I've got a working prototype of the schematic below for a blinking tail light using a 555 timer and two LEDs as a voltage limiter for the 555 circuit (LEDs 1 and 2). All LEDs are flashing when the switch is on, and two of them stay on without flashing when it is off, which is what I wanted. This will run off of a 3W dynamo hub.
The circuit is a very basic astable monovibrator circuit where the flashing rate of the LEDs is driven by R1 and C1. Of course, there is a rectifier between the dynamo and the circuit.
I'm not sure about the current limits for the 555 - I'm using the CMOS version TLC555CP (http://pdf1.alldatasheet.com/datasheet-pdf/view/28913/TI/TLC555CP.html)
Am I going to fry the thing running it on a dynamo hub? As shown, There would be about 300 mA (I think - that may be incorrect) available through the switch at high speeds. Which parameter from the data sheet should I be looking at?
I've considered running another resistor between the switch and the R/V+ pins (#s 4 and 8 on the pinout), but that seems inefficient. Is there a better way to limit the current (if I actually need to do that)?
The circuit is a very basic astable monovibrator circuit where the flashing rate of the LEDs is driven by R1 and C1. Of course, there is a rectifier between the dynamo and the circuit.
I'm not sure about the current limits for the 555 - I'm using the CMOS version TLC555CP (http://pdf1.alldatasheet.com/datasheet-pdf/view/28913/TI/TLC555CP.html)
Am I going to fry the thing running it on a dynamo hub? As shown, There would be about 300 mA (I think - that may be incorrect) available through the switch at high speeds. Which parameter from the data sheet should I be looking at?
I've considered running another resistor between the switch and the R/V+ pins (#s 4 and 8 on the pinout), but that seems inefficient. Is there a better way to limit the current (if I actually need to do that)?
Last edited: