Hi

I am new on here and come seeking some advice (have posted this in both the general and automotive sections)

Using single-throw switches (like this https://www.carbuildersolutions.com/uk/black-billet-aluminium-switch-fan - available as single- or double-pole, momentary or latched) I want to achieve two things for a customised car dashboard:

1. Replicate a two-position switch;
so from off, press on, switches on one circuit, press again, switches on a second circuit, press again, switches off
(for two-speed fan and two-speed wipers: off - slow - fast - off and headlights: off - side - main - off)

2. Also, alongside the lights switch, a momentary switch where, if main lights are off (ie off or sides on), press to flash and if main lights are on, it’ll toggle between full and dipped beam.

In each case, there is a relay between these switches and the actual devices, so we’re dealing with 12V and low currents.

How would you suggest this can easily be achieved?

 

Welcome to AAC!

two-speed wipers: off - slow - fast - off

Aren't there also intermittent and flick wipe to consider?

low currents.

What is your definition of 'low'? Screen wiper motors can be quite current-hungry. What is the stall/starting current of yours?
Headlights draw a substantial current too.

 

Thanks Alec_t...

The dashboard is for a Caterham 7. More often than not, I drive it with an aeroscreen which means the wiper switch is mostly redundant and rarely used.

For that reason, I hadn’t considered having a flick or intermittent function too (but if that could be added as a function, I’d be interested; but it not really important)

 

This doesn't mean such a switch doesn't exist, but I've never heard of a switch like that. Not unless there is electronics behind the switch to control the sequencing of the switch. In that case you would (probably) want a momentary push button to cycle through the steps you look for.

Electronics may consist of flip-flops or shift registers. As you push the button for the first time you turn on a function of your design. The next push toggles to a higher or lower state. OR a different circuit, since relays will be involved, and relays can not give you high - medium and low (for instance).

There's going to be considerable amount of engineering to accomplish what you seek. It's definitely doable, but not so simple as finding a switch that can do all the functions you seek. Perhaps a rotary switch may better serve your purpose if you can tolerate turning a knob instead of pushing a button.

 

Goal #2: You don't need to decipher whether the headlamps are on or not - you can simply flash the high beams, regardless of the headlight condition (except if you have the high beams already on, but then you can use the same relay that flashes them to flash them off (if they're on)). {see post #7}

[edit] As I contemplate how a single DPDT relay would do this - I come to the conclusion that it would not work. You would need two separate relays, one for when the high beams are on and one to interrupt the signal. Will take some more thought.

 

Adding the electronics would introduce a layer of complexity and hence increased risk of failure. Have you checked with your insurer that they would accept such a vehicle mod?

 

Figured it out:

 

Thanks for the responses...

Apologies, I didn’t phrase my question well. I want to use the switches I posted the link to.

As Tonyr1084 suggested, I had anticipated a momentary push button activating some circuitry (but what? that’s my question!) in the manner I described with subsequent pushes changing the output: one push: A on, subsequent push: B on, third push: off.

With respect to my second query, again a momentary switch, that’ll usually be fine to flash the lights but I’d like it (when the headlights are on) to toggle between full and dipped beams.

 

Not sure what you mean by "Dipped Beam".

With regards goal #1, you would need some sort of electronics to toggle between situations. I have imagined using a Dual D Flip Flop. In the initial state, circuits A & B are off. Press a momentary button (or even a toggle switch) and circuit A goes on. Toggle it off and back on a second time and A goes off and B goes on. Toggle it a third time and both A AND B are BOTH ON! You might not want that condition. Toggle it a fourth time and both A & B go off. You COULD add a 2 input AND gate to reset the FF back to the original state and avoid having both A & B on at the same time, but now you're up to a count of 2 IC's.

Another solution would be a shift register. Each time you toggle on (or push button) you move from output #0 to #1, then to #2 (with each push, meaning each time the clock pulse goes positive). With the next push output #3 goes active but for a very brief moment because #3 can be connected to a reset pin which resets the system to output #0 (the off state). It's a single chip solution, but in the automotive electrical environment there is going to be a tremendous amount of electronic noise, which can inadvertently toggle your switches repeatedly, leaving you virtually no control over the circuit. What @Alec_t said about insurance is of concern. Insurance may refuse to cover an accident should it be caused by components in the car acting without human control. As for the lights, if the police (in the US) find a vehicle whose exterior lights are not acting properly the driver/owner may be issued a "Fix-it Ticket". At which time the owner has to restore the vehicle to normal operation then take the vehicle to either an inspection station or to a police station and prove the vehicle is in compliance with DOT regulations. (Department Of Transportation)

Many years ago I attempted to build an electronic circuit for my car. It lasted about two weeks before it was dead. Dead from all the transient spikes caused by components switching on and off automatically (as they should). Electronics in a car have to be very robust and well designed to protect against uncommanded actions and failed components.

Using the switch you want will be difficult. But using the clock pulse needed for the shift register or the FF means de-bouncing the switch, another problem that needs to be engineered into the solution. Like I said, it's all doable, but it needs to be done right. And not just "Right" but Right and RELIABLY. Otherwise turning on something and have it NOT come on OR not turning something on and having it COME ON ANYWAY can be an issue, potentially an accident waiting to happen. Automotive engineers spend a lot of time making sure their designs can withstand far and above what may be expected in an automobile because if something they designed goes wrong and you have an accident - the car manufacture can be held responsible for damages. If YOU modify the car then YOU are going to be held responsible should something go wrong.

It's doable. But it might not be wise. Off road use should be non problem, but operating a car on the street MUST meet DOT standards.

 

Not sure what you mean by "Dipped Beam".

European for low beams.

 

European for low beams.

My illustration (post #7) showed the high beam. It could also be used on the low beam (dropped beam).

@shortbus thanks for the clarification. I should have been able to figure that out.

 

Thanks...

George Bernard Shaw was right... “two countries separated by the same language”!

 

@shortbus thanks for the clarification. I should have been able to figure that out.

I'm on a metal shaping forum, mostly car oriented, that has many European and Australian members, you start to learn a little about things they talk about. Bonnets, boots, wings, etc.