Bike Turning Signal Indicator

This turning signal indicator circuit could be used for a bike, or a car, or almost anything that requires flashing indicator bulbs. It uses the UAA1041B integrated circuit that reduces the component count drastically. This device is for use in automotive applications and has important safety features such as defective lamp protection, overvoltage protection, short-circuit detection with relay shutdown to prevent risk of fire, reverse battery protection, and built-in integrated suppression clamp diode.

Just recently, I was looking for such a circuit to install in a vintage bike, and saw some awful over complicated circuits using the 555 timer IC. I thought that this circuit is more useful for anyone who wants to install indicator lights to vintage automobiles or bikes. The heart of the circuit is an IC that has an operating voltage range of 8 V to 18 V to cater for a wide range of applications. The IC drives the flasher relay at a rate determined by the values of R1 and C1. For safety, the relay should be the type used in the automotive industry.

The 21-watts light bulbs L2, L3, L4, and L5 are for the turn signals, whilst L6 is the dashboard indicator light. If you are one of those people who always forget to disengage the handbrake, then bulb L1 connected to handbrake switch S2 provides an additional warning on the dashboard, however, it is optional of course.

This is a very clever little circuit with many features, because it has a shunt resistor RS that detects defective bulbs and short circuits. When a light bulb fails the flashing frequency doubles, which is a very useful protection. There is also overvoltage protection so that when the supply voltage exceeds 20.2 V, the relay disengages to protect your bulbs.