Hi all,
I’ve been lurking around here for a while slowly learning (thanks!) but i don’t have much value to add, so first time poster here.
I’m an electrician to start with, so excuse my lack off EE expertise. Trained in the elevator industry but now float around a few industries.
I’m putting together a pilot light for some 3ø switch gear, I have a basic idea of the function and have tested a few variations and it works in principle. First let me start with the design criteria.
4 Led indicators, all LEDs to be isolated from mains potential. 1 LED per Phase to indicate power present. 4th led is to flash if Neutral, earth or any of the Phases are open circuit/disconnected.
In my PoC stage i’m connecting the three phase LEDs each to a phase and Wye point via a 68k resistor, a diode and a bypass diode (for return path). I then connect another similarly arranged (sans the bypass diode) LED between the Neutral & Earth and the Wye point. This basic circuit gives me effective indication of 3 phases, earth and neutral continuity, provided that I have at least 2/5 inputs hi.
I then moved onto a rectified version, with the three phases getting full bridge rectification (with respect to the Wye point) with earth and neutral getting half wave via a few resistors.
I have mains isolated 12v supply available via seperate means.
I have a basic 555 timer for the flashing LED, which is bread board tested and works fine.
Im using a quad NAND IC to get the 555 circuit to flash in the event any of the 5 inputs goes low. However I’m struggling with the logic and the opto couplers (pc817).
The optos drive an LED on the emitter no problem, so they seem to be switching just fine, but they drop ~9v between Collector and emitter (even without the led in circuit). Not sure if this the problem or just one of many.
I’ve done quite a bit of trial and error and I just can’t figure it out. Should I be driving the logic via transistors? Is there a much simpler/easier way to do this?
I’m trying to avoid using any chips that need programming. The idea is it needs to be serviceable by anyone who can get hold of basic parts and tools. Also trying to keep parts count to an absolute minimum.
The LED display will be on a seperate board, so first attachment is a basic signal flow, the second shows an expanded view.
Thanks in advance everyone and happy holidays.
I’ve been lurking around here for a while slowly learning (thanks!) but i don’t have much value to add, so first time poster here.
I’m an electrician to start with, so excuse my lack off EE expertise. Trained in the elevator industry but now float around a few industries.
I’m putting together a pilot light for some 3ø switch gear, I have a basic idea of the function and have tested a few variations and it works in principle. First let me start with the design criteria.
4 Led indicators, all LEDs to be isolated from mains potential. 1 LED per Phase to indicate power present. 4th led is to flash if Neutral, earth or any of the Phases are open circuit/disconnected.
In my PoC stage i’m connecting the three phase LEDs each to a phase and Wye point via a 68k resistor, a diode and a bypass diode (for return path). I then connect another similarly arranged (sans the bypass diode) LED between the Neutral & Earth and the Wye point. This basic circuit gives me effective indication of 3 phases, earth and neutral continuity, provided that I have at least 2/5 inputs hi.
I then moved onto a rectified version, with the three phases getting full bridge rectification (with respect to the Wye point) with earth and neutral getting half wave via a few resistors.
I have mains isolated 12v supply available via seperate means.
I have a basic 555 timer for the flashing LED, which is bread board tested and works fine.
Im using a quad NAND IC to get the 555 circuit to flash in the event any of the 5 inputs goes low. However I’m struggling with the logic and the opto couplers (pc817).
The optos drive an LED on the emitter no problem, so they seem to be switching just fine, but they drop ~9v between Collector and emitter (even without the led in circuit). Not sure if this the problem or just one of many.
I’ve done quite a bit of trial and error and I just can’t figure it out. Should I be driving the logic via transistors? Is there a much simpler/easier way to do this?
I’m trying to avoid using any chips that need programming. The idea is it needs to be serviceable by anyone who can get hold of basic parts and tools. Also trying to keep parts count to an absolute minimum.
The LED display will be on a seperate board, so first attachment is a basic signal flow, the second shows an expanded view.
Thanks in advance everyone and happy holidays.
