This article shows you how to make a touch garden light shown in the photo below:

I used a encasement from an old solar garden light.

The light turns on when the two contacts from the circuit are connected by human hands or human fingers.

You can see my circuit working in this video:

I thought of this idea after reading the following article that contains similar circuit to mine:

https://www.instructables.com/id/Cheap-Touch-Lamp

Step 1: Design the Circuit

I drawn the circuit in PSpice simulation software:

My circuit uses a Darlington pair unlike the circuit in the link above that uses voltage follower current amplification. I tried using a single Darlington pair power transistor and I found that the gain was insufficient for the LEDs to turn ON.

Calculate the maximum LED current:

IledMax = (Vs - Vled - VceSat1 - Vbe2) / Rd / 2

Rd = 33 ohms + 47 ohms = 80 ohms:

= (4.5 V - 2 V - 0.2 V - 0.7 V) / 80 ohms / 2

= 0.01 A = 10 mA

Rd = 82 ohms:

= (4.5 V - 2 V - 0.2 V - 0.7 V) / 82 ohms / 2

= 0.00975609756 A = 9.75609756 mA

Calculate the time constant, the approximate time it takes for LEDs to turn OFF after the contacts are disconnected:

Tc = Rbe * Cbe = (1*10^6 ohms) * (470*10^-9 F) = 0.47 seconds

After 5 times constants (5*Tc = 2.35 seconds) the Cbe capacitor is considered to be completely discharged.

Step 2: Simulations

Simulations show the predicted maximum bright LED current of about 14 mA.

Step 3: Make the Circuit

I placed this circuit at the bottom part of the device:

You can see the four NPN BJT transistors (connected in Darlington pair), the 33 ohm Rd1 resistor and the 470 nF Cbe capacitor.

I placed this circuit inside the glass ball:

You can see the 10 kohm Rb resistor, 47 ohm Rd2 resistor (Rd = Rd1 + Rd2 = 33 ohm + 47 ohm = 80 ohms) and the two bright LEDs.

Step 4: Encasement

I placed the first circuit inside the metal part of the garden light.

Step 5: Put the Lid On

I attached the lid with masking tape:

You can see how well the lid covers the circuit:

Step 6: Testing

At first I made the circuit without the Rbe resistor to see what happens. 

You can see that without the Rbe resistor the lamp takes a long time to turn OFF.