circuit boards. I had to actually build this from scratch. I amazed myself when it worked.

See the diagram above. I redrew this based on a pencil sketch that I found here on Instructables. The first challenge was to read and follow the schematic. Next was having the parts. Then getting it to work.

Parts

  • Breadboard
  • Light Sensor Transistor
  • NPN Transistor
  • Resistor
  • Jumper Wires
If you know how to do this, it is easy and works great. There is only one modification you will need to make based on your preference and what lights you use. The schematic calls for a 100k resistor. While this worked great on sensitivity it sent too much voltage through to the lights. Too much means the light output was too bright. Even with a 9 volt battery connected and resistors inline the lights things were to bright. So I experimented with resistors until I found the brightness I liked. I end up using a 470K resistor. PERFECT for my liking.

NOTE: By modifying the resistor to dim the LEDs this also made the sensor LESS sensitive which was a good thing. With the 100k resistor simply waving your hand over the sensor would trigger the circuit. Now with the 470K resistor, you need a nearly dark room to trigger circuit.

After 2 weeks the 9 volt battery is powering just fine. With daylight the LEDs are off, and as the room becomes darker the LEDs become brighter.


IMG_2947.JPG

title2.jpg

I am really happy with the final result.

I am really happy that I persevered with the challenge of the Light Sensor Circuit. I might take it a step forward and have a few made by one of these online fab shops just to have a few on hand.

If anyone has any advice on how to get some PCBs made with the cicuit included in this project please let me know.

And of course if you see in possible improvements, please advise.

Thanks and keep Making!

DIYWaterDog
 

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ScottWang

Joined Aug 23, 2012
7,397
OK.. not sure what I am missing to be not included in completed projects. Thought I met all requirements. Can you please explain what I have missed?

DIYWaterDog
The completed projects forum was created for the member who like to sharing their project, including PCB, components list , circuits, photos, theories explanation, code(if it has), and upload all the project to the forum, not just a link, if just a link then it can post in the ee resource forum and let our members who is interested the project, so they can duplicate it.
 

Reloadron

Joined Jan 15, 2015
7,501
Really pretty cool and a real nice job. Motivated me to think about something using rifle cartridges. Creative how you used the primer pockets for the LEDs. Thanks for posting it.

Ron
 

Thread Starter

truwebs

Joined Apr 2, 2016
78
The completed projects forum was created for the member who like to sharing their project, including PCB, components list , circuits, photos, theories explanation, code(if it has), and upload all the project to the forum, not just a link, if just a link then it can post in the ee resource forum and let our members who is interested the project, so they can duplicate it.
I believe I have posted all information related to the circuit build including images, parts, and process. The link is there for those who care at all about the woodworking. Are you saying all the woodworking steps and images should be included as well?
 

Thread Starter

truwebs

Joined Apr 2, 2016
78
Really pretty cool and a real nice job. Motivated me to think about something using rifle cartridges. Creative how you used the primer pockets for the LEDs. Thanks for posting it.

Ron
Me too. Asked a friend that shoots other firearms for his shell casings. He asked why, and I said I didn't know yet. I'll figure it out when I get them. :)
 

ScottWang

Joined Aug 23, 2012
7,397
I believe I have posted all information related to the circuit build including images, parts, and process. The link is there for those who care at all about the woodworking. Are you saying all the woodworking steps and images should be included as well?
I will discuss with other mods and see how they think.
 

Reloadron

Joined Jan 15, 2015
7,501
Me too. Asked a friend that shoots other firearms for his shell casings. He asked why, and I said I didn't know yet. I'll figure it out when I get them. :)
Tempted to make something similar, I have plenty of brass cases. I have an old "Bullet Clock" which was in my office till I retired. The guys got a kick out of it.

Ron
 

ScottWang

Joined Aug 23, 2012
7,397
Looking forward to hearing what they have to say.
You need to add the current limiting resistor in series with c of bjt as 16mA(360Ω or 390Ω) for 5mm LED and 8mA (910Ω)for 3mm LED, our mods team still discussing for this project.

If the LED has internal current limiting resistor then please make a clarify in the post.
 
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