I am building a battery backup for an aquarium pump, which runs on 24V DC from an adapter plugged into a standard AC American outlet. The easy, expensive and inefficient solution is to buy a UPS, which has a DC battery, an inverter to convert to AC which runs the adapter to convert back to DC. I don't want to lose 40% of my backup power to conversion in an emergency.
I've seen plans online without details, probably because this is a simple project and I am just not familiar with this type of circuit. A 12V DC battery (runs pump half speed) is maintained on a trickle charger and connected to a DPDT relay, which when power goes out, cuts power to the adapter and connects power from the battery. When the power comes back on, the relay disconnects the battery and restores the adapter. Most designers feel the need to include fuse(s) or some sort of timer for circuit protection, but I don't understand how or why.
I haven't used a DPTP relay before, and am not sure which spec I need. I know I need to run DC power from the battery through the NO terminals. I can run either AC power from the mains through the COIL terminal of the relay, or 24V DC power from the the adapter or any voltage from a seperate adapter. The pump draws 40 watts on 24 volts DC. So should I buy a DC or AC relay? Can you give me an example of a relay similar to what I should buy?
Assuming I don't run current from the mains through the NC terminal, I don't understand the need for any circuit protection. I assume the NC and NO are never both closed on a DPDT relay, but if they were, worst case is running 24V accross the terminals of a large 12V battery for a brief period of time.
I've seen plans online without details, probably because this is a simple project and I am just not familiar with this type of circuit. A 12V DC battery (runs pump half speed) is maintained on a trickle charger and connected to a DPDT relay, which when power goes out, cuts power to the adapter and connects power from the battery. When the power comes back on, the relay disconnects the battery and restores the adapter. Most designers feel the need to include fuse(s) or some sort of timer for circuit protection, but I don't understand how or why.
I haven't used a DPTP relay before, and am not sure which spec I need. I know I need to run DC power from the battery through the NO terminals. I can run either AC power from the mains through the COIL terminal of the relay, or 24V DC power from the the adapter or any voltage from a seperate adapter. The pump draws 40 watts on 24 volts DC. So should I buy a DC or AC relay? Can you give me an example of a relay similar to what I should buy?
Assuming I don't run current from the mains through the NC terminal, I don't understand the need for any circuit protection. I assume the NC and NO are never both closed on a DPDT relay, but if they were, worst case is running 24V accross the terminals of a large 12V battery for a brief period of time.