Guru
Joined: 05/10/2019
Location: United KingdomPosts: 8888
| Posted: 07:30am 29 May 2024 |
Is there no way to bypass the power supply and feed them with DC directly? It would be a lot easier.
Trouble is, at this point in the chain you probably don't want to be introducing mains supply noise, which makes any UPS a bit more complicated. The cheap end aren't true sine wave inverters.
The size is very much going to depend on the battery, which depends on how long you want it to run for.
If you can't find a commercial one, I'd suggest using a RP2040-Zero to generate a nice fixed sine wave. Then (maybe use a pot to set the voltage) level) into any cheap-n-cheerful Chinese 50W or so mono amp driving a little mains transformer in reverse from a 6V motorbike battery - you probably want this to be rugged. The RP2040-Zero could handle mains detection and give a bit of overrun when it returns and could also start/stop the sine wave as necessary. It could also monitor the battery voltage and switch the charger into boost mode when needed. Keep the battery on continuous trickle charge while it powers the inverter. No changeover to bother about then. LM317T would be a suitable device for the charger when fed from a simple power supply, I think.
Edited 2024-05-29 17:31 by Mixtel90