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[Reply #15 on:]

Take your 12V powered op-amp, connect the 0-5V signal to the + input.
Use a resistor divider and set the -input to 0.5V.
When the + input is >0.5V, the output will be ~12V.
When the +input is <0.5V, the output will be ~0V.
The 0 & 12V will be determined by the load you put on the op-amp, and how close to the rails the op-amp can drive.

I don't see how that helps with the need for your code to continuously the T1803 chip tho.

[Reply #16 on:]

Sorry. Away from home. The change in the voltage can change how bright the leds are by changing the input voltage. I attached a pot to the 12 volt wire for the strip and changing the resistance changed the brightness.

Is there a way that the 0-12 voltage can be a smoother line.

I attached an image of the graph.

Basically the blue line is the input voltage and the red is the output. The gain is 2.4.
For example when the blue line is at 5v the red is at 12v and when the blue is at 0v the red is also at 0v. All of the values in-between are proportional between the red and blue lines with a gain of 2.4. Can an Op-amp be used to accomplish this?

[Reply #17 on:]

couldnt you change the brightness with PWM though??

(Im confused)


I am interested in this RGB LED Strip from RadioShack.. (as they are always close and everywhere)..

so Im following this thread to see where you end up on communicating/controlling it..

[Reply #18 on:]

Unfortunately no. That would be too easy. A pwm's max voltage is 5v but the strip needs 12v in order to run properly. I am exploring different options. If the op amp doesn't work I will be attempting to try a digital pot.

[Reply #19 on:]

I meant cant you just PWM the strip -though- the transistor as mentioned above??

(also...why the op-amp?)

[Reply #20 on:]

I tried the transistor. It doesn't work. Plus the fact that the strip needs constant voltage in order to store the data. Each tm1803 has 24 bits of memory. Just like regular ram, the memory is reset when power is lost.