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saand · 03-18-2011, 11:11 AM

Hi Daox,
ok now i have a better idea what your trying to do a few things you may want to know
- a starter i think off the top of my head can take up to maybe 100 amps as you have a 12v or 24v electric motor attempting to rotate your engine which has lots of mass and lots of friction (when cold)
- So you will need to keep this in mind if you are not using the standard key ignition solenoid, if your choosing your own solenoid make sure it can do enough current, if it isn't specified to do the current your starter will take then it can weld the solenoid contacts which would kill your battery and maybe your starter. (fairly low risk of this happening but it could be bad)
- since your multimeter probably has a 10 amp fuse in it you might just be able to change the fuse inside the multimeter to get it working again. I have tried to measure more than 10 amp with multimeters plenty of times

- I am not sure what sort of photoresistor your using but its likely it will respond to daylight so if its not housed in a dark enclosure the feedback from this may work in daylight and not in night or the other way around. Something to look out for incase it trigures when you dont want it to.

To clarify what i think you want to do, here are my assumptions about what you want this system to do for you
- at any time if your in neutral and if the clutch pedal is not depressed you want to turn the engine off
- you plan to measure the shifter is in neutral using the optical feedback using the absense of light to detect if the shifter is blocking the light path. (Note, if there is an issue with the LED or wiring the system will think you are always in neutral)
- you will turn the engine off by opening the NC (normally closed) contact which connects the crankshaft position sensor to the ECU. The ECU will then stop firing the cylinders so engine turns off
- when you shift out of neutral into any other gear you want the system to energize the starter motor. (Note when writing the code you will want to check that the crankshaft position sensor isn't showing any RPM's incase you quickly go in and out of neutral so the engine trys to start the engine even though it is still rotating)
- When the engine is off, if the clutch is depressed you want to have the starter to start immediately while the shifter is still in neutral (or does it matter if the shifter is in neutral or not)
- When starting the motor you will have the starter motor engaged until the you start seeing quick enough crankshaft position sensing changing or RPM of the engine. Alternatively you will have the starter on for a predetermined time say 2 seconds?

So what i am seeing from the assumptions above is that you dont actually need the system to know when the clutch is depressed. This however may cause the code to be changed a bit but here is how i see the code working
- When starting the car in the drive way, The controller is energized when you turn the ignition switch to accessories or on. The controller has the crankshaft position sensor connected to the ECU. The controller checks the crankshaft position sensor, it shows no rpms so it knows the engine is off. The controller then powers the solenoid to bridge the ignition switch. The starter does not start because the clutch is not depressed. The clutch pedal is depressed the RPMs get high enough and the controller denergizes the starter solenoid by denergizing the solenoid across the ignition switch.
- The controller sees that the RPMs are high so the engine is on, the car may be in neutral and if it is and stays in neutral for more than a certain time out the engine is turned off by opening the contact between the crankshaft sensor and the ECU
- The engine is rotating and the controller sees that the RPMs are high, the shifter is put into a gear before the neutral time out and the car is in gear. The controller does nothing other than notes that the state of the shifter is not in neutral.
- The car approaches a stop light, its put into neutral. The controller knows that the shifter was previously not in neutral, it now knows the shifter is in neutral and it knows that the engine is running so it opens the contact between the crankshaft sensor and ECU.
- The engine is reving down. The controller either has a time out then reconnects the crankshaft sensor and ecu or it sees the crankshaft sensor RPM speed reduce to 0 then it reconnects the crankshaft sensor to the ECU. The controller then powers the solenoid that bridges the ignition switch so that as soon as the clutch is depressed the starter will start.
- engine restarting occures by depressing clutch

So if all my assumptions are correct (that is a big if) you will not need to sense when the clutch is connected but you may need to keep your foot down on the clutch long enough for the engine to start.

Now if i am wrong, other ways to measure if the clutch switch is depressed is as follows
- instead of the zener, the regulator and connection to optical circuit you can use other inputs on the arduino. Place say 2 by 100k ohm resistors, 1 across the ignition switch and one across the clutch switch. Then have an input from each side of the clutch switch go into the arduino (making sure you have an appropriate resistive divider to take it down to the correct voltage for inputs to the arduino). If the clutch switch is closed the voltage on both sides of the clutch switch will be the same either 12v or 0v depending on the state of the starter motor and the ignition switch. If the voltages across the clutch switch are different 12v or 0v then the clutch switch is open. Note: this relies on the resistance of the starter coil being low. also you may have issues with either system when the clutch or ignition switch disengage due to voltage spikes

I believe with the existing schematic you have placed above that the 5v reg will blow up because the resistance of the starter will be relatively low with respect to ground so either the 5v reg wont be able to maintain 5v or the solenoid will energize or you may be lucky and it will be just at the right voltage where not much current is taken and there isn't enough energy to close the starter.

