Micro electronics - stop 12V 9A in reverse direction?

Lisapete

Lisapete

Lisapete

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Am really scratching the gray matter in this.

Have a rotary switch. Single pole so single power inlet in this case. Power is 12V 9A. Off each output is a LED. This is only to show the status, Ie position 2 has been selected.

I also need to take a 2nd feed (output) from said selection to a push to make switch aka launch button / big red button.

Imagen all this being done the 11 times :). So selection 1 to 11, a single led to represent each channel as it be.

So then a 2nd output per channel goes to this switch. Along this 2nd input am I right in thinking I would fit a diode to stop currrent passing back down into the switch so it would light the LED's?

How do I work out what raiting/type I need?

Hope I've explained this as best as possible.
 
Just wire the leds via a resistor in parallel with the output for each pos on the rotatry.

o5e13a.jpg
 
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Unless you're planning on putting another power supply the other side of the switch (which would be daft) where is the current to light the LED going to come from if not the 12V supply?

What purpose does the rotary switch serve at all if you have to press a button anyway? A bit more info might be useful.
 
So this is a 12 way launch controller for rocketry.

The rotary switch is for user selection, ie: which pad to launch.

I want to be able to select which pad and the LED to illuminate to show it's selected.

Only 1 push button, launch button is be used.

Each output is to a relay at the other end.

So safety key in (this arms the system and turns power on, an LED and Buzzer sounds).
Select pad number 4
4th LED along lights up
Press and hold launch button triggers a relay which passes the 12v at the pad box to the rocket and lift off.
 
I have built rocket launchers before.

Are you having a test for continuity too?

Maybe the led can only glow when you have continuity through the igniter, then punch the big red button to fire.

Do you need the relay?
 
Pinter75 said:
I have built rocket launchers before.

Are you having a test for continuity too?

Maybe the led can only glow when you have continuity through the igniter, then punch the big red button to fire.

Do you need the relay?
Click to expand...

Relay is a must

No test for continuity, iginters are far too sensitive these days for that.
 
I may not be understanding properly what you're trying to do, but couldn't you do as Pinter75 posted in the picture, with the "to whatever" wire going to the collector of a transistor, with the emitter going to the corresponding igniter, and the base of all the transistors connected to your main "launch" button?

That way, you'll have your 1 launch button, and the selectable switch with illumination for which is selected.
 
This is to be a 12 way launch control box. So you can select rockets 1-12 and let them off each singly.

I have a 12 way single pole rotary switch. When I select any position I want an LED to illuminate for that selected output on the switch.

There will be a push to make switch before the single pole on the switch as this is the launch button. This can be relocated if needed.

I need all outputs (switch selectable) to go there own relays which is triggered by selecting numbers 1-12 and then pressing the launch button but I want the led to be illuminated when making the selection before pressing launch button.

I've had a play with it using some test leads thinking the hands on would help me work it out but no such luck. I've been able to get the LEDs to work for switch selection but this was without the push to make switch in place, so a live feed into the switch was used. No relays used as only testing the LED stays idea.

Would a diode do the job of preventing the current/power going in a direction I don't want?

I'm not sure the best was to lay this all out.

It's almost I need a different circuit for the LED status.
 
Surely if you are designing a circuit from scratch, would it not be easier just to replace the rotary switch with a dual pole 12 position one? That one one pole can lead to the LEDs and the other can lead to the switch.
 
I dont really understand what your wanting.

You'd be safer drawing a circuit diagram of what you have in your mind.

But...I'd do a similar circuit as per Pinter75's diagram.

Use the 'To whatever' to control 12 individual relays. Then common up all the relay inputs to the push button, and connect the outputs to the respective rocket.
 
I'd probably go a little higher than 470 for a normal LED off 12V. find one of the many led resistor calculators out there and plug in the numbers for the led's you plan to use. RS/farnell or CPC will likely be much cheaper for components.
 
abbotsmike said:
I'd probably go a little higher than 470 for a normal LED off 12V. find one of the many led resistor calculators out there and plug in the numbers for the led's you plan to use. RS/farnell or CPC will likely be much cheaper for components.
Click to expand...

I bought these LED http://www.ebay.co.uk/itm/131240697108

Waiting for them too arrive to see what is already fitted but have asked the seller
 
Never had trouble with 470R on 12v, although I admit that it does drive them quite hard. Maybe not quite so good for the standard red types, etc.

one of thos rule of thumb things that you bcome ingrained with, picking 330R for 9v, 470R for 12v, etc

Feel free to up it up 680R, this will kep th forward current below 15mA on a part with a voltage drop of 2v

Anything upto 1k will work, but it might be a bit dim at 1k!
 
I'll be honest, all of my work is at 24V or higher, and throwing a 2k2 in suits everything I end up using (typically low current ones), so I just thought half that at 12v will do!
 
I know Maplins is not cheap but I need to play ASAP and I can pick the stuff up today. So what should I get as they list a few options
 
Lisapete said:
I know Maplins is not cheap but I need to play ASAP and I can pick the stuff up today. So what should I get as they list a few options
Click to expand...

As the resistor is just for an LED, any will do, however from a quick look at the ebay page you mentioned, they're designed to run directly off 12v anyway, so you won't need a resistor, as the LED package will have one built in.
 
R.C.Anderson said:
As the resistor is just for an LED, any will do, however from a quick look at the ebay page you mentioned, they're designed to run directly off 12v anyway, so you won't need a resistor, as the LED package will have one built in.
Click to expand...

I can only but try once I'm home.

Thank you too all here that have helped. Beer??
 
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