2 Pin Flasher Automotive

Thread Starter

Gaurav Gupta_1568212829

Joined Sep 11, 2019
22
I ripped an automotive 2 pin flasher used in two wheeler circuit attached.
I replicated it, but it didn't worked and I am not sure why?
Can anyone analyse the circuit and tell me if the circuit is correct? Or I need to build some other flashing circuit available on internet for reference?

I even searched the internet and tried to build some reference designs but it didn't worked either. Link attached.

https://www.brighthubengineering.co...this-heavy-duty-flasher-unit-in-your-mo-bike/
 

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DNA Robotics

Joined Jun 13, 2014
600
That article says How to Build a Heavy Duty 12 Volt Flasher Unit.
And uses 2 incandescent bulbs. You may need more load on it than an LED.
They do say that you can change the capacitor to speed it up or slow it.
 

Thread Starter

Gaurav Gupta_1568212829

Joined Sep 11, 2019
22
That article says How to Build a Heavy Duty 12 Volt Flasher Unit.
And uses 2 incandescent bulbs. You may need more load on it than an LED.
They do say that you can change the capacitor to speed it up or slow it.
LED flashes then gets dim and stay on dim. I will try with incandescent bulb but I need to do it with both incandescent and LED.
 

Tonyr1084

Joined Sep 24, 2015
5,966
It's been my experience with those electronically controlled flashers (not sure if they're similar to yours or not) when a bulb burns out the flash rate doubles; which is an indication that one of the bulbs is non-functional. And I'm talking about incandescent bulbs. So instead of having two bulbs drawing current, when one burns out it's only drawing half the current. Two LED's don't even draw close to that much current.

Also experienced is the need for resistors needing to be added to the circuit for making LED tail lights flash. Again, there's that demand of current to make them work properly. I'm thinking your LED's are not draining enough current. Since Q1 is supposed to do the work of switching, perhaps R5 is too high. It switches on then drops into the resistance range and acts like a variable resistor as opposed to acting like a switch.
 

Thread Starter

Gaurav Gupta_1568212829

Joined Sep 11, 2019
22
It's been my experience with those electronically controlled flashers (not sure if they're similar to yours or not) when a bulb burns out the flash rate doubles; which is an indication that one of the bulbs is non-functional. And I'm talking about incandescent bulbs. So instead of having two bulbs drawing current, when one burns out it's only drawing half the current. Two LED's don't even draw close to that much current.

Also experienced is the need for resistors needing to be added to the circuit for making LED tail lights flash. Again, there's that demand of current to make them work properly. I'm thinking your LED's are not draining enough current. Since Q1 is supposed to do the work of switching, perhaps R5 is too high. It switches on then drops into the resistance range and acts like a variable resistor as opposed to acting like a switch.
I have attached the image of LED panel the rated supply for this panel is 12V/1A. I will try it with incandescent bulb and will reduce the value of R5.
 

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bwilliams60

Joined Nov 18, 2012
1,397
In the automotive industry we started with a flasher and then moved to a HD flasher. Then LED lighting came along and nobody could figure out why they wouldn't flash when they replaced incandescents with LEDs. Lo and behold we found a special flasher just for LEDs. Now ther are several and it depends on the number of LEDs in the circuit. These guys are right. Your circuit is made for incandescent bulbs and now you have to change the formula. Nice starter project into the LED world.
 

Reloadron

Joined Jan 15, 2015
5,934
Using the link in post 1 I get to this circuit:
12 V Flasher.png

Designed as mentioned around incandescent automotive lamps. You can use a circuit like this but for a motorcycle application with LED lamps you need to add what's called a motorcycle turn signal load. That or just get a circuit designed for LED turn signals.

Ron
 

crutschow

Joined Mar 14, 2008
27,172
Below is the LTspice simulation of a two-terminal flasher circuit that is essentially independent of the bulb current down to a few mA.
The circuit is a very low current CMOS multivibrator using one 4093 chip driving a MOSFET switch.
It is powered by the stored charge on C2 that is recharged through D1 and the lamps when they are off, which makes the operation basically load independent.

The simulation shows the operation for lamb loads of 1k, 100, and 3 ohms.

If the circuit doesn't operate properly with an all LED load, the add a 1k ohm resistor across the LEDs.

1611359738549.png
 
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