Sense when a generator has started ?

Thread Starter

SteveDouglas

Joined Apr 30, 2009
49
I have a 12kw portable generator setup for power outages and using an interlock in the main panel, all works perfect but, I have to go out and press the starter button to fire it up.

So, I bought THIS as it is Tuya based and is controlled from the app that controls all my home automation, it also intergrates with a 433mhz remote. However, if I start it using the app (set to engage the starter motor for 3 seconds) and it doesn't start I have to try again. And, if I set it to engage the starter relay to be on too long I risk damaging the starter, etc.

I think I need a sensor that once the engine has started will disengage the start relay, via an optocoupler or similar.

Anyone have any ideas or suggestions ?
 

crutschow

Joined Mar 14, 2008
30,803
How about a SPDT AC relay powered by the generator AC output, which opens the start circuit when the relay becomes energized (using the normally-closed relay contact).
No electronics needed.
 
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strantor

Joined Oct 3, 2010
6,112
How about an AC relay powered by the generator AC output, which opens the start circuit when the relay becomes energized (using a normally-closed relay contact).
+1
It may require a timer relay. Depending on the generator. If the generator starts outputting voltage from the first revolution, and ordinary relay might trigger before the generator is up to speed. If the generator waits until it's up to speed before activating the output voltage, then an ordinary relay should be fine.
 

crutschow

Joined Mar 14, 2008
30,803
Depending on the generator. If the generator starts outputting voltage from the first revolution, and ordinary relay might trigger before the generator is up to speed
The engine doesn't need to be up to speed before you disengage the starter, it just has to start running on its own.
A starter turns the engine over at 200-300 RPM, so when the engine starts and goes above that speed, the starter can disengage.
At that low RPM there is not likely to be significant AC output, so the relay would not cut off the starter before the engine is fully started.
 
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Ian0

Joined Aug 7, 2020
6,312
This is what is generally used to control and monitor generators
https://www.deepseaelectronics.com/genset
It will deal with all the starting, stopping, temperature and oil pressure monitoring and emergency stop.

One easy way to determine if the generator is running is to take a wire from the oil-pressure switch.
 

Ya’akov

Joined Jan 27, 2019
6,575
The engine doesn't need to be up to speed before you disengage the starter, it just has to start running on its own.
A starter turns the engine over at 200-300 RPM, so when the engine starts and goes above that speed, the starter can disengage.
At that low RPM there is not likely to be significantly AC output, so the relay would not cut off the starter before the engine is fully started.
Though the second condition—overly long cranking—is not prevented by this approach. I suppose you’d have to add a timeout/retry feature so it didn’t just crank until the magic smoke was released from the starter.
 

Ya’akov

Joined Jan 27, 2019
6,575
One thing that strikes me is safety considerations. I am not sure exactly what risks this entails but I would be very careful to fully analyze the potential dangers including unintended operation and unexpected starts (among other things I can‘t immediately imagine).

I am not sure there is something to be concerned about, just that being concerned about whether there is something, is warranted.
 

crutschow

Joined Mar 14, 2008
30,803
overly long cranking—is not prevented by this approach
The TS stated in the first post that he can control the start time from his app, so he just sets that to the maximum continuous crank time the starter can tolerate.
If/when it starts before that, the relay will disengage the starter.
 
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Ya’akov

Joined Jan 27, 2019
6,575
The TS stated in the first post that he can control the start time from his app, so he just sets that to the maximum continuous crank time the starter can tolerate.
If it starts before that, the relay will disengage the starter.
I missed that in the original post.
 

Thread Starter

SteveDouglas

Joined Apr 30, 2009
49
How about a SPDT AC relay powered by the generator AC output, which opens the start circuit when the relay becomes energized (using the normally-closed relay contact).
No electronics needed.
Right, great idea, I think I was trying to over complicate it. I'll give that a try, it should work fine. Thanks !

This is what is generally used to control and monitor generators
https://www.deepseaelectronics.com/genset
It will deal with all the starting, stopping, temperature and oil pressure monitoring and emergency stop.

One easy way to determine if the generator is running is to take a wire from the oil-pressure switch.
I'm sure those units are not inexpensive and I don't really need anything that nice. This particular engine doesn't have a pressure switch, I have a small tractor with a low oil light and the light will go out after a few seconds of cranking even if it doesn't start so it may not work anyway.

