using switches that already have a purpose

[bowser22]

In my car, I have my high beam switch and my hazard light switch. Both of these have 12 volts coarsing through them, I cant figure out how to make a circuit for a picaxe to read the status of the switches. I want to make a light flash when both the high beam switch is on and the hazard is on at the same time. I thought about using 2 small npn transistors connected to the input pin then write a program to run only when both are switched on. I know I cant just connect 12v right to the input pin cause id blow my picaxe. please help.
Thanks

 

[JimB]

Both of these have 12 volts coarsing through them

I think you actually mean coursing.
This gives me mental images of electrons on horseback charging though the switch chasing some elusive quarry.
(Sorry, the devil made me say that!)

To give a serious answer to your initial question, a simple attenuator which reduces the 12 volts (probably nearer to 14v when the engine is running) down to 5 volts.

There was a thread about this on here a few months ago.

If you make a voltage divider with a 2.2k and a 1k resistor in series, connect the top of the 2.2k to the 12v, the bottom of the 1k to 0v and the junction of the two resistors to the input of your picaxe, you will be good to go.

JimB

 

[MikeMl]

One complication is that the flashers power up the same lamps as are used for turn signals. How do you propose to separate the two functions?

 

[MikeMl]

Here is how I would do it. The three inputs are taken from the wires powering the respective lamps. Note that the LED is on only when all three signals: HiBeam, Left and Right are high (on). The LED will automatically follow the flash rate. The diode and-gate takes care of the situation when either Right or Left is powered; Right and Left are powered only if the Flasher is on; not when the turn signals are on. Powering the collector of the transistor from the HiBeam lead precludes the LED lighting unless the HiBeams are on.

Who needs micro-processors for something this simple?

 

[bowser22]

I plan on building a circuit that uses relays to flash the high beams like a police car. Ive already completed the relay side and tested it. I just want to implement it into what I already have my allowing the picaxe to read the inputs and when theyre both high to flash the high beams in a pattern, Therefore I can still use my 4 way flashers when the switch is pressed and my high beams when theyre switched. But when both are switched on its complete cool-ness lol

 

[MikeMl]

So replace Q1 in my circuit with an NPN darlington power transistor, and replace R1/D1 with your 12V relay coil. A snubber diode across the relay coil should be added.