Sorry for the long reply but hopefully this gives you a few options and im sure there are a few typo's up there

Also thanks for sending me a pm, i am not often on ecomodder at the moment so if you do want me to reply please send me a pm so i catch the post.

good luck

03-18-2011, 11:11 AM	#25 (permalink)
saand Wiki Writer Join Date: Jul 2010 Location: Melbourne, Australia Posts: 236 bugler - '91 Mazda 626 90 day: 35.89 mpg (US) Thanks: 15 Thanked 25 Times in 22 Posts	Hi Daox, ok now i have a better idea what your trying to do a few things you may want to know - a starter i think off the top of my head can take up to maybe 100 amps as you have a 12v or 24v electric motor attempting to rotate your engine which has lots of mass and lots of friction (when cold) - So you will need to keep this in mind if you are not using the standard key ignition solenoid, if your choosing your own solenoid make sure it can do enough current, if it isn't specified to do the current your starter will take then it can weld the solenoid contacts which would kill your battery and maybe your starter. (fairly low risk of this happening but it could be bad) - since your multimeter probably has a 10 amp fuse in it you might just be able to change the fuse inside the multimeter to get it working again. I have tried to measure more than 10 amp with multimeters plenty of times - I am not sure what sort of photoresistor your using but its likely it will respond to daylight so if its not housed in a dark enclosure the feedback from this may work in daylight and not in night or the other way around. Something to look out for incase it trigures when you dont want it to. To clarify what i think you want to do, here are my assumptions about what you want this system to do for you - at any time if your in neutral and if the clutch pedal is not depressed you want to turn the engine off - you plan to measure the shifter is in neutral using the optical feedback using the absense of light to detect if the shifter is blocking the light path. (Note, if there is an issue with the LED or wiring the system will think you are always in neutral) - you will turn the engine off by opening the NC (normally closed) contact which connects the crankshaft position sensor to the ECU. The ECU will then stop firing the cylinders so engine turns off - when you shift out of neutral into any other gear you want the system to energize the starter motor. (Note when writing the code you will want to check that the crankshaft position sensor isn't showing any RPM's incase you quickly go in and out of neutral so the engine trys to start the engine even though it is still rotating) - When the engine is off, if the clutch is depressed you want to have the starter to start immediately while the shifter is still in neutral (or does it matter if the shifter is in neutral or not) - When starting the motor you will have the starter motor engaged until the you start seeing quick enough crankshaft position sensing changing or RPM of the engine. Alternatively you will have the starter on for a predetermined time say 2 seconds? So what i am seeing from the assumptions above is that you dont actually need the system to know when the clutch is depressed. This however may cause the code to be changed a bit but here is how i see the code working - When starting the car in the drive way, The controller is energized when you turn the ignition switch to accessories or on. The controller has the crankshaft position sensor connected to the ECU. The controller checks the crankshaft position sensor, it shows no rpms so it knows the engine is off. The controller then powers the solenoid to bridge the ignition switch. The starter does not start because the clutch is not depressed. The clutch pedal is depressed the RPMs get high enough and the controller denergizes the starter solenoid by denergizing the solenoid across the ignition switch. - The controller sees that the RPMs are high so the engine is on, the car may be in neutral and if it is and stays in neutral for more than a certain time out the engine is turned off by opening the contact between the crankshaft sensor and the ECU - The engine is rotating and the controller sees that the RPMs are high, the shifter is put into a gear before the neutral time out and the car is in gear. The controller does nothing other than notes that the state of the shifter is not in neutral. - The car approaches a stop light, its put into neutral. The controller knows that the shifter was previously not in neutral, it now knows the shifter is in neutral and it knows that the engine is running so it opens the contact between the crankshaft sensor and ECU. - The engine is reving down. The controller either has a time out then reconnects the crankshaft sensor and ecu or it sees the crankshaft sensor RPM speed reduce to 0 then it reconnects the crankshaft sensor to the ECU. The controller then powers the solenoid that bridges the ignition switch so that as soon as the clutch is depressed the starter will start. - engine restarting occures by depressing clutch So if all my assumptions are correct (that is a big if) you will not need to sense when the clutch is connected but you may need to keep your foot down on the clutch long enough for the engine to start. Now if i am wrong, other ways to measure if the clutch switch is depressed is as follows - instead of the zener, the regulator and connection to optical circuit you can use other inputs on the arduino. Place say 2 by 100k ohm resistors, 1 across the ignition switch and one across the clutch switch. Then have an input from each side of the clutch switch go into the arduino (making sure you have an appropriate resistive divider to take it down to the correct voltage for inputs to the arduino). If the clutch switch is closed the voltage on both sides of the clutch switch will be the same either 12v or 0v depending on the state of the starter motor and the ignition switch. If the voltages across the clutch switch are different 12v or 0v then the clutch switch is open. Note: this relies on the resistance of the starter coil being low. also you may have issues with either system when the clutch or ignition switch disengage due to voltage spikes I believe with the existing schematic you have placed above that the 5v reg will blow up because the resistance of the starter will be relatively low with respect to ground so either the 5v reg wont be able to maintain 5v or the solenoid will energize or you may be lucky and it will be just at the right voltage where not much current is taken and there isn't enough energy to close the starter. Sorry for the long reply but hopefully this gives you a few options and im sure there are a few typo's up there Also thanks for sending me a pm, i am not often on ecomodder at the moment so if you do want me to reply please send me a pm so i catch the post. good luck