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Which starter to buy?
Nissan Automobiles Nissan Automobiles Discussions (alt.autos.nissan)
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#31
 
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Re: Which starter to buy? -
10-06-2006
, 12:59 AM
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On Thu, 05 Oct 2006 01:29:29 -0400, Steve T <fotocord (AT) yahoo (DOT) com wrote: metoo wrote: On Wed, 04 Oct 2006 00:07:22 -0400, Steve T <fotocord (AT) yahoo (DOT) com wrote: metoo wrote: simple E=I*R I=E/R 12 volts devided by 400,000 ohms ( I just measured between indexfinge and thumb on one hand to indexfinger and thumb on other hand, squeezed hard lowest reading i saw was about 4000,000 ohms) = .03 millamps. Not enough to feel. Touch the main terminal of the starter with 1 hand on the frame and you will not feel anything when someone cranks the car UNTILL they release the key and the counter EMF (caused by the magnetic lines of flux collapsing) will produce hundreds or thousands of volts at low current will shock the hell out of you because then 4000 volts devided by 400,000 ohms will allow 10 millamps to go thru you and that sir could be lethal!! When you let off the key, the solenoid disengages, so any EMF wouldn't transfer to the post being held. the solenoid disengaging is what causes the counter-EMF The magnetic flux being developed by the coil all of a sudden have no where to go so they collapse back to the coil. With no return path to ground. the very high resistance makes the voltage so high at the post. Basic electronics. The solenoid is a relay. When you disengage it, any EMF would NOT discharge to the positive post on the solenoid the battery cable connects to, the coil isn't connected to that post! There might be some voltage at the trigger wire but the low ohms of a solenoid coil (go measure one) isn't going to create a high voltage spike that would cause a severe shock like an ignition coil is going to. Basic electronics.. Ok you got me. I do remember using the master key ( Any metal that you can find, wire, screwdriver, key,etc) more then once to energize the solenoid and get it started. many times I remember a hell of a shock. |
Hmm I think I would stop doing something that gave me a hell of a shock
after the first time it happened, but hey that's just me...
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You made me think about it because you are right. Next time I do it I will be sure to take the screwdriver off the solenoid before I take it off the hot post and that should allow me to avoid the hi voltage of the counter-emf. However I still disagree with you about the high voltage spike. without going into a lot of detail ( I have been employed in the electronic field since 67 and earned my BSEE in 73) I will just remind you that the dc resistance of that ignition coil is also very low. |
high voltage is created on the high ohm side of the coil.
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I would take a bet that I could measure at least 1000 volts within .5 milliseconds of the collapse of the magnetic field in most solenoids |
with this voltage spike being sent back to the ignition switch and quickly
burning them or the starter relay up if this was the case. 1000 volts is
going to jump across relay points in free air and they sure wouldn't last
very long.
--
Steve
http://www.atlantaracing.com
#32
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metoo wrote: On Thu, 05 Oct 2006 01:29:29 -0400, Steve T <fotocord (AT) yahoo (DOT) com wrote: metoo wrote: On Wed, 04 Oct 2006 00:07:22 -0400, Steve T <fotocord (AT) yahoo (DOT) com wrote: metoo wrote: simple E=I*R I=E/R 12 volts devided by 400,000 ohms ( I just measured between indexfinge and thumb on one hand to indexfinger and thumb on other hand, squeezed hard lowest reading i saw was about 4000,000 ohms) = .03 millamps. Not enough to feel. Touch the main terminal of the starter with 1 hand on the frame and you will not feel anything when someone cranks the car UNTILL they release the key and the counter EMF (caused by the magnetic lines of flux collapsing) will produce hundreds or thousands of volts at low current will shock the hell out of you because then 4000 volts devided by 400,000 ohms will allow 10 millamps to go thru you and that sir could be lethal!! When you let off the key, the solenoid disengages, so any EMF wouldn't transfer to the post being held. the solenoid disengaging is what causes the counter-EMF The magnetic flux being developed by the coil all of a sudden have no where to go so they collapse back to the coil. With no return path to ground. the very high resistance makes the voltage so high at the post. Basic electronics. The solenoid is a relay. When you disengage it, any EMF would NOT discharge to the positive post on the solenoid the battery cable connects to, the coil isn't connected to that post! There might be some voltage at the trigger wire but the low ohms of a solenoid coil (go measure one) isn't going to create a high voltage spike that would cause a severe shock like an ignition coil is going to. Basic electronics.. Ok you got me. I do remember using the master key ( Any metal that you can find, wire, screwdriver, key,etc) more then once to energize the solenoid and get it started. many times I remember a hell of a shock. Hmm I think I would stop doing something that gave me a hell of a shock after the first time it happened, but hey that's just me... |
HMM I have always felt a need to charge up every once in a while It
keeps me from being stupid like you
Quote:
| You made me think about it because you are right. Next time I do it I will be sure to take the screwdriver off the solenoid before I take it off the hot post and that should allow me to avoid the hi voltage of the counter-emf. However I still disagree with you about the high voltage spike. without going into a lot of detail ( I have been employed in the electronic field since 67 and earned my BSEE in 73) I will just remind you that the dc resistance of that ignition coil is also very low. But there isn't large voltage created on the low ohm side is there? The high voltage is created on the high ohm side of the coil. |
You better read up Google is your friend, I don't need to tell you
again, you just want to argue!
