Power Electronics · Avionics
Rocket E-Bay Power System
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Overview
I made an E-Bay power system for the Terrapin Rockets IREC competition rocket, Helios. It allows the onboard Li-ion battery to be charged safely and conveniently without disassembling the rocket, while also supplying regulated 3.3V power to the electronics.
The main component in the circuit is the MCP73831 linear charge management controller, which I chose for its simplicity and small format.
Design Approach
Design Purpose
- —Access to the rocket's avionics bay is limited, so the battery is charged directly through external connectors
- —This eliminates the need to remove the internal components in order to charge
- —Two 2-pin JST connectors interface with Vin and Vbattery
- —A 2-pin Dupont header on the PROG pin allows the charge current to be changed without changing the soldered passive components, which makes the circuit easy to reconfigure
Charge Current Regulation
- —The MCP73831 sets the charge current with a single external resistor connected between the PROG pin and ground
- —The relationship is I_REG = 1000 V / R_PROG, with the current in mA and the resistance in kΩ
- —The Dupont header allows R_PROG to be adjusted, which makes the circuit adaptable to different battery sizes
Simulation & Testing
I tested the board by using it to charge a battery through the external connectors, confirming that the battery can be charged without opening up the avionics bay.
Key Features
- —Charges the onboard Li-ion battery through external connectors, without disassembling the rocket
- —Supplies regulated 3.3V power to the onboard electronics
- —MCP73831 linear charge management controller
- —Adjustable charge current through the PROG resistor, using a Dupont header
- —Two 2-pin JST connectors for Vin and Vbattery
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