Hey guys,

I am going to wire my gps power supply in properly to the cigarette lighter so it doesnt need to be plugged in. I am going to put a switch in, and want a soft-push type.

Having looked on Maplins website, most switches seem to be rated for 240v A.C. currents. Are these suitable for 12v D.C. currents?? If not, can anyone recommend any decent switches i can use?

cheers.

Yeah they should be fine, it's not like there's going to be a huge resistance on the contacts.
I always use DPDT types, means connecting both wires, but I'm just a bit of a fussy old buggah like that

Im a little confused. Surely the only wires are going to be the live feed and the earth wire and these would both have to be connected anyway??

Yeah, SPST will do the job......at work I'm constanly farting around with AC stuff so double pole is force of habit

OK, i called into Maplins today and picked up this switch as recommended by the guy:

http://www.maplin.co.uk/Module.aspx?ModuleNo=34859&TabID=1&source=15&WorldID=&doy=22m1

The guy said it would work fine, but if i wanted the LED to light up, it would need a resistor. He got me one that appears to be brown, followed by a big gap then blue, blue, yellow, pink.

Having not done any electronics for a while, i need some advice on how to wire it all up. The maplins guy bridged the positive and negative terminals on one side with the resistor and told me that i need bridge the other terminals with a piece of wire. Surely this is just gonna short out the switch????

_ -
_ - The switch's terminals look like that <== with the top half marked with a "-" in the plastic and the bottom half with a "+". The guy bridged the + _- with the resistor.

I hope this makes sense and someone can help me.

Cheers.

Thier "FAQ" section is a bit confusing

"Q: what voltage range will this switch work on? (Rob Roach: 14/10/2004 15:42:06 )
A: Any voltage above 2.2v, a resistor is needed however (the value of which is dependant upon the supply voltage.

Q: Does the illimination activate when the switch is in the "ON" position, or is it always illuminated? (Roger Donoghue: 20/10/2004 16:11:42 )
A: Can be wired either way.

Q: What resistor do I need to use this on 12v DC? (Martin: 13/11/2004 18:44:29 )
A: Requires mains voltage for illumination,wont light with 12V DC. "

The answer says it will work with any voltage above 2.2v and will need a resistor, the then last answer says it won't work on 12vdc........

If there are only 2 terminals on it then the LED is powered buy whatever is going throught the switched circuit, which means anything more than 2.2v will pop the LED.

i'd be poking it with a multimeter to sus out which ones are for the led, then try putting 3v through it and slowly upping it till the led looks too bright, then get a resistor

Cheers guys,

Ive taken it apart now and there are 2 terminals to go into and come out of the LED and 2 for the switch. I was confusing myself and then talking it through with my dad made a bit more sense.

another quick one, is there a right way and a wrong way to connect a resistor in?? I dont fancy a "capacitor incident"

Nope, resistors are do not have a polarity so you're quite safe.

Hi,
If you've taken the switch apart, why don't you replace the LED for a 12v version, you can get these in maplin, about 18p each and no need for a resistor, I use them for replacing the back-lighting in car radio's.

p.s. Theres no wrong way to wire a resistor, not like electrolytic caps.

Thanks
Paul T

But bare in mind that the LED is polarity sensitive, if you do it the wrong way around nothing will happen it just won't turn on however

great idea, cheers paul & bogie.

So just to confirm that if i change the LED, there will be no need for any resistor in the circuit at all???

thanks other paul - i knew about the LED polarity, its the longer leg thats the +ve (i can remember that )

off up to uni now (crap )

Yep, well I remember that the flat on the side with the leg is negative which I believe is always the shorter leg.

If you have a 12V LED then no, you won't need a resistor. The resistor simply causes a "voltage loss" accross it to make it the voltage that the LED requires. Simpliest way to consider it, i.e. if you have a 5v LED you would use's power rating to work out it's current therefore use that in OHMs law to see how to get the voltage from say 12v to 5v.

Please bare in mind I haven't ever studied electronics properly

littleyellowcar said:

Hey guys,

I am going to wire my gps power supply in properly to the cigarette lighter so it doesnt need to be plugged in. I am going to put a switch in, and want a soft-push type.

Having looked on Maplins website, most switches seem to be rated for 240v A.C. currents. Are these suitable for 12v D.C. currents?? If not, can anyone recommend any decent switches i can use?

cheers.

Click to expand...

that is a good idea man... i might have to try somethin like that when it is time for some under car neons, a switch like that would work awesome for neons!

like it

IIRC, a 3.3V LED (blue, white UV and green ones are 3.3v) needs a 470-ohm resistor to run from 12v... BUT car systems run at around 14.4v (as the alternator has to push out more volts than the battery in order to charge it) so you also need to use a 56-ohm resistor in series with the 470-ohm one. If the LED is a 1.7v one (red or orange) then it needs a 470-ohm resistor and a 150-ohm resistor, again in series.

These switches are very good quality, I have used them to replace all my poorly lite buttons in my integrale and may well do it to the Cinq in the future, if I can work out a way to use them in the Cinq button holders as in the integrale its one panel which I replaced with carbon fibre and cut holes into for the buttons to sit. There is one which is engraved NEON, they are lite up blue (except hazards which is red)

They were also recently used by Jaguar for one of there prototype show cars.

http://www.motorspeed.com/cgi-bin/m...ode=1&Product_Code=TRILLOGY_ENGRAVED_SWITCHES

Aaron.

cheers for that - the buttons look well smart

I take it to wire them in, its purely, connect the live feed up to each terminal on the rear???

They're very easy to use as you get clear instructions with them, & you can wire up more than one thing to one switch, what you don't see in the pick is you get a 10amp connector block that clicks onto the back of the switch show and it has 4 or maybe 6 prongs. I managed to use them fine in the 'grale where some switches had 6 wires going in and out of them tho have to admit I could never quite work out how to get the rear wiper to park itself after you switch it off, so have to time it just right to get it to sit in the right place!

You will need a flat surface to mount them on tho, either than or my idea for the Cinq would be to get a blank switch, cut out the back off so its hollow then cut an appropriate hole i the front, mount the engraved switch in hole and then the switches are in the standard place. Although it may be tricky with Cinq buttons as they have that weird angled front to them, but as a little pointer I have replaced mine all with flat front buttons that I took out the 'grale as they are interchanged able, so I'm sure you could find some buttons from other cars in the FIAT range similar.

Aaron.

Cheers Aaron.

I would mount the switch on the blank next to the lekky window buttons.