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Generator Auto Start - When to Stop Cranking
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frostheave:

--- Quote from: schmitt trigger on February 08, 2019, 05:30:40 pm ---There are many "clamp on" current sensors available on Amazon and Ebay, which should be minimally invasive if you decide to follow this route.

--- End quote ---

Yes, that would be a possible alternative if the relay method does not work.
Thanks.
frostheave:

--- Quote from: fourtytwo42 on February 08, 2019, 05:40:03 pm ---I feel I have to share a funny story regarding this! ....

--- End quote ---

Yeah, those glow plugs are important to use when it's cold.
Your point is well taken.  I want to make the system as idiot proof as possible!
frostheave:

--- Quote from: NorthGuy on February 08, 2019, 06:46:25 pm ---
--- Quote from: frostheave on February 08, 2019, 05:03:27 pm ---5) Trying to measure a tacho signal from the charging coil for the starting battery may be possible with no special sensors?
6) Measure AC output frequency.  Once the alternator is producing ~35+Hz, stop cranking.  Requires measuring Hi Voltage frequency.

--- End quote ---

Unless you have a fancy variable speed inverter generator, the AC frequency is the tachometer. As soon as a threshold frequency is achieved, you stop cranking. But also run a timer - don't crank for too long if there's no AC, and if this is the case, shut down the generator and disable automatic starts until a human inspects it.

After the start I wait some time to let the generator warm up without a load, then I turn on the load relay.

--- End quote ---

Thanks NorthGuy. 

Nothing fancy about the gen.  I will be using an Arduino for the controls.  Is there some advantage to monitoring frequency vs. voltage?
frostheave:

--- Quote from: ejeffrey on February 08, 2019, 07:39:05 pm ---
--- Quote from: frostheave on February 08, 2019, 05:03:27 pm ---6) Measure AC output frequency.  Once the alternator is producing ~35+Hz, stop cranking.  Requires measuring Hi Voltage frequency.

--- End quote ---

Easy enough to do with a small transformer.  A standard 12V power transformer will allow you to get the voltage and frequency with an isolated measurement.  This will also let you monitor while running.

Does your generator have built-in load switch that only connects the output once at the target RPM?  That would make sense to avoid loading the generator at startup and to avoid producing too low voltage/frequency during startup.  If so, then your simple relay solution is probably the best.

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Thanks a lot ejeffrey.

I have a separate transfer switch that will be controlled by the Arduino in order to transfer between commercial and generator power.  Yes, the programming will include a generator warmup and cool down period as well as only transferring loads when the generator is running and warmed up. 

I was wondering how I could sense the frequency and your transformer solution is so simple!  If my voltage/relay method does not pan out, I'll definitely give this a try.

Bob
Bratster:

--- Quote from: frostheave on February 08, 2019, 09:59:11 pm ---
--- Quote from: NorthGuy on February 08, 2019, 06:46:25 pm ---
--- Quote from: frostheave on February 08, 2019, 05:03:27 pm ---5) Trying to measure a tacho signal from the charging coil for the starting battery may be possible with no special sensors?
6) Measure AC output frequency.  Once the alternator is producing ~35+Hz, stop cranking.  Requires measuring Hi Voltage frequency.

--- End quote ---

Unless you have a fancy variable speed inverter generator, the AC frequency is the tachometer. As soon as a threshold frequency is achieved, you stop cranking. But also run a timer - don't crank for too long if there's no AC, and if this is the case, shut down the generator and disable automatic starts until a human inspects it.

After the start I wait some time to let the generator warm up without a load, then I turn on the load relay.

--- End quote ---

Thanks NorthGuy. 

Nothing fancy about the gen.  I will be using an Arduino for the controls.  Is there some advantage to monitoring frequency vs. voltage?

--- End quote ---
If this is a basic generator, frequency will be very strictly tied in with RPM.

I'm guessing the generator running RPM will probably be 3600 for 60 Hertz.

That's what the ones that I have installed at various sites are.

Sent from my Fi Moto x4 using Tapatalk

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