![]() The SO18 package simply sits inside the SO18W package’s pads. (The ISP header pins are used for the outputs).Īlso of note is the current sense resistor, which due to a schematic check error (I missed it) isn’t actually used, theoretically one could greenwire the high side of the sense resistor to pin 1 of JP6, which would allow you to sense the sum current from both channels.Īlso noteworthy is that the LED driver allows two packages to be used for the ULN2803: SO18W and SO18. JP6 is provided for these other functionalities so that access to ADCs is available. Given that the function of the LED daisy chain driver is entirely software driven, the controller can also be used for arbitrary functions requiring up to 500ma sink outputs. Trigger is not yet implemented as this archery timer only required two boards to be daisy chained, but potentially could be useful if the chain was very long in which case the new input characters would not be latched into the output variables until trigger undergoes an edge transition (it is tied to INT0) The Timer1ISR simply uses a switch statement and defined port manipulation macros to set the outputs. Timer1 is set to trigger a ISR at 62.5khz, which yields a final flicker rate of 3.125khz, which is well above the human threshold of perception. Timer1 is used to handle PWM control, with 20 levels of overall brightness control. Brightness is controlled by sending a special control character followed by a decimal brigthness value from 0-19, which is then stored in a brightness variable. Remaining characters are passed down the UART output.īecause the Atmega is not capable of more than 6 PWM outputs, the outputs are bit bang output with a global brightness. If a non decimal character is followed by a decimal, then the decimal output for that character is also enabled. The first two non decimal characters arriving down the line are stored as the outputs. The main loop handles serial data processing only. Software was written using the Arduino core. Black and Decker Lead Acid Battery ChargerĬontrol of each output channel (low side sink) is controlled by an Atmega328p.Off the shelf components were used for the primary controller: ![]() Outside loop is composed of 4 chains with two more chains inside, to allow for two brightness levels.Six inch long segments allow up to 6 chains of 4 leds a piece.No external configurations needed for position in chain.Software interprets characters sent down the pipe and outputs to two eight segment digits (7 seg + decimal).UART in, UART out, with power and trigger.2x ULN2803A (16 channel output 500ma ea).CREE Screenmaster LEDs designed for visibility up to 70mģ custom PCBs were designed in the process of building this system:.3 digits, 1 colon, and a traffic light (Green, Yellow, Red).The Yellow Jacket Archery Club requested a timer to control the shooting line simulating the shot clocks used in competitions.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |