Brake lights - A and not B circuit help

Thread Starter

Doberfrann

Joined Jan 17, 2016
12
Hello,

This is a little circuit that I want to have on my motorbike.

I have a set of 3 red LED lights and a set of 3 blue LED lights.

A is a switch that turns on and off the blue lights. (Lights)
B is a button which turns on the red lights. (Brakes)

When B (brake) is pressed it should turn off A. I already tested that is A and not B.

My problem is I need to put it on a circuit and I'm not sure how to make a not gate. I read is a PNP, and I cannot use diodes.
I haven't done circuits in 15 years, and I completely forgot everything. I have been wrongly suggested an XOR gate that I have made out of diodes, to realise later that was not what I was looking for. I cannot draw the schematics by myself.

Can someone please help me?

IC.png
 

Thread Starter

Doberfrann

Joined Jan 17, 2016
12
And that's a PNP, it would haven take less if you would have shown me. I don't know this stuff, that's why I'm asking for help.
 

djsfantasi

Joined Apr 11, 2010
6,503
No, it's an NPN. You're welcome for the link. It shows you how to do it and explains it. I gave you a simple (...for Dummies) resource since I understood you don't know this stuff.
 

Thread Starter

Doberfrann

Joined Jan 17, 2016
12
I already found that. I already looked up an And gate before.

Sorry, my bad, I written a wrong post. I meant to say that I don't know anything and I'm not asking to learn how to make it, I just want someone to tell me how to do the whole thing.

So, is there a way how to make the not gate with diodes and resistors since you mentioned it? I cannot find that, I always find the one with NPNs. That would help me more since I have them already at home.
 

djsfantasi

Joined Apr 11, 2010
6,503
So, is there a way how to make the not gate with diodes and resistors since you mentioned it? I cannot find that, I always find the one with NPNs. That would help me more since I have them already at home.
No. A NOT gate requires an active component. I.e., a transistor.
 

WBahn

Joined Mar 31, 2012
25,910
I asked this over in your other thread on this same topic:

You have two functions, one for the blue lights and one for the red lights.

Which function are you saying that AB' is for?

What do your switches do when activated? Do they pull a terminal HI or do they pull it LO?
 

Thread Starter

Doberfrann

Joined Jan 17, 2016
12
A is a switch that turns on and off the blue lights. (Lights)
B is a button which turns on the red lights. (Brakes)

When B (brake) is pressed it should turn off A.

A | B |B'| Switch AND NOT Brakes
0 | 0 | 1 | 0
0 | 1 | 0 | 0
1 | 0 | 1 | 1 (blue LED on)
1 | 1 | 0 | 0 (blue LED off)
 

eetech00

Joined Jun 8, 2013
1,937
What is the battery voltage?
How much current for each light?

If transistors or diodes are used, we'll need to know this.

Can you install a relay somewhere?
 

Thread Starter

Doberfrann

Joined Jan 17, 2016
12
the battery it's 12v, I'm not sure about the current for the lights. the mechanic connected everything up with no electronics straight to the battery.

I have some space for a relay
 

djsfantasi

Joined Apr 11, 2010
6,503
But I think that the TS doesn't have access to a pushbutton. He only has the output from the brake pedal/handle. The logic diagram he posted shows that. He is using a pushbutton and SPST switch only to represent the brakes and light switch.
 

WBahn

Joined Mar 31, 2012
25,910
There is a fundamental question that I can't get the TS to answer.

He has a brake switch that is activated when he engages the brakes. Does that switch provide +12 V power to the brake lights, or does it provide 0 V (i.e., a path to ground) for the lights?

Similarly, does the switch he is using to power the blue lights provide +12 V or does it provide 0 V when activated?
 
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