One thing that strikes me is safety considerations. I am not sure exactly what risks this entails but I would be very careful to fully analyze the potential dangers including unintended operation and unexpected starts (among other things I can‘t immediately imagine).

I am not sure there is something to be concerned about, just that being concerned about whether there is something, is warranted.
Yeah I thought about that aspect but someone is usually home to hear if it starts unexpectedly and it's in a metal enclosure outside. So far the Smart Life home automation app I use has never done anything unexpected, no lights turning on or off or gate opening and closing or garage door opening or closing either, so I'm pretty confident it will be ok.

The TS stated in the first post that he can control the start time from his app, so he just sets that to the maximum continuous crank time the starter can tolerate.
If/when it starts before that, the relay will disengage the starter.
Exactly.

I think the 120 VAC relay will work, I'm curious what something like the Generac standby generators use for this, probably a dedicated engine/generator controller (?)

Thanks for all the help and ideas, I'll post back after I try it.
 

Reloadron

Joined Jan 15, 2015
6,979
I'm curious what something like the Generac standby generators use for this, probably a dedicated engine/generator controller (?)
The larger Generac and similar units use a complete uC controlled system. I have an 18 KW whole house system, natural gas fuel and here is the sequence which I can change the timing on. Mains power fails and it waits about 5 seconds to make sure it's not just a power glitch. There are times we go black for maybe 2 to 3 seconds and power is back. After a 5 second delay the generator starts and in the event it does not start the starter disengages for about 10 seconds and it tries again. I think it will make 4 attempts before it gives up. Once the generator is running it waits about 10 seconds and then does an automatic transfer. When mains power returns it waits about 10 seconds and does the transfer back to mains utility power. The generator continues to run about another few minuets just as a cooldown.

One problem with all this magic is every Sunday at 11:00 AM the generator does an "exercise" routine where it starts and runs about 15 min. It does not transfer at all it just runs. My old unit was 11 years old, a 13 KW unit. So here I was fat dumb and happy. We had a severe summer storm and lost mains utility power. Generator started as always but we sat in the dark. I ran downstairs and did a manual transfer but the genset already did that. No power and a sump about to overflow. Just great! Thank God I had my old Coleman Power Mate 4 KW unit in the garage. I added gas and it came right up. Next a long AWG 12 extension cord to my pumps. Ever since that day once a month I deliberately kill mains utility and let the system do its thing. The fact that a generator starts and runs is no guarantee it makes power. :)Anyway in a nutshell my system has a dingle circuit board with a uC on it dedicated to all of the start/transfer/shutdown operations. Yes, a dedicated controller as you mention.

If all you want to do is detect a start I would so as suggested. Place a simple relay at the output. If the genset is a 240 VAC out I would use a 240 VAC relay coil. This will disengage the starter. I would then maybe if you want have a short delay and let automatic transfer happen. You really don't want transfer unless you know the generator has voltage out.

Ron
 

Thread Starter

SteveDouglas

Joined Apr 30, 2009
49
Thanks for that detailed explanation Ron. And I thought about ordering a 240 VAC relay and wish I had but by the time you posted the 120 relay was already on the way.

I'm happy to say that the relay works perfect as a starter interlock, the relay engages and opens the start circuit the moment the engine starts. I even tried to engage the starter by remote as soon as the engine was running and it of course doesn't.

I added the 7 pin remote port since the enclosure the generator is in is metal so the actual remote unit will be mounted in a plastic enclosure on the outside to receive the WiFi and 433mhz signal. I considered modding the relay board to add an external WiFi antenna but I'd have to also add the 433 antenna so I decided not to.

Thanks for all the help !


20220908_190008.jpg
120 VAC Relay


20220908_190252.jpg
Remote start/stop port added
 
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Thread Starter

SteveDouglas

Joined Apr 30, 2009
49
Why does it require two signals?
It doesn't "require" two signals, it's either/or. The WiFi is for control via the Smart Life app on phones, which allows one to not have to keep a 433 remote or to find it and I hope to set a schedule in the app to exercise the generator every Saturday for 15 minutes as described by Ron above. This keeps the fuel fresher in the carb ( I always use Stabil when I fill gas cans) and keeps critters from nesting in the unit, etc.

Or if I want to just grab the keyfob remote I can use that. The other positive is that if one doesn't work for whatever reason, I expect the other will. Either way, at least I'll never have to go out in the wind, rain or dark to fire it up.
 
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