Hi, my name is mircho & I am arduinoholic.
I am pretty new to Arduino & electronics in general, have some lengthy software development experience.
Let's say I've got to know what a transistor can be used for 2 month ago.
But now I have a pretty trivial and non arduino problem. The turn signals on my 1991 suzuki motorcycle stopped working - they won't turn on at all. The bulbs are intact and are ok. The switch on the handlebar is ok. I traced the wires to a small black box that clicks when the turn signal switch is toggled. But this is only a single click.
There are only 2 connectors to that small box. The resistance between the connectors is low - few ohms.
Inside of it I found a (probably) capacitor, resistor (very low value < 1 ohm) and a coil. When energized the coil closes switch and then the resistance between the connectors rises to something like 65 ohms. Obviously something in this setup causes the coil do energize and de energize at ~ 1Hz frequency. I assume the only faulty part can be the capacitor.
I have a cheap source of electronic components but expensive for auto and motor parts.
So my question is what is the simplest way to recreate this behavior with electronics? I immediately came out with an idea of using a 555 IC, but I am pretty sure there are other ways also.
Thank you in advance for even only reading this.
If you already know how to use transistors then you could just have the circuit set up with the transistor gate hooked to a toggle switch. It'd keep the light on.
To get it to flash you could stick an arduino in there to drive the fet and set it so when switch is high then pulse the output that is connected to the fets gate.
I will try to illustrate the situation:
Currently I have bypassed the flash relay and the turn light are just on when I activate the turn switch.
I might be just wrong about how this "relay" functions and about the change in resistance, as this behavior might be because of the malfunction.
An arduino may be overkill for this. I would just buy a $5 two terminal turn signal flasher from Autozone and wire it in series between the switch and the bulb (or between power and the switch)
If you're going to use a transistor, you'll have to get a pretty beefy one to handle the 50W or whatever turn signal bulbs. My guess is that this LC circuit you found actually drives a relay.
The relay is what makes the click-click sound on a turn signal, so if you're not hearing that, the relay or a connection leading to it has failed. Turn signal relays are usually well-stocked at Autozone and cheap, so I'd try replacing it and see what you come up with before I tried to make a custom circuit.
I am thinking of using this mosfet: PHP3055E (found it in good condition on an ATI video card). The bulbs on each side total to about 45W (together with the control light). At 12V that would be < 5 Amps. If I read the data sheet correctly that would not be a problem.
Where I live I have good supply for electronics components and very poor for spare motorcycle parts. Or at least I don't know any.
Built the blinker with a 555 IC, 7809 regulator and just "in front" of it a diode and a 15v zener for protection and electrolyte and .1 mF condensators for decoupling. The switching part is a IRF9630 TO-220 package.
It worked only few minutes. Now the P-MOSFET seems fried and damaged by heat. The rest of the circuit works - I tested the output from the 555 and it's ok. I obviously had something wrong, but I cannot find out what.
Quick search in google for the MOSFET:
http://www.sullivan-county.com/ele/pdf/irf9630.pdf
(just trying to help to anyone willing to decipher the datasheet for me)
hi mircho,
firstly i am no where near an electronics whizz kid (and im also new to the forum). but i may have an idea why the fet has died.
a while ago i build a jacobs ladder project using an old car ignition coil, it kept dying after a few minutes, the circuit worked the coil refused to.
only after i brushed against the main transistor did i find out why, the thing was red hot. i'd been pushing enough power through it to toast the thing, one heatsink later working like a dream.
so i would suggest you check how hot the fet is getting when the circuit is in use, just in case its getting hot enough to burn out.
if i understand the datasheet correctly (and trust me i am proberbly wrong). but the fet can disapate a maximum of 75 watts of heat, if your using two bulbs that can generate 50watts each am i right in thinking this would make the fet try and disapate 100watts ??? (seriously guys feel free to correct me i am clutching at straws for the reason the fet is burning out )
hope this has been of help to you, if not sorry for wasting your time.
btw hi everyone im new 
Kris
A standard car/bike flasher is a bimetal strip that heats up and bends as the power flows, breaking the connection and turning the light off. When it cools, it reconnects and turns on the lamps for a while. Replacement flashers are pretty cheap.
But as a project, you really should try to make it more fancy. In about 1977 or so, Yamaha put in a simple AND logic, so the switch would stay on until both X seconds and Y feet were traveled. (It still used the bimetal flasher). So it would be a cool hack to sense wheel rotations, and time. Just a few lines of code for your arduino.
As others have said, the bulbs draw a lot of current, many amps, which will take some serious FET relays