James_D
New member
Where does the charging light get wired to? my engine is Ford Essex V6 petrol marinised with alternator. thank you JD
Charging circuit light.
- Thread starter James_D
- Start date
roly_voya
New member
Normally the D+ terminal on the alternator. It works by comparing the batt voltage with the alternator output voltage and normally needs to see the positive side of the field coil input to do this.
VicS
Well-known member
[ QUOTE ]
Normally the D+ terminal on the alternator
[/ QUOTE ] It may be D+ or D+/61 but sometimes the main output may be marked D+. Unfortunately there is no standard and the markings vary between manufacturers.
It's not the big terminal, nor the earth terminal if there is one, nor one marked W or AC. That probably leaves just one, thats it!
The other side of the lamp is fed from the ignition switch when it is in the normal running position.
Normally the D+ terminal on the alternator
[/ QUOTE ] It may be D+ or D+/61 but sometimes the main output may be marked D+. Unfortunately there is no standard and the markings vary between manufacturers.
It's not the big terminal, nor the earth terminal if there is one, nor one marked W or AC. That probably leaves just one, thats it!
The other side of the lamp is fed from the ignition switch when it is in the normal running position.
William_H
Well-known member
The charge light is connected between battery supply +ve (on when ignition on) and the regulator. Sometimes to the field coil then regulator to ground.
This circuit provides a path from the battery to the field coil to provide a magnetic field to the rotor that will start the alternator charging when it is turning. However when the alternator starts to charge there is usually another 3 diodes that provide power directly to the field coil via the regulator as an alternative to the power supplied via the light.
Hence if the light is on the alternator is not charging (belt broken or similar. If however the brushes fail to make contact with the slip rings so there is no field current (a common failure mode) then the light will not light either before engine starts or when running.
A volt meter or ampmeter is the best way to determine correct charging but the light can identify some faults. olewill
This circuit provides a path from the battery to the field coil to provide a magnetic field to the rotor that will start the alternator charging when it is turning. However when the alternator starts to charge there is usually another 3 diodes that provide power directly to the field coil via the regulator as an alternative to the power supplied via the light.
Hence if the light is on the alternator is not charging (belt broken or similar. If however the brushes fail to make contact with the slip rings so there is no field current (a common failure mode) then the light will not light either before engine starts or when running.
A volt meter or ampmeter is the best way to determine correct charging but the light can identify some faults. olewill
rogerthebodger
Well-known member
Is it possible to use a LED to replace the normal incandescent lamp in the charging light circuit.
VicS
Well-known member
[ QUOTE ]
Is it possible to use a LED to replace the normal incandescent lamp in the charging light circuit
[/ QUOTE ] On its own no because the normal bulb provides the initial field current until the alternator is able to provide its own. An LED would not provide enough current.
You could do it with an led and a shunt resistor I guess but I don't see what there is to gain
Is it possible to use a LED to replace the normal incandescent lamp in the charging light circuit
[/ QUOTE ] On its own no because the normal bulb provides the initial field current until the alternator is able to provide its own. An LED would not provide enough current.
You could do it with an led and a shunt resistor I guess but I don't see what there is to gain
rogerthebodger
Well-known member
[ QUOTE ]
I don't see what there is to gain
[/ QUOTE ]
Its just on both my main engine and generator control panel I have LED indicators for oil pressure , water temperature , water flow alarms and it would be nice to use LED for charge indicator to make it look the same.
I don't see what there is to gain
[/ QUOTE ]
Its just on both my main engine and generator control panel I have LED indicators for oil pressure , water temperature , water flow alarms and it would be nice to use LED for charge indicator to make it look the same.
VicS
Well-known member
[ QUOTE ]
it would be nice to use LED for charge indicator to make it look the same.
[/ QUOTE ] Fair enough but put a resistor in parallel** that is equal in resistance to the bulb that you would otherwise have used. R=V²/W where V is obviously the volts of your system and W is the power of the bulb you are replacing. Use a resistor with a power rating equal to or greater than the power of that bulb.
**That's in parallel with the led and any series resistor you may be using with it.
it would be nice to use LED for charge indicator to make it look the same.
[/ QUOTE ] Fair enough but put a resistor in parallel** that is equal in resistance to the bulb that you would otherwise have used. R=V²/W where V is obviously the volts of your system and W is the power of the bulb you are replacing. Use a resistor with a power rating equal to or greater than the power of that bulb.
