Pseudo-Random Lamp

It's been more than half a year since I put an original electronic design on my blog. The credit for conceiving the idea goes to electronics editor and friend Alan Winstanley. The circuit (pseudo) randomly switches a 12V lamp inside one's house, every ten minutes or so, so that there is the impression of activity. That is, it deters (one hopes) would-be thieves. OBSERVATION: A few notes: LP1 is ideally a LED device, otherwise one is wasting a lot of power. TR1 will easily handle 10 Watts (up to 43 Watts with a suitable heat sink). A supply decoupling capacitor would be a good idea: say 100μ (positive to positive, negative to negative). The make of IC is not critical: any CMOS 4093 IC will do. C1 and C2 should be in good condition, since charge current is small. The circuit itself uses next to nil power, so everything will depend on the power which the lamp draws: the Wattage divided by two. Perfectionists might put a 10k resistor between 1C1 pin 10 and TR1's gate. You'll see that the design uses British conventions. You may click on the image to enlarge.