Quote:
| I would take a bet that I could measure at least 1000 volts within .5 milliseconds of the collapse of the magnetic field in most solenoids I have no idea but is seems if this was true, you'd have a major problem with this voltage spike being sent back to the ignition switch and quickly burning them or the starter relay up if this was the case. 1000 volts is going to jump across relay points in free air and they sure wouldn't last very long. maybe that is way we put damping diodes and capacitors across relay |
But that voltage is there and you can do something about it if you
want to. lots of designs don't do anything about it.
You better read up Google is your friend, I don't need to tell you
again, you just want to argue!
#33
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On Fri, 06 Oct 2006 00:59:01 -0400, Steve T <fotocord (AT) yahoo (DOT) com wrote: I do remember using the master key ( Any metal that you can find, wire, screwdriver, key,etc) more then once to energize the solenoid and get it started. many times I remember a hell of a shock. Hmm I think I would stop doing something that gave me a hell of a shock after the first time it happened, but hey that's just me... HMM I have always felt a need to charge up every once in a while It keeps me from being stupid like you |
same thing over and over many times and then call me stupid? How many
times did it take for you to figure out not to put your hand on a red hot
cooktop eye?
Quote:
| You made me think about it because you are right. Next time I do it I will be sure to take the screwdriver off the solenoid before I take it off the hot post and that should allow me to avoid the hi voltage of the counter-emf. However I still disagree with you about the high voltage spike. without going into a lot of detail ( I have been employed in the electronic field since 67 and earned my BSEE in 73) I will just remind you that the dc resistance of that ignition coil is also very low. But there isn't large voltage created on the low ohm side is there? The high voltage is created on the high ohm side of the coil. You better read up Google is your friend, I don't need to tell you again, you just want to argue! |
made for. Hint: it's to create the high voltage that can shock you. Hint 2:
A starter solenoid doesn't have a secondary winding.
Quote:
| I would take a bet that I could measure at least 1000 volts within .5 milliseconds of the collapse of the magnetic field in most solenoids I have no idea but is seems if this was true, you'd have a major problem with this voltage spike being sent back to the ignition switch and quickly burning them or the starter relay up if this was the case. 1000 volts is going to jump across relay points in free air and they sure wouldn't last very long. maybe that is way we put damping diodes and capacitors across relay coils. |
current flow at anything over their base voltage. Doesn't mean these can be
felt by a human (they can't) much less kill them.
Quote:
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But that voltage is there and you can do something about it if you want to. lots of designs don't do anything about it. |
would fry a starter relay or switch in a VERY short period of time.
--
Steve
http://www.atlantaracing.com
#34
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#35
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Yes I heard about you dumbass flamers try to be a expert in my field and just show what a Aholde you can be. http://www.naisweb.com/e/relaye/mech...a/idapm4w.html http://www.naisweb.com/e/relaye/mech...i/idaqy5w.html I am sure you can find fault in my links above since no one knows more then you about anything. I will design electronic circuits and you can tell me how they will work or not, |
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