**That's in parallel with the led and any series resistor you may be using with it.
moody1
New member
[ QUOTE ]
[ QUOTE ]
it would be nice to use LED for charge indicator to make it look the same.
[/ QUOTE ] Fair enough but put a resistor in parallel** that is equal in resistance to the bulb that you would otherwise have used. R=V²/W where V is obviously the volts of your system and W is the power of the bulb you are replacing. Use a resistor with a power rating equal to or greater than the power of that bulb.
**That's in parallel with the led and any series resistor you may be using with it.
[/ QUOTE ]
We have a 12v LED as charge light and as long as wired correct way round is fine. Lights when supplying exciting voltage, goes of as Alternator takes over. There are no other bits / items fitted.
[ QUOTE ]
it would be nice to use LED for charge indicator to make it look the same.
[/ QUOTE ] Fair enough but put a resistor in parallel** that is equal in resistance to the bulb that you would otherwise have used. R=V²/W where V is obviously the volts of your system and W is the power of the bulb you are replacing. Use a resistor with a power rating equal to or greater than the power of that bulb.
**That's in parallel with the led and any series resistor you may be using with it.
[/ QUOTE ]
We have a 12v LED as charge light and as long as wired correct way round is fine. Lights when supplying exciting voltage, goes of as Alternator takes over. There are no other bits / items fitted.
VicS
Well-known member
[ QUOTE ]
We have a 12v LED as charge light and as long as wired correct way round is fine
[/ QUOTE ] It must either be of a design that provides adequate current or there is some other provision for providing the current. An alternator, at least one which is designed to be used with an filament bulb, must be provided with adequate current to energise the field windings initially or it will not start to generate. I have no doubt that with the increasing use of LEDs as indicators there are ways around the problem but Roger's question was simply about using an LED in place of a bulb.
We have a 12v LED as charge light and as long as wired correct way round is fine
[/ QUOTE ] It must either be of a design that provides adequate current or there is some other provision for providing the current. An alternator, at least one which is designed to be used with an filament bulb, must be provided with adequate current to energise the field windings initially or it will not start to generate. I have no doubt that with the increasing use of LEDs as indicators there are ways around the problem but Roger's question was simply about using an LED in place of a bulb.
moody1
New member
[ QUOTE ]
[ QUOTE ]
We have a 12v LED as charge light and as long as wired correct way round is fine
[/ QUOTE ] It must either be of a design that provides adequate current or there is some other provision for providing the current. An alternator, at least one which is designed to be used with an filament bulb, must be provided with adequate current to energise the field windings initially or it will not start to generate. I have no doubt that with the increasing use of LEDs as indicators there are ways around the problem but Roger's question was simply about using an LED in place of a bulb.
[/ QUOTE ]
Large LED 12v bought from local Car accessory shop. Nothing special as we know. Of course not being "experts" we may have been sold something very special. But somehow I doubt it.
After reading this and other posts from "experts" when we come to replace later we will use a normal filament bulb to keep all happy.
[ QUOTE ]
We have a 12v LED as charge light and as long as wired correct way round is fine
[/ QUOTE ] It must either be of a design that provides adequate current or there is some other provision for providing the current. An alternator, at least one which is designed to be used with an filament bulb, must be provided with adequate current to energise the field windings initially or it will not start to generate. I have no doubt that with the increasing use of LEDs as indicators there are ways around the problem but Roger's question was simply about using an LED in place of a bulb.
[/ QUOTE ]
Large LED 12v bought from local Car accessory shop. Nothing special as we know. Of course not being "experts" we may have been sold something very special. But somehow I doubt it.
After reading this and other posts from "experts" when we come to replace later we will use a normal filament bulb to keep all happy.
VicS
Well-known member
[ QUOTE ]
After reading this and other posts from "experts" when we come to replace later we will use a normal filament bulb to keep all happy
[/ QUOTE ]
If it works it works fair enough but it surprises me that an ordinary LED is a suitable replacement for a filament bulb based on what I know about the way alternators work.
There is certainly no need to replace it with a bulb just to keep others happy. I cant see the point in that.
A rational explanation of how and why it works would be far more useful to us all than sarcastic remarks!
