Micro 555 timer circuit
One of the smallest 555 I.C circuits you'll ever see!

Step 1: The Idea

Micro 555 timer circuit
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

Micro 555 timer circuit
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

Micro 555 timer circuit
Micro 555 timer circuit
Micro 555 timer circuit
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.

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