Straight Bussin, no cap fr fr.

[nikitis]

I can follow a trace on a PCB. The lights for the center area at least were bi-directional. The outside lights like where the warning signs were located at could take led's. I installed the LED for the center area, didn't work, multi-metered, getting powered, reversed the LED, (reverse entails lifting up, and turning 180 degrees to swap the contacts as they are plastic lock-in bulbs, also didn't work, power still on the rail. So it forced me to take a closer look at the PCB Traces of it, and the ground trace was connected to the power trace in multiple places around the center gauge cluster bulbs only. Regardless power was not flowing directionally through the LED itself in either orientation and would not come on. I hand tested the same LED with a 12v battery, and it came on no problem. It is that way. It may be DC, but maybe it is only flowing directionally one way at the beginning to end of the line, but the way the traces were connecting the lights the lights couldn't operate bi-directionally. They are a chain of lights.

The supposed positive and negative traces on the PCB were like below. didn't matter which direction you put the LED's in, it's bi-directional. The lines are obviously the traces on the PCB, connecting both sides of the lights.

LED's won't work on a circuit like this. At the end of it, it's possible there is a one direction flow, but because the traces were all connected like above, the bulbs couldn't tell and can't take LED's. I could MAYBE in theory cut each circle trace with an exacto knife carefully, and make it depend on the LED in one direction and it might work. Like so:

 

[Mr P]

Your drawing looks like one single wire that has positive at one end, ground at the other. That is a direct, short-to-ground circuit that cannot power any light.

 

[ewo1]

Led's have an Anode and a Cathode.
Basically a positive leg and a negative leg.

Some LED's are simply wired pos/neg and they turn on.
then there are LED's that will change color based on the voltage polarity.
These are called bi-polar LED's.

When you replace an incandescent with an LED you will have to ensure that LED resistance is enough in order to even work on the circuit.

this is why you need to change the blinker flasher from incandescent to LED because the LED do not provide enough impedance or resistive load to turn on properly.

There are hundreds of different type of LED's in use today as compared to 1970!
Many are application specific.

 

[ewo1]

This circuit is wired in such a way that all bulbs will turn on but if one bulb fails, it will not affect the others. Kinda like your xmas lights....

this circuit would still require an extra component in order to "relieve the "dead short" effect if and when all the lights went out.
One common item used for short circuit protection would be a low value resistor, like maybe a one ohm 1/8 watt, something that would pop open like a fuse.

this was very commonly used on the tip ring lines of fax machines. These resistors would protect the modem circuitry from Telco spikes on the line.
I know, i repaired hundreds of fax machines in my life.

Using incandescent bulbs, another way of clamping voltage to ground, adding resistors in parallel to the bulbs, something like this.

 

[ewo1]

By cutting the traces like you suggested, the LED's would work but if one went out, they all go out, making troubleshooting fun! You will also might have to add a load resistor to each LED in order for them to turn on

 

[Mr P]

Electrical folks, get in here and clear up this trainwreck....er, bus wreck.

 

[ewo1]

There's not a train wreck in my line of sight, maybe a bit of exaggeration goin on but nothing serious.
Most folks and yes lot's of mechanics, know nothing of Ohm's law and Dc theory.
It is becoming a lost art.

Oh and I got the "electronics" credentials to back it up...

Ohm's Law - DC Circuits - Basics Electronics

Ohm's Law

ecstudiosystems.com

 

[ewo1]

*

 

[Mr P]

When you replace an incandescent with an LED you will have to ensure that LED resistance is enough in order to even work on the circuit.

Prove that. I think your claim is false. I think any circuit that was designed for powering an incandecant bulb can power an LED...enough to make it light. Any dimming or pulsing controls might not work, depending on design.

this is why you need to change the blinker flasher from incandescent to LED because the LED do not provide enough impedance or resistive load to turn on properly.

Not at all, actually backward. An old "flasher" used the heat generated from the load (amperage) of the bulbs to heat a bimetallic spring which flexed one way when heated and the opposite when cooling. Hence, a switched circuit based on load. LEDs will not draw enough amperage to create that heat.


* LED....yall are right on several aspects. Diodes = check valve = directional in that regard. Anode/cathode, all correct.

 

[Mr P]

A "factory" wiring diagram of dash lighting would solve this cicuit problem. I'd wager that it's a case of bad contacts (LED to PC and misidentification of a circuit.

 

[ewo1]

knock, knock, knock...
anyone home?
you said the same damn thing i did...

this is why you need to change the blinker flasher from incandescent to LED because the LED do not provide enough impedance or resistive load to turn on properly.

