Did you look at the design I showed? No transistor needed, and minimum parts. I figure the battery would last for years off it.

Yes, but I need it to switch off when the car is switched on, and on again when the car is switched off - automatically.

 

OK. In that case, you're running at about 1.5Hz, duty cycle around 22%, your peak current draw is around 32mA and minimum current draw avg is about 7.2mA, about 12.66mA average over time.

It's actually pulling less than that, so it's not too bad. The thing about the circuit I made up is that you can use poly, metal film, or ceramic capacitors, that will be more reliable and have less leakage current than the electrolytic capacitor that you're forced to use. Also, the capacitance being of much smaller value will enable you to use a physically smaller capacitor - but if size isn't an issue, that's up to you. Switching to a CMOS 555 will reduce the average current use by quite a bit. Remember, any power taken out of the battery will eventually need to be put back in, and over time that could amount to a good bit of change spent on gasoline. If you can reduce the power used in a circuit that will be running 100% of the time that the vehicle isn't in use, you'll come out ahead in petrol saved and battery life extended.


A PNP transistor with a suggested 300mA Ic capability minimum, a 1uF bypass capacitor, and a 10k Ohm resistor connected from the base of the transistor to the ACC circuit.

Thanks for the the info, i'll give that circuit a go when I make a 2nd unit for my own car.

Meanwhile im guessing from that last paragraph that these are the extra components i'd need to add to my current circuit, correct? If so that'd be great, I really don't wanna desolder the circuit board i've already made, but where in the diagram do these fit?

 

Meanwhile im guessing from that last paragraph that these are the extra components i'd need to add to my current circuit, correct?

Yes.

If so that'd be great, I really don't wanna desolder the circuit board i've already made, but where in the diagram do these fit?

In the wire that goes from the battery to your +V supply to your flasher circuit. In my schematic diagram, the parts are Q1, C3, and R4.

By the way, you also should have pin 4 of the 555 timer connected to +V.

 

Ok, now would these following components be what i need?

Transistor 2nd from the top http://www.jaycar.co.nz/productResu...esize=10&keywords=PNP+transistor&form=KEYWORD

Capacitor http://www.jaycar.co.nz/productView.asp?ID=RZ6627&keywords=1uf+capacitor&form=KEYWORD

 

Yes.


In the wire that goes from the battery to your +V supply to your flasher circuit. In my schematic diagram, the parts are Q1, C3, and R4.

By the way, you also should have pin 4 of the 555 timer connected to +V.

Thanks! you're a legend. Just one more thing, that schematic that you posted, what components do I change to alter the flash rate?

 

R1, R2, C1.

Best to leave C1 at 1uF.
Decreasing R1 to around 510k and increasing R2 to around 160k will do a reasonable job of duplicating the duty cycle of your circuit, but use much less current on average; particularly if you use a CMOS 555.

R2 must be less than 49% the value of R1, or else the timer will get "stuck".
The smaller that R2 is, the less time the LED will remain on.

The larger the pair of them are, the slower the flash rate.

 

And is this the cmos timer you mentioned, I searched for it as TLC555 and nothing came up but I found this, wondering if its the same/similar thing

http://www.jaycar.co.nz/productView.asp?ID=ZL3455&keywords=cmos+ic&form=KEYWORD

 

Yes, that is one; apparently the only CMOS 555 version that they carry. (I checked)

 

Yes, that is one; apparently the only CMOS 555 version that they carry. (I checked)

Ok thanks. And thanks again to yourself and everyone else for the help, one very helpful board of guys, i'll let you know how I get on.