UKH

It's been over 20 years since I was a pretty competent GCSE electronics student, and it seems I've forgotten almost everything. I've tried Google and YouTube, but drawing a blank, so I'm hoping someone here can help. 

The background: I'm modifying a toy ikea kitchen for my kids. Just simple stuff like a white light which comes on when the oven door is opened, and a red light when they turn a knob as if they've turned it on. So far, so easy. However, the stove hob has two rings which currently light up when a push button is pressed, and off when it is pressed again. There's an unmarked IC and other bits in there, but that's the 'user experience'. The push button appears to be a simple, normally open switch. However, I'd like to convert this to run off turn switches too, like the oven. What I'm struggling with though is how to recreate the push button switch behaviour (closed briefly to turn on, close briefly to turn off) with a rotating switch (closed to turn on, opened to turn off). I feel like a simple bit of capacitor + resistor + transistor and I could trigger a relay to take the place of the push button to turn it on but I don't know how I could get it to provide another short pulse when the turn switch is opened again, in order to turn the lights off. 

I'm hoping that description is not too confusing -  any pointers would be greatly appreciated!

If I am following correctly, can you find a multi-position knob and make the MIDDLE position (that you turn ‘through’) be the one that is wired up to create the pulse?

The push button switch is momentary on (for the duration of the push).

Use the same circuit (chip you describe) to toggle on/off but with a rotary momentary on switch??

Google for something like

Rotary momentary switch

Presumably NO normally off

I was going to suggest going digital with an Arduino or Pi Pico to read all switches and control all things, but that can’t beat a pulsing multi-position knob.

I'm no help with the electronics but what a great idea for a present for your kids!

That way it can be just like a real oven that is rendered completely useless when a superfluous and EOL'd microcontroller fails 😂. (Though I am a big fan of microcontrollers, as you know)

You're a bad man.

“I'd like to convert this to run off turn switches too, like the oven.” So the oven turn switch already makes the red light come on, if so what makes that work? I am thinking of adding some sort of disk behind the hob controls that can operate a micro limit switch and do away with the electronics.

I did a search on “Ikea toy cooker wiring” and there are others modding their ovens too, but I couldn't see one with turn switches for the hob.

Could you not take the simpler route and put a second switch in there?

I know we cant let these things beat us, but sometimes good enough is better than perfect. Use the time saved playing cooking with your kids.

I think you might have it. Single pole, triple throw, where only position 2 is wired up. Turn from position 1 to 3, and you've briefly made and broken the circuit. Turn from position 3 to 1 and you've done the same again.  Bingo! 

Of *course* you were I would have put money in that being your response! I like your thinking, but I still feel like I'm cheating if I use a 555!

Sorry, I meant like the *real* oven. There's currently no wiring in the toy oven at all. 

Fortunately, one of the buttons is broken anyway, so I didn't have much to lose in opening it up (looks like water ingress and corrosion - it's second hand)

HERESY! Actually, I don't disagree, but the 5 year old is really looking forward to a project, and the 1 year old will enjoy playing. 5 is not too young to handle a soldering iron, is it?

Sounds like the current switch is a momentary switch (just connected or disconnected when pressed and returns to the default when not pressed) and the IC is a flip-flop (it might also auto-off after a while to save the battery?)

So... it looks like to can implement the same behaviour with a normal switch: pressed in "on", pressed out "off", by removing the IC.  This normal switch could easily be a rotary one.

So just get a normal switch and bypass the IC by wiring it directly to the light.

[caveat assuming the light is an LED the IC might also provide some sort of constant current circuit or a battery saving boost circuit to regulate the supply so you might need to install a resistor between switch and LED if you remove the IC - if so just use 1k - otherwise you'll burn the LED out.]

So that was my original thought - power source -> resistor -> new switch -> LED module. Easy peasy. But, when I took it apart to see why one of the LED modules wasn't lighting, I measured the working one with my multimeter and found a voltage of 1.5V, so I tried jumping that directly across the non-functional LED module and it didn't light. I guess maybe the IC might be doing some exotic stuff like pulsing the current, but my multimeter is not an oscilloscope, so I can't see it. I think the suggestion with the single pole triple throw switch will fit my needs and be essentially as simple as if I just swapped the existing button out anyway.

Depends which end   

I'd keep it super simple if you want rotary switches, just hard wire them to the lights, ditch the latching circuit. At most you might need a series resistor for the light, that's easy enough to figure out. A 5yo can understand a simple switch circuit for a teaching moment and you get a nice clicky switch action. With the right couple of resistors you might manage off, low high...

Jk

Would need a serverless backend with a no-SQL data layer, and an nginex reverse proxy tunneling oauth2 to secure the oven at web scale.

what you really want is a small sound player, run by a picaxe or similar chip, that shouts "help! let me out!  It's getting hot in here!" if the toy oven is left on too long

https://picaxe.com/hardware/project-kits/picaxe-14-audio-kit/

or at least an Apollo Guidance Computer