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Joined: 21/06/2018
Location: AustraliaPosts: 1292
| Posted: 02:32pm 18 Jul 2024 |
I decided to continue the staged inverter discussion back on the thread where the Nano controller & Power PCB and Variac builds started.
The staged startup got very complicated very quickly so I went back and had a hard think about minimising the circuitry and parts to achieve what I needed. The basic functionality I chose works like this.
A threshold is set near 22A of load current (from stage 1) which sets a re-triggerable monostable with a 10 second timeout, so the first sinewave that exceeds the 22A threshold starts the 10 second timer. Subsequent pulses even if 4.5A lower will still retrigger the timer due to the hysteresis fed back from the 10 sec timer.
The 10 sec timer when untriggered or timed out prevent optical pulses to the second Power PCB and also holds off the 30A relay from turning on.
The instant the 10 second timer is triggered it triggers another ~ 2 second timer, during that 2 seconds the soft start relay is pulled in for the 2 second soft start interval, when the 2 second timer times out, the 30A relay is triggered to turn on and a small delay to the soft start relay turn off, ensures overlap such that the soft start relay opens after the 30A relay is engaged.
The same signal that turns on the 30A relay also enables the opto drive to the second stage which should be just before the 30A relays pull in time.
After there has been no more current pulses greater then 17A for 10 seconds the first monostable times out which immediately disengages the second stage opto drive and the 30A relay.
A single pulse exceeding the threshold will cause the engagement of the second stage for about 8 seconds (after the 2 second soft start) before disabling the second stage again. The KW thresholds for extended on / off are ~ >5kW and <4KW
The manual bypass was a bit trickier as it needed to retrigger the first monostable as long as the switch was closed so I employed the second half of the comparator as a pulsing circuit to fool the first comparator that we are continuously exceeding the trigger threshold to start the second stage.
I have not built it yet - only in my head but here is the circuit I intend to build up to test as soon as I am well enough to get back in the workshop, been down with man flu
The circuit uses some MM2 logic (mickey mouse) the resistor/diode bits function as and gates, maybe not pretty but will work as required I believe.
2Stage.pdf
Comments questions criticisms all welcome.
Re: Cpoc and the question about a remote WIFI LCD, Poida can confirm the following, some of the Wemos type wifi chips I understand can act as a data modem and as the LCD is a uni directional receive only comms I would not be surprised if just putting the LCD data into the modem input of a TX Wemos & using a second RX Wemos to drive the data to the remote Nano LCD might just work.
Re interfacing to the home assistant device though is beyond my area of expertise and interest, best left to a software specialist/hacker (talented one...).
Edited 2024-07-19 01:12 by wiseguy