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Basically, this will be my first Arduino project.  I know it will be difficult, but whenever I start something new, I always start difficultly.  Ok, so i have a big lawnmower engine, with electric start.  To start, you need to push the throttle all the way up, so the choke is engaged, turn the key to start, and when the engine catches (or when it actually starts) turn the key to run, and pull the throttle down, only to the point were the choke is off, so the arduino somehow needs to know when the engine has actually started, so it can open the relay to start the engine, and pull the throttle down.  I want to have two arduinos for this, one to detect when the power is out, transfer the load from utility to the generator, and tell the second arduino the power is out.  When the second arduino knows the power is out, it has to start the engine to keep my servers running.  How could i do this from a hardware and software point?  For hardware i was thinking about using a 5 volt power adapter and connecting it to the first arduino, (the arduinos and servers would be on a UPS, but is only for the time in between the failure and the time the generator can take the load)   Below is a script of how things should happen. 

A
First arduino:  wait for failure
Power from utility fails
First arduino : tells second the power is out
Second Srduino: starts engine
first arduino:  transfers load to the inverter
first arduino:waits for power to turn back on
first arduino: when power is on, tell second arduino
second arduino: open the 'run' relay, to shut down the engine

Go to A


It dosent matter where the throttle is when the engine is not running
Please help

Thanks  smiley
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I want to have two arduinos for this
Why?
Assuming that it can be done at all, I can't see any reason why it couldn't be done with one Arduino.

Pete
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Just so I can have more equipment I guess ( it will look cooler). And in the future, mabye I can have another two serving as a backup. 
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i think this would be more reliable if you had an electric choke....
that said maybe you could monitor the sparkplug wire and when it has X amount of spark its probably running and pull back the choke.
You have a relay for the choke but what actual mechanics is going to "pull the lever back"?  a motor?  a servo?  A heavy weight and a string?
Now you need (want...  I say its adding difficulty you dont need) the 2 arduinos to talk to each other.  How far away are they?  wireless or not?  
How are you planning on telling when the power goes out?  

Quote
Please help
what is the question?
if you are asking can i do this using arduino I would say yes.  Probably not what I would choose as my first project.
Are you asking if its a cool project?  Again I'd say yes.  On the farm we have a tractor PTO we hook up to the generator and its all manual.  But I havent gotten good enough at arduino to  have it drive the tractor over from the barn when needed smiley-wink
So you build your piece and ill  start working on the ROV tractor and we'll mash it up and make a billion.
If you are asking for a complete bill of materials and the code to go with it I doubt you'll get it here.  People around here are pretty bad at spoonfeeding.  And trust me I've tried..

Post some links to some of the sensors/relays/servos you are thinking of using.
Or the start of your arduino sketch.
« Last Edit: August 16, 2012, 09:12:11 pm by jointtech » Logged

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Well, the arduinos will be right next to each other, probably both in the server room.  Not wireless, and i was wondering if i could just do that by hading the first arduino send an analog signal to the second, like just positive 5V.To trigger the power failure scripts on the first one, I was wondering if i could use a 5 volt cell phone charger and connect the positive to one of the analog pins.  Would this work? The arduinos would be on a UPS, and the cell phone charger (trigger) would not be.  The engine, im going to take out and put in an enclosure (its a perfectly good engine, but the transmission in the lawn mower died, and it would be more cost effective to replace the whole think as it is 15 years old), and connect it to an alternator with various belts and pullys and what not.

Could i replace the existing choke with an electric?  The problem is, the choke is activated when the throttle is engaged all the way, plus some. 
 
Tomorrow ill post a video to youtube showing the engine just in case a person who is better than me at mechanics shows up. 
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You can use RC servos to actuate the throttle and choke. Both the throttle and choke are very low torque so any servo should do fine. A hall sensor can monitor the engine RPMs (by watching the flywheel magnet pass) and you'll also need a large transistor (~1A) to switch power to the coil on the starter solenoid. Might be safer to use a small electromechanical relay for electrical isolation. If you're ordering parts you might want to include at least one 10K potentiometer so you can interface it with the Arduino to allow throttle adjustment when the engine is running; the throttle will be mechanically under control of a servo and you won't have any ability to adjust it otherwise.

Your startup procedure:
* Set the choke
* Set the throttle
* Power the starter solenoid
* Watch pulses from the hall sensor for engine speed. You would need to watch the rate of pulses; a slower rate would indicate the starter is firing, and a faster rate would indicate that the engine has started. You could also program it to just watch for ~10 RPMs and then disengage the starter; if you still see pulses then the engine is running.

If the engine has started:
* Disengage the solenoid
* Unset the choke
* Set the throttle

If the engine has not started, e.g. if the hall sensor has seen ~10 pulses with no increase in the rate of those pulses, then you might want to shut everything off and start back from the beginning. You should wait ~30 seconds or so so that the starter can cool down.

As an alternative to using a hall sensor you could also use a resistor and zener shunt regulator circuit to watch the pulses on the alternator. Since there are more pulses per RPM that would give you a more accurate measure of the current speed of the engine.
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Sounds overly complicated in some areas. Seperate the throttle and choke. Leave the throttle full on. Typical B&S engines and similar have have an air vane throttle controller, which might also operate the choke and be used as an engine start indicator. Best to study the parts of your engine. How will you switch the normal and emergency power? How will you know when normal power is restored?
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Ok so to determine when the power is on or off, i want to have a 5volt cell phone charger connected to an outlet (without battery backup, of corse) and have it connect to one of the first arduino's pins.  I will be posting a video on youtube today about the engine. 
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Sounds overly complicated in some areas. Seperate the throttle and choke. Leave the throttle full on. Typical B&S engines and similar have have an air vane throttle controller, which might also operate the choke and be used as an engine start indicator.

The choke blocks the airflow from the air filter to increase suction on the fuel line when the intake cycle occurs. You might be able to get away without the choke but you'd be cranking the engine a lot more before any fuel reaches the carb. That's hard on the starter.

Btw jm, if you need to choke the engine when it's running you probably need to clean your carb smiley-wink
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The Coffman device used a large blank cartridge containing Cordite that, when fired, pushed a piston forward. A screw thread driven by the piston engaged with the engine turning it over.
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