Help to design circuit

[FrankB]

Hi
I need some assistance to design a 12volt circuit to switch lighting in the cabin of an ambulance. Basically when the main lights are on, both LED strips are illuminated, however when the 'dim' button pressed, it will need to switch the brightest strip off but keep dim strip on. The set up is a 3 wire system, common -VE return with 2 + 12 volt feeds one for bright one for dim.

I know I will need some kind of switching circuit that will switch power off from bright strip when the dim button is pressed and power is fed through the dim wire but not sure how to create this. Can anyone help with a diagram and parts list??

Thanks

[KMoffett]

So currently (pun intended) the Bright and Dim LED strips are the "main lights", or are they parallel to other "main lights"?

Assuming the latter, if you have the Dim on and the Bright off, do you want them both to come on when the Main Lights are shut off and turned on again?

Once you hit the Dim button, the Dim stays on and the bright goes off, do you want the Bright to come back on if you hit the Dim button again? Like toggling between Dim and Bright+Dim while the Main Lights are on?

Ken

[FrankB]

Hi Ken.

Basically, I have 2 push buttons on a control panel. One is for main lighting and one is for Dim. When main lights are on, I need both light strips on. When the dim button pressed I need the circuit to turn off the bright strip but keep the dim strip on. There are 3 wires.

Negative (ground/ earth)

12v positive ( live when main lights on)
12v Positive ( live when dim button pressed)

What I need is some kind of switching circuit that will turn main light off when current applied via the 2nd 12volt positive but when the dim button turned off then the main lights come on.

The 1st 12 volt feed has to be turned on in order for the dim circuit to work. Very complicated to explain, but hope it's a bit clearer.

Frank

[FrankB]

Hi Ken.

Basically, I have 2 push buttons on a control panel. One is for main lighting and one is for Dim. When main lights are on, I need both light strips on. When the dim button pressed I need the circuit to turn off the bright strip but keep the dim strip on. There are 3 wires.

Negative (ground/ earth)

12v positive ( live when main lights on)
12v Positive ( live when dim button pressed)

What I need is some kind of switching circuit that will turn main light off when current applied via the 2nd 12volt positive but when the dim button turned off then the main lights come on.

The 1st 12 volt feed has to be turned on in order for the dim circuit to work. Very complicated to explain, but hope it's a bit clearer.

Frank

[FrankB]

Hi Ken

Sorry, yes they need to toggle between main and dim when dim button pressed.

Also circuit will need to be as compact as possible

Frank

[KMoffett]

Is "main light" just the "Bright Strip" and the "Dim Strip", or are there other lights included in the "main light"?

Ken

[KMoffett]

OK, in reading back through the posts,I think I get it. How much current do the Bright LEDs and Dim LEDs draw?

Ken

[FrankB]

Hi Ken

I haven't tested that yet, however the strips have built in resistor protection for each LED and, at present they are just fed directly from the 12 volt supply.

Frank

[FrankB]

Hi Ken

Just checked and its around 0.35 -0.4 amps draw

Frank

[pebe]

Hi Ken,

Re your problem uploading a file, I have tried to upload a .GIF file and have got the same problem.

I have sent a PM to the Admin, and hope it will soon be sorted.

Peter

[KMoffett]

Peter,

Thanks. I tried .gif and .jpg formats and different file sizes. I also hit "Save draft" for the text after I couldn't upload the schematic. But when I tried to recover it yesterday, it was blank.

Ken

[pebe]

Ken,
No news yet from Admin. But I note that text can now be saved and loaded, though pics are still a no-go.

Check your PM inbox in case Admin contacts you directly.

Peter

[KMoffett]

Frank,
We haven't forgotten you. Just having technical problems posting a schematic.
Ken

[KMoffett]

Frank,

Until they get the upload problem resolved, send me a "private message" in the Forum with your email address. I'll send you the schematic of the circuit I'm proposing. Then post it back here when I can.

Ken

[KMoffett]

OK, we can post images again. I'm assuming that the "main" switch is latching (push-on/push-off), not just momentary with some other latching circuitry. With that, I've attached a relatively simply circuit. With the main switch on both the brights and dims are turned on. When the "Bright ON/OFF" buttoned is momentarily pressed the brights are turned off. When "Bright ON/OFF" buttoned is momentarily pressed again, the brights come back on. The dims are on as long as the main switch is on.

Ken