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  • HackerBoxes 0007: Digital Soundscapes

    As a heads up, the LM3915 chip has two modes. The first is a dot mode (where one LED it lit up at a time) and the second is a bar mode (where all the previous LED's are lit up). This is controlled by pin 9. When 9 is pulled to high the chip is in Bar mode, when disconnected it is in dot mode. J3 allows pin 9 to be connected to the V+ rail. It looks like the jumper was not part of the kit/omitted from the instructions. Using bar mode makes the LEDs brighter (they are always on) and, in my case, made one of the lower LED work. I suspect the high sample rate and dot mode combine to effectively control the LED brightness by Pulse With Modulation (PWM). If the low LED's are not being triggered much during a track/song, they get perceived as dead/off. Switching to Bar eliminates the P...see more »As a heads up, the LM3915 chip has two modes. The first is a dot mode (where one LED it lit up at a time) and the second is a bar mode (where all the previous LED's are lit up). This is controlled by pin 9. When 9 is pulled to high the chip is in Bar mode, when disconnected it is in dot mode. J3 allows pin 9 to be connected to the V+ rail. It looks like the jumper was not part of the kit/omitted from the instructions. Using bar mode makes the LEDs brighter (they are always on) and, in my case, made one of the lower LED work. I suspect the high sample rate and dot mode combine to effectively control the LED brightness by Pulse With Modulation (PWM). If the low LED's are not being triggered much during a track/song, they get perceived as dead/off. Switching to Bar eliminates the PWM effect on the lower LED's, allowing these "dead" LED to work. Hope this helps, if nothing else it gives another option in your setup.

    As a heads up, the LM3915 chip has two modes. The first is a dot mode (where one LED it lit up at a time) and the second is a bar mode (where all the previous LED's are lit up). This is controlled by pin 9. When 9 is pulled to high the chip is in Bar mode, when disconnected it is in dot mode. J3 allows pin 9 to be connected to the V+ rail. It looks like the jumper was not part of the kit/omitted from the instructions. Using bar mode makes the LEDs brighter (they are always on) and, in my case, made one of the lower LED work. I suspect the high sample rate and dot mode combine to effectively control the LED brightness by Pulse With Modulation (PWM). If the low LED's are not being triggered much during a track/song, they get perceived as dead/off. Switching to Bar eliminates the P...see more »As a heads up, the LM3915 chip has two modes. The first is a dot mode (where one LED it lit up at a time) and the second is a bar mode (where all the previous LED's are lit up). This is controlled by pin 9. When 9 is pulled to high the chip is in Bar mode, when disconnected it is in dot mode. J3 allows pin 9 to be connected to the V+ rail. It looks like the jumper was not part of the kit/omitted from the instructions. Using bar mode makes the LEDs brighter (they are always on) and, in my case, made one of the lower LED work. I suspect the high sample rate and dot mode combine to effectively control the LED brightness by Pulse With Modulation (PWM). If the low LED's are not being triggered much during a track/song, they get perceived as dead/off. Switching to Bar eliminates the PWM effect on the lower LED's, allowing these "dead" LED to work. Hope this helps, if nothing else it gives another option in your setup.

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