Electronics Make my own adjustable 12v flasher?

I tried without any luck to find an adjustable flasher for my car, so how about making my own?

I currently use a 2 prong flasher, one side is +12 with the turn signal is on, and the other side feeds the lamps.

I want to be able to adjust the flash rate anywhere from half a second to several seconds.

My googling turns up automotive relays and 555 timers, any pointers?

 

Fisrt off, can I ask why you are wanting to do this?

When you say 2-prong flasher, are you talking about the round flasher with one prong horizontal and the other vertical?

http://www.carolinaclassictrucks.com/KeepItClean-FF552NL-p-keep-it-clean.html

 

This is probably a language difference but I cant work out what youre asking about. I think youre talking about variable flash rate indicators (turn signals) in which case youre on the right track with the 555 timers but id be thinking mosfets rather than relays.

The 555 circuit youre after is called an astable and although most circuit diagrams on the net wont show it the 555 timer has an enable input that you would wire up to the input signal. A search for the 555 datasheet would be a good starting point if you want to read up about it alternativly there are lots of sites on the net that will explain the 555 timer and how to use it.

Moriquendi

 

2JSC,

That's exactally what I'm after. But it's hard to justify spending $40 on something I can probably build with $10 worth of parts from Radioshack and learn something in the process.

The reason I want to do this is; I've installed sequential tail lights and 60 flashes per minute doesn't give them time to sequence fully. I need about an extra half of a second.


Basically I just need something that will operate a 12v relay at 60 times per minute with a little adjustment. I can make it work from there, it's getting to this point I'm unsure about.

 

A 1Hz 555 astable would do the trick, wire the output to the relay. Chuck a diode to counteract the back emf and your good to go, something like this:
http://www.fast-files.com/getfile.aspx?file=1881
depending on the relay you might want to put a transistor or mosfet between that and the output of the 555.

 

This might be what you need. You will need to modify it a bit to get the timing down to 1 second.

 

With auto lighting one side of the bulb-holder is often grounded to chassis so you need to watch that when picking a semiconductor switching device. Relays may be crude but they're more idiot-proof.

 

Thats true but I was thinking of the lifespan, when ever someone talks about hooking a relay up to an oscillator I wonder just how long it will last. Could always use a P-channel fet. I take the point about robustness though.

Moriquendi

 

How about a solid state relay?

 

That would be a perfect starting point, and the price is right.

I'm afraid of completely breaking it trying to slow it down more than 2.5 seconds. I assume it would be done by just adding another resistor inline with the one pot?

 

To the RC portion of the circuit, you will need to either exchange the resistor for one of smaller value or placing a resistor in parallel to the resistor. You can also exchange the timing capacitor for one of lower value as well but it is up to you.

It is a little hard to tell from the picture where the timing resistor may lie. I will have to see the back of the board to be sure.

 

They're just as delicate as a discrete mosfet but much more expensive unfortunatly.

Moriquendi

 

Too bad we can't see the back.. I did find this better picture.. Looks like all 3 resistors are the same?

If it's going to be that easy to adjust, I think I'll order one. It'll be a learning experience for a electronics newb like me.

 

dude just use my circuit, if you want adjustment just swap out the 3.9k resistor for a 5k pot and adjust until suited