Toggle On/Off circuit

[millsd60]

Does anyone have, or know of, or know how to, design a circuit to toggle on/off an electrical item. What I mean by that is, I want to press a button to switch the circuit on, then press the button again to switch it off. Bit like modern car main beam /dip beams work i.e. you pull the stalk once, to go to high beam, then pull it again to switch to low beam.

My plan is this.....I saw Purple Ronnie's car at the GD open day and noticed he had two red buttons on the steering wheel...I think they were wired up to the horn?
What I would like to do, is wire them up to the indicators. I.e. you press the left switch to turn left and the right switch to turn right....but how to do the toggle bit of it is driving me insane.
I going to put a timer on it, so if I fire the indicators but forget to cancel them, they will auto cancel when the timer reaches 60 seconds or so....

So...anyone know of a toggle circuit?

[pcoghlan]

Probably a daft reply but surely this is functionality built into the physical switch itself?

If you look at a hazard warning lights switch it is pressed once to turn the lights on and pressed again to to turn them off. Isn't this what you are looking for?

Another example is the heated rear window switch in many cars (esp BMW) which again is pressed once to turn on and again to turn off. It is a very slim switch which may be more suitable for you.

If the above makes sense then you just need to identify a suitable switch.

Paul

[Kevin W]

Sounds like you need to wire up a latch behind each switch, although some switches come wired with a mechanical latching action. I'd have to look up my old student notes to remember that stuff, but I'll bet Wilf has got the very circuit stored away in his grey matter. Just wondering though, don;t your indicators need to be self-cancelling for SVA? Might be wrong, but could be a pain to implement.

The other potential problem is getting reliable connection onto something which rotates by >360 degrees (or maybe you have a quick rack). Commercial items often use metal slip rings with 'brushes' which slide round, providing a permanent connection to a live feed irrespective of turn angle. If you don;t do this, then you'll have to have some coiled up cable which will eventually wear out. The only other alternative I can think of is to use a fibre-optic link but again could be complicated to implement.

You might be better off just wiring these ebuttons to the horn - be a lot easier to get right.

Kevin

[Andy302]

Yes it normally is a function of the switch. its called a latching switch, i.e it latches in one state until operated again when it unlatches.

I expect however that the switches mounted in the steering wheel in question (I believe momo) are momentary, i.e only operate for the duration of the press. And changing them will be a mare.

Hence what you need is a circuit which, when given a switch input operates the indicator, then when either a given time elapses or the switch is pressed again cancels the indicator.

This is a latching circuit, best built around logic gates and a timer for the reset and a couple of relays to handle the power reqired to operate two lamps. Now sadly Ive forgotten to much about this to be able to knock one up on the back of a fag packet, plus I dont smoke! So Ill go away and look in my books to see what I can find. Youve got me thinking now!!

Andy
Ill get one, one day!

[StuartH]

If you can't get mechanical latching, What you need is a T-Flip-flop (great name eh!!) and a debouncing-hysteresis circuit (RC filter and a schmidt trigger buffer) for the switch.

Or thinking about it - what would be even better is a monostable multivibrator (even better name!!). This is a circuit that is triggered by a signal then outputs a pulse of a fixed length - this would also have the advantage of not requiring debouncing as oscillations in the switch contact would just cause it to retrigger - the pulse width could be adjusted to be say 20 seconds or so after which time the indicators would switch off. Whilst your at it you may as well add a solid state 'flasher circuit' and a solid state relay, then thats all your bits and bobs in one place - fortunately the flasher and monostable can be built out of one dual '555' timer IC.

I'm not sure if this meets the requirements for cancelation, so on my potential new and improved dashboard I'm planning on having optical switches mounted on the column somewhere to cancel the indicators, all switches will be momentary types with latching done with S-R flip-flops (set by switch - reset by controller IC), everything else will also be under control of the controller IC, so goodbye to the cr*ppy electro-mechanical relays etc...

Stuart

[StuartH]

see above

Will draw circuits (if required)

Stuart

[VinceGledhill]

I think the difficulty you will find will not be in the finding of suitable swiches. There are plenty of them out there. Circuitry has been solved above nice one guys... I think the problem will be as aforementioned in the getting the numbers of wires involved through the turning part of your steering wheel.

You could always go for a telephone type wire coming from the top of your dash onto the hub of the steering wheel. As the steering is turned the curly wire would wrap itself round the boss.

Regards
Vince@gledhill.info

[wilf]

Without resorting to electronics , a plain old "latching relay" will do what you want - an RS catalog is useful for this kind of thing. (An account with RS at work is even more useful!!).
Trouble is that the two buttons on "purple tart's" car run to a common slip ring under the steering wheel boss, so you can't get them to do two different things (e.g. l/r indicators).
It could be done if you were to make two separate concentric sliprings insilated from each other, and arrange for wipers from each switch to go to one or the other of them.

OR - you could look at a very slim column mount indicator stalk, available from the likes of Vehicle Wiring Products, or a vintage/classic specialist like Holdens.
OR - you can get latching "on/off/on" switches from above for dash mounting.
I am not sure how much clearance you have between the steering wheel and the dash on a GD, from memory I don't think it's very much. Do all GD's use dash mounted indicator switches?
The hazard warning light type switchs usually incorporate a mechanical latch to give their push on/push off action.
BMW etc heated windscreen switches are I think, momentary contact swithces, what they do happens via the car's electronics.
Vince the tight Yorkshire ex-auto electrician should also be able to help??

BTW - You do NOT need self cancelling indicators for SVA.

HTH

Wilf

[STEVE T]

Have a look at this site I have been looking for the same thing and found this . It send a radio signal to a relay and lets you switch what ever you want.
http://www.painlessperformance.com/rfcenter.htm


Regards Steve T

[VinceGledhill]

Vince the tight Yorkshire ex-auto electrician...

You little fat git.

Oh... back on the indicator thingy. Have you thought about the gizmo that is in the latest kit-car magazine? It's an copy of an old "lucas" dash mounted indicator switch. Looks good to me. And a good solution.

IMHO during the build one comes up with all manner of solutions to a problem that one faces. Then tips and a different perspective from in here seems to help.

So what is the standard GD solution?

Regards
Vince@gledhill.info