After reading this and other posts from "experts" when we come to replace later we will use a normal filament bulb to keep all happy
[/ QUOTE ]
If it works it works fair enough but it surprises me that an ordinary LED is a suitable replacement for a filament bulb based on what I know about the way alternators work.
There is certainly no need to replace it with a bulb just to keep others happy. I cant see the point in that.
A rational explanation of how and why it works would be far more useful to us all than sarcastic remarks!
tinkicker0
New member
Concur. It will be interesting to know the current path across the LED.
Must have some sort of voltage regulating circuitry built in to the casing that does it and the LED is not directly in the circuit.
more importantly where did it come from and how much did it cost.
Must have some sort of voltage regulating circuitry built in to the casing that does it and the LED is not directly in the circuit.
more importantly where did it come from and how much did it cost.
VicS
Well-known member
An investigation of what is on offer at the local car accessory shop is called for. Unfortunately that's only Halfords for me but I've got to go to the pet-shop next door tomorrow.
William_H
Well-known member
A typical LED will draw about 25 milliamps at 12v via a resistor.
A typical lamp for the indicator will be 3watt or 250 milliamps.
So this current will be the current given to the field coil to initiate charging. Obviously 15ma is enough to do the job. However I thinkl I would rather be more sure with 250ma. It may just be the difference when the brushes get a bit grotty or the idle speed is low.
If you wan to use an LED then a resistor of 50 ohms (or47ohms) of 5 watt rating should be wired in place of the bulb. With the LED and it's own series resistor (if external) wired across in paralell to the 50 ohm resistor. olewill
A typical lamp for the indicator will be 3watt or 250 milliamps.
So this current will be the current given to the field coil to initiate charging. Obviously 15ma is enough to do the job. However I thinkl I would rather be more sure with 250ma. It may just be the difference when the brushes get a bit grotty or the idle speed is low.
If you wan to use an LED then a resistor of 50 ohms (or47ohms) of 5 watt rating should be wired in place of the bulb. With the LED and it's own series resistor (if external) wired across in paralell to the 50 ohm resistor. olewill
VicS
Well-known member
[ QUOTE ]
Obviously 15ma is enough to do the job
[/ QUOTE ] Sorry Will why is it obvious that 15mA is enough? Have I missed something or is that a misprunt?
In defence of our moody friend some very bright LEDs do draw quite a substantial current although they would be a lot brighter than one needs as an indicator bulb. I see 350 mA and more in the catalogue. Unless we know what he bought we are a bit in the dark!
Obviously 15ma is enough to do the job
[/ QUOTE ] Sorry Will why is it obvious that 15mA is enough? Have I missed something or is that a misprunt?
In defence of our moody friend some very bright LEDs do draw quite a substantial current although they would be a lot brighter than one needs as an indicator bulb. I see 350 mA and more in the catalogue. Unless we know what he bought we are a bit in the dark!
moody1
New member
[ QUOTE ]
[ QUOTE ]
Obviously 15ma is enough to do the job
[/ QUOTE ] Sorry Will why is it obvious that 15mA is enough? Have I missed something or is that a misprunt?
In defence of our moody friend some very bright LEDs do draw quite a substantial current although they would be a lot brighter than one needs as an indicator bulb. I see 350 mA and more in the catalogue. Unless we know what he bought we are a bit in the dark!
[/ QUOTE ]
Large red LED - believed to have circuit bits in the case. Current draw unknown, but certainly more than standard LED I'm sure.
Les Smiths car access shop. On the counter at cash-desk was a display with allsorts of high power LED's etc. Hubby was looking for various LED's for panels and switches. He noted the large high power one and fitted it. It worked. Only change was that we have to speed up engine a touch after starting to get charging going. Which is not unlike the ignition light on many old cars !
Oh and my sarcasm is based on reading so much expert opinion that at times has been seen to be not so expert. Previous expert advice on this thread has implied that LED cannot do this job.
[ QUOTE ]
Obviously 15ma is enough to do the job
[/ QUOTE ] Sorry Will why is it obvious that 15mA is enough? Have I missed something or is that a misprunt?
In defence of our moody friend some very bright LEDs do draw quite a substantial current although they would be a lot brighter than one needs as an indicator bulb. I see 350 mA and more in the catalogue. Unless we know what he bought we are a bit in the dark!
[/ QUOTE ]
Large red LED - believed to have circuit bits in the case. Current draw unknown, but certainly more than standard LED I'm sure.
