Of course vehicles not fitted with direction indicators, the road is getting smaller every day. And the subject is practically ceased to be relevant. However, due to the fact that the factory electronic relay pointer yet often fail, chores and losses related to the acquisition the new block. So hams we have where to put my mind and hands.
In the article by A. Kozarova "Switch loading" ("Radio", 1991, vol. 7, pp. 37 - 39) described noncontact low-voltage circuit breaker. The design is simple and, as I think it is very promising; its author, apparently, deliberately not given practical recommendations on the use of this device, relying on a creative approach ham radio.
Offer readers two options relay direction indicators developed on the basis of the load switch. In Fig. 1 shows a diagram of the relay, suitable for use in onboard DC. It is without any circuit changes in the vehicle's electrical system, it will replace traditional the thermal relay.
Logic elements DD1.1, DD1.2 assembled generator interrupt frequency. Elements DD1.3 and DD1.4 - buffer inverters signal generator. Transistors VT1, VT2 of the current amplifier are connected in parallel. Power transistor VT3 - breaker current signal lamps (the diagram shows the lamp HL1 and HL2, symbolizing two group of lamps left and right sides of the Board).
All transistors operate in a switch mode. Diode VD1 prevent release down DD1 chip in an emergency change of polarity of connection of the relay to the on-Board network; it must be germanium.
Those who are interested in the details of operation of the load switch, I recommend read the above article.
For vehicles with side AC is suitable relay direction indicators collected by the circuit of Fig. 2. It differs from previous what is powered by a diode rectifier VD1-VD4, and the fact that the current interrupter assembled on the composite transistor VT1, VT2, R2.
In modern systems of direction indicators is provided additional mode alarm emergency stop when flashing simultaneously lamps on both sides of the Board. We hope that readers will be able to independently to finalize described the relay for this mode.
Author: I. Careplace, POS Kaduy Vologda region.