Hey there,
Wondered if any one could shed some light on a quite annoying problem I can seem to solve.
Im using a ULN2803 to drive 8 LED's. One per pin...
And I have it all working so I can choose which Leds are on and which are off using a PIC16f877a.
The problem I am having is a need to Dim the whole bank of LED's. Because the ULN2803 is a low side drive I figured I would just use a brushed motor ESC (electronic speed controller) to change the voltage on the high side of the entire bank. Unfortunately this doesn't work, and I have spent days trying to figure out why, and how to fix it.
When I reduce the voltage from the ESC, instead of dimming the LED's that are currently lit and meant to be lit. It starts to brighten the non-lit LED's. And if I turn it all the way down the non-lit LED's come on and increas in brightness until they are the same brightness as the meant to be lit LED's. Make sense?
Does any one know why this is and how I could fix it? Is it possible to do something like this with the ULN2803? Maybe its just using the ESC that the problem. Any help / pointers would be greatly appreciated. Thanks.
Wondered if any one could shed some light on a quite annoying problem I can seem to solve.
Im using a ULN2803 to drive 8 LED's. One per pin...
And I have it all working so I can choose which Leds are on and which are off using a PIC16f877a.
The problem I am having is a need to Dim the whole bank of LED's. Because the ULN2803 is a low side drive I figured I would just use a brushed motor ESC (electronic speed controller) to change the voltage on the high side of the entire bank. Unfortunately this doesn't work, and I have spent days trying to figure out why, and how to fix it.
When I reduce the voltage from the ESC, instead of dimming the LED's that are currently lit and meant to be lit. It starts to brighten the non-lit LED's. And if I turn it all the way down the non-lit LED's come on and increas in brightness until they are the same brightness as the meant to be lit LED's. Make sense?
Does any one know why this is and how I could fix it? Is it possible to do something like this with the ULN2803? Maybe its just using the ESC that the problem. Any help / pointers would be greatly appreciated. Thanks.