One of the smallest 555 I.C circuits you'll ever see!
Step 1: The Idea
So far this has just been a project of mine to shrink down a 555 timer circuit as small as I can using micro electronics.
It has later evolved into making the circuit dark activated, and now the idea is to use a UV LED in a solar jar & have a solar cell charge the battery during the day.
The circuit is pretty self explanatory.
Use a 500k variable resistor to change R4 depending at what dark level you want your circuit to activate & also to allow for any difference in different LDRs as these can vary .
Again use a VR for R2 to change the speed of your flashing LED. I've used a 3M ohm resistor which is extremely high in value, but I wanted my LED to flash on and off very slowly.
Change R3 to allow for different LEDs.
The PCB is actually a piece of spare cut off. I etched and soldered the circuit as I went, under a x10 magnification scope with a scalpel blade.
As you can see from the PCB, the LDR is missing, at first I soldered it to the back side of the circuit, but later moved it to the same side as the LED, where you can see the two VIAs.
I used a 0.4mm sized soldering tip to solder all the components too as this was really difficult & I needed a tiny needle point tip to solder most joints.
Step 2: Parts List
Surface mount 555 timer IC - LM555CMM (MSOP-8 size)
SMT Tant capacitor - 1uf (106 code) 16v Size A
All resistors are 0603 size, 1% tolerance
Transistor - SMT 3904, size SOT-323
LED - 5mm Ultra violet
Solar cell is 5.5v / 80ma (monocrystalline)
Rechargeable battery is 4.8 NI-CD / 280mah.
Step 3: Solar Jars
I'll take another picture of it working once the battery is fully charged but here at last is the solar jar.
I need to pick some glow in the dark paint perhaps & paint the inside of the jar so the UV has something to light up.
There are two solar jars that I've made without the timer part of the circuit.