Build Your Own LED Turn Signals!

Now you have me thinking... I have this extra case and some extra parts. Is it possible to make a small circuit that would have two switches. One for the blinkers and one for the tail light. That would have two adjustments one for the blinkers and one for the blink rate of the tail light (if I had the switch in the position for the tail light to blink).


Sure is! Basically, you'd need to build a parallel circuit that is very similar to the one you already built (but not quite!), and then run both circuits off the same battery and put them in the same enclosure. I have attached a diagram of the circuit you'd need to use for your tail light. The turn signal circuit stays exactly the same.

I based this tail light circuit on the same parts that you already used in the previous circuit, so you won't have to buy any new parts. A few things to note:

Switch Position 1: Flashing. In this state, the CD4047BE is powered up and in astable mode, just as before.

Switch Position 2: Solid on. In this state, the LED is directly connected to +12V and ground, so it will stay on solid, which is what we want. If you look at the diagram carefully, though, you'll see that the CD4047BE (the IC that creates the UP-DOWN-UP-DOWN voltage signal used in making the lights flash) is still powered up in this position. This is unnecessary, and will waste a little bit of electrical power (much smaller than what the LED uses, though), but it is an unavoidable consequence of trying to use the same parts that you used before. On the whole, you shouldn't be able to notice if the CD4047BE were on or off, based on battery life.

Switch Position 3: Off. In this state, neither the CD4047BE nor the LED itself is receiving power. In essence, we're just disconnecting the whole circuit from the battery.

And don't forget that, in this circuit, the second pole of the DP3T switch is connected to ground, not to +12V! This means that you'll have ground connected to one pin of the switch, and +12V connected to another, which, unless you're really careful with your soldering and stray wire strands, is a recipe for a short!! Do I remember correctly that your other enclosure is plastic? If so, that will make your life a lot easier in terms of preventing unintended case shorts.

If you have any questions, just let me know!
 

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When I read this electrical stuff, I'm lost after the first few sentences...reminds me of us medical people being accused of talking over people's heads and not even realizing it.....a real pain in the insertion point of the sternocleidomastiod into the trapezius muscule!!!!(pain in the neck)lol.
 
Hi there,

I was hoping to build something like this with a group of youth, what woudl i need to change (if anyhting) to have this run from a 9v battery?

t
 
Hi there,

I was hoping to build something like this with a group of youth, what woudl i need to change (if anyhting) to have this run from a 9v battery?

t
I wouldn't recommend an ic anymore, this was back in 2009, now I would recommend a pre-built circuit or even a pre-made flasher.

My question for you is how many leds are you looking to power, and is it a turn signal that you are trying to make?

You can also get 2 9v batteries and hook up to a 12v regulator chip, it will give you the 12v you want at a very reasonable price and with a stupidly simple add on to the circuit (like 5 more solder joints and only 3 components, 1 if you want to skip the capacitors which you could pull off on this design.)
 
Cool read, a lot, but cool. Didn't realize the thread was started almost 10 years ago, and last reply a year ago.
I'm building a turn signal circuit using( 555 timer, 3 resistors, one capacitor) x 2. one circuit for left and one for right and a motorcycle style handlebar mount SPDT switch.
The circuit powers 3 LEDs, two 5mm and one 3mm per side (L/R). It's powered by an 8.4v Li-Ion battery pack recharged by a 12v mini gen (AC) rectified to DC. through a current limiting charge circuit. Everything is on breadboard at the moment. I'm using PCB design software to design and print the circuitry to be transferred to blank PCB board and etched for component placement and soldering. will post schematics and step by step pics when done and tested.
This is a WAY late reply, hope to keep the thread going. Like to see other plans and ideas on the subject.
 
Cool read, a lot, but cool. Didn't realize the thread was started almost 10 years ago, and last reply a year ago.
I'm building a turn signal circuit using( 555 timer, 3 resistors, one capacitor) x 2. one circuit for left and one for right and a motorcycle style handlebar mount SPDT switch.

I take it you are using the 555 chip for self canceling turn signals?
 
Does a 555 have that function?
Yea. I have been letting this circuit flash for 3 days strait just to make sure no resistors are going to get hot and to see how long the 6 cell Li-Ion battery pack will hold up. Could have went another day before voltage level would have been at an unsafe level for safe recharging.
 
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