Blinker circuit

ferball

ferball

New Member
I have been working on a simple LED blinker circuit for some DIY directional signals for my bike. I am no electrical engineer, so it was a fun exercise in basic electronics. I figure I would post my final circuit here for anyone else who might be inclined to try it.

I finally settled on a basic flip flop circuit that is supposed to light two LEDs alternately. It is a simple circuit that requires less than 10 bucks worth of parts from radio shack. The basic circuit is posted below. What I discovered is that if you replace one of the LEDs with a resistor you can control the flash rate. SO make the circuit and swap a resitor for one of the LEDs then you can find a flash rate by simple trial and error with out having to rebuild the circuit, or crazy math. I run mine off of a 6v battery, and the only difference is I used a 10u capacitor instead of 100u and I took out the resistor in front of the single LED so I could make a brighter cluster it all seems to work fine.
 

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That`s a nice setup you got there! You may also choose different transistors with higher/lower β (amplification). This may also reduce og speed up the blinking.

I`ll build this one these days and test it out!
 
I honestly know very little bout transistors and stuff, I just bought the NPN type from the shack, and trial and error until I got the circuit to work, my soldering caused more problems than the components. So I was stoked with the discovery of the fact that changing on LED for a resistor changed the flash rate.
 
A quick and dirty way is to use a relay and an electrolytic capacitor. If you use a multi-pole relay with a high current rating on the contacts, you can switch lights, horns, etc.
Sorry for the lousy drawing, but I hope it gets the idea across.
relay.JPG
 
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My understanding was that most relays (the automotive type) relied on heat to flip the switch, and because of that they were not conducive to efficient low voltage designs. My ultimate goal is to have an entire 6v system running of a small 6v SLA that is recharged by the white wire or a dynamo/solar. So a relay with a high current draw was nixed. Not that the relay would not work, but it was inefficient or (so I was led to believe). If I build my circuits right I should be able to power it on 4 AA batteries and not have to change them weekly if the SLA does not work out.
 
Relays operate on electromagnetic principle. I found a relay on Digi-Key with a coil rating of 23.3 mA @ 6V. RELAY 1A 6VDC LOW PROFILE PCB - TQ2-6V
If you want real low current draw, consider using CMOS technology 4049 or similar :
Again, please excuse the lousy drawing. I think the 10Ks can be replaced with 1Ks, but breadboard it up and see.
blinker.JPG
 
... But you know, they also make flashing LEDs with the multivibrator circuit built into the LED, so to really simplify stuff, you can go that route.
 
I tried a CMOS timer circuit, never got it to work, I think I may have fried it. Now I am wondering why I never thought of relays before...I think I got stuck on the idea of resetting the relay to create the blink, like in automotive the heat resets the switch, I never considered using a capacitor to create the reset, it probably would have been simplier than my circuit... now we have a thread for reference for next time...
 
I like that circuit, you can build it out of parts you pull out of old radios and TVs and you don't need any fancy ICs.
 
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