Les Smiths car access shop. On the counter at cash-desk was a display with allsorts of high power LED's etc. Hubby was looking for various LED's for panels and switches. He noted the large high power one and fitted it. It worked. Only change was that we have to speed up engine a touch after starting to get charging going. Which is not unlike the ignition light on many old cars !
Oh and my sarcasm is based on reading so much expert opinion that at times has been seen to be not so expert. Previous expert advice on this thread has implied that LED cannot do this job.
VicS
Well-known member
[ QUOTE ]
Large red LED - believed to have circuit bits in the case
[/ QUOTE ] Thanks for the info. I looked at what Halfords had on offer but there was no info on current consumption or even what power they were equivalent too.
What you observe regarding having to speed the engine up a bit to get it to start charging is in line with the LED passing a smaller current than the bub it replaced. Shunting it with a resistor of a suitable value would return the situation to normal if you wished to do that.
On my time line at least old cars had dynamos, not alternators, and they are a totally different kettle of fish. They do not need an external current source to start them charging as they retain sufficient magnetism to start generating without.
I am still quite certain that a "standard" LED with a forward current of a few milliamps will not be suitable as the warning light for an alternator, at least if you want it to start generating without increasing the engine revs appreciably. I notice that the 12volt ones in the Maplin catalogue pass only 8.5mA, even less than the 25mA quoted for the standard ones.
Knowing Roger Shaw's passion for experimentation and making gear from basic components I suspect he would probably have tried to use either a ready ballasted 12volt LED or a standard 2.5volt one with a separate series resistor. However he now knows that if he is prepared have an exceptionally bright warning light (no bad thing perhaps) and to have to rev the engine a bit to get the charging started he can buy something from the South African equivalent of Les Smiths
Large red LED - believed to have circuit bits in the case
[/ QUOTE ] Thanks for the info. I looked at what Halfords had on offer but there was no info on current consumption or even what power they were equivalent too.
What you observe regarding having to speed the engine up a bit to get it to start charging is in line with the LED passing a smaller current than the bub it replaced. Shunting it with a resistor of a suitable value would return the situation to normal if you wished to do that.
On my time line at least old cars had dynamos, not alternators, and they are a totally different kettle of fish. They do not need an external current source to start them charging as they retain sufficient magnetism to start generating without.
I am still quite certain that a "standard" LED with a forward current of a few milliamps will not be suitable as the warning light for an alternator, at least if you want it to start generating without increasing the engine revs appreciably. I notice that the 12volt ones in the Maplin catalogue pass only 8.5mA, even less than the 25mA quoted for the standard ones.
Knowing Roger Shaw's passion for experimentation and making gear from basic components I suspect he would probably have tried to use either a ready ballasted 12volt LED or a standard 2.5volt one with a separate series resistor. However he now knows that if he is prepared have an exceptionally bright warning light (no bad thing perhaps) and to have to rev the engine a bit to get the charging started he can buy something from the South African equivalent of Les Smiths
rogerthebodger
Well-known member
Thanks Vic and all th others
[ QUOTE ]
Knowing Roger Shaw's passion for experimentation and making gear from basic components
[/ QUOTE ]
You know me so well
The LED's I plan to use are 10 mm in size so the current will be more than the normal 5 mm which I use for other indicators on my switch panels which I normally run at 10mA
When I get to wiring up the alternators I will "experiment" with both alternators and will post results
Thanks again Vic.
[ QUOTE ]
Knowing Roger Shaw's passion for experimentation and making gear from basic components
[/ QUOTE ]
You know me so well
The LED's I plan to use are 10 mm in size so the current will be more than the normal 5 mm which I use for other indicators on my switch panels which I normally run at 10mA
When I get to wiring up the alternators I will "experiment" with both alternators and will post results
Thanks again Vic.
VicS
Well-known member
[ QUOTE ]
The LED's I plan to use are 10 mm
[/ QUOTE ] FWIW the max forward current for the standard 10mm LEDs listed in the Maplin catalogue is 25 or 30mA depending upon the colour and 30mA for the "Super bright" versions. They are 2.5 volt ones of course.
The LED's I plan to use are 10 mm
[/ QUOTE ] FWIW the max forward current for the standard 10mm LEDs listed in the Maplin catalogue is 25 or 30mA depending upon the colour and 30mA for the "Super bright" versions. They are 2.5 volt ones of course.
