This unit integrates several support hardware items for operation of a remotely operated telescope.
The functions the device performs are:
1) supplies filtered DC power for the telescope mount
2) controls two unipolar, 5 wire steppers motors
3) provides a charger output for a DSLR camera battery
4) supplies +5Vdc for powered USB hub
5) accepts two, I2C LM75 temperature sensors
6) accepts one, DHT22 single wire humidity temperature sensor
7) provides proportionally controlled 15V Dew heater outputs based on humidity and temperature
8) supplies two +15Vdc/30W outputs for camera thermoelectric coolers
Control of the various functions is managed using and Arduino Mega and Nano. Control of each function is split between the Mega and Nano.
Page 7 of the entire project. The Arduino Nano circuit card assembly. Since this portion will of the project will exclusively communicate with an ASCOM driver, it has its own dedicated USB interface. The Arduino Mega has its own USB interface.
The hardware component count is kept low, with the help of code. The Arduino stepper library is used to energize the appropriately coils. N channel FETs with logic level Vgs thresholds are used to individually energize the stepper coils, keeping the part count and stepper driver cost low. In the code, to reduce coil heating when not moving, the digital outputs drive each gate low sending each FET to an open drain state. When a movement command is received, the gates are returned to their previous state before using the stepper library.
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01/25/2019 at 13:14