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Having purchased an LX200GPS telescope from Meade, I needed a portable power supply. Rather than buy one, I decided that it would make a nice PIC project. The power supply is housed in a standard plastic toolbox. Two 12V SLA batteries are connected in parallel to give 14 Amp hrs of capacity. A SLA "Smart" charger, built around the TI UC2906, is used to charge and maintain the batteries. Three LEDs provide the status of the charger: Green - floating at 13.8V, Orange - controlled over-charge, and Red - Bulk charge. The 16F88 PIC is used to monitor the current draw through two plug-in power ports using MAX471 High-side current monitoring ICs. The battery voltage is also measured and a timer is used with the current draw data to calculate the total power drawn from the batteries. This information is display on a backlit two line LCD display. The brightness of the backlighting for the LCD is controlled by the PIC using PWM and a FET. A push button on the power supply cycles through four different dimming levels.
Telescope SLA Charger Schematic Telescope SLA Charger Component Placement Telescope SLA Charger Bill of Materials Telescope Power System Schematic Telescope Power System Component Placement - Top |
