The post explain how to make a simple mini running light circuit using a couple of ICs 555 and UAA170
As the figure shows, the UAA170 circuit is being used to work sixteen LEDs as running lights, which is its usual function.
An astable multivibrator, 555, is used here, but without its output connected to the UAA170.
Circuit Description
Instead, the UAA170 driver is connected to the junction of an RC network and supplied by a triangular voltage with the period set by P1. A tantalum capacitor should be used at position C1 to limit the leakage current.
The input voltage at IC2 should remain below 6 V at all times. To thus control the triangular voltage, Zener diode D17 is used to keep the supply voltage to IC1 below 9.1 V. An 8.2 V or even 6.8 V type may be used instead.
The voltage range covered by the LEDs is decided by the voltage at pins 12 and 13. Pin 5 of IC1 provides the reference voltage for D16. this comes at 2/3 of the voltage to the 555.
The potential at the R4-R5 junction, or pin 12 of IC2, which adds up to 3 V, provides the reference voltage for D1.
Since 30 mA current is consumed bythis mini running light circuit, two PP3s connected in series and a 12 V regulator are necessary for the battery supply to be possible.
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