To be honest, i don't quite get what the schematic, and the voltage reference does, could you explain it to me?

Does the "33R" get the entire current from the led's through it?

If so, i'll need a high wattage resistor for that, right?

I've seen a lot of constant current led driver circuits, however i've never seen anyone using just one transistor.

With the right resistor at the base of a transistor, you can determin the current flowing through it, right?
Why does it not seem possible to make a constant current power led driver this way?

My initial setup was:
...
What i understood you meant was:

They will never work.

Could you explain what you mean by that..?

Then you are missunderstand what I was saying. Can you draw what you are doing.

My initial setup was:

Leds
 |
 |
Collector

Base ------2k5-----ULN2803 output

Emitter
 |
 |
18v


What i understood you meant was:

Leds
 |
 |
Collector

Base --- 2k5 --- ULN2803 output
 |                      |
4k7                    |
 |                      |
Emitter ----------4k7
 |
 |
18v

(edited, misdrew something)

A PNP transistor is effectively a diode from base to emitter ( base cathode ) and pulling too much current from the base WILL destroy the transistor, Short the base to ground and the transistor WILL explode or shut down the power supply, in either case the transistor is toast. ALL PNP transistors need some method of current limiting (A resistor) in the base circuit. If it was an NPN directly pulling the base down, likely the NPN is toast as well.

Bob

To be honest, i don't quite see how this is relevant..?

Also, when not connecting anything to the transistor except for 12v on the emitter and the collector to the 'anode' of the led strips, i measure about 11v from the collector to ground..

So then i'd have the the emitter to 18v, a 2k5 from base to the ULN, a 4k7 from the emitter to base, and another 4k7 from the emitter to the ULN?

Loose the 2K5 and yes.

Without the 2k5 nothing's happening at all..

Ik hooked up my scope to the collecter and to ground, and noticed something what i consider 'odd'.

When using 12v, I read about 3v when the transistor should be off, and 12v when it should be on.

When using 18v, i read about 12v when the transistor should be off, and 14v when it should be on.

What could this mean?

So then i'd have the the emitter to 18v, a 2k5 from base to the ULN, a 4k7 from the emitter to base, and another 4k7 from the emitter to the ULN?

You need pull ups to the +ve and a resistor in series with the base.

Could you please explain what kind of resistors from where to where that should be?

I'm trying to multiplex small segments of LED Strips.
I'm sinking using TLC5940's, i'm sourcing using a ULN2803 driving PNP transistors. (BC577)

I started out at 12v, which neatly gave me about 20mA on each rgb led channel.
Since I'm multiplexing I wanted to increase the current going to the LED strips.
I did this by increasing the voltage to 18v.

Now, however, the transistors are not 'shutting down' completely, does anyone know how this happens?

I'm using a 2.5kohm resistor between the base and the ULN2803 outputs.

Well, using in that case. I'd just like to stick with my own code.

I was thinking about sending PWM signals through the transmitter, and having the reciever calculating an average, which will indicate which button it is.

Is that possible?

I only need like 16 buttons or so, implementing a whole library seems a bit overkill..
I was thinking about sending PWM signals through the transmitter, and having the reciever calculating an average, which will indicate which button it is.

Does that sound possible?

Hello,

I'd like to make a remote control with an atmega328 and a 433MHz transmitter, which will be recieved by another atmega328 and a 433MHz Reciever.

I understand how I can send high or low signals with it, but how can I get it to understand different signals? Or transmit something like the value of a potmeter?

Okay nevermind, it's acting the same again, after 3 min.