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hardware_specs_and_theory_of_operation [2019/12/20 12:28] turo [Networking] |
hardware_specs_and_theory_of_operation [2019/12/20 14:22] turo [Data output] |
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+ | {{::lightkraken_photo_top.jpg?600|}} | ||
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==== What is this? ==== | ==== What is this? ==== | ||
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=== Implementation === | === Implementation === | ||
- | The PoE section of the Lightkraken board is based on a [[https://www.bourns.com/docs/Product-Datasheets/sm51625el.pdf|Bourns SM51625EL]] transformer and [[http://www.ti.com/lit/ds/symlink/tps2372.pdf|Texas Instrument TPS2372 PoE PD interface]]. It is rated for 70W of power, or 1.2A at the input. | + | The PoE section of the Lightkraken board is based on a [[https://www.bourns.com/docs/Product-Datasheets/sm51625el.pdf|Bourns SM51625EL]] transformer and [[http://www.ti.com/lit/ds/symlink/tps2372.pdf|Texas Instruments TPS2372 PoE PD interface]]. It is rated for 70W of power, or 1.2A at the input. |
The rectifier uses two [[https://www.mouser.jp/datasheet/2/149/FDMQ8205A-1079456.pdf|Fairchild FDMQ8205A MOSFET bridge]] ICs. During prototyping it was determined that using Schottky or regular diodes (to reduce cost) for the rectifier section generated too much heat. The use of the FDMQ8205A part is recommended in the Texas Instruments application notes. | The rectifier uses two [[https://www.mouser.jp/datasheet/2/149/FDMQ8205A-1079456.pdf|Fairchild FDMQ8205A MOSFET bridge]] ICs. During prototyping it was determined that using Schottky or regular diodes (to reduce cost) for the rectifier section generated too much heat. The use of the FDMQ8205A part is recommended in the Texas Instruments application notes. | ||
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* 23.5V @ 3A (70W) | * 23.5V @ 3A (70W) | ||
- | There is a 3-position switch on the board which allows you to select the output voltage. Left position is 5.4V, middle is 12V and right position is 23.5V. | + | There is a 3-position switch on the board which allows the selection of the output voltage. Left position is 5.4V, middle is 12V and right position is 23.5V. |
5.4V was selected instead of 5V to slightly extend the physical range of addressable LEDs without color change due to voltage drop. Virtually all LED chips rated for 5V also support 5.4V without any negative effects. | 5.4V was selected instead of 5V to slightly extend the physical range of addressable LEDs without color change due to voltage drop. Virtually all LED chips rated for 5V also support 5.4V without any negative effects. | ||
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* RGBW 8-bit sequential DMX data. RGBW is automatically converted to RGB if such a strip is used. | * RGBW 8-bit sequential DMX data. RGBW is automatically converted to RGB if such a strip is used. | ||
* sRGB 8-bit sequential DMX data. This will convert the received data using the reverse sRGB transfer function ("gamma correction"). | * sRGB 8-bit sequential DMX data. This will convert the received data using the reverse sRGB transfer function ("gamma correction"). | ||
+ | |||
+ | ==== Data output ==== | ||
+ | |||
+ | There are 4 data lines which can either drive two 1-Wire or two serial data (Clock+Data) signals at 5V TTL. | ||
+ | |||
+ | If the device is configured for Analog RGB mode some of the data lines are hard-rewired to Power MOSFETs instead of to the internal 5V TTL voltage and can drive up to 6A of power. | ||
+ | |||
+ | === Implementation === | ||
+ | |||
+ | The data lines are connected to the SPI peripheral pins of the MCU. The MCU does output LED data using DMA+SPI. | ||
+ | |||
+ | The data output pins on the terminals are driven using real 5V TTL through a MOSFET based level shifter. There is a dedicated linear regulator which provides 5V, derived from the voltage the DC/DC converter does output. So even with long cables there should be no signal dropout because of a voltage drop. | ||
+ | |||
+ | All data output lines have a 500 Ohm impedance matching resistor in line. This resistor was chosen to handle the most common LED strip setups. In specific cases this 0603 sized resistor might not be appropriate and has to be customized. | ||
+ | |||
+ | Note: Do not use consume any significant current on the 5V data lines. The linear regulator can only handle a few millamps before it goes into thermal shutdown. | ||
==== Reality check ==== | ==== Reality check ==== | ||
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+ | ==== Simplified design flow chart ==== | ||
+ | {{::signal_power_flow.png?600|}} | ||