Not at all, actually backward. An old "flasher" used the heat generated from the load (amperage) of the bulbs to heat a bimetallic spring which flexed one way when heated and the opposite when cooling. Hence, a switched circuit based on load. LEDs will not draw enough amperage to create that heat.

 

[ewo1]

yeah, only enough o make it light. OMG...
boy o boy...
You have a unique way of flipping things around and not making a valuable contribution..

you basically said the same thing I did but in different words...
when you gonna become a positive contributor???

I can argue with you all year long but neither of us are gonna win so let's work on helping others go forward!

When you replace an incandescent with an LED you will have to ensure that LED resistance is enough in order to even work on the circuit.

Prove that. I think your claim is false. I think any circuit that was designed for powering an incandecant bulb can power an LED...enough to make it light. Any dimming or pulsing controls might not work, depending on design.

 

[ewo1]

* LED....yall are right on several aspects. Diodes = check valve = directional in that regard. Anode/cathode, all correct.

Diodes are also used for voltage regulation, ac waveform filtering to DC, and is some instances they are used as a fusible device within a circuit, meant to "pop" if certain conditions are met, a safety design in the circuit in order to prevent a catastrophic failure. Also used in high power switching, and also in optical switching circuits too.
The terms anode and Cathode are only used to identify the polarity of a diode, super important when placing into a circuit!
Diodes were also once used in logic gate switching circuits. That all done with semiconductors today.

 

[Mr P]

knock, knock, knock...
anyone home?
you said the same damn thing i did...

Uh, no. You said an LED needed "more resistance" to work a flasher. More resistance = less current.

I say they need to draw MORE current, that is the opposite of what you claimed.

 

[ewo1]

Uh, no. You said an LED needed "more resistance" to work a flasher. More resistance = less current.

I say they need to draw MORE current, that is the opposite of what you claimed.

ok let's look at this.
an 1157 light bulb has about 14 ohms of "resistance"
An automotive LED build has around 3-4 ohms.

And you tell me that more resistance = less current.

so why is it then that in order for the automotive led's (turn , stop lights) require a load resistor added to the circuit in order to mimic the current draw of the original incandescent light bulb?

Typically these "load" resistors are in the range of 8-10 ohms.
Add 3-4 ohms and you are in the 14 ohms of resistance range of functionality.

I get the feeling you understand this but your choice of words sends an opposite message.
We both are correct, more current creates heat which is required to make the flashers operational.

In the case of adding LED's, the circuit needs MORE resistance to operate as it does with incandescent.
It's that simple.

 

[Mr P]

lol

You either need more, or less, beer! lol

Adding resistance to a cicuit will reduce amperage, right? What are we missing????? lol

Maybe I need the beer. Last one was new years Eve....of 1997!

 

[ewo1]

ok, let's check your math
you tell me why an LEd "load resistor-flasher" is NOT required

1157-14 ohms
LED-4 ohm

OHMS LAW
I=V/R

12v / 14 ohms = .85 amp
12v / 4 ohms = 3 amps

this "current" is going thru the "Light/Led" bulb, not the relay.
the switching action is done via the swinging terminals of the relay.

How does the relay coil "heat up" and know when to toggle?

Explain that please....

If the LED resistance value was the same as the 1157, would we still need the LED flasher relay?

do your best to explain!
And please make sure the math works out...
Take a look at calculated voltage drops too!

 

[Carl635]

Maybe you should be saying that more resistance is a smaller ohms number?

 

[ewo1]

Maybe you should be saying that more resistance is a smaller ohms number?

What's happening is that there is a single focus on one item... It don't always work that way.
You got to take into consideration things like, the light bulb 12v feed...is it coming from the same feed as the relay coil?
Is it coming from an independent source like a body control module.

We're gonna spin this into oblivion but...Ohms law, Kirchhoffs voltage and current laws, do not lie!

 

[Mr P]

ok, let's check your math
you tell me why an LEd "load resistor-flasher" is NOT required

1157-14 ohms
LED-4 ohm

OHMS LAW
I=V/R

12v / 14 ohms = .85 amp
12v / 4 ohms = 3 amps

this "current" is going thru the "Light/Led" bulb, not the relay.
the switching action is done via the swinging terminals of the relay.

How does the relay coil "heat up" and know when to toggle?

Explain that please....

If the LED resistance value was the same as the 1157, would we still need the LED flasher relay?

do your best to explain!
And please make sure the math works out...

The bold in the quote is a straw man argument. You've COMPLETELY changed the issue.

Go back to post #329. If you can't see it clearly now, try again later.