Hi,

New here so hi to everyone!!

I have installed footwell lights that come on with the headlights. I also want them to come on with the interior lights when the doors open.

To do this I know I need an or gate to control the 2 12v input to have the lights turn on.

Any help would be great!!

Thanks,
Craig.

 

The CD4001 is a quad 2-input OR gate with a maximum supply voltage of 15V, but a car battery being charged comes perilously close to that.
Maybe you could use something like the circuits below:

 

Hi thanks for the reply.
Thanks for the information on using diodes or transistors as it's a 12v circuit. What would be the best way to make and package the circuit up?

 

Probably the easiest to start with is stripboard and there are 'project boxes' available for this purpose. I don't where you are in the world so I don't know what suppliers you have.
http://www.mouser.co.uk/Search/Refine.aspx?Keyword=stripboard
http://www.mouser.co.uk/Enclosures/Enclosures-Boxes-Cases/_/N-5g3p?Keyword=project+box&FS=True

 

The CD4001 is a quad 2-input OR gate with a maximum supply voltage of 15V, but a car battery being charged comes perilously close to that.
Maybe you could use something like the circuits below:

The opposite transistor Vbe reverse voltage will be exceeded when one of the transistors turns on so you would need to add a diode in series with each base input to prevent zapping the transistor.

Likely the two diode circuit is a better and easier way to do what you need.

 

The opposite transistor Vbe reverse voltage will be exceeded when one of the transistors turns on so you would need to add a diode in series with each base input to prevent zapping the transistor.

Likely the two diode circuit is a better and easier way to do what you need.

Yes, of course, because we have a 12V to 15V supply voltage.

 

Use 2SD2704K.

 

Use 2SD2704K.
View attachment 133518

But two diodes would be easier.

 

What powers the footwell lights now? Are they simply connected straight to the headlights power? If so, is it your intent to have them powered directly from wither the headlights or dome lights, or is there a relay driving the footwell lights and you want to control the relay? Also, what is the current needed by the footwell lights?

ak

 

Hi sorry I have been on holiday.

Thanks for all the replies!!

At the moment they are connected to and powered by the interior lighting circuit that comes on when the headlights are either switched on manually or on the auto setting. That is the first input, I want you also add the dome light circuit, so they will also come on when the doors unlock/open.

 

From a quick search on Digi-Key, here are in-stock dual diodes, common cathode, non-surface-mount, 4 A to 20 A. They start at 84 cents for a single piece in a TO-220 package. The schematic is in post #2.

https://www.digikey.com/products/en/discrete-semiconductor-products/diodes-rectifiers-arrays/286?FV=1c0003,11400aa,1140006,1140050,f2c0002,f300001,f30000d,f300098,f300002,f300014,f300015,f300016,f300138,f300008,f300009,1f140000,ffe0011e,ffec0332&mnonly=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&cad=0&datasheet=0&nstock=0&photo=0&nonrohs=0&newproducts=0&quantity=&ptm=0&fid=0&pageSize=500

what is the current needed by the footwell lights?

ak