LED alternator indicator light flickering when off -- thoughs?
01-26-2009, 12:11 AM
#16
Wow, you're really getting to the bottom of this...I suspect the LED flickering is due to AC voltage induced so even though the measured average is 0.1v above battery but there may be underlying AC voltage that is lower than 8v that makes the LED flicker? just a guess.
Also, are you sure the zener polarity is correct that the zener triangle symbol and LED triangle symbol are pointing at different directions when connected in series? If they are not, your zener will act kinda like a 1.5v zener instead of 5.1v.
Um, if you use the bulb to replace the power resistors, if the bulb fails, your alternator will fail too. Or you put the bulb paralell to the power resistors?
Also, are you sure the zener polarity is correct that the zener triangle symbol and LED triangle symbol are pointing at different directions when connected in series? If they are not, your zener will act kinda like a 1.5v zener instead of 5.1v.
Um, if you use the bulb to replace the power resistors, if the bulb fails, your alternator will fail too. Or you put the bulb paralell to the power resistors?
01-26-2009, 12:03 PM
#17
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below is circuit as it stands now...
When I tried the 250 ohm, it was as shown here.
Ahsai -- good point on the lamp failure alternator (maybe) doesn't work. I should probably just put bulb in parallel with one of to 50 ohm power resistors.
Didn't think of measuring the AC volts to see what I get when alternator is running. Don't have scope at home to look at waveform.
Was gonna do quick check in car, but that's going to need to wait. I started car yesterday to do a quick check on something and bottom weld in one of the oil coolers let go (about an 8" crack). Glad I only ran for about 10- 15 sec "only" had a 3 foot pool of oil to clean up. ...cooler was new, porsche 964/993.
When I tried the 250 ohm, it was as shown here.
Ahsai -- good point on the lamp failure alternator (maybe) doesn't work. I should probably just put bulb in parallel with one of to 50 ohm power resistors.
Didn't think of measuring the AC volts to see what I get when alternator is running. Don't have scope at home to look at waveform.
Was gonna do quick check in car, but that's going to need to wait. I started car yesterday to do a quick check on something and bottom weld in one of the oil coolers let go (about an 8" crack). Glad I only ran for about 10- 15 sec "only" had a 3 foot pool of oil to clean up. ...cooler was new, porsche 964/993.
Last edited by JoeMag; 12-23-2014 at 12:04 PM.
01-26-2009, 04:55 PM
#18
Hi Joe,
Your circuit looks good to me. I still can't explain the flickering since LEDs don't lie
Maybe you can use a 12v or so zener and see if that helps eliminating the flickering.
You got me curious to google and I found this info interesting http://www.alternatorparts.com/under...lternators.htm
It has a pretty good description of the idiot light under WARNING LAMP. I must admit I didn't know it warns you for TWO failure scenarios - alt not working and battery too low. I know the former but not the latter. It's actually a pretty clever design, simlpe yet effective. So to duplicate the full functionality (if you care), it'll take more circuits.
Your circuit looks good to me. I still can't explain the flickering since LEDs don't lie
Maybe you can use a 12v or so zener and see if that helps eliminating the flickering.You got me curious to google and I found this info interesting http://www.alternatorparts.com/under...lternators.htm
It has a pretty good description of the idiot light under WARNING LAMP. I must admit I didn't know it warns you for TWO failure scenarios - alt not working and battery too low. I know the former but not the latter. It's actually a pretty clever design, simlpe yet effective. So to duplicate the full functionality (if you care), it'll take more circuits.
01-26-2009, 06:17 PM
#19
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In my case, it's race car, and I just care if alternator is working. Really what you're looking for is failure of alternator belt / loss of cooling.
01-26-2009, 09:03 PM
#20
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Looking at the circuit above, I don't see anything that would cause a problem. What about the test setup, were you using a car battery for the 12V power source and was it connected to the main output of the alternator? The battery acts like a big capacitor for the alternator which makes the output a clean DC voltage.
01-27-2009, 01:59 PM
#21
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In test setup I am using a car battery. Batt = Batt positive connected to Alternator Out (8mm post) and Alternator gnd connected to Batt negative.
