AboutDave Nyce Expertise I have been an electronics engineer for 25 years. I can answer questions on analog and digital circuits and my specialty is sensors.
Experience I am the inventor on 23 US patents, and also some foreign ones. Developed sensors for over 25 years. Licensed private pilot (airplane and rotorcraft), have HAM radio license. I'm not an expert in computer networking.
I have a project where I need to flash ten LEDs in succession in a repeating cycle, like an LED chaser. But rather than one LED going off and the next coming on instantaneously I need to have the LEDs fade into one another. Thus the first LED brightens from zero to full brightness then dims. While it is dimming the second LED simultaneously brightens and when it reaches full brightness, the first LED will have turned off. And so on. The sum of brightness of the pair of LEDs at any time is equal to one LED fully on.
I've researched this despite being new to electronics and have come up with a 555 in astable mode sending pulses to a 4017 decade counter. I also read an LED can be made to brighten while another simultaneously dims using two op amps. But that's as far as I've got. I don't know how the pulses coming from the 10 pins of the 4017 can be made to do what I want.
The time it takes for the 10 LEDs to undergo one cycle is about two to three seconds, and this needs to be controllable. The timing with which the LEDs fade in and out is not critical, providing the sum LED brightness remains constant throughout the cycle.
If you have any ideas or suggestions, I'd be most appreciative. They will guide my research efforts which have now stalled.
Thanks.
Regards,
Usuff
Answer The normal way to make a light chaser is different from your request. Usually, every fourth light comes on at the same time. You use a 4 bit shift register to drive the lights. For example, with 100 lights, 25 of them will be connected to each bit. The first light and every fourth one thereafter connected to the first bit, the second and every fourth thereafter to the second bit, etc. This gives a seemingly fading light sequence due to the persistence in the observer's eye.
Your counter outputs each need to go through a resitsor to the base of a power transistor (the power of which is rated to handle the number of LEDs), with the emitters going to ground and the collectors going to the cathode of the LEDs. The anodes of the LEDs go through resistors to the positive supply, the resistance of which set the LED current.
If you use your op amp circuit, that would require a transistor in the output circuit in order to drive more than 1 or 2 LEDs.
I'm sorry that I can't give you a schematic on this website, but that would also take more